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Determination of donepezil, an acetylcholinesterase inhibitor, in human plasma by high-performance liquid chromatography with ultraviolet absorbance detection
Abstract
A simple and sensitive high-performance liquid chromatographic (HPLC) method with UV absorbance detection is described for the quantification of donepezil, a centrally and selectively acting acetyleholinesterase inhibitor, in human plasma. After sample alkalinization with 0.5 ml of NaOH (0.1 M), the test compound was extracted from I ml of plasma using isopropanol-hexane (3:97, v/v). The organic phase was back-extracted with 75 microl of HCl (0.1 M) and 50 microl of the acid solution was injected into a C18 STR ODS-II analytical column (5 microm, 150x4.6 mm I.D.). The mobile phase consisted of phosphate buffer (0.02 M, pH 4.6), perchloric acid (6 M) and acetonitrile (59.5:0.5:40, v/v) and was delivered at a flow-rate of 1.0 ml/min at 40 degrees C. The peak was detected using a UV detector set at 315 nm, and the total time for a chromatographic separation was approximately 8 min. The method was validated for the concentration range 3-90 ng/ml. Mean recoveries were 89-98%. Intra- and inter-day relative standard deviations were less than 7.3 and 7.6%, respectively, at the concentrations ranging from 3 to 90 ng/ml. The method shows good specificity with respect to commonly prescribed psychotropic drugs, and it could be successfully applied for pharmacokinetic studies and therapeutic drug monitoring.
... To comprehensively investigate the pharmacokinetic profiles of DNP and PTX combination treatment, which has not yet been reported for new drug development, the establishment of an assay that simultaneously determines the concentrations of both drugs in a biological sample is essential. However, to the best of our knowledge, there is no report on simultaneous quantification methods for PTX and DNP, and numerous quantitative assays to determine PTX or DNP in biological matrices by high-performance liquid chromatography (HPLC) and liquid chromatography-tandem mass spectrometry (LC-MS/MS) [25][26][27][28][29][30][31][32][33][34][35][36][37][38][39][40][41][42] possess several limitations. For example, PTX quantification methods performed via HPLC with UV detection and LC-MS/MS for humans [25,27,[29][30][31][32][33] and rats [25,28] require large volumes of plasma samples (i.e., 0.2-1 mL plasma), with limited ranges of quantification concentrations of between 1 and 50 ng mL −1 [25][26][27][28][29][30][31]33]. ...
... Furthermore, some methods analyzed only PTX [27] and/or its metabolites together [25,26,[28][29][30][31][32][33], in spite of the presence of the various PTX metabolites including PTX-M1, PTX-M4, and PTX-M5 at detectable levels in plasma [17,24]. Likewise, analytical methods for DNP determination performed via HPLC with UV detection and LC-MS/MS in humans [33,34,[34][35][36][37][38][39][40][41] and rats [35,42] require large sample volumes (i.e., 0.1-1 mL plasma) [34][35][36][37][38][39][40][41]; however, these assays have been reported to have low recovery rates [34,37,38]. Along with various extraction techniques, such as LLE [36,37,40,42], SPE [34,38,39,41], and PP [35], not only DNP [34][35][36][37]41] but also both DNP and its metabolites [38][39][40] were analyzed. ...
... Furthermore, some methods analyzed only PTX [27] and/or its metabolites together [25,26,[28][29][30][31][32][33], in spite of the presence of the various PTX metabolites including PTX-M1, PTX-M4, and PTX-M5 at detectable levels in plasma [17,24]. Likewise, analytical methods for DNP determination performed via HPLC with UV detection and LC-MS/MS in humans [33,34,[34][35][36][37][38][39][40][41] and rats [35,42] require large sample volumes (i.e., 0.1-1 mL plasma) [34][35][36][37][38][39][40][41]; however, these assays have been reported to have low recovery rates [34,37,38]. Along with various extraction techniques, such as LLE [36,37,40,42], SPE [34,38,39,41], and PP [35], not only DNP [34][35][36][37]41] but also both DNP and its metabolites [38][39][40] were analyzed. ...
This study developed a simple, rapid, reproducible, and analytical method using liquid chromatography and electrospray ionization (ESI) with tandem mass spectrometry (LC-MS/MS) to simultaneously quantify pentoxifylline (PTX), its pharmacological active metabolites, lisofylline (PTX-M1) and 1-(3-carboxypropyl)-3,7-dimethylxanthine (PTX-M5), and donepezil (DNP) in rat plasma, using PTX-d6 and DNP-d7 as the internal standards. The LC-MS/MS procedure was performed at the ESI interface, operating in positive ionization and multiple reaction monitoring (MRM) modes; the monitoring of transitions comprised m/z 279.3 > 181.1 for PTX, m/z 281.1 > 263.1 > 160.90 for PTX-M1, m/z 267.1 > 249.0 > 220.9 for PTX-M5, m/z 380.3 > 90.9 for DNP, m/z 285.3 > 187.1 for PTX-d6 (IS1), and m/z 387.3 > 98.3 for DNP-d7 (IS2). After plasma protein precipitation (PP) with methanol, chromatographic separation was performed with an Imtakt Cadenza® CD-C18 (100 × 3 mm, 3 µm) column, using an isocratic mobile phase consisting of 0.1% formic acid in water and methanol (20:80, v/v) at a flow rate of 0.2 mL/min. The retention times of DNP, PTX-M5, PTX, and PTX-M1 were 2.24, 2.50, 2.68, and 2.72 min, respectively, with a total run time of 5 min. This method was validated over a linear concentration range of 5–8000, 10–5000, 20–15,000, and 2–500 ng mL−1 for PTX, PTX-M1, PTX-M5, and DNP, respectively, with a high correlation coefficient (r2 ≥ 0.99). The established method was fully validated in terms of selectivity, the lower limit of quantitation, precision, accuracy, recovery, matrix effect, stability, and dilution integrity according to the regulatory guidelines from the U.S. Food and Drug Administration and the Korea Ministry of Food and Drug Safety. The validated method was successfully applied to a pharmacokinetic study on the concurrent administration of DNP and PTX in rats.
... Internal standard: E2020-d 7 was used (500 ng/mL in 0.0001 M HCl). 2011), isopropyl alcohol (IPA)-n-hexane (Matsui et al., 1999) or extracting from plasma after bringing pH of the plasma to basic pH using IPA-n-hexane (Yasui-Furukori et al., 2002;Lu et al., 2004;Nakashima et al., 2006), TBME (Kim et al., 2011;Iordachescu et al., 2012), ACN (Noetzli et al., 2012), hexane (Apostolou et al., 2007) and EtoAc (Xie et al., 2006). Park et al. (2008) reported that selective and good recovery was achieved with twofold extraction of basic pH plasma samples with TBME (Park et al., 2008). ...
... Nakashima et al.'s (2006) group used a structurally close analog of donepezil, whereas Abonassif et al. (2011) used pindolol as an IS for quantification on HPLC using fluorescence detection. Cisapride was used as an IS in quantification of donepezil using a UV detector (Yasui-Furukori et al., 2002). Labeled donepezil was used as IS by several researchers to avoid complexities in quantification approach on LC-MS/MS (Matsui et al., 1995(Matsui et al., , 1999Iordachescu et al., 2012;Meier-Davis et al., 2012;Noetzli et al., 2012). ...
... Radwan et al. (2006) shared an analytical approach with protein precipitate supernatant subjected to UV detection at 268 nm for rat plasma. Yasui-Furukori et al. (2002) published UV detection at 315 nm for donepezil from human plasma. Samples were alkalinized and subsequently subjected to liquid-liquid extraction with isopropanol-hexane solution. ...
Alzheimer's disease (AD) is a neurological disorder and is the most frequent type of dementia among elderly people. Donepezil, rivastigmine, galantamine, tacrine and memantine are the US Food and Drug Administration approved oral drugs used in the treatment of AD. Quantitation of these drugs in various biological matrices and monitoring them in long-term treatment is essential to titer the dose of these drugs and ensure patient compliance. This review provides a comprehensive account of various HPLC and LC-MS/MS assays, which have been successfully employed to measure the drug levels in various biological matrices arising from preclinical and clinical studies. In addition, this review collates various considerations such as internal standard selection, extraction schemes, matrix effect, selectivity evaluation and optimization of mass spectrometric conditions to enable the development of sound bioanalytical methods for quantitation of Alzheimer's drugs. Overall LC-MS/MS methods have proven to be the choice of bioanalytical method for the quantification of Alzheimer's drugs in both preclinical and clinical studies. In conclusion, important features of LC-MS/MS methodology for Alzheimer's drugs include shortened analysis time, increased throughput, selectivity and lower cost of analysis. Copyright © 2014 John Wiley & Sons, Ltd.
... For the determination of donepezil in human plasma or urine samples, reversed-phase high-performance liquid chromatography (RP-HPLC) with UV (Tiseo et al., 1998;Yasui-Furukori et al., 2002), fluorescence (Haginaka and Seyama, 1992;Nakashima et al., 2006), and tandem mass spectrometry (MS/MS) detection (Thevis et al., 2006;Xie et al., 2006;Apostolou et al., 2007;Lee et al., 2007) were reported. The simultaneous determination of donepezil enantiomers were performed by chiral HPLC with MS (Matsui et al., 1995), MS/MS (Matsui et al., 1999), and fluorescence detection (Haginaka and Seyama, 1992). ...
... The simultaneous determination of donepezil enantiomers were performed by chiral HPLC with MS (Matsui et al., 1995), MS/MS (Matsui et al., 1999), and fluorescence detection (Haginaka and Seyama, 1992). The sample preparation procedures for the extraction of donepezil from plasma and urine samples consist of liquidliquid extraction (Matsui et al., 1999;Yasui-Furukori et al., 2002;Nakashima et al., 2006;Xie et al., 2006;Apostolou et al., 2007;Lee et al., 2007). Those methods used a large amount of plasma samples (500-1000 µL plasma) in order to obtain the high sensitivity (Matsui et al., 1995(Matsui et al., , 1999Yasui-Furukori et al., 2002;Nakashima et al., 2006;Xie et al., 2006;Lee et al., 2007) and the matrix effect in RP-HPLC with MS/MS detection was observed (Apostolou et al., 2007). ...
... The sample preparation procedures for the extraction of donepezil from plasma and urine samples consist of liquidliquid extraction (Matsui et al., 1999;Yasui-Furukori et al., 2002;Nakashima et al., 2006;Xie et al., 2006;Apostolou et al., 2007;Lee et al., 2007). Those methods used a large amount of plasma samples (500-1000 µL plasma) in order to obtain the high sensitivity (Matsui et al., 1995(Matsui et al., , 1999Yasui-Furukori et al., 2002;Nakashima et al., 2006;Xie et al., 2006;Lee et al., 2007) and the matrix effect in RP-HPLC with MS/MS detection was observed (Apostolou et al., 2007). ...
A selective, sensitive and rapid hydrophilic interaction liquid chromatography with electrospray ionization tandem mass spectrometry was developed for the determination of donepezil in human plasma. Donepezil was twice extracted from human plasma using methyl tert-butyl ether at basic pH. The analytes were separated on an Atlantis HILIC Silica column with the mobile phase of acetonitrile: ammonium formate (50 mM, pH 4.0) (85:15, v/v) and detected by tandem mass spectrometry in the selective reaction monitoring mode. The calibration curve was linear (r = 0.9994) over the concentration range of 0.10-50.0 ng/mL and the lower limit of quantification was 0.1 ng/mL using 200 muL plasma sample. The coefficient of variation and relative error for intra-and inter-assay at four QC levels were 2.7 to 10.5% and -10.0 to 0.0%, respectively. There was no matrix effect for donepezil and cisapride. The present method was successfully applied to the pharmacokinetic study of donepezil after oral dose of donepezil hydrochloride (10 mg tablet) to male healthy volunteers.
... However sensitivity of those methods were found as very poor. In addition, more sensitive high-performance liquid chromatography with UV Detection (HPLC-UV) methods for determination of Donepezil in pharmaceutical preparations [8][9][10] and plasma [11,12] were also reported. Nonetheless, most of the above methods have low precision and/or require long time. ...
... The shorter columns with the same or fixed period did not allow for a proper peak symmetry and number of plates as achieved in Ace 5 C18 (250 x 4.6 mm, 5 μm) and LiChrospher 100 RP-18 (250 x 4.6 mm, 5 μm) columns. Thus we decided to use 250 mm column length (Ace 5 C18 (250 x 4.6 mm, 5 μm) in validation study as reported in previous studies [8,9,11,12,16]. After the selection of the chromatographic column, the mobile phase was chosen as a mixture of 0.05 M phosphate buffer (mobile phase A) (pH 2.0) and acetonitrile (mobile phase B) (55:45, v/v). ...
Donepezil HCl is a hydrochloride salt of a piperidine derivative with neurocognitive enhancement activity. For the determination of Donepezil HCl in pure and tablet dosage form, a sensitive, quick, precise and precise HPLC-UV method was developed and validated. Chromatographic separation was achieved within 5 min on the column of Ace 5 C18 (250 x 4.6 mm, 5 μm particle size) using an isocratic method. A mobile phase was pumped at a rate of 1.2 mL min-1 and comprises a mix of 0.05 M phosphate buffer pH 2,0 and acetonitrile (55:45). The temperature of the column has remained at 30 °C. The wavelength of the detection was 268 nm. The proposed method showed excellent linearity between 1.4 and 100 μg mL-1 and determination coefficient was 0.9999. The detection limit was 0.40 μg mL-1 and the quantitation limit was 4.20 μg mL-1. This method was statistically validated according to ICH guidelines for linearity, accuracy, precision, detection limit, quantitation limit, and selectivity. The method can be used for routine checking of drug quality due to its simplicity and precision in pharmaceutical companies.
... Donepezil hydrochloride (Figure 1a), {2-((1-benzylpiperidin-4-yl)methyl)-5,6-dimethoxy-2,3-dihydro-1H-inden-1-one hydrochloride} (DH) is a reversible inhibitor of acetylcholinesterase acting in the central nervous system. [1,2] It is indicated for the treatment of mild to moderate dementia of Alzheimer's type (1) and is well tolerated when 5 mg daily of the drug is prescribed, [3] also it is the second drug approved by the FDA for the treatment of Alzheimer's disease, which is commercially available as Aricept ® . [4,5] A survey of the literature reveals that different analytical techniques were used for the determination of DH in human biological samples using HPLC with UV detection, [3] fluorescence detection, [5] and mass spectroscopy. ...
... [1,2] It is indicated for the treatment of mild to moderate dementia of Alzheimer's type (1) and is well tolerated when 5 mg daily of the drug is prescribed, [3] also it is the second drug approved by the FDA for the treatment of Alzheimer's disease, which is commercially available as Aricept ® . [4,5] A survey of the literature reveals that different analytical techniques were used for the determination of DH in human biological samples using HPLC with UV detection, [3] fluorescence detection, [5] and mass spectroscopy. [4,[6][7][8] Capillary electrophoresis was also used for its analysis in plasma. ...
A simple, eco-friendly, stability-indicating HPLC method was developed for the determination of Donepezil Hydrochloride (DH) in tablet dosage form in presence of its pharmacopoeial related compound (Donepezil related compound A) and its different degradation products. The chromatographic conditions were optimized to achieve the highest performance parameters using Zorbax Eclipse Plus C18 rapid resolution column (4.6 × 100 mm, 3.5 µm), with a mobile phase composed of 72.5% acetate buffer pH 5.5 and 27.5% ethanol, flowing at 1 ml min⁻¹. The Diode Array Detector (DAD) was set at 315 nm and the column oven was adjusted at 45 °C. The method was validated according to the ICH guidelines with respect to system suitability, specificity, linearity, precision, accuracy, ruggedness, robustness, detection and quantitation limits. Linear response (r = 0.9999) was observed over the range of 2–28 µg/ ml of donepezil, with detection and quantitation limits of 0.031 and 0.103 µg/ ml, respectively. The mean relative standard deviation (R.S.D %) of the results of precision and accuracy of the drug were ≤2%. Forced degradation studies were performed on standard DH and test Demepezil® 5 mg tablets under various conditions and the method was found to be stability indicating. The purity of the DH peak was confirmed using the DAD. In the developed method two principles of green chromatography were adopted (reduce and replace) by reducing solvent consumption through the utilisation of a short column (10 cm) with a smaller particle size (3.5 µm) instead of a normal 25 cm with a 5 µm particle size and by replacing hazardous solvents of the official USP method as acetonitrile with ethanol. Furthermore, the greenness of the method was assessed using National Environmental Methods Index label, Eco scale methods and Environmental Assessment Tool.
... A number of methods have been developed until today for the determination of donepezil in serum and plasma. [5][6][7][8][9][10][11][12][13][14][15][16][17] In most cases, High Pressure Liquid Chromatography, coupled with mass spectrometry or tandem mass spectrometry, was used. [5][6][7][8][9][10][11] UV and fluorescence have also been used for detection. ...
... [5][6][7][8][9][10][11] UV and fluorescence have also been used for detection. [12][13][14][15][16] The use of Ultra High Performance Liquid Chromatography (UHPLC), coupled with mass spectrometry or tandem mass spectrometry, has only been reported once. [17] To the best of our knowledge, a fully validated method for the determination of donepezil in CSF has not been published until today. ...
Donepezil is an acetylcholinesterase inhibitor administered to patients who suffer from Alzheimer’s Disease (AD). We have currently developed and validated a UHPLC-DAD method for the determination of donepezil in cerebrospinal fluid. The retention time of the drug was 2.4 min and the total time of analysis was 6 min. Validation was performed in terms of linearity, selectivity, accuracy, precision, and stability. Following validation, the method was applied to clinical cerebrospinal fluid samples. The currently developed method is a reliable tool for monitoring CSF donepezil levels in patients under treatment with this drug.
... D N P i s m e t a b o l i z e d b y t h e C Y P 4 5 0 isoenzymes 2D6 and 3A4 and undergoes glucuronidation 2 . Previous investigations have shown that DNP in biological fluids can be detected using highperformance liquid chromatography (HPLC) equipped with a ultraviolet spectrometric (UV) [3][4][5][6][7][8][9]17 , fluorescence (FL) 10,11 or mass spectrometric (MS) [12][13] detector as well as can also be analysed by Capillary electrophoresis 16,17 . The HPLC/UV method has been used to determine DNP in human plasma 9, 10, 12, 14 but the method is insensitive (1.0 ng/mL) and requires a large volume of blood sample (1.0mL) 3-9 . ...
... The maximum on-column loading of DNP was only 0.42ng/ml per injection volume of 10μl for DNP. This was considerably less compared to the reported procedure [3][4][5][6][7][8][9] , which helps in maintaining the efficiency and the lifetime of the column. Moreover, the limit of quantification is low enough to monitor DNP concentration in pharmacokinetic study with good intra and inter-assay reproducibility (%CV) for use in quality controls. ...
Donepezil is used worldwide for the treatment of Alzheimer's disease, where it is used to increase cortical acetylcholine. We present a simple liquid chromatography-tandem mass spectrometry (LC-MS/MS) method developed and validated for the quantification of Donepezil in Human Plasma. Quetiapine was used as the internal standard. The simple and cost effective Liquid-Liquid Extraction method is applied for the extraction of Donepezil and Internal standard from Plasma. A rapid isocratic separation of Donepezil is achieved by a short C18 column using mobile phase of Acetonitrile and 1mM Ammonium acetate buffer (92:8 v/v, (%)) at flow rate of 0.5 ml/min. The run time is 2.5 minutes suggests high throughput of the proposed method. The collision-induced transition m/z 380 à 91 was used to analyze donepezil in selected reaction monitoring mode. The signal intensity of this transition was found to relate linearly with donepezil concentrations in plasma from 0.1-42 ng/ml. The lower limit of quantification of the LC-MS/MS method was 0.1ng/ml. The intra-and inter-day precisions were below 10.0% and the accuracy was between + 5.0% and -5.0%. The validated LC/MS/MS method was applied to pharmacokinetic study on healthy male volunteer who received single oral dose of 10 mg Donepezil hydrochloride. The maximum plasma concentration observed was 17.05ng/ml at 2.5 hours post dosing. This validated LC-MS/MS is rapid, sensitive, specific and cost-effective method for determining donepezil in human plasma samples.
... However, different chromatographic methods are described to determine the single compounds in human blood, sometimes with their related metabolites. Although some methods are described using gas chromatography, 19,20 the majority uses liquid chromatography coupled with tandem mass spectrometry, 21-31 ultraviolet, 32,33 or fluorescence detection. 12 In case of mass spectrometry (MS), the analysis is mostly done by electrospray in the positive mode 21,23,26,27 rather than by atmospheric pressure chemical ionization. ...
... 34 The use of isotope-labeled internal standards to increase the robustness of the method is described in two of the published methods. 25,29 Because most of these analytical methods are developed for pharmacokinetic studies after single doses, 21,22,[26][27][28]32,33 the covered concentration ranges are narrow and would not be adequate for TDM in steady-state conditions of different dosages, in which a large range of plasma concentrations is expected. ...
A simple liquid chromatography mass spectrometry method was developed and validated for the simultaneous determination of antidementia drugs, including donepezil, galantamine, rivastigmine and its major metabolite, NAP 226-90, and memantine.
A solid phase extraction procedure with a mixed-mode sorbent was used to isolate the drugs from 0.5 mL human plasma. Reverse phase chromatographic separation of the compounds was obtained with a gradient elution of an ammonium acetate buffer at pH 9.3 and acetonitrile and the analytes were detected by mass spectrometry in the single ion monitoring mode.
The method was validated according to the recommendations of the Food and Drug Administration, including assessment of trueness (-8.0% to +10.7%), imprecision (repeatability: 1.1-4.9%, intermediate imprecision: 2.1-8.5%), selectivity and matrix effects variability (less than 6%) as well as short- and long-term stability in plasma. The calibration ranges were from 1 ng/mL to 300 ng/mL (rivastigmine and memantine) and 2 ng/mL to 300 ng/mL (donepezil, galantamine, and NAP 226-90).
The method was successfully applied to patients' samples and might contribute to evaluate whether a therapeutic drug monitoring-guided dose adjustment of antidementia drugs could contribute to minimize the risk of adverse reactions and to increase the probability of efficient therapeutic response.
... Different spectroscopic methods were published for DPZ estimation suffering from low sensitivity [6,7]. Different HPLC methods either with UV or fluorescence detection have been published for determination of DPZ [8][9][10][11]. Additionally, HPLC methods hyphenated with tandem mass spectrometry were published for determination of DPZ which have suffered from difficult extraction methods for the drug from biological fluids. ...
White and Green Analytical Chemistry are innovative approaches in analytical chemistry that prioritize both sustainability and efficiency. Together, these approaches aim to advance scientific research while minimizing environmental impact and enhancing safety. This integration of environmental consciousness into analytical practices represents a significant step forward in achieving sustainable scientific progress. In the present study, a sensitive eco-friendly HPLC-DAD method was carried out and validated to allow concurrent determination of Donepezil HCl (DPZ) and Curcumin (CUR) in their pure form and laboratory made nano-liposome formulation. Optimum seperation was accomplished by utilising Zobrax Eclipse Plus C18 column (4.6*100 mm,5 μm) with gradient elution of the mobile phase composed of 0.02 M phosphate buffer at pH 3.2 and ethanol at flow rate of 1.5 ml/min. A diode array detector (DAD) was implemented for detection at 273 nm and 435 nm for DPZ and CUR, respectively, with the column oven set at 40 °C. The method was validated according to ICH specifications in terms of accuracy, precision, linearity range, detection and quantification limit. The calibration plots were linear with correlation coefficients (r2) = 0.999 over the range (0.1–100 µg/ml) and (0.1–100 µg/ml) for DPZ and CUR, successively. The validated HPLC-DAD approach was adopted to analyse both medications in laboratory prepared nano-liposomal formulation in which the analytes were successfully quantified with good recovery values and no disrubtion from the added excipients. The investigation of whiteness, blueness, and greenness metrics revealed a major benefit of the suggested approach over previous reported ones.
... Several studies have suggested the use of HPLC with UV for quantitation of donepezil in pharmacokinetic studies, pharmaceutical preparations and TDM [6][7][8] . However while the most common method have high sensitivity, their limitation include long chromatographic run times and the need for an additional extraction process. ...
An ultra-high performance liquid chromatography-photodiode array detection (UHPLC-PDA) method was developed and validated for determination of the concentration of donepezil in patient’s plasma. Plasma spiked with diphenhydramine as an internal standard was used for the solid phase extraction. The eluent solution was diluted with 0.05% trifluoroacetic acid and injected into an UHPLC system. Chromatographic separation was performed on a reverse phase column (1.8 µm, 100 mm x 2.1 mm I.D.) and using acetonitrile with 0.05% trifluoroacetic acid in milli-Q water as the mobile phase. The gradient program for the mobile phase involved a flow rate of 0.45 mL/min and 3 min total run time. The photodiode array (PDA) detector was chosen to operate at 230 nm. The retention times were 1.70 and 2.11 min for donepezil and diphenhydramine, respectively. The method was developed and fully validated according to United Stated Food and Drug Administration (USFDA) guidance. The linearity of the method revealed a coefficient of determination or square of r greater than 0.998 in the concentration range 10-250 ng/mL. Extraction recoveries ranged from 84.6-85.6% with good repeatability. A simple, rapid, and reproducible UHPLC/PDA method for quantifying the concentration of donepezil in patient’s plasma was thus developed and completely validated. This method was successfully utilized to measure the plasma concentration of 105 Thai patients with Alzheimer’s disease and vascular dementia.
... Stock solution of donepezil (50 μg/ml) was prepared in methanol, and dilutions were prepared in the range of 5-50 μg/ml [14]. Maximum absorbance (λ max ) was observed for the stock solution using UV/Vis spectrophotometry, Shimadzu. ...
Alzheimer disease (AD) is very common among the older people. There are few medications available as oral and suspension dosage forms for the management of AD. Due to the rising cases of AD and the associated risks of the existing line of treatment, oil in water (o/w) nanoemulsion (NE) loaded with donepezil was prepared to explore intranasal route of administration. The NE was prepared using labrasol (10%), cetyl pyridinium chloride (1% in 80% water), and glycerol (10%), with a drug concentration of 1 mg/ml. The developed NE was characterized for particle size, polydispersity index (PDI), and zeta potential. In vitro release studies were conducted to observe the release of drug. Further in vivo studies of developed NE were done on Sprague Dawley rats using technetium pertechnetate (99mTc) labeled formulations to investigate the nose to brain drug delivery pathway. The nanoemulsion showed particle size of 65.36 nm with a PDI of 0.084 and zeta potential of −10.7 mV. In vitro release studies showed maximum release of 99.22% in 4 h in phosphate-buffered saline, 98% in 2 h in artificial cerebrospinal fluid, and 96% in 2 h in simulated nasal fluid. The cytotoxicity and antioxidant activity of the NE showed dose-dependent cytotoxicity and % radical scavenging activity (%RSA). The images of giemsa staining also confirmed that the developed formulation has no impact on the morphology of cells. Scintigrams showed maximum uptake of NE in the brain. The findings suggested that the developed NE loaded with donepezil hydrochloride could serve as a new approach for the treatment of Alzheimer via nose to brain drug delivery.
Graphical abstract
... A few methods were developed for the determination of DZ, including spectrophotometry [3,4] and voltammetry [5,6], that suffer from low sensitivity and are not applied for analysis of the cited drug in biological fluids. The HPLC/UV methods [7][8][9] suffer from low sensitivity and long analysis time. Moreover, CE/UV [10] and LC/MS [11] have several disadvantages, such as expensive instrumentation (for both), reduced sensitivity and decreased resolution for CE [12] if compared to HPLC methods. ...
The aim of this paper is to develop sensitive, accurate, reproducible and robust RP-HPLC with fluorescence detection for estimation of donepezil (DZ) in rabbit plasma using silodosin as the internal standard (IS). The prepared samples were quantified on reversed phase column Luna C18(2) (150 × 4.6 mm i.d., 5 µm particle size) operated at room temperature using the mobile phase consisting of methanol: 0.1% acetic acid (50 : 50, v/v) at a flow rate of 1 ml min⁻¹. The method was fully validated according to bioanalytical validation guidelines of FDA in terms of system suitability, selectivity, sensitivity, precision and stability. It was found that the increase in peak areas followed the increase of DZ concentration in the range of 2.56–200.00 ng ml⁻¹ with LOD of 0.85 ng ml⁻¹. The method was successfully applied for the determination of DZ in rabbit plasma using manual shaking dispersive liquid–liquid microextraction.
... 8 Furukori, et al. have reported a HPLC-UV method using liquid-liquid extraction (LLE) process by n-hexane and IPA (97 : 3), with a run time of 15 min and sample volume 1000 mL of human plasma. 9 A simultaneous method has also been developed for the estimation of DNP and memantine in plasma. 10 A UPLC-MS/MS method has been reported for the estimation of DNP in human serum, using PP by ACN. ...
A simple, sensitive and robust HPLC–PDA assay was developed and validated for rapid determination of donepezil hydrochloride (DNP), a potent acetylcholinesterase inhibitor in rat plasma and tissues. All biological samples were prepared by the solid-phase extraction method using loratadine as an internal standard. Separation of the analytes was achieved on a Waters Nova-Pak C18 column (3.9 × 150 mm, 4 μm) using an isocratic mobile phase of acetonitrile and ammonium formate (pH 6.4; 0.01 M) (62 : 38% v/v) at a flow rate of 1 mL min⁻¹. All validation parameter results were within the acceptable range described in the guidelines for bioanalytical method validation. The method showed linearity in the concentration range of 50–5000 ng mL⁻¹ with LOD of 20 ng mL⁻¹ and LLOQ of 50 ng mL⁻¹. Moreover, the advantage of this method over previously published methods is the short analysis run time of 6 min in HPLC itself, alongside its application not only for plasma samples but also in tissues, with low LLOQ. The method was successfully applied for studying the compartmental pharmacokinetics, tissue distribution and pharmacodynamics. A two-compartmental micro model was statistically fitted for the assessment of pharmacokinetic parameters. The tissue distribution studies suggest that the kidneys, lungs and liver are the primarily responsible organs for metabolism and elimination of DNP. Pharmacodynamic studies were performed by measuring acetylcholinesterase inhibitory activity of DNP, which indicated that the pharmacokinetic and pharmacodynamic data are in correlation with each other.
... [3] Previously, quantitative analysis of donepezil was performed mainly by using high-performance liquid chromatography (HPLC) with an ultraviolet or fluorescence detector. [4][5][6] These methods have several merits. For example, samples can be easily prepared and analyzed; however, these methods also have some drawbacks. ...
An ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed and validated for the quantification of donepezil in human plasma. Donepezil and donepezil-D4 were extracted from human plasma by liquid-liquid extraction using a mixture of hexane and ethyl acetate (70:30 v/v). The extracted samples were analyzed using a Thermo Hyper-sil Gold C18 column with 5% acetic acid in 20 mM ammonium acetate buffer (pH 3.3) and 100% acetonitrile as a mobile phase with the 60:40 (v:v) isocratic method, at a flow rate of 0.3 mL/min. The injection volume was 3 μL, and the total run time was 3 min. Inter-and intra-batch accuracies ranged from 98.0% to 110.0%, and the precision was below 8%. The developed method was successfully applied to the quantification of donepezil in human plasma. The mean (standard deviation) maximum concentration and the median (range) time to maximum concentration were 8.6 (2.0) ng/mL and 2.0 h (1.0~5.0 h), respectively, in healthy Koreans after oral administration of 5 mg donepezil.
... In literature, there are plenty of references about determination of donepezil by chromatography techniques [32,33]. Likewise, there are electrochemical methods for donepezil measurement with similar detection limits as our method [23, International Journal of Analytical Chemistry 34] and some spectrophotometric methods for quantification of donepezil in pharmaceuticals or human plasma [35,36]. ...
Smartphones are widely spread and their usage does not require any trained personnel. Recently, smartphones were successfully used in analytical chemistry as a simple detection tool in some applications. This paper focuses on immobilization of acetylcholinesterase (AChE) onto commercially available pH strips with stabilization in the gelatin membrane. AChE degrades acetylcholine into choline and acetic acid which causes color change of acid-base indicator. Smartphone served as a tool for measurement of indicator color change from red to orange while inhibitors blocked this process. AChE inhibitors were measured with limits of detection, 149 nM and 22.3 nM for galanthamine and donepezil, respectively. Organic solvents were measured for method interferences. Measurement procedure was performed on 3D printed holder and digital photography was evaluated using red-green-blue (RGB) channels. The invented assay was validated to the standard Ellman’s test and verified on murine plasma samples spiked with inhibitors. We consider that the assay is fully suitable for practical performance.
... The plasma therapeutic level ranges from 30 to 75 ng/mL, and 50% of acetylcholinesterase inhibition is achieved when the concentration reaches 15.6 ng/mL [8,9]. An optimal plasma level is greater than 50 ng/mL [10]. ...
The clinical response to donepezil in patients with mild and moderate dementia was investigated in relation to the drug plasma concentration and APOE and CYP2D6 polymorphisms. In a prospective naturalistic observational study, 42 patients with Alzheimer’s disease (AD) and AD with cerebrovascular disease who took donepezil (10 mg) for 12 months were evaluated. Their DNA was genotyped, and the donepezil plasma concentrations were measured after 3, 6, and 12 months. Good responders scored ≥–1 on the Mini-Mental State Examination at 12 months in comparison to the baseline score. The study results indicated the good response pattern was influenced by the concentration of donepezil, but not by APOE and CYP2D6 polymorphisms.
... Several analytical methods have been reported in the literature for the determination of donepezil, and its impurities [3][4][5][6][7][8][9][10][11][12][13][14][15][16] . During the process development of donepezil hydrochloride one unknown impurity was detected consistently in HPLC analysis along with the potential known impurities. ...
Donepezil hydrochloride is a reversible inhibitor of the enzyme acetyl cholinesterase. During the process development of donepezil hydro-chloride at lab scale, we observed an unknown impurity at levels 0.05-0.2% in a simple isocratic reversed phase high performance liquid chromatography (HPLC) analysis with the known potential impurities. This new unknown impurity was isolated using preparative liquid chromatography. Based on the complete spectral analysis, this new impurity was designated as 2-((1-benzylpiperidin-4-yl)methyl)-2-((4-((5,6-dimethoxy-1-oxo-2,3-dihydro-1H-inden-2-yl)methyl)piperidin-1-yl)methyl)-5,6-dimethoxy-2,3-dihydro-1H-inden-1-one (dimer impurity of donepezil). Impurity isolation and structure elucidation were discussed.
... On the other hand, since the performance of UV detector has been recently improved, the determination of medicaments in biological samples was also achieved by an HPLC-UV method. Levomepromazine, clozapine and their main metabolites in human plasma (11) , aspirin in human serum (59) , docetaxel and paclitaxel in plasma (83) , DP in plasma (27,84) , fluoroquinolones such as enoxacin, ofloxacin and norfloxacin in chicken blood (15) , non-steroidal anti-inflammatory drugs, ketoprofen, meloxicam (28) , flurbiprofen (29) , ibuprofen and dicrofenac sodium (60) and triazolam (53) in plasma were determined. An HPLC-UV detection was also applied to pharmacokinetic studies of tenatoprazole (55) , ferulate sodium (56) , clopidogrel (14) and paclitaxel (58,85,86) . ...
The performance of high-Performance liquid chromatography (HPLC) instruments has been remarkably progressed. As a result, an HPLC method plays a conspicuous role in analysis of medicaments in formulations and biological samples. The varied detection methods used for HPLC such as ultra violet (UV), mass spectrometry (MS), fluorescence (FL) and chemiluminescence (CL) detections in addition to electrochemical detection (ECD) with suitable pretreatment or labeling were chosen in response to the purpose of analysis. Analysis of medicaments in formulations was mainly performed by UV detection, meanwhile EC, MS, FL and CL detections with high sensitivity were used for analysis of medicaments in biological samples. The sensitivity ranging from microgram to picogram level could be achieved. In this review, current HPLC methods for determination of medicaments in formulations and biological samples were described. Furthermore, their advanced applications for chiral analysis and pharmacokinetic drug-drug interaction evaluation of medicaments were presented.
... Several analytical methods have been reported in the literature for the determination of donepezil, and its impurities [3][4][5][6][7][8][9][10][11][12][13][14][15][16] . During the process development of donepezil hydrochloride one unknown impurity was detected consistently in HPLC analysis along with the potential known impurities. ...
Donepezil hydrochloride is a reversible inhibitor of the enzyme acetyl cholinesterase. During the process development of donepezil hydro-chloride at lab scale, we observed an unknown impurity at levels 0.05-0.2% in a simple isocratic reversed phase high performance liquid chromatography (HPLC) analysis with the known potential impurities. This new unknown impurity was isolated using preparative liquid chromatography. Based on the complete spectral analysis, this new impurity was designated as 2-((1-benzylpiperidin-4-yl)methyl)-2-((4-((5,6-dimethoxy-1-oxo-2,3-dihydro-1H-inden-2-yl)methyl)piperidin-1-yl)methyl)-5,6-dimethoxy-2,3-dihydro-1H-inden-1-one (dimer impurity of donepezil). Impurity isolation and structure elucidation were discussed.
... It is used in the management of Alzheimer's disease where it is used to increase cortical acetylcholine. Enantioselective LC-MS-MS [2], High-performance liquid chromatography [3,4], UV and Spectrofluorimetric method [5] has been reported for Donepezil HCl. No specific method has so far been reported for the estimation of Donepezil HCl by HPTLC in pharmaceutical dosage forms. ...
A simple, rapid, reliable and accurate HPTLC method has been developed for the quantitative
determination of Donepezil HCl in bulk and tablets. Various aliquots of the sample solution were
spotted automatically by means of camag Linomat 5 applicator on precoated silica gel 60 F254 on
aluminium sheet as stationary phase pre washed with methanol using Methanol: Chloroform (8:2 v/v)
as mobile phase. The spots were scanned at 254 nm. The Rf value of Donepezil HCl was 0.54 ± 0.02.
Calibration curves were linear in the range of 200-1000 ng spot-1. The limit of detection and limit of
quantification were found to be 120 ng spot-1 and 165 ng spot-1 respectively. The suitability of this
method for the quantitative determination of compound was proved by validation in accordance with
requirements of pharmaceutical regulatory standards.
... In humans, donepezil is metabolized mainly by the hepatic cytochrome P-450 2D6 and 3A4 isozymes. 2 Elimination of donepezil from the blood is characterized by a dose independent elimination half-life of about 70 h. 3,4 Because plasma donepezil concentrations are related linearly to acetylcholinesterase inhibition, 5 plasma donepezil concentration is a useful tool to predict donepezil efficacy. ...
Aim
A selective, and sensitive LC–MS/MS method has been developed and validated for quantification of donepezil in human plasma using donepezil D7 as an internal standard (IS).
Methods
The analyte and IS were extracted by liquid–liquid extraction using dichloromethane and hexane mixture and separated by isocratic elution on C18 analytical column with 0.1% formic acid and methanol in the ratio of 70:30 (flow rate of 1 ml/min) as the mobile phase in the positive ion mode. Multiple Reaction Monitoring transitions for donepezil and internal standard are 380.2/91.2 and 387.2/98.2 respectively.
Results
The lower limit of quantification was 50 pg/ml with the linearity range of 50 pg/ml–25,000 pg/ml and the method was validated as per international regulatory guidelines for its selectivity, stability, accuracy, precision, and recovery.
Conclusion
The method can be readily applicable to pharmacokinetic and bioequivalence studies to support different regulatory submissions.
... Due to this, 5% isopropanol was used in the further experiment to maximally decrease the influence of the solvent on the AChE activity. Choice of isopropanol as the convenient solvent is supported by the found studies related to stability of enzyme and extraction of pesticides [19,20]. ...
Electrochemical biosensor based on electric eel acetylcholinesterase (AChE) (EC 3.1.1.7) was performed for assay of nerve agents – tabun, sarin, soman, cyclosarin, and VX. The biosensor used AChE as biorecognition element. The presence of nerve agents was accompanied by a strong inhibition of AChE activity. Enzyme activity is easily measurable by electrochemical oxidation of thiocholine created from acetylthiocholine (ATChCl) by AChE-catalyzed hydrolysis. The tested nerve agents were successfully assayed. The best limits of detection were achieved for sarin (5.88×10−10 M) and VX (8.51×10−10 M) after one-minute assay. The biosensor was found long term stable at low as well as laboratory temperature.
... Previous studies have reported quantification of donepezil in pharmaceutical preparations (3)(4)(5) and in plasma (6,7) by HPLC with UV detection. However, most of the above mentioned methods have a common limitation of low sensitivity and long chromatographic run time. ...
Determination of donepezil hydrochloride in human plasma and pharmaceutical formulations by HPLC with fluorescence detection
A sensitive, isocratic reversed-phase high performance liquid chromatographic method involving fluorescence detection was developed for the determination of donepezil hydrochloride in tablets and in human plasma. Pindolol was used as an internal standard. Good chromatographic separation was achieved by using an analytical column C18. The system operated at room temperature using a mobile phase consisting of methanol, phosphate buffer (0.02 mol L ⁻¹ ) and triethyl amine (pH 3.5) (55: 45: 0.5, V/V/V ) at a flow rate 0.9 mL ⁻¹ min. The analyte and internal standard were extracted from human plasma via liquid-liquid extraction. The proposed method was validated for sensitivity, selectivity, linearity, accuracy and precision. The calibration curve was linear over the range of 5-2000 ng mL ⁻¹ of donepezil with detection limit of 1.5 ng mL ⁻¹ . Intra- and inter-day relative standard deviations were less than 2.5 %. The method was found to be suitable for quality control of donepezil hydrochloride in bulk drug as well as in human plasma.
... For the determination of donepezil in human plasma some high-performance liquid chromatographic methods (Haginaka and Seyama, 1992;Lee et al., 1992;Matsui et al., 1999a;Yasui-Furukori et al., 2002;Radwan et al., 2006;Nakashima et al., 2006) and liquid chromatography-mass spectrometric methods (Matsui et al., 1995;Matsui et al., 1999b;Hao et al., 2003;Lu et al., 2004;Xie et al., 2006;Apostolou et al., 2007;Patel et al., 2008;Shah et al., 2009) have been reported. Most of the LC-MS/MS methods reported so far were only for quantification of donepezil alone. ...
A rapid and sensitive liquid chromatography-tandem mass spectrometric (LC-MS/MS) assay method has been developed and fully validated for simultaneous quantification of donepezil and its active metabolite, 6-o-desmethyl donepezil in human plasma. Analytes and the internal standard were extracted from human plasma by liquid-liquid extraction technique using a 30:70 v/v mixture of ethyl acetate and n-hexane. The reconstituted samples were chromatographed on a C(18) column by using a 70:30 v/v mixture of acetonitrile and ammonium formate (5 mm, pH 5.0) as the mobile phase at a flow rate of 0.6 mL/min. The calibration curve obtained was linear (r ≥ 0.99) over the concentration range of 0.09-24.2 ng/mL for donepezil and 0.03-8.13 ng/mL for 6-o-desmethyl donepezil. The results of the intra-day and inter-day precision and accuracy studies were well within the acceptable limits. The proposed method was successfully applied for the estimation of the drug in real time plasma samples for pharmacokinetic studies.
A simple, reliable and sensitive RP-HPLC bioanalytical method with PDA as detector was developed for the estimation of donepezil HCl in the rabbit plasma and validated. The biological samples were extracted and analysed using loratadine as internal standard. The sample analysed with Inertsil ODS 150mm x 4.6mm, 5.0µm particle size column using 70:30 v/v of 0.1% trifluoroacetic acid and acetonitrile mobile phase at flow rate of 1mL/min. All the parameters validated were within the limits proposed in bioanalytical method validation guidelines. The linearity was observed in the range of 5-200ng/mL with LOD of 0.9ng/mL. The method was observed to have short analysis time of 6 min and also found to be successful in studying the pharmacokinetic parameters of donepezil HCl.
Context: A new, simple, selective, and affordable HPTLC technique for the analysis of donepezil hydrochloride (DH) and its associated compounds was developed and verified in accordance with ICH guidelines. Method: Donepezil Hydrochloride and Related Substances were densitometrically analyzed in the absorbance mode at 320 nm. The stationary phase was 60 F—254 silica gel pre-coated on aluminium TLC plates. Butanol, water, and glacial acetic acid were the components of the mobile phase (4:5:1, v/v/v). Result: It was discovered that this method provides compact places for DH (RF 0.53± 0.03) .Testing for stability indicators (force degradation) was done in acidic and alkaline conditions, as well as with dry heat and photodegradation. The degradation products were clearly distinguished from the pure drug by their markedly differing RF values. For Validation of method linearity, precision, robustness, limit of detection (LOD), limit of quantification (LOQ), ruggedness, and accuracy parameters are verified. LOD and LOQ were found to be 80.85 and 245 ng per spot, respectively, and linearity was found in the range 400-1200 ng per spot with a considerably high value of the correlation coefficient r2 = 0.999 is found. A 0.43% coefficient of variance is discovered. Conclusion: The approach was repeatable and specific for estimating donepezil hydrochloride and related compounds, according to statistical analysis Donepezil Hydrochloride can be quantified even when there are degraded products and related compounds present. It is commercially available for the estimation of related compounds and Donepezil hydrochloride.
Objectives:
Elderly people with dementia are commonly suffered from sleep disorders. So, the use of Donepezil hydrochloride as anti-Alzheimer drug and Trazodone hydrochloride as antidepressants with hypnotic action is very important in these cases. This study reports about novel and sensitive RP-HPLC method with fluorescence detection for simultaneous bioanalytical determination of Donepezil hydrochloride (DON) and co-administered, Trazodone hydrochloride (TRA) in their pure forms, spiked human plasma and tablets.
Materials and methods:
Elution of both drugs was achieved with excellent resolution using a RP-C18 Hypersil Gold column and an isocratic mobile phase consisting of phosphate buffer (50mm, pH 4.6): methanol: acetonitrile (60:35:5) with a flow rate of 1.5mL/min and 20μL as injection volume. A Fluorescence detector at 300nm for excitation and 400nm for emission was used.
Results:
Retention times were 4.3 and 6.3min for Donepezil hydrochloride and Trazodone hydrochloride, respectively. Linearity ranges of the assay were 25-1000 and 50-5000ng/mL and the limits of detection (LOD) and quantitation (LOQ) were 8.52, 15.47 and 25.81, 46.89ng/mL for Donepezil hydrochloride and Trazodone hydrochloride, respectively.
Conclusion:
The high sensitivity of the proposed method enabled the successful determination of the cited drugs in spiked human plasma with mean percentage of recoveries of 91.58±3.34 and 100.30±5.11 for Donepezil hydrochloride and Trazodone hydrochloride, respectively.
A rapid and novel method combining dispersive liquid-liquid microextraction and high- performance liquid chromatography coupled with fluorescence detection was developed for the determination of donepezil in human urine. Parameters affecting extraction efficiency and chromatographic determination, such as the type and volume of the extraction and disperser solvent, and pH of sample for dispersive liquid-liquid microextraction, and mobile phase composition, pH, column oven temperature, and flow rate for chromatographic determination, were evaluated and optimized. Using a C18 core-shell column (7.5 × 4.6 mm, 2.7 µm), the determination of donepezil was accomplished within 5 min. Under optimum conditions, developed method was linear in the range of 0.5-25 ng mL⁻¹ with the correlation coefficient >0.99. Limit of detection was 0.15 ng mL⁻¹. The relative standard deviation at three concentration levels (2, 12.5 and 20 ng mL⁻¹) was less than 11% with accuracy in the range of 96.9-102.8%. The results of this study demonstrate that the use of dispersive liquid-liquid microextraction and core-shell column can be considered as a powerful tool for the analysis of donepezil in human urine.
Galantamine (GAL), donepezil (DON) and rivastigmine (RIV) are cholinesterase inhibitors administered to patients who suffer from Alzheimer’s disease (AD). We have currently developed and validated an HPLC-DAD method for the determination of GAL, DON, RIV in cerebrospinal fluid (CSF), blood serum and urine. The retention times of the drugs were 1.5, 2.2 and 3.1 min, respectively and the total time of analysis was 5 min. Validation was performed in terms of linearity, selectivity, accuracy, precision, and stability. Following validation, the method was applied to clinical CSF, blood serum and urine samples. The currently developed method is a reliable tool for monitoring CSF, serum and urine galantamine, donepezil and rivastigmine levels in patients under treatment with these drugs.
Two simple and sensitive visible spectrophotometric methods (M 1 and M 2) have been developed for the estimation of Donepezil hydrochloride (DH) in bulk and dosage forms. Method M 1 involves Internal salt formation of aconitic anhydride, dehydration product of citric acid [CIA] with acetic anhydride [Ac 2O] to form colored chromogen with an absorption maximum of 580 nm and the method M 2 is based on the formation of green colored coordination complex by the drug with cobalt thiocyanate which is quantitatively extractable into nitro benzene with an absorption maximum of 620 nm. Beer's law obeyed in the concentration range of 8-24μg/ml for method M 1and 16-48 μg/ml for method M 2. Commercially available tablets were analyzed and the results are statistically compared with those obtained by the reference method and validated by recovery studies. The results are found satisfactory and reproducible. These methods are applied successfully for the estimation of the Donepezil hydrochloride in the presence of other ingredients that are usually present in dosage forms. These methods offer the advantages of rapidity, simplicity and sensitivity and normal cost and can be easily applied to resource-poor settings without the need for expensive instrumentation and reagents.
A stability indicating chiral high-performance liquid chromatographic (HPLC) method was developed and subsequently validated for the separation and simultaneous determination of S-(+)- and R(-)-donepezil hydrochloride (DP) in tablet products. Baseline resolution was achieved by using Chiralcel-OJ-H column with a mobile phase consisted of ethanol-n-hexane- triethylamine (20:80:0.3, v/v/v). The detection wavelength was 268 nm. Arotinolol was chosen as internal standard to guarantee a high level of quantitative performance. Chromatographic peak purity data of DP enantiomers using photodiode array detector indicated no co-eluting peaks with the main peaks of drugs, which demonstrated the specificity of the assay method for their estimation in presence of degradation products. Denepezil enantiomers and their drug products were exposed to thermal, photolytic, hydrolytic and oxidative stress conditions and the stressed samples were analyzed by the proposed method. The described method was linear over the range of 25 - 2500 ng / ml (r= 0.999) with detection limit of 10 ng/ml for both enantiomers. The recoveries of S-(+)- and R(-)-DP from tablets preparations ranged from 98.0 to 100.5 % and 98.0 to 100.8 %, respectively. The intra-day and inter-day precision and accuracy were evaluated by calculating the % RSD (n = 6) and the % error were found to be in the ranges of 0.58 - 1.29% and -1.07 - 1.04% for both enantiomers, respectively. The proposed method can be useful in the quality control of drug products.
This book is a compilation of summarized analytical methods designed to serve the needs of pharmacologists, toxicologists, and other allied health professionals involved the development, use, or monitoring of pharmaceuticals. The summaries are structured monographs on 511 different drug entities detailing 964 different analytical methods, providing the reader with a thorough description of method validation. These analytical methods include not only high performance liquid chromatography (HPLC), but also gas chromatography (GC), immunoassay, electrophoresis, ultra performance liquid chromatography (UPLC) coupled with UV (UPLC-UV) detection and mass spectrometry (UPLC-MS/MS). With more detailed and complete summaries than sketchy and abbreviated formats used in the other books, this book provides a thorough description of method validation and results, as well as the operating parameters.
A simple, accurate and sensitive voltammetric method for determination of donepezil (DNZ) using ß-cyclodextrin modified carbon paste electrode (CDMCPE) is developed. CDMCPE exhibited significantly increased sensitivity and selectivity for DNZ compared to the bare carbon paste electrode (CPE). Effect of accumulation potential, accumulation time, pH of buffer, etc., on peak currents for the determination of DNZ was studied using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Peak currents showed a linear response in the concentration range 4.2 x 10 -8 to 5.6 x 10 -7 M and 3.2 x 10 -9 to 4.2 x 10 -8 M at CPE and CDMCPE respectively. Limit of detection (LOD) and limit of quantification (LOQ) were found to be 1.2 x 10 -9 and 0.40 x 10 -8 M. The proposed method has been successfully applied for the determination of DNZ in spiked urine samples, serum samples and pharmaceutical formulations.
A stability indicating HPLC method for the estimation of donepezil hydrochloride in tablets was developed and validated. Donepezil hydrochloride is a reversible inhibitor of acetylcholinesterase, indicated for the treatment of mild to moderate dementia of the Alzheimer's type. The HPLC method was performed with a reversed phase C 18 column (250 mm X 4.6 mm id, 5mm particle size), detection at 230 nm and a mixture of methanol, water and ortho phosphoric acid for pH adjustment at 4 (60:40) as mobile phase. Typical retention time for donepezil was 4.23 min. Forced degradation studies were carried out. The drug was found to be stable to the dry heat, photo-degradation, oxidation, basic, and acidic condition attempted which indicate drug is highly stable. Quantification was achieved with ultraviolet detection at 230 nm over the concentration range 2 – 60μg/ml with range of recovery 99.14 – 100.84 % for donepezil by the RP-HPLC method. The method was statistically validated for linearity, accuracy, precision and selectivity following ICH recommendations. Due to its simplicity and accuracy, the method can be used for routine quality control analysis.
The effect of deprotenizing agents on recovery of donepezil hydrochloride in the development of a simple, rapid, selective and sensitive high performance liquid chromatography method for quantification of donepezil hydrochloride in human plasma was described. The deprotenizing agents were comprised of, perchloric acid, methanol, acetonitrile, chloroform and their mixtures. The chromatographic separation was carried out using reversed phase C18 column (Agilent Eclipse Plus C18) with UV detection at 268 nm. The mobile phase was comprised of 0.01 M potassium dihydrogen phosphate buffer, methanol and acetronitrile (50:30:20, v/v) adjusted to pH 2.7 with phosphoric acid (80%). A combination of perchloric acid and methanol gave a cleaner sample with a good recovery of donepezil hydrochloride of above 96%. The method showed intraday precision and accuracy in the range of 6.82% to 1.5% and 3.13% to 1.12% respectively, while interday precision and accuracy ranged between 1.06% to 4.71% and 13.01% to 6.43% respectively. The standard calibration curve was linear from 30ng/mL to 4000ng/mL, with a correlation coefficient of 0.9965±0.0034. The retention time of donepezil was 5.9 min with a run time of 7.0 min. The method can be applied to analyze large batch plasma samples in pharmacokinetic studies.
Over the last decades, cholinesterase (ChE) biosensors have emerged as a sensitive and rapid technique for toxicity analysis in environmental monitoring, food, and quality control. These systems have the potential to complement or replace the classical analytical methods by simplifying or eliminating sample preparation protocols and making field testing easier and faster with significant decrease in costs per analysis. In this study, a new bienzymatic biosensor based on butyrylcholinesterase (BuChE) and sulfhydryl oxidase (SOX) enzymes was developed. This system makes use of the biocatalyzed hydrolysis of butyrylthiocholine to butyric acid and thiocholine that acts as a SOX substrate. Measurements were performed by following of the consumed oxygen level related to butyrylthiocholine concentration in the enzymatic reactions. Bienzymatic system was characterized and applied for detection of donepezil which is a reversible inhibitor of cholinesterase and belongs to a new class of cholinesterase inhibitors having an N‐benzylpiperidine and an indanone moiety, by following of the decrease in biosensor response as a result of competitive inhibition.
Donepezil hydrochloride is a white powder and is freely soluble in water and in chloroform, sparingly soluble in glacial acetic acid and in ethanol, slightly soluble in acetonitrile, very slightly soluble in ethyl acetate, and insoluble in n-hexane. Donepezil hydrochloride (E2020) is the second drug approved by the United States food and drug administration (FDA) for the treatment of mild to moderate alzheimer's diseases (AD). It is a new class of acetyl cholinesterase (AChE) inhibitor having an N-benzylpiperidine and an indanone moiety that shows longer and more selective action. Donepezil HCl, a piperidine, is a highly selective inhibitor of the enzyme AChE that is chemically unique from other AChE inhibitors. In vitro and preclinical studies have demonstrated that Donepezil is approximately 1200 times more selective for AChE in the brain than for butyrylcholinesterase (BuChE) in the periphery. Phase II and III studies conducted in the United States have shown that Donepezil produces statistically significant improvements in cognition and global function in patients with AD. Its clinical efficacy and minimal side-effect profile are thought to be related to its specific inhibition of AChE in the areas of the brain, affected by the cholinergic deficit that typifies this disease. Assessment of the potential impact of hepatic dysfunction on the pharmacokinetic and adverse event profiles of Donepezil is of primary importance, as Donepezil is orally administered and subject to extensive first-pass metabolism. The methods of analysis, pharmacology, physical properties, and preparation are also presented in this chapter.
Donepezil HCl is a drug to relive from Alzheimer's disease which is a progressive,
degenerative disease of the brain, causes thinking and memory to become seriously
impaired. It is the most common form of dementia and not official in Indian
pharmacopoeia. Literature survey has been revealed that there is no relevant visible
spectrophotometric method has been reported for the estimation of Donepezil HCL in
bulk and in dosage forms. Hence an attempt has been made to develop and validate a
simple, economic, rapid and accurate method. The developed method involves formation of
extractable ion pair complex of drug with azo-dye in acidic medium. De-ionized water is
used as extracting solvent for Eriochrome Black T dye. Extractable complex shows reddish
colored complex within a span of 05 minutes. The λmax was 510 nm. The method was used
to determine the concentrations in between the range of 0.2- 25 µg ml
-1
. The calibration
curve was plotted. The regression equation is Y= 0.080x+ 0.045. The correlation coefficient
obtained was 0.995. The complex was stable for 30 minutes. The proposed method was
simple, sensitive and economical for the quantitative determination of Donepezil HCl and
was successfully employed for the estimation of bulk drug and in formulation
A novel, simple, specific and sensitive high performance liquid chromatography (HPLC) assay for the detection and quantification of donepezil in serum of demented patients has been developed and validated. The analytical procedure involves an offline serum preextraction using solid phase extraction (SPE) cartridges (Oasis® HLB, Waters Co). The chromatographic analyses were performed on a Dionex HPLC system with a Phenomenex Luna Phenyl-Hexyl analytical column, and a mobile phase with the two components 0.02 mol/l phosphate buffer and acetonitrile. The flow rate was 0.4 ml/min. For the detection of donepezil three different UV wavelengths were used as an interference-control check. Interference tests between donepezil and 100 of the most commonly used concomitant medications allow quantification of donepezil under the polypharmaceutical conditions of the daily clinical routine. The retention time for donepezil was 12.1 min. The method was validated according to the guidelines of the Society of Toxicology and Forensic Chemistry (GTFCh): The calibration curve was linear over a concentration range from 5 to 160 ng/ml (n=8/r²>0.999). No endogenous compounds were found to interfere with the analyte, which was shown by retention times for the comedication most often prescribed to demented patients. The method had an accuracy of >85%. Intra- and inter-assay coefficients of variation were <6% and <8%, respectively, at three different concentrations. The limit of quantification (LOQ) and the limit of detection (LOD) were found to be 6.1 and 1.7 ng/ml for donepezil. Application of the method to patient serum samples discovered that concentrations suggested as "therapeutic" in the literature may only be reached either by high, off-label dosages or by utilization of inhibitory metabolic effects of the comedication.
The aim of the study was to predict donepezil responders among patients with Alzheimer disease (AD) based on cognitive tests and positron emission tomography. The Mini-Mental State Examination, Digit Symbol subtest (DigSm) of Wechsler Adult Intelligence Scale Revised, and Trail-Making Test A were administered for 80 patients with AD to assess global function, attention, and executive function, respectively. The same tests and the Clinical Global Impression (CGI) scale were conducted after treatment with oral donepezil (5 mg/d) for 6 months (study 1). [C]-Donepezil positron emission tomography examinations were conducted before and after treatment for 30 randomly selected patients. The distribution volume (DV), which indicates the density of donepezil-binding sites, was calculated using Logan graphical analysis (study 2). In study 1, 35 patients were identified as responders based on the CGI and Mini-Mental State Examination changes. These patients had higher baseline DigSm scores compared with nonresponders. In study 2, 15 patients were responders. DigSm correlated with DV at baseline. DV at baseline and %DV change in responders were higher than in nonresponders, and these variables correlated with ΔDigSm and CGI scores. Higher baseline attention may predict responsiveness to donepezil in patients with AD, and higher acetylcholinesterase levels result in a greater clinical effect.
This study aimed to examine the feasibility of developing donepezil transdermal delivery systems (TDSs).
Solution and pressure-sensitive adhesive (PSA) TDS were formulated using various vehicles and fatty acids, and the in vitro permeation study was conducted using the hairless mouse skin.
Permeation fluxes (μg/cm(2)/h) from solution formulations were generally low (0.05-3.40), except for formulations including isopropyl alcohol (IPA, 51.19), ethyl alcohol (27.32) and water (24.07). Dose-dependent permeation fluxes were obtained (r(2) = 0.9754). Even though the addition of fatty acids to IPA failed to increase donepezil permeation rates, it shortened lag times. Compared to those from solution formulations, permeation profiles from PSA TDS were totally different, and penetration rates were considerably low. PSA TDS comprising diethylene glycol monoethyl ether (DGME)-propylene glycol monolaurate (PGML) co-solvents (40:60) showed the highest permeation flux (0.10 ± 0.0024 μg/cm(2)/h).
IPA-containing solution formulations and DGME-PGML (40: 60)-containing PSA TDS were found to be favorable candidates for donepezil transdermal delivery.
Alzheimer's is a neurodegenerative disease. Its symptoms are attributed to a deficiency of cholinergic neurotransmission. The drugs of choice for the treatment of Alzheimer's disease are acetylcholinesterase (AChE) inhibitors. Starting in the 1980's from non-specific AChE inhibitors, the first-generation drugs such as physostigmine, a second generation of more selective and better tolerated products has been developed. Methods to detect and quantify these drugs and their metabolites in biological samples have been developed for analysis in plasma, blood, urine and cerebrospinal fluid. Diverse detection techniques have been used, such as ultraviolet, fluorescence, electrochemical and mass spectrometry. In this review, the methods applied to the analysis of these drugs and their metabolites in different biological matrices are reviewed and discussed. The stability of these drugs in biological matrices and under stress-conditions is also included in the discussion.
The aim of our study was to evaluate the impact of CYP3A4, CYP3A5, and ABCB1 polymorphisms on donepezil disposition and clinical outcome.
Fifty-four Italian patients diagnosed with probable mild to moderate Alzheimer's disease, treated with donepezil (37 patients 5 mg/day, 17 patients 10 mg/day) were genotyped for CYP3A4 (*1B, *3, and *4), CYP3A5 (*2, *3, and *6) and ABCB1 (3435C>T, 2677G>T/A, and 1236C>T) polymorphisms. All patients were evaluated for the degree of cognitive impairment with Mini Mental State Examination (MMSE) screening test at baseline (before treatment) and after at least 3 months of donepezil treatment at stable dose, when the drug plasma levels were measured.
Three patients carried one detrimental CYP3A4 allelic variant, and 12 carried one functional CYP3A5*1 allele. No statistically significant association was found between CYP3A4 or CYP3A5 genotypes and plasma donepezil concentrations, or between genotypes and clinical response (as measured by change in MMSE score). Nine ABCB1 haplotypes were observed, the most common being 1236C/2677G/3435C (46%) and 1236T/2677T/3435T (41%). Patients homozygous for the T/T/T haplotype had slightly though not significantly lower plasma donepezil concentration-to-dose ratios than those carrying other genotypes [median (95% CI) 0.18 (0.13-0.45) vs. 0.31 (0.30-0.44) mg/l/mg/kg, respectively]. These patients also showed a slightly better clinical response (as measured by change in MMSE score) than the other genotype groups [median (95% CI) 0 (-1.3 to 3.3) vs. -1.0 (-2.1 to 0.0), respectively].
Our data suggest that the CYP3A4 and CYP3A5 polymorphisms are unlikely to influence donepezil metabolism and/or clinical outcome. On the other hand, the ABCB1 polymorphisms may play a role in donepezil disposition and clinical outcome.
To measure cerebrospinal fluid (CSF) activity of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) in patients with Alzheimer's disease (AD) participating in randomized clinical trials from three European centers, before and after long-term treatment with different AChE inhibitors (AChEIs).
Of the 144 patients included in the study, 104 were treated with donepezil, 15 with galantamine, 16 with rivastigmine, and nine with placebo. CSF AChE and BChE activities were measured at baseline and after 1- year treatment.
Donepezil and galantamine groups showed a significant increase in CSF AChE activity at follow-up, while no changes for BChE activity were observed; in donepezil group, a positive correlation between plasma concentration and AChE activity was documented. Conversely, in rivastigmine group, a decrease in CSF activity of both enzymes was observed. CSF AChE and BChE activities were not correlated with the clinical outcome in any group considered. CSF biomarkers did not show any change after treatment.
AChEIs differently influence the activity of target enzymes in CSF independent of their pharmacodynamic effects.
The construction and electrochemical response characteristics of polyvinylchloride (PVC) membrane sensors for donepezil HCl (DP) are described. The sensing membranes incorporated ion-association complexes of DP cation and sodium tetraphenyl borate (sensor 1), phosphomolybdic acid (sensor 2), or phosphotungstic acid (sensor 3) as electroactive materials. The sensors displayed a fast, stable, and near-Nernstian response over a relatively wide DP concentration range (1 x 10(-2) to 1 x 10(-6) M), with cationic slopes of 53.0, 54.0, and 51.0 mV/ concentration decade over a pH range of 4.0 to 8.0. The sensors showed good discrimination of DP from several inorganic and organic compounds. The direct determination of 2.5-4000.0 microg/mL DP showed average recoveries of 99.0, 99.5, and 98.5%, and mean RSDs of 1.6, 1.5, and 1.7% at 100.0 microg/mL for sensors 1, 2, and 3, respectively. The proposed sensors have been applied for direct determination of DP in two pharmaceutical preparations. The results obtained for determination of DP in tablets using the proposed sensors compared favorably with those obtained using an HPLC method. The sensors have been used as indicator electrodes for potentiometric titration of DP.
A selective, rapid and simple liquid chromatography-tandem mass spectrometry (LC-MS/MS) method is described for assay of donepezil in human plasma using escitalopram as an internal standard. Chromatographic separation was achieved on a Betabasic-C(8), 5 microm, 100 x 4.6 mm column using methanol:water:formic acid (90:9.97:0.03, v/v/v) as mobile phase. Detection of donepezil and internal standard was achieved by ESI MS/MS in positive ion mode using 380.20/91.10 and 325.13/262.00 transitions, respectively. The linearity over the concentration range of 0.15-50 ng/mL for donepezil was obtained and the lower limit of quantification was 0.15 ng/mL. For each level of quality control samples, inter-day and intra-day precisions (RSD) were < or =8.92 and 10.35% and accuracy (%RE) were < or =7.33% and 9.33%, respectively. The recovery was more than 88.50% for both donepezil and internal standard by solid-phase extraction, eliminating evaporation and reconstitution steps.
Field-amplified sample stacking (FASS) in capillary electrophoresis (CE) was used to determine the concentration of donepezil, an acetylcholinesterase inhibitor, in human plasma. A sample pretreatment by liquid-liquid extraction with isopropanol/n-hexane (v/v 3:97) and subsequent quantification by FASS-CE was used. Before sample loading, a water plug (0.5 psi, 6 s) was injected to permit FASS. Electrokinetic injection (7 kV, 90 s) was used to introduce sample cations. The separation condition for donepezil was performed in electrolyte solutions containing Tris buffer (60 mM, pH 4.0) with sodium octanesulfonate 40 mM and 0.01% polyvinyl alcohol as a dynamic coating to reduce analytes' interaction with capillary wall. The separation was performed at 28 kV and detected at 200 nm. Using atenolol as an internal standard, the linear ranges of the method for the determination of donepezil in human plasma were over a range of 1-50 ng/mL. The limit of detection was 0.1 ng/mL (S/N=3, sampling 90 s at 7 kV). One female volunteer (54 years old) was orally administered a single dose of 10 mg donepezil (Aricept, Eisai), and blood samples were drawn over a 60 h period for pharmacokinetic study. The method was also applied successfully to monitor donepezil in sixteen Alzheimer's disease patients' plasmas.
The effects of ginkgo supplementation on the steady-state plasma concentration of donepezil and the activity of cholinesterase in red blood cells and cognitive function were examined. Fourteen inpatients with Alzheimer's disease received donepezil 5 mg/day, supplemented with extracts of Ginkgo biloba 90 mg/day for 30 days. Blood samples were collected before and during ginkgo supplementation and 30 days after its discontinuation, together with an assessment of cognitive function. Plasma drug concentration was measured using high-performance liquid chromatography (HPLC), and cholinesterase in red blood cells was measured using Ellman methods. Cognitive function was evaluated using the Mini-Mental Scale Examination (MMSE). Plasma concentration of donepezil during ginkgo supplementation (mean +/- SD [95% confidence interval]; 24.4 +/- 12.6 ng/mL [17.1-31.7 ng/mL]) was not significantly different from that before ginkgo supplementation (22.7 +/- 10.3 ng/mL [16.8-28.7 ng/mL]) or that 4 weeks after its discontinuation (25.0 +/- 12.9 ng/mL [17.6-32.4 ng/mL]). There was no significant difference between cholinesterase in red blood cells before ginkgo supplementation (1.75 +/- 0.21 U [1.63-1.87 U]), during ginkgo supplementation (1.91 +/- 0.27 U [1.76-2.07 U]), and 4 weeks after its discontinuation (1.83 +/- 0.29 U [1.66-2.00 U]). Ginkgo supplementation did not alter MMSE scores throughout the study. The present study shows that ginkgo supplementation does not have major impact on the pharmacokinetics and pharmacodynamics of donepezil.
Background
Donepezil hydrochloride (Aricept) is a selective acetylcholinesterase inhibitor developed for the treatment of Alzheimer disease. This phase 3 study was 1 of 2 pivotal trials undertaken to establish the efficacy and safety of using donepezil in patients with mild to moderately severe Alzheimer disease.Objectives
To further examine the efficacy and safety of using donepezil in the treatment of patients with mild to moderately severe Alzheimer disease. To examine the relationships between plasma donepezil concentrations, inhibition of red blood cell acetylcholinesterase activity, and clinical response.Methods
This was a 12-week, double-blind, placebo-controlled, parallel-group trial with a 3-week single-blind washout. Outpatients at 23 centers in the United States were randomized to receive placebo, 5 mg of donepezil hydrochloride, or 10 mg of donepezil hydrochloride (5 mg/d during week 1 then 10 mg/d thereafter) administered once daily at bedtime. Primary efficacy was measured using the Alzheimer's Disease Assessment Scale–Cognitive Subscale (ADAS-cog) and Clinician's Interview−Based Impression of Change including caregiver information (CIBIC plus).Results
A total of 468 patients entered the study, more than 97% of whom were included in the intention-to-treat (end point) analyses. The use of donepezil produced statistically significant improvements in ADAS-cog, CIBIC plus, and Mini-Mental State Examination scores, relative to placebo. The mean drug-placebo differences, at end point, for the groups receiving 5 mg/d and 10 mg/d of donepezil hydrochloride were, respectively, 2.5 and 3.1 units for ADAS-cog (P<.001); 0.3 and 0.4 units for CIBIC plus (P≤.008); and 1.0 and 1.3 units for Mini-Mental State Examination (P≤.004). On the CIBIC plus scale, 32% and 38% of patients, respectively, treated with 5 mg/d and 10 mg/d of donepezil hydrochloride demonstrated clinical improvement (a score of 1, 2, or 3) compared with placebo (18%). The mean (± SEM) donepezil plasma concentrations at study end point were 25.9 ± 0.7 ng/mL and 50.6 ± 1.9 ng/mL in the groups receiving dosages of 5 mg/d and 10 mg/d, respectively. Corresponding mean (± SEM) percentages of inhibition of red blood cell acetylcholinesterase activity were 63.9% ± 0.9% and 74.7% ± 1.2% for these 2 dosages, respectively. There was a statistically significant positive correlation between plasma concentrations of donepezil and acetylcholinesterase inhibition; the EC50 (50% effect) was obtained at a concentration of 15.6 ng/mL. A plateau of inhibition (80%-90%) was reached at plasma donepezil concentrations higher than 50 ng/mL. The correlations between plasma drug concentrations and both ADAS-cog (P<.001) and CIBIC plus (P=.006) were also statistically significant, as were the correlations between red blood cell acetylcholinesterase inhibition and change in ADAS-cog (P<.001) and CIBIC plus (P=.005). The incidence of treatment-emergent adverse events with both dosages of donepezil (68−78%) was comparable with that observed with placebo (69%). The use of 10 mg/d of donepezil hydrochloride was associated with transient mild nausea, insomnia, and diarrhea. There were no treatment-emergent clinically significant changes in vital signs or clinical laboratory test results. More important, the use of donepezil was not associated with the hepatotoxic effects observed with acridine-based cholinesterase inhibitors.Conclusion
Donepezil hydrochloride (5 and 10 mg) administered once daily is a well-tolerated and efficacious agent for treating the symptoms of mild to moderately severe Alzheimer disease.
Double peaks in the plasma concentration-time profile following oral administration have been reported for several compounds. A pharmacokinetic model incorporating discontinuous absorption was developed to simulate concentration-time profiles with double peaks. The gastrointestinal (GI) tract was divided into N compartments, with absorption occurring only from the second and Nth compartments. A two-compartment model was used to describe systemic drug disposition. The effect of gastric emptying and GI transit rate constants (Kl and K1, respectively), number of hypothetical gut compartments, and absorption rate constant at each site (Ka1, Ka2) on the time of occurrence of each peak (Tp1, Tp2), the theoretical fraction of the dose absorbed at each site (phi 1, phi 2), and the contribution of the second site to systemic drug exposure (expressed as phi 2rel) were examined. Simulated concentration-time profiles demonstrated that Tp2 was determined by Kt and N, while Tp1 was determined by K1 and Kt. Changes in Ka1 and Ka2 had no effect on Tp1 or Tp2. phi 1, phi 2, and phi 2rel were determined by Ka1, Ka2, and Kt, and simulations indicated that a secondary peak in the concentration-time profile will be evident only when phi 2rel is substantial. In addition, concentration-time data for ranitidine and cimetidine, which displayed double peaks, were fit with the model. The present model described both data sets well, and realistic pharmacokinetic and physiologic parameters (absorption rate constants, systemic bioavailabilities, GI residence times) were obtained.
The efficacy and safety of donepezil as a treatment for patients with mild to moderate Alzheimer's disease (AD) was investigated in a multicenter, double-blind study. Patients were randomly assigned to treatment with placebo (n = 162), 5 mg/d donepezil (n = 154), or 10 mg/d donepezil (n = 157) for 24 weeks followed by a 6-week, single-blind placebo washout. The primary efficacy measures were the cognitive portion of the Alzheimer's Disease Assessment Scale (ADAS-cog) and the Clinician's Interview Based Assessment of Change-Plus (CIBIC plus), with the Mini-Mental State Examination (MMSE), Clinical Dementia Rating Scale-Sum of the Boxes (CDR-SB), and patient rated Quality of Life (QoL) used as secondary measures. Cognitive function, as measured by the ADAS-cog, was significantly improved in the 5- and 10-mg/d donepezil groups as compared with the placebo group at weeks 12, 18, and 24. Clinician's global ratings on the CIBIC plus also improved in both the 5- and 10-mg/d donepezil groups relative to placebo. At the end of the 6-week placebo washout phase, ADAS-cog scores and CIBIC plus ratings were not significantly different for the three groups. Significant treatment benefits were also observed consistently in both the 5- and 10-mg/d groups on the MMSE and the CDR-SB, but there was no consistent effect on the patient-rated QoL. Cholinergic side effects (primarily diarrhea, nausea, and vomiting) were reported more often in the 10-mg/d group than either the 5-mg/d or placebo groups. Side effects were transient and generally mild in severity. These data indicate that donepezil is a well-tolerated drug that improves cognition and global function in patients with mild to moderate AD.
A rapid, sensitive and enantioselective LC-MS-MS method using deuterium-labeled internal standard was developed and evaluated for the simultaneous quantitative determination of donepezil enantiomers in human plasma without interconversion during clean-up process and measurement. The use of an avidin column allowed the separation of donepezil enantiomers, which were specifically detected by MS-MS without interference from its metabolites and plasma constituents. Evaluation of this assay method shows that samples can be assayed with acceptable accuracy and precision within the range from 0.0206 ng/ml to 51.6 ng/ml for both R-donepezil and S-donepezil. This analytical method was applied to the simultaneous quantitation of donepezil enantiomers in human plasma.