Journal of Pharmaceutical Sciences (J Pharmaceut Sci)

Publications in this journal

• Article: Organic nitrate metabolism and action: Toward a unifying hypothesis and the future-a dedication to Professor Leslie Z. Benet.

  Nathaniel A Page, Ho-Leung Fung
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  ABSTRACT: This review summarizes the major advances that had been reported since the outstanding contributions that Professor Benet and his group had made in the 1980s and 1990s concerning the metabolism and pharmacologic action of organic nitrates (ORNs). Several pivotal studies have now enhanced our understanding of the metabolism and the bioactivation of ORNs, resulting in the identification of a host of cysteine-containing enzymes that can carry out this function. Three isoforms of aldehyde dehydrogenase, all of which with active catalytic cysteine sites, are now known to metabolize, somewhat selectively, various members of the ORN family. The existence of a long-proposed but unstable thionitrate intermediate from ORN metabolism has now been experimentally observed. ORN-induced thiol oxidation in multiple proteins, called the "thionitrate oxidation hypothesis," can be used not only to explain the phenomenon of nitrate tolerance, but also the various consequences of chronic nitrate therapy, namely, rebound vasoconstriction, and increased morbidity and mortality. Thus, a unifying biochemical hypothesis can account for the myriad of pharmacological events resulting from nitrate therapy. Optimization of the future uses of ORN in cardiology and other diseases could benefit from further elaboration of this unifying hypothesis. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci.
  Journal of Pharmaceutical Sciences 05/2013;
• Article: Quantitative expression of human drug transporter proteins in lung tissues: Analysis of regional, gender, and interindividual differences by liquid chromatography-tandem mass spectrometry.

  Atsushi Sakamoto, Takehisa Matsumaru, Norio Yamamura, Yasuo Uchida, Masanori Tachikawa, Sumio Ohtsuki, Tetsuya Terasaki
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  ABSTRACT: The purpose of the present study was to clarify the expression levels of transporter proteins in human lung tissue and to analyze regional and interindividual differences in primary cultured epithelial cells. Organic cation/carnitine tranporter 1 (OCTN1) protein expression was highest (2.08 ± 1.19 fmol/μg protein) in human lung tissue, followed by multidrug resistance-associated protein 1 (MRP1) and breast cancer resistance protein expression (1.41 ± 0.41, 1.30 ± 1.29 fmol/μg protein, respectively). Interestingly, the same expression levels of OATP2B1 protein were demonstrated among the epithelial cells derived from all pulmonary regions for the first time. These results suggest that OCTN1 may be the best target transporter protein for pulmonary disease drug design, and OATP2B1 may be an alternative target. MRP1 protein expression was also high and mainly localized in bronchial and alveolar regions. Regarding interindividual differences, the MRP1 protein showed a significant 18-fold maximal difference in the bronchial region among five donors. Sixteen of the 18 transporters showed higher expression in female lungs than in male lungs, especially MRP8 showed a 7.32-fold maximal difference. In conclusion, the protein expression profiles of pulmonary drug transporters and regional, gender, and interindividual differences were clarified. These findings may provide significant insights for pulmonary disease drug design and indicate that administration by inhalation may be viable. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci.
  Journal of Pharmaceutical Sciences 05/2013;
• Article: Selectivity in the impact of P-glycoprotein upon pulmonary absorption of airway-dosed substrates: A study in ex vivo lung models using chemical inhibition and genetic knockout.

  Ghaith Al-Jayyoussi, Daniel F Price, Danielle Francombe, Glyn Taylor, Mathew W Smith, Chris Morris, Chris D Edwards, Peter Eddershaw, Mark Gumbleton
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  ABSTRACT: P-glycoprotein (P-gp) mediated efflux is recognised to alter the absorption and disposition of a diverse range of substrates. Despite evidence showing the presence of P-gp within the lung, relatively little is known about the transporter's effect upon the absorption and distribution of drugs delivered via the pulmonary route. Here, we present data from an intact isolated rat lung model, alongside two isolated mouse lung models using either chemical or genetic inhibition of P-gp. Data from all three models show inhibition of P-gp increases the extent of absorption of a subset of P-gp substrates (e.g. rhodamine 123 and loperamide) whose physico-chemical properties are distinct from those whose pulmonary absorption remained unaffected (e.g. digoxin and saquinavir). This is the first study showing direct evidence of P-gp mediated efflux within an intact lung, a finding that should warrant consideration as part of respiratory drug discovery and development as well as in the understanding of pulmonary pharmacokinetic (PK)-pharmacodynamic (PD) relationships. © 2013 Crown copyright.
  Journal of Pharmaceutical Sciences 05/2013;
• Article: Hepatocyte composition-based model as a mechanistic tool for predicting the cell suspension: Aqueous phase partition coefficient of drugs in in vitro metabolic studies.

  Patrick Poulin, Sami Haddad
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  ABSTRACT: This study is an extension of a previously published microsome composition-based model by Poulin and Haddad (Poulin and Haddad. 2011. J Pharm Sci 100:4501-4517), which was converted to the hepatocyte composition-based model. The first objective was to investigate the ability of the composition-based model to predict nonspecific binding of drugs in hepatocytes suspended in the incubation medium in in vitro metabolic studies. The hepatocyte composition-based model describes the cell suspension-aqueous phase partition coefficients, which were used to estimate fraction unbound in the incubation medium (fuinc ) for each drug. The second objective was to make a comparative analysis between the proposed hepatocyte composition-based model and an empirical regression equation published in the literature by Austin et al. (Austin RP, Barton P, Mohmed S, Riley RJ. 2004. Drug Metab Dispos 33:419-425). The assessment was confined by the availability of experimentally determined in vitro fuinc values at diverse hepatocyte concentrations for 92 drugs. The model that made use of hepatocyte composition data provides comparable or superior prediction performance compared with the regression equation that relied solely on physicochemical data; therefore, this demonstrates the ability of predicting fuinc also based on mechanisms of drug tissue distribution. The accuracy of the predictions differed depending on the class of drugs (neutrals vs. ionized drugs) and species (rat vs. human) for each method. This study for hepatocytes corroborates a previous study for microsomes. Overall, this work represents a significant first step toward the development of a generic and mechanistic calculation method of fuinc in incubations of hepatocytes, which should facilitate rational interindividual and interspecies extrapolations of fuinc by considering differences in lipid composition of hepatocytes, for clearance prediction in the physiologically-based pharmacokinetics (PBPK) models. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci.
  Journal of Pharmaceutical Sciences 05/2013;
• Article: Inhibitory effects of hesperetin derivatives on guinea pig phosphodiesterases and Their ratios between high- and low-affinity rolipram binding.

  Hsin-Te Hsu, Wen-Hung Wang, Cheng-Ying Han, Chun-Nan Chen, Chi-Ming Chen, Wun-Chang Ko
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  ABSTRACT: The phosphodiesterase (PDE)4 molecule exists as two distinct conformers, PDE4H and PDE4L , which have high and low affinities, respectively, for the selective PDE4 inhibitor, rolipram. The inhibition of PDE4H and PDE4L is associated with adverse responses, such as nausea, vomiting, and gastric hypersecretion, and with anti-inflammatory and bronchodilator effects, respectively. We determined the therapeutic (PDE4H /PDE4L ) ratios of hesperetin-7-O-methylether, hesperetin-5,7,3'-O-trimethylether (HTME), hesperetin-7-O-acetate, hesperetin-7,3'-O-diacetate, hesperetin-5,7,3'-O-triacetate (HTA), hesperetin-5,7,3'-O-tripropionate, hesperetin-5,7,3'-O-tributyrate, hesperetin-5,7,3'-O-triisobutyrate, and hesperetin-5,7,3'-O-tripivatate, and compared these ratios to those of hesperetin, hesperetin-7,3'-O-dimethylether, hesperidin, and hesperidin-3'-O-methylether to identify derivatives with therapeutic ratios and to characterize the structure-activity relationships among these compounds. The activities of PDE isozymes 1 through 5 were measured using a two-step procedure using [(3) H]adenosine 3',5'-cyclic monophosphate or [(3) H]guanosine 3',5'-cyclic monophosphate as substrates. The inhibitory concentration (IC50 ) for 50% of PDE4 inhibition and effective concentration (EC50 ) for replacing 50% of [(3) H]rolipram binding on high-affinity rolipram-binding sites was taken as the PDE4L and PDE4H value, respectively. The HTME and the HTA dually inhibited PDE3 and PDE4, and displayed PDE4H /PDE4L ratios of 18.3 and 20.8, respectively, suggesting that they may be candidate drugs for treating asthma and chronic obstructive pulmonary disease (COPD) because the combined inhibition of PDE3 and PDE4 has synergistically anti-inflammatory and bronchodilator effects in COPD patients. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci.
  Journal of Pharmaceutical Sciences 05/2013;
• Article: Involvement of carnitine/organic cation transporter OCTN1/SLC22A4 in gastrointestinal absorption of metformin.

  Noritaka Nakamichi, Hiroyo Shima, Satoshi Asano, Takahiro Ishimoto, Tomoko Sugiura, Kazuki Matsubara, Hiroyuki Kusuhara, Yuichi Sugiyama, Yoshimichi Sai, Ken-Ichi Miyamoto, Akira Tsuji, Yukio Kato
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  ABSTRACT: Metformin is a widely used oral anti-diabetic, but the molecular mechanism(s) of its gastrointestinal membrane permeation remains unclear. Here, we examined the role of carnitine/organic cation transporter OCTN1/SLC22A4, which is localized on apical membranes of small intestine in mice and humans, in metformin absorption. The maximum plasma concentration (Cmax ) after oral administration of metformin (50 mg/kg) in octn1 gene knockout mice (octn1 (-/-) ) was higher than that in wild-type mice, with only a minimal difference in terminal half-life, but Cmax in octn1(-/-) mice given a higher dose (175 mg/kg) was lower than that in wild-type mice. Systemic elimination of metformin after intravenous administration was similar in the two strains, suggesting the possible involvement of OCTN1 in the gastrointestinal absorption. OCTN1-mediated uptake of metformin was observed in human embryonic kidney 293 cells transfected with mouse OCTN1 gene, but much lower than the uptake of the typical substrate [(3) H]ergothioneine (ERGO). In particular, the distribution volume for OCTN1-mediated uptake increased markedly and then tended to decrease as the metformin concentration was increased. Efflux of metformin preloaded in intestinal epithelial cell line Caco-2 was inhibited by ERGO. Overall, the present findings suggest that OCTN1 transports metformin and may be involved in its oral absorption in small intestine. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci.
  Journal of Pharmaceutical Sciences 05/2013;
• Article: A toxicity risk index, an index for warning idiosyncratic drug toxicity.

  Miyoshi Morimoto, Kazuo Samizo, Shin Ohta, Takashi Mizuma
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  ABSTRACT: Drug toxicity impedes drug development and its clinical use. In the present study, a toxicity risk index (TRI), which is an index for warning idiosyncratic drug toxicity (IDT), was proposed. The TRI of drugs was defined as a function of dose, pharmacokinetic parameters, and toxicokinetic data from covalent binding experiment. Twenty drugs, which were classified into three categories by a report (Nakayama S, Atsumi R, Takakusa H, Kobayashi Y, Kurihara A, Nagai Y, Nakai D, Okazaki O. 2009. Drug Metab Dispos 37:1970-1977), were studied with TRI. The three categories were BBW (drugs with a block box warning for IDT), WNG (drugs without a black box warning but with a warning for IDT), and SAFE (drugs without any warning). The TRIs of drugs classified as SAFE were distinctly different from those classified as BBW. The TRI of the SAFE drugs were lower than 0.456 (nmol/mg protein). In contrast, the TRI of the BBW drugs were higher than 1.10 (nmol/mg protein). These results warned us that a drug candidate, where the TRI is higher than 1.0 nmol/mg protein, should be categorized as a BBW drug. Further study with more data of TRI will give a cutoff value with a statistical meaning. Thus, TRI may be useful for decision making in drug development and its clinical use. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci.
  Journal of Pharmaceutical Sciences 05/2013;
• Article: Drug adsorption on bovine and porcine sclera studied with streaming potential.

  Lasse Murtomäki, Tuomas Vainikka, Silvia Pescina, Sara Nicoli
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  ABSTRACT: The affinity of a drug to a biological membrane can affect the distribution and the availability of the active compound to its target. Adsorption is usually determined with in vitro distribution studies based on partitioning of the drug between buffer and tissue, which have limitations such as the high variability of the uptake data and the need for high accuracy in the measurement of drug concentration. Furthermore, distribution studies yield solute concentrations in the bulk of the tissue, whereas electrokinetic phenomena such as streaming potential and electroosmosis reflect the electric charge density on a membrane surface. Streaming potential thus can be used in studying the conditions, by which the charge sign and density can be regulated. That, in turn, has significance to electroosmotic transport mechanism during iontophoresis. In this communication, the adsorption of model compounds methylprednisolone sodium succinate, propranolol, and cytochrome C on bovine and porcine sclera is determined as a function of their concentration by measuring streaming potential. Both membranes had negative streaming potential, proving that they carry negative charge, but had different values at negative and positive pressure differences, which is addressed to the structural asymmetry of these membranes. Bovine sclera had a clearly higher value of streaming potential, ca. -26 nV/Pa, than porcine sclera, ca. -7 nV/Pa (10 mM NaCl solution). All the model compounds were adsorbed on bovine and porcine sclera already in the millimolar concentration range and can have an impact to electroosmosis during transscleral iontophoresis. The results obtained help to better elucidate the phenomena involved in transscleral transport, both in passive diffusion and in iontophoresis, supporting the future application of iontophoresis to the noninvasive delivery of drugs to the posterior segment of the human eye. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci.
  Journal of Pharmaceutical Sciences 05/2013;
• Article: Rational development of solid dispersions via hot-melt extrusion using screening, material characterization, and numeric simulation tools.

  Damir E Zecevic, Karl G Wagner
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  ABSTRACT: Effective and predictive small-scale selection tools are inevitable during the development of a solubility enhanced drug product. For hot-melt extrusion, this selection process can start with a microscale performance evaluation on a hot-stage microscope (HSM). A batch size of 400 mg can provide sufficient materials to assess the drug product attributes such as solid-state properties, solubility enhancement, and physical stability as well as process related attributes such as processing temperature in a twin-screw extruder (TSE). Prototype formulations will then be fed into a 5 mm TSE (∼1-2 g) to confirm performance from the HSM under additional shear stress. Small stress stability testing might be performed with these samples or a larger batch (20-40 g) made by 9 or 12 mm TSE. Simultaneously, numeric process simulations are performed using process data as well as rheological and thermal properties of the formulations. Further scale up work to 16 and 18 mm TSE confirmed and refined the simulation model. Thus, at the end of the laboratory-scale development, not only the clinical trial supply could be manufactured, but also one can form a sound risk assessment to support further scale up even without decades of process experience. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci.
  Journal of Pharmaceutical Sciences 05/2013;
• Article: Parameterization of annealing kinetics in pharmaceutical glasses.

  Ian M Hodge
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  ABSTRACT: Numerical simulations indicate that neglecting the canonical nonlinearity of glassy-state annealing kinetics in pharmaceutical (and other) glasses leads to good KWW fits to the dependence of enthalpy on annealing time, but with spurious KWW parameters that are affected by nonlinearity. A simplified treatment of nonlinearity that uses the Struik shift factor is found to be a useful approximation for these analyses, and can account for previously reported differences between linear and nonlinear KWW parameters (Kawakami K, Pikal MJ. 2005. J Pharm Sci 94:948-965). © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci.
  Journal of Pharmaceutical Sciences 05/2013;
• Article: Sustained ibuprofen release using composite poly(lactic-co-glycolic acid)/titanium dioxide nanotubes from Ti implant surface.

  Huiying Jia, Lei L Kerr
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  ABSTRACT: Developing coatings on implant surface as drug carriers can reduce organ toxicity and effectively deliver drug locally to the target compared with the oral approach. Titanium dioxide (TiO2 ) nanotube has great potential for this application for widely used Ti implants because of its high surface area, ability to promote bone growth, and biocompatibility. However, there are two issues needed to be solved before further advancing TiO2 nanotubes technology as drug carriers: uncontrolled drug release and poor mechanical properties. In this study, a drug carrier using a composite of biodegradable polymer/TiO2 nanotubes is engineered. Ibuprofen is selected as a concept drug because it is a commonly used anti-inflammatory, fever, and pain-reducing drug. In addition, ibuprofen has a very short plasma half-life of only 1-3 h. A simple characterization method is developed to investigate the infiltration of polymer into TiO2 nanotubes. Good infiltration was observed of polymer into TiO2 nanotubes. The synthesized drug carrier demonstrated much better sustained drug release profiles for ibuprofen of 5 days (low-molecular-weight polymer) and 9 days (high-molecular-weight polymer) compared with 30 min of pure TiO2 nanotubes. The drug carrier also exhibited much improved mechanical strength and flexibility compared with pure TiO2 nanotubes. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci.
  Journal of Pharmaceutical Sciences 05/2013;
• Article: Passivation of high-surface-energy sites of milled ibuprofen crystals via dry coating for reduced cohesion and improved flowability.

  Xi Han, Laila Jallo, Daniel To, Chinmay Ghoroi, Rajesh Davé
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  ABSTRACT: Ibuprofen micronization with dry coating is investigated to examine its influence on passivation/stabilization of high-surface-energy sites and reduced cohesion. A fluid energy mill was used to micronize ibuprofen particles down to 5-28 μm with or without simultaneous nanosilica coating. Powder flow property and dispersibility were characterized using FT4 powder tester and Rodos/Helos laser diffraction particle sizer. Surface energy was characterized using a next generation inverse gas chromatography instrument. Uncoated micronized ibuprofen showed an increased Lifshitz-van der Waals (LW) dispersion component of surface energy with increasing milling intensity. In contrast, dry-coated milled powders showed a significant reduction in the LW component, whereas physical mixture of uncoated micronized ibuprofen and silica exhibited no reduction in surface energy, indicating that dry coating is necessary for the passivation of high-energy sites of ibuprofen created during micronization. Surface energy of pure micronized ibuprofen was highly heterogeneous, whereas dry-coated ibuprofen had greatly reduced heterogeneity. Micronization with dry coating also improved flowability and bulk density as compared with pure active pharmaceutical ingredient micronization without coating, or just blending with silica. Overall, dry coating leads to decreased cohesion and improved flowability because of reduced LW dispersive component of surface energy and creating nanoscale surface roughness. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci.
  Journal of Pharmaceutical Sciences 05/2013;
• Article: Inhibition of crystal nucleation and growth by water-soluble polymers and its impact on the supersaturation profiles of amorphous drugs.

  Shunsuke Ozaki, Ikuo Kushida, Taro Yamashita, Takashi Hasebe, Osamu Shirai, Kenji Kano
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  ABSTRACT: The impact of water-soluble polymers on drug supersaturation behavior was investigated to elucidate the role of water-soluble polymers in enhancing the supersaturation levels of amorphous pharmaceuticals. Hydroxypropyl methylcellulose (HPMC), polyvinylpyrrolidone (PVP), and Eudragit L-100 (Eudragit) were used as representative polymers, and griseofulvin and danazol were used as model drugs. Supersaturation profiles of amorphous drugs were measured in biorelevant dissolution tests. Crystal growth rate was measured from the decrease in dissolved drug concentration in the presence of seed crystals. Nucleation kinetics was evaluated by measuring the induction time for nucleation. All experiments were performed in the presence and absence of polymers. The degree of supersaturation of the amorphous model drugs increased with an increase in the inhibitory efficiency of polymers against crystal nucleation and growth (HPMC > PVP > Eudragit). In the presence of HPMC, the addition of seed crystals diminished the supersaturation ratio dramatically for griseofulvin and moderately for danazol. The results demonstrated that the polymers contributed to drug supersaturation by inhibiting both nucleation and growth. The effect of the polymers was drug dependent. The detailed characterization of polymers would allow selection of appropriate crystallization inhibitors and a planned quality control strategy for the development of supersaturable formulations. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci.
  Journal of Pharmaceutical Sciences 05/2013;
• Article: Absolute measurement of species differences in sodium taurocholate cotransporting polypeptide (NTCP/Ntcp) and its modulation in cultured hepatocytes.

  Xi Qiu, Yi-An Bi, Larissa M Balogh, Yurong Lai
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  ABSTRACT: Species differences among membrane transporters can be remarkable and difficult to properly assess by conventional methods. Herein, we employed the first use of stable isotope labeling in mammals or stable isotope-labeled peptides combined with mass spectrometry to identify species differences in sodium taurocholate cotransporting polypeptide (NTCP/Ntcp) protein expression in liver tissue and to characterize the modulation of protein expression in sandwich-cultured human (SCHH) and rat hepatocytes (SCRH). The lower limit of quantification was established to be 5 fmol on column with a standard curve that was linear up to 2000 fmol. The accuracy and precision were evaluated with three quality control samples and known amounts of synthetic proteotypic peptides that were spiked into the membrane protein extracts. The overall relative error and coefficient of variation were less than 10%. The expression of Ntcp in mouse and rat was significant higher than that in human (five-fold) and monkey (two-fold) and ranked as mouse > rat > monkey > human. In the cultured hepatocytes, although significant downregulation of Ntcp expression in SCRH at day 5 after the culture was detected, NTCP expression in SCHH was comparable to the suspension hepatocytes. The results suggested that NTCP/Ntcp modulation in cultured hepatocytes is species specific. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci.
  Journal of Pharmaceutical Sciences 05/2013;
• Article: Studies on pharmacokinetic mechanism of phenytoin resistance in refractory epilepsy.

  Ming-Liang Lai, Yu-En Tien, Ying-Syuan Huang, Jin-Ding Huang
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  ABSTRACT: P-glycoprotein (P-gp) is a drug efflux pump in many organs, including the intestine and liver. Two single nucleotide polymorphisms (SNPs) of P-gp gene, 2677G>T and 3435C>T, were reported to influence function and expression of P-gp and have the controversial effects on drug disposition. Phenytoin is one substrate of P-gp. Persistent low phenytoin levels in plasma and P-gp overexpression in brain in several refractory epilepsy patients were reported. P-gp polymorphisms may also affect phenytoin efficacy by altering its bioavailability (F). Because two P-gp SNPs, 2677G>T and 3435C>T, may affect P-gp expression in tissue, we examined phenytoin disposition in patients of different P-gp haplotypes, G/G2677C/C3435 and T/T2677T/T3435. We found that the mean absolute F of phenytoin in T/T2677T/T3435 subjects (91%) is slightly higher than in G/G2677C/C3435 subjects (82%). There was no difference in the maximum concentration (Cmax ) and the area under the serum concentration-time curve of phenytoin administered orally between two genotypic groups. However, the time of maximum concentration was higher in T/T2677T/T3435 subjects (10 h) than in G/G2677C/C3435 subjects (6 h). The study ruled out the possibility that genetic polymorphisms of P-gp may affect phenytoin efficacy through the decreased absorption or the increased elimination. P-gp SNPs could affect phenytoin efficacy in refractory epilepsy patients probably because of central nervous system. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci.
  Journal of Pharmaceutical Sciences 05/2013;
• Article: An updated review on drug-induced cholestasis: Mechanisms and investigation of physicochemical properties and pharmacokinetic parameters.

  Kyunghee Yang, Kathleen Köck, Alexander Sedykh, Alexander Tropsha, Kim L R Brouwer
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  ABSTRACT: Drug-induced cholestasis is an important form of acquired liver disease and is associated with significant morbidity and mortality. Bile acids are key signaling molecules, but they can exert toxic responses when they accumulate in hepatocytes. This review focuses on the physiological mechanisms of drug-induced cholestasis associated with altered bile acid homeostasis due to direct (e.g., bile acid transporter inhibition) or indirect (e.g., activation of nuclear receptors, altered function/expression of bile acid transporters) processes. Mechanistic information about the effects of a drug on bile acid homeostasis is important when evaluating the cholestatic potential of a compound, but experimental data often are not available. The relationship between physicochemical properties, pharmacokinetic parameters, and inhibition of the bile salt export pump among 77 cholestatic drugs with different pathophysiological mechanisms of cholestasis (i.e., impaired formation of bile vs. physical obstruction of bile flow) was investigated. The utility of in silico models to obtain mechanistic information about the impact of compounds on bile acid homeostasis to aid in predicting the cholestatic potential of drugs is highlighted. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci.
  Journal of Pharmaceutical Sciences 05/2013;
• Article: Systematic investigation of parameters affecting the performance of an agitated filter-dryer.

  Ekneet Kaur Sahni, Robin H Bogner, Bodhisattwa Chaudhuri
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  ABSTRACT: A systematic experimental investigation of contact drying operation was carried out in an agitated Charles Thompson filter-dryer. In this study, the effect of process parameters (wall temperature, impeller speed, fill level) on the drying performance in the filter-dryer is quantified as a function of bed temperature and solvent concentration. In addition, the impact of drying conditions on the particle size distribution was also examined. It was found that in the range of parameters investigated, drying rate increased with wall temperature and reduced bed depth. The effect of impeller speed was variable where favorable drying conditions were strongly dependent on the particle properties. Moreover, decrease in the particle size was evident with an increase in impeller speed and decrease in the bed depth due to increased collision frequency and reduction in the fill volume both leading to particle attrition respectively. Besides, the average wall to solid heat transfer coefficient is also estimated for variable operating conditions. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci.
  Journal of Pharmaceutical Sciences 05/2013;
• Article: Prediction of drug-polymer miscibility through the use of solubility parameter based flory-huggins interaction parameter and the experimental validation: PEG as model polymer.

  Seema Thakral, Naveen K Thakral
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  ABSTRACT: Important consideration for developing physically stable solid dispersion is miscibility of drug in carrier matrix. It is possible to predict thermodynamics of binary system through free energy calculations based on Flory-Huggins interaction parameter (χdp ). In present study, PEG 6000 as model polymer and dataset comprising commonly used drugs/excipients was selected. The three-dimensional solubility parameter based on group contribution method was utilized for systemic calculation of χdp of the polymer with each compound in data set. On the basis of the values of χdp , it was possible to categorize all the compounds into three distinct categories, Types I and II: compounds predicted to be miscible and immiscible respectively with the polymer in all proportions and Type III: compounds expected to exhibit composition dependent miscibility behavior. The Bagley plot showed that majority of points for Type I fall in a region, which can approximately be delimited by a circle. Experimental verification through thermal analysis revealed that though it was possible to predict correctly miscibility behavior of Type II class compounds, distinction between Types I and III was less evident. Hence, solubility parameter based χdp may be used as an initial tool for fast screening of immiscible combination of polymer and drug. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci.
  Journal of Pharmaceutical Sciences 05/2013;
• Article: Propagation of error in ocular pharmacokinetic parameters estimate of azithromycin in rabbits.

  Linjun You, Jie Qian, Xiabing Wu, Xiaoyang Sun, Mengxiang Su, Bin Di, Yingxiang Du, Baiyang Mao
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  ABSTRACT: The ocular pharmacokinetic (PK) of azithromycin in rabbit eye tissues was evaluated following single-dose and multiple-dose administrations of azithromycin. Because of destructive sampling, only the average ocular tissue concentration-time curve could be captured and used to estimate the PK parameters failing to obtain their standard deviations. In the present study, formulas were explained in details to estimate the major PK parameter errors in destructive sampling. The PK parameters were obtained by analyzing average ocular tissue concentration-time curve and their standard deviations were calculated using the formula proposed in this paper. A case study was included to elucidate the potential application of the formulas. F-test for equality of variances and independent-samples t-test were carried out between test formulation and reference formulation in PK parameters. Thus, a new and simple method was proposed to compare PK behavior for these studies using destructive sampling, which can be potentially applied into other cases in the future. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci.
  Journal of Pharmaceutical Sciences 05/2013;
• Article: When is protein binding important?

  Jules Heuberger, Stephan Schmidt, Hartmut Derendorf
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  ABSTRACT: The present paper is an ode to a classic citation by Benet and Hoener (2002. Clin Pharm Ther 71(3):115-121). The now classic paper had a huge impact on drug development and the way the issue of protein binding is perceived and interpreted. Although the authors very clearly pointed out the limitations and underlying assumptions for their delineations, these are too often overlooked and the classic paper's message is misinterpreted by broadening to cases that were not intended. Some members of the scientific community concluded from the paper that protein binding is not important. This was clearly not intended by the authors, as they finished their paper with a paragraph entitled: "When is protein binding important?" Misinterpretation of the underlying assumptions in the classic work can result in major pitfalls in drug development. Therefore, we revisit the topic of protein binding with the intention of clarifying when clinically relevant changes should be considered during drug development. © 2013 Wiley Periodicals, Inc. and the American Pharmacists Association J Pharm Sci.
  Journal of Pharmaceutical Sciences 05/2013;