Liliana Rivera-Espinosa

Instituto Nacional de Pediatría, Ciudad de México, Mexico City, Mexico

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Publications (18)33.2 Total impact

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    ABSTRACT: Ifosfamide blood concentrations are necessary to monitor its therapeutic response, avoiding any adverse effect. We developed and validated an analytical method by UPLC-MS/MS to quantify ifosfamide in dried blood spots (DBS). Blood samples were collected on Whatman 903® filter paper cards. Five 3 mm disks were punched out from each dried blood spot. Acetonitrile and ethyl acetate were used for drug extraction. Chromatographic separation was carried out in an Acquity UPLC equipment with a BEH-C18 column, 2.1 x 100 mm, 1.7 μm (Waters®). The mobile phase consisted in 5 mM ammonium formate and methanol:acetonitrile (40:48:12 v/v/v) at 0.2 mL/min. LC-MS/MS detection was done by ESI+ and multiple reaction mode monitoring, ionic transitions were m/z1+ 260.99 > 91.63 for ifosfamide and 261.00 > 139.90 for cyclophosphamide (internal standard). This method was linear within a 100-10000 ng/mL range and it was accurate, precise and selective. Ifosfamide samples in DBS were stable for up to 52 days at -80°C. The procedure was tested in 14 patients, ages 1 month to 17 years (9 males and 5 females), with embryonic tumours treated with ifosfamide, alone or combined, at a public tertiary referral hospital. Ifosfamide blood levels ranged from 11.1 to 39.7 μmol/L at 12 hours after the last infusion, while 24-hour levels ranged from 0.7-19.7 μmol/L. The median at 12 hours was 19.5 μmol/L (Q25 14.4-Q75 29.0) and 3.8 μmol/L (Q25 1.5-Q75 9.9) at 24 hours, p<0.001. This method is feasible to determine ifosfamide plasma levels in paediatric patients.
    Full-text · Article · Nov 2015 · PLoS ONE
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    ABSTRACT: Oxidative stress is a biochemical state of imbalance in the production of reactive oxygen and nitrogen species and antioxidant defenses. It is involved in the physiopathology of degenerative and chronic neuronal disorders, such as epilepsy. Experimental evidence in humans and animals support the involvement of oxidative stress before and after seizures. In the past few years, research has increasingly focused on the molecular pathways of this process, such as that involving transcription factor nuclear factor E2-related factor 2 (Nrf2), which plays a central role in the regulation of antioxidant response elements (ARE) and modulates cellular redox status. The aim of this review is to present experimental evidence on the role of Nrf2 in this neurological disorder and to further determine the therapeutic impact of Nrf2 in epilepsy.
    Full-text · Article · Aug 2015 · International Journal of Molecular Sciences
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    ABSTRACT: Purpose: In response to the lack of pediatric formulations of metformin to control type 2 diabetes mellitus, hyperinsulinemic obesity, and dyslipidemias, we developed liquid formulations of metformin by dissolving 3 generic brands of 500-mg metformin(*,)(†,)(‡) tablets in water sweetened with sucralose. The physicochemical stabilities of these drugs were assessed and compared with those of formulations made with the innovative brand of metformin.(∥) A method to measure metformin plasma levels was proposed and then tested in 2 healthy subjects. This method may be useful to survey treatment compliance in the future. The biological safety profiles of the metformin solutions were assessed preliminarily in a system of hormone-dependent cancer cells (human breast cancer MCF-7 cells). Methods: Metformin solutions stored at 25°C exposed to light and at 25°C, 4°C, and 40°C protected from light, underwent physicochemical analysis by ultra-performance liquid chromatography with ultraviolet detection, the mobile phase consisting of 0.2 M potassium monobasic phosphate (pH 6.5), 4.6 mM sodium dodecyl sulphate (SDS), and acetonitrile (63:7:30) at a flow rate of 0.8 mL/min in a Symmetry C8 150 × 4.6 mm column (Milford, Massachusetts) at 40°C (236 nm). MCF-7 cells were grown in 96-well ELISA plates (2 × 10(5) cells/well) and were exposed to 10, 20, and 40 mg/mL sucralose(§), Stevia rebaudiana (Svetia; Metco, S.A. de C.V., México, D.F., Mexico), and metformin (50 mg/mL) for 48 hours. Cytotoxicity was determined using the WST-1 colorimetric assay (Roche, USA) in an Epoch ELISA reader (BioTek, Winooski, Vermont) at 440 nm. Findings: All brands of metformin were stable at all storage conditions for up to 30 days and retained >90% of the initial amount. Sucralose and Stevia rebaudiana caused zero cytotoxicity (ANOVA, P ≤ 0.05). The ultra-performance liquid chromatography with ultraviolet detection method was adapted to determine metformin level in very small blood samples (40 μL), which was linear within the range of 20 to 600 ng/mL metformin (retention time 2 minutes). Metformin was physically and chemically stable within the processed blood for up to 30 days at 4°C. Implications: Extemporaneous formulations of metformin may be developed at low cost from either the innovator or generic brands, and both sucralose and Stevia rebaudiana sweeteners may be well tolerated; however, the minimum amount of sweetener is recommended to avoid any endocrine disturbance. The analytical method is accurate and precise to clinically measure metformin levels in patients taking the extemporaneous formulation orally. Study registry identification number: 100/2013.
    No preview · Article · Jun 2015 · Clinical Therapeutics
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    ABSTRACT: Oxidative stress, which is a state of imbalance in the production of reactive oxygen species and nitrogen, is induced by a wide variety of factors. This biochemical state is associated with diseases that are systemic as well as diseases that affect the central nervous system. Epilepsy is a chronic neurological disorder, and temporal lobe epilepsy represents an estimated 40% of all epilepsy cases. Currently, evidence from human and experimental models supports the involvement of oxidative stress during seizures and in the epileptogenesis process. Hence, the aim of this review was to provide information that facilitates the processing of this evidence and investigate the therapeutic impact of the biochemical status for this specific pathology.
    Full-text · Article · Nov 2014 · Oxidative medicine and cellular longevity
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    ABSTRACT: Background: The recent use of antidiabetic drugs such as metformin and glyburide for the treatment and control of childhood obesity, insulin resistance and type II diabetes mellitus in children and adolescents, has encouraged physicians to determine plasma levels of these drugs for the right dose adjustment. Objective: To implement and validate a UPLC-UV method to quantify metformin and glyburide in blood samples. Materials and methods: Only a 0.1 mL-volume blood sample was used. Both drugs are removed by precipitation with methanol. Quantitation was carried out with mobile phase of 4.6 mM potassium phosphate monobasic (KH2PO4) 0.1 M pH = 6.5, sodium dodecyl sulphate (SDS) and acetonitrile (63:7:30), at 0.8 mL/min through a VARIAN Pursuit®C8 150 x 3.9 mm column at 40°C, 236 nm. Results: The method allows the measurement of 20 to 600 nanograms of metformin and from 100 to 2 000 nanograms of glyburide per milliliter of blood. Both drugs are physicochemically stable in blood samples for up to 30 days at 4°C. Conclusion: Our method allows quantification of metformin and glyburide in paediatric blood samples, to support the clinicians to monitor treatment compliance, bioavailability and pharmacokinetic profiles.
    No preview · Article · Sep 2014
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    ABSTRACT: Pharmacological management of insulin resistance and dyslipidaemias in children and adolescents is required to prevent the development of metabolic syndrome (MS) and type II diabetes mellitus (DM2). Material and method: we developed extemporaneous formulations from 500 mg-tablets from three generic brands, commercially available in Mexican drugstores: MedimartTM, Farmacias del AhorroTM and Primer NivelTM, dissolved in water sweetened with Splenda, which made them palatable and allowed customised dose adjustment. Solutions were stored at four environmental conditions: 25°C exposed to light, 25°C protected from light, 4°C and 40°C, and their physicochemical stability was assayed. The stability of the drug was determined by ultra performance liquid chromatography and ultraviolet detection (UPLC-UV) and by measuring the pH of the stock solution. The mobile phase consisted of (KH2PO4) 0.1 M, pH = 6.5, 4.6 mM sodium dodecyl sulphate (SDS) and acetonitrile (63:7:30) at 0.8 mL/min, column VARIAN Pursuit C8 150 3.9 mm tempered at 40°C, with detection at 236 nm. Results: Metformin from all trademarks was stable at all storage conditions for up to 30 days, retaining more than 90% of the initial amount of active drug, with a pH of 7.4 ± 0.3. Conclusion: Metformin extemporaneous formulations may be developed from either the innovator or generic brands, having the advantage of saving money and conserving the stability of its physic°Chemical properties.
    No preview · Article · Mar 2014
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    ABSTRACT: It is estimated that at least 100 million people worldwide will suffer from epilepsy at some point in their lives. This neurological disorder induces brain death due to the excessive liberation of glutamate, which activates the postsynaptic N-methyl-D-aspartic acid (NMDA) receptors, which in turn cause the reuptake of intracellular calcium (excitotoxicity). This excitotoxicity elicits a series of events leading to nitric oxide synthase (NOS) activation and the generation of reactive oxygen species (ROS). Several studies in experimental models and in humans have demonstrated that certain antiepileptic drugs (AEDs) exhibit antioxidant effects by modulating the activity of various enzymes associated with this type of stress. Considering the above-mentioned data, we aimed to compile evidence elucidating how AEDs such as valproic acid (VPA), oxcarbazepine (OXC), and topiramate (TPM) modulate oxidative stress.
    Full-text · Article · Dec 2013 · Oxidative Medicine and Cellular Longevity
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    ABSTRACT: Hepatic encephalopathy (HE) is a common complication of cirrhosis, of largely reversible impairment of brain function occurring in patients with acute or chronic liver failure or when the liver is bypassed by portosystemic shunts. The mechanisms causing this brain dysfunction are still largely unclear. The need to avoid complications caused by late diagnosis has attracted interest to understand the mechanisms underlying neuronal damage in order to find markers that will allow timely diagnosis and to propose new therapeutic alternatives to improve the care of patients. One of the experimental approaches to study HE is microdialysis; this technique allows evaluation of different chemical substances in several organs through the recollection of samples in specific places by semi-permeable membranes. In this review we will discuss the contributions of microdialysis in the understanding of the physiological alterations in human hepatic encephalopathy and experimental models and the studies to find novel alternative therapies for this disease.
    Full-text · Article · Aug 2013 · International Journal of Molecular Sciences
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    ABSTRACT: Oxidative stress, a state of imbalance in the production of reactive oxygen species and nitrogen, is induced by a wide variety of factors. This biochemical state is associated with systemic diseases, and diseases affecting the central nervous system. Epilepsy is a chronic neurological disorder with refractoriness to drug therapy at about 30%. Currently, experimental evidence supports the involvement of oxidative stress in seizures, in the process of their generation, and in the mechanisms associated with refractoriness to drug therapy. Hence, the aim of this review is to present information in order to facilitate the handling of this evidence and determine the therapeutic impact of the biochemical status for this pathology.
    Full-text · Article · Jan 2013 · International Journal of Molecular Sciences
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    ABSTRACT: The bacteriostatic agent 4,4'-diaminodiphenylsulfone or dapsone (DDS) and some of its N,N'-dialkylated analogs have shown anticonvulsant and neuroprotective properties in different experimental models. In this study, we tested the ability of five DDS analogs (N,N'-dimethyldapsone, N,N'-diethyldapsone, N,N'-dipropyldapsone, N,N'-dibutyldapsone and N,N'-ditosyldapsone) to attenuate quinolinic acid-induced toxicity in vivo. Male Wistar rats were treated with either DDS or analogs (12.5mg/kg and equimolar doses respectively) 30min before quinolinic acid intrastriatal stereotaxic injection (240nmol/μl). Six days after injury, circling behavior was evaluated by counting ipsilateral turns for 1h after apomorphine challenge (1mg/kg, sc). Twenty-four hours later, rats were sacrificed and their corpora striata were dissected out to determine GABA content. Hemotoxicity of the analogs was assessed as the ability to produce methemoglobin (MHb) in vivo. Blood was sampled from tail vein within 18h after drugs administration. Methemoglobin levels were determined by visible spectrophotometry and mean profiles of MHb-percentage versus time were obtained. All of the analogs tested decreased the number of ipsilateral turns/hour, reducing up to 67% the turns counting (p<0.05) when compared to those induced in animals receiving quinolinic acid with no treatment. N,N'-dimethylated, N,N'-diethylated and N,N'-dibutylated analogs significantly prevented the decrease of intrastriatal GABA content (p<0.05). Methemoglobin produced by the administration of analogs was significantly lower than the levels of the group receiving dapsone (p<0.05). The neuroprotective effect of analogs and their diminished hemotoxicity make them potential candidates for therapeutic applications.
    Full-text · Article · Sep 2012 · Neuroscience Letters
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    Liliana Carmona-Aparicio · Liliana Rivera-Espinosa · Hugo Juarez-Olguin

    Full-text · Chapter · Apr 2012
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    ABSTRACT: A liquid extemporaneous metformin formulation from Glucophage® tablets was prepared in drinking water sweetened with 10% Splenda®, then stored for 30 days at 25 °C exposed to and protected from light, at 4 and 40 °C. Physicochemical integrity was determined by UPLC-UV using a VARIAN Pursuit C8 column 150 × 3.9 mm at 40 °C, with detection at 236 nm. Mobile phase was 0.1M KH2PO4 (pH = 6.5): 4.6 mM SDS: acetonitrile (63:7:30 v/v) eluted at 0.8 mL/min. Microbial colony forming units per milliliter (CFU/mL) were determined in soy agar trypticasein (SAT), McConkey agar, and Sabouraud media at 37 and 29 °C for 72 and 96 h. The solution retained over 90% of the initial amount of metformin, showing zero-growth of enteric or aerobic mesophilic bacteria and was able to restore normal glucose levels in chronically hyperglycemic Wistar rats. This metformin formulation may be helpful managing insulin resistance in pediatric endocrinology.
    Full-text · Article · Jan 2012 · LATIN AMERICAN JOURNAL OF PHARMACY
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    ABSTRACT: Sildenafil extemporaneous formulations, used to treat pulmonary arterial hypertension (PAH) in hospitalised children, must be also stable and uniform in content. In this study, we determined content uniformity, stability and therapeutic efficacy of sildenafil in gelatine capsules containing 5 mg from three brands (Viagra ® , Maxifort ® and Apodefil ®). The powder from crushed tablets was distributed into 32 gelatine capsules for each brand. Content uniformity and stability at 25 and 40°C were analysed by HPLC-UV (µ µ µ µBondapack C 18 column, H 2 KPO 4 35 mM (pH 6.0)/ acetonitrile (53:47 v/v), 0.8 ml/min). Therapeutic efficacy of unitary doses was assessed in 25 patients (14 boys and 11 girls), according to clinical improvement and systolic pulmonary arterial pressure (SPAP) decrease, before and after taking sildenafil. Unitary doses showed content uniformity (4.93 ± 0.327 ≈ 5 mg) and were stable for 30 days at 25 and 40°C. SPAP values decreased to normal in 64% of the patients. Dyspnoea disappeared in 85% (11/13) and cyanosis in 67% (6/9). Two children (8%) showed no therapeutic response. Individualised doses of sildenafil in gelatine capsules are stable, uniform in content, and therapeutically effective, being an alternative to treat PAH in hospitalised and ambulatory patients.
    Full-text · Article · Jan 2012 · African journal of pharmacy and pharmacology
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    ABSTRACT: The aim of this work was to assess the stability and sedative effect of midazolam in chocolate bars. The stability of 5 g chocolate bars containing 6 mg midazolam hydrochloride was evaluated at room temperature (25 ± 2 °C), at 4 and 40 °C, by HPLC. Drug plasma levels were measured and the sedative effect was confirmed in six healthy volunteers according to the Ramsay's scale. Data regarding chocolate bar administration were compared to those from the apple juice solution. Pharmacokinetic data were processed using the WinNonLin 5.2 software. Midazolam in chocolate bars remained stable for 14 days at room temperature and exposed to light; for 90 days at 4 and 40°C protected from light, and showed a longer shelf life, better flavour and appearance, inducing the same sedative effect as the apple juice preparation. Raspberry flavour masked midazolam unpleasing taste most favourably.
    No preview · Article · Dec 2011 · LATIN AMERICAN JOURNAL OF PHARMACY
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    ABSTRACT: Neurodegenerative diseases constitute a worldwide health problem. Metals like iron and copper are essential for life, but they are also involved in several neurodegenerative mechanisms such as protein aggregation, free radical generation and oxidative stress. The role of Fe and Cu, their pathogenic mechanisms and possible therapeutic relevance are discussed regarding four of the most common neurodegenerative diseases, Alzheimer's, Parkinson's and Huntington's diseases as well as amyotrophic lateral sclerosis. Metal-mediated oxidation by Fenton chemistry is a common feature for all those disorders and takes part of a self-amplifying damaging mechanism, leading to neurodegeneration. The interaction between metals and proteins in the nervous system seems to be a crucial factor for the development or absence of neurodegeneration. The present review also deals with the therapeutic strategies tested, mainly using metal chelating drugs. Metal accumulation within the nervous system observed in those diseases could be the result of compensatory mechanisms to improve metal availability for physiological processes.
    Full-text · Article · Jul 2010 · Chemico-biological interactions
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    ABSTRACT: Valproic acid has been associated with a highly variable intersubject absorptive phase; therefore, magnesium salt (magnesium valproate [MgV]) was developed to diminish variation during enteric absorption. The aims of this study were to assess the pharmacokinetics of single oral doses of MgV 500-mg solution, suspension, and enteric-coated tablets in a healthy Mexican population, and to compare formulation-related differences. This was a randomized, single-dose, 3-period, 6-sequence crossover study in healthy Mexican volunteers aged 18 to 45 years. In each period, subjects received single oral doses of 500-mg MgV solution, suspension, and enteric-coated tablet formulations, with a 7-day washout period between each dosing period. Serial blood samples were collected at 0 hour (prior to MgV administration) and at 0.5, 1, 1.5, 2, 2.5, 3, 3.5, 4, 6, 9, 12, 24, 48, and 72 hours after dosing. Valproate was measured by a new method of ultraperformance liquid chromatography coupled with mass spectrometry. Pharmacokinetic parameters of interest were C(max), T(max), AUC(0-72), AUC(0-infinity), t(1/2), V(d)/F, CL/F, and mean residence time (MRT). Formulation-related differences were assayed in accordance with the Mexican regulatory bioequivalence criteria. Log-transformed values of C(max) and AUC were used to construct a classic 90% CI. Bioequivalence was established if the 90% CI for the mean test:reference ratio of log-transformed C(max) and AUC were within the range of 0.80 to 1.25. Tolerability was assessed based on subject interview, vital sign monitoring, and clinical assessment. A total of 24 healthy volunteers (12 women and 12 men; mean [SD] age, 28.79 [6.5] years; height, 164 [9.8] cm; weight, 65.42 [8.95] kg; and body mass index, 24.28 [2.11] kg/m(2)) were included. For the MgV solution, the mean (SD) pharmacokinetic parameters of C(max), T(max), AUC(0-72), AUC(0-infinity), t(1/2), V(d)/F, CL/F, and MRT were 59.75 (8.24) microg/mL, 0.542 (0.14) hours, 1099.67 (241.70) microg h/mL, 1156.30 (264.01) microg h/mL, 16.19 (2.36) hours, 9633.68 (1892.70) mL, 418.35 (92.01) mL/h, and 18.36 (1.44) hours, respectively. For the MgV suspension, the mean (SD) pharmacokinetic parameters of C(max), T(max), AUC(0-72), AUC(0-infinity), t(1/2), V(d)/F, CL/F, and MRT were 55.04 (7.72) microg/mL, 0.773 (0.51) hour, 1057.76 (223.37) microg h/mL, 1111.09 (245.07) microg h/mL, 16.32 (2.20) hours, 1069.05 (1775.64) mL, 435.43 (99.59) mL/h, and 18.41 (1.43) hours, respectively. For the MgV enteric-coated tablets, the mean (SD) pharmacokinetic parameters of C(max), T(max), AUC(0-72), AUC(0-infinity), t(1/2), V(d)/F, CL/F, and MRT were 54.88 (6.73) microg/mL, 2.79 (0.89) hours, 1100.79 (216.70) microg h/mL, 1163.61 (238.36) microg h/mL, 16.48 (2.10) hours, 9675.15 (1659.36) mL, 412.36 (85.24) mL/h, and 19.95 (1.53) hours, respectively. The 90% CIs for the tablets:solution ratio were 82.15 to 95.44, 94.60 to 105.39, and 95.43 to 105.95 for C(max), AUC(0-72), and AUC(0-infinity), respectively. The 90% CIs for the suspension:solution ratio were 84.79 to 98.50, 88.89 to 99.02, and 89.15 to 98.97, respectively. The 90% CIs for the tablets:suspension ratio were 89.90 to 104.43, 100.84 to 112.34, and 101.60 to 112.80, respectively. This single-dose study found that the 3 formulations (solution, suspension, and enteric-coated tablets) of MgV met the regulatory criteria for bioequivalence in these healthy, fasting, Mexican volunteers.
    No preview · Article · Sep 2009 · Clinical Therapeutics
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    ABSTRACT: The aim of the present work was to develop a chromatographic technique coupled with mass spectrometry for the measurement of lamotrigine in plasma. Lamotrigine and guanabenz (internal standard) were measured by selected reaction monitoring. The method was validated and applied in a bioequivalence trial on 26 female volunteers. Lamotrigine chewable tablets (100 mg) were administered and monitored for up to 96 h. The method was linear between 0.05 and 5.0 µg/ml, with acceptable stability, accuracy and precision. Mean maximum plasma concentration was 1.37 µg/ml and was reached at 1.6 h postdose. Elimination half-life was 32.7 h. Lamotrigine tablets were bioequivalent. Ultra-performance liquid chromatography with tandem mass spectrometry represents a powerful tool in terms of sensitivity, specificity and high-throughput analysis.
    No preview · Article · Apr 2009 · Bioanalysis
  • B. Ramírez-Mendiola · L. Rivera-Espinosa · J.L. Chávez-Pacheco

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