Bioequivalence of 2 formulations of montelukast (5 mg chewable tablet) in the fasting state: an open-label randomized, single-dose, 2-period, crossover study / Estudo de bioequivalência entre duas formulações de comprimidos mastigáveis de Montelucaste de 5 mg em condições de jejum: um estudo randomizado, de dose única, aberto, dois períodos, cruzado

Introduction: Montelukast, a selective and active leukotriene receptor antagonist, is one of the most common agents in asthma treatment for both adults and children. Objective: To assess whether the pharmacokinetic profiles of two formulations of montelukast were similar after a single 5 mg dose (chewable tablets), administered orally under fasting conditions, sampling blood before and 36 hours after administration. Methods: This was a randomized, 2-sequence, 2-period, crossover study of 2 chewable tablet formulations of the drug: Singulair®, provided by Merck Sharp and Dohme Farmacêutica Ltda. (reference), and generic montelukast, manufactured by Eurofarma Laboratórios S.A. (test). Plasma samples obtained from 35 participants were analyzed for montelukast through high-performance liquid chromatography coupled to tandem mass spectrometry, with montelukast-d6 as the internal standard. Peak montelukast concentrations were 299.313 (SD, 11.039) ng/mL for the reference formulation and 279.803 (SD, 10.085) ng/mL for test formulation. Results: Statistical analysis showed no significant differences between AUC0-36h, AUC0-inf, or Cmax between formulations, with the following test/reference ratios: 102.458 for AUC0-36h, 102.522 for AUC0-inf, and 93.490 for Cmax. No serious adverse events were reported during the trial. Our results demonstrated the bioequivalence of Singulair® and Eurofarma's generic montelukast. Conclusions: Our results revealed that the new generic tablets are clinically safe and can be used interchangeably with the brand name product. Eurofarma's montelukast offers a safe, effective, and cheaper treatment option for people with asthma or allergic rhinitis.

Introdução: O montelucaste, um antagonista seletivo e ativo dos receptores de leucotrienos, é um dos agentes mais comumente usados na prática clínica no tratamento da asma, tanto em adultos quanto em crianças. Objetivo: Avaliar se os perfis farmacocinéticos de duas formulações de montelucaste eram semelhantes após uma dose única de comprimidos mastigáveis de 5 mg, administrados por via oral em jejum, coletando amostras de sangue desde antes da administração até 36 horas depois disso. Métodos: Estudo comparativo randomizado, 2 sequências e 2 períodos, cruzado, de dois medicamentos em comprimidos mastigáveis: Singulair®, fornecido pela Merck Sharp e Dohme Farmacêutica Ltda. (referência) e Montelucaste 5 mg, fabricado pela Eurofarma Laboratórios S.A. (teste). Amostras de plasma obtidas de 35 indivíduos elegíveis foram analisadas para montelucaste por cromatografia líquida de alta eficiência acoplada a espectrometria de massa em tandem, tendo Montelucaste-d6 como padrão interno. As concentrações máximas de montelucaste foram 299,313±11,039 ng/mL para referência e 279,803±10,085 ng/mL para formulação de teste. Resultados: A análise estatística não mostrou diferenças significativas para AUC0-36h, AUC0-inf e nem para Cmax entre as formulações, apresentando as razões Teste/Referência: 102,458 para AUC0-36h, 102,522 para AUC0-inf e 93,490 para Cmax. Nenhum evento adverso grave foi relatado durante o estudo. De acordo com a regulamentação brasileira, o atual estudo farmacocinético demonstrou bioequivalência entre os agentes individuais e forneceu evidências de bioequivalência entre Singulair® e Montelukast fabricado pela Eurofarma. Resultado: Os resultados mostraram que os novos comprimidos genéricos são clinicamente seguros e podem ser trocados pela marca original. O montelucaste da Eurofarma oferece uma opção de tratamento mais barata, segura e eficaz para indivíduos com asma ou rinite alérgica.

Bioequivalence/bioavailability Study of a New Formulation of Imatinib Mesylate 100 mg Coated Tablets versus Glivec® in Brazilian Healthy Male Volunteers in Fed State / Estudo de Bioequivalência/Biodisponibilidade de uma Nova Formulação de Mesilato de Imatinibe versus Glivec® em Voluntários Saudáveis Brasileiros em Condições Alimentares / Estudio de Bioequivalencia/Biodisponibilidad de una Nueva Formulación de Mesilato de Imatinib versus Glivec® en Voluntarios Saludables Brasileños Bajo Condiciones Alimentarias

Introduction: Imatinib mesylate is currently the first-line oral treatment for all stages of chronic myeloid leukemia (CML) and is also used in some cases of gastrointestinal stromal tumor (GIST) and acute lymphoblastic leukemia (ALL). Objective: Investigate the bioavailability of two products containing imatinib mesylate, 100 mg coated tablet, to determine if they are bioequivalent. Method: The study was conducted using an open-label, randomized, balanced design and the formulations were administered orally in a single dose to 48 healthy adult males, in fed state, followed by sequential blood withdraws for the next 72 hours. Forty-eight male healthy volunteers were selected to participate in the study. Test formulation from Eurofarma Laboratórios S.A. Brazil was compared to from Novartis Biociências S.A. The comparative bioavailability of the formulations was assessed based on statistical comparisons of relevant pharmacokinetic parameters obtained from drug concentration data from collected blood samples measured using an analytical method based on high-performance liquid chromatography coupled to mass spectrometry. Results: The ratio of the geometric means between the test and the reference, with a 90% confidence interval, of pharmacokinetic parameters for Cmax was 102.26% (94.17-111.04%) and for AUC0-t was 101.24% (95.19-107.68%). Conclusion: Imatinib mesylate 100 mg (test product) from Eurofarma Laboratórios S.A. was considered bioequivalent to the reference Glivec® 100 mg manufactured by Novartis Biociências S.A, and the test product can be interchangeable with the reference, based on their pharmacokinetic performance

Introdução: O mesilato de imatinibe é atualmente o tratamento oral de primeira linha para todos os estágios de leucemia mieloide crônica (LMC) e é usado também em alguns casos de tumores gastrointestinais (GIST) e na leucemia linfoide aguda (LLA). Objetivo: Investigar a biodisponibilidade de dois produtos contendo mesilato de imatinibe de 100 mg em comprimidos revestidos para determinar se são bioequivalentes. Método: Estudo conduzido usando um desenho aberto, randomizado e balanceado. As formulações foram administradas de forma oral em única dose a 48 participantes saudáveis do sexo masculino após alimentação, seguido de coletas de sangue por 72 horas. Quarenta e oito participantes saudáveis foram selecionados para participar do estudo. A formulação teste da Eurofarma Laboratórios S.A. foi comparada com a formulação referência da Novartis Biociências S.A. A biodisponibilidade relativa das formulações foi avaliada em comparações estatísticas dos parâmetros farmacocinéticos relevantes obtidos de concentrações de droga das amostras coletadas mediante a utilização de um método analítico baseado em cromatografia líquida de alta performance acoplada à espectrometria de massas. Resultados: A razão das médias geométricas entre teste e referência com intervalo de confiança 90% dos parâmetros farmacocinéticos para Cmáx foi de 102,26% (94,17-111,04%) e para ASC0-t foi de 101,24% (95,19-107,68). Conclusão: Mesilato de imatinib 100 mg (produto teste) da Eurofarma Laboratórios S.A. foi considerado bioequivalente ao Glivec® 100 mg produzido por Novartis Biociências S.A., e o produto teste pode ser intercambiável como referência com base em seu desempenho farmacocinético

Introducción: El mesilato de imatinibe es actualmente el tratamiento oral de primera línea para todos los estadios de leucemia mieloide crónica (LMC) y es usado también en algunos casos de tumores gastrointestinales (GIST) y leucemia linfoide aguda (LLA). Objetivo: Investigar la biodisponibilidad de dos productos de mesilato de imatinibe de 100 mg en comprimidos revestidos para determinar si son bioequivalentes. Método: Estudio ejecutado usando un diseño abierto, aleatorizado y balanceado. Las formulaciones fueron administradas de forma oral en dosis única a 48 participantes saludables de sexo masculino en condiciones de alimentación, seguidas de muestras de sangre por 72 horas. Cuarenta y ocho participantes saludables fueron seleccionados para participar del estudio. La formulación de prueba de Eurofarma Laboratórios S.A. fue comparada con la formulación referencia de Novartis Biociências S.A. La biodisponibilidad relativa de las formulaciones fue evaluada mediante comparaciones estadísticas de los parámetros farmacocinéticos relevantes obtenidos de concentraciones del fármaco de muestras recolectadas con la utilización de un método analítico basado en cromatografía de alto rendimiento acoplada a espectrometría de masas. Resultados: La relación de las medias geométricas entre la prueba y la referencia con un intervalo de confianza del 90% de los parámetros farmacocinéticos para Cmax fue 102,26% (94,17-111,04%) y para AUC0-t fue 101,24% (95,19-107,68). Conclusión: El mesilato de imatinib 100 mg (producto de prueba) de Eurofarma Laboratórios S.A. fue considerado bioequivalente al Glivec® 100 mg producido por Novartis Biociências S.A. y el producto de prueba puede ser intercambiable con el de referencia en función de su desempeño farmacocinético

Capecitabine bioequivalence in healthy volunteers.

Capecitabine is a prodrug and is selectively activated by tumor cells to its cytotoxic moiety, 5-fluorouracil, by thymidine phosphorylase, which is generally expressed at high levels in tumors. Clinical and pharmacokinetic studies of capecitabine have been performed in patients with cancer. This study aims to evaluate the bioequivalence of two capecitabine formulations (150-mg tablet) using healthy male subjects under nonfasting conditions. The study was conducted as an open, randomized, three-period, semi-replicated design with three sequences (RRT, RTR, TRR) with a 1-week washout interval. The subjects were selected for the study after having their health status previously assessed by a clinical evaluation and laboratory tests (biochemical and hematological parameters, and urinalysis). A single capecitabine tablet (150 mg) was given in each occasion. Plasma capecitabine concentrations were analyzed by liquid chromatography coupled with tandem mass spectrometry (HPLC/MS/MS) with positive ion electrospray ionization using multiple reactions monitoring (MRM). The geometric mean and 90% confidence intervals (CI) of capecitabine/Xeloda® (T/R) percent ratio were 104.34% (98.74 - 110.25%) for AUClast, 103.06% (97.48 - 108.96%) for AUCinf, and 104.07% (88.13 - 122.90%) for Cmax. Since the 90% CI for Cmax, AUClast, and AUCinf ratios were all inside the 80 - 125% interval proposed by the US Food and Drug Administration Agency, it was concluded that the capecitabine formulation elaborated by Eurofarma Laboratórios Ltda. is bioequivalent to Xeloda® formulation for both the rate and the extent of absorption. The drug was well tolerated by the subjects, indicating that it is safe to perform capecitabine bioequivalence studies in healthy male subjects.
.

Bioequivalência de cloridrato de propafenona 300mg em comprimido revestido em administração pós-prandial em adultos saudáveis / Bioequivalence of propafenone hydrochloride 300mg film coated tablets in healthy adults

OBJETIVO: Avaliar a bioequivalência de duas formulações de cloridrato de propafenona 300mg em comprimido revestido.MÉTODOS: Estudo randomizado, cruzado, aberto, com dois tratamentos, duas sequências e quatro períodos com 60 participantes sadios de ambos os sexos. Os voluntários foram internados em quatro oportunidades durante 24 horas; em cada período, os sujeitos receberam a formulação teste ou a formulação referência, em regime pós-prandial. Foram coletadas 23 amostras de sangue após administração da droga para determinação plasmática da propafenona. Para quantificação da droga, foi utilizada técnica de cromatografia líquida acoplada à espectrometria de massas sequencial. RESULTADOS: As formulações foram consideradas clinicamente bem toleradas. A concentração máxima e a área sob a curva de zero a 36 horas foram comparadas: a média geométrica da razão entre as formulações teste e referência para concentração máxima foi de 110,16%, com intervalo de confiança de 99,44% a 122,04% e coeficiente de variação de 33,95%. A média geométrica da razão entre as formulações teste e referência para a área sob a curva de zero a 36 horas foi de 107,92%, com intervalo de confiança de 99,58% a 116,96% e coeficiente de variação de 26,39%. A média geométrica da razão entre o medicamento teste e referência para área sob a curva de zero ao infinito foi de 107,12%, com intervalo de confiança de de 99,11% a 115,78% e coeficiente de variação de 25,48%. CONCLUSÃO: As formulações teste e referência foram estatisticamente bioequivalentes, de acordo com sua taxa e extensão de absorção.

OBJECTIVE: To evaluate the bioequivalence of two 300mg profanone hydrochloride coated tablets. METHODS: Randomized, cross-over, openstudy, with two treatments, two sequences, and four periods with 60 healthy participants of both genders. The volunteers were admitted in four opportunities over 24 hours; on each period, the subjects received a test formulation, or a reference formulation, in a postprandial administration. Twenty-three samples of blood were collected after oral administration of the drug for determining plasma level of propafenone. Liquid chromatography-mass spectrometry was used for quantifying propafenone. RESULTS: The formulations were considered clinically well tolerated. The maximum concentration and the area under the curve from zero to 36 hours were compared: the geometric mean of the ratio between the test and reference formulations for maximum concentration was 110.16%, with confidence interval of 99.44% - 122.04%), coefficient of variation of 33.95%. The geometric mean of the ratio between the test and reference formulations for the area under the curve of zero to 36 hours was 107.92%, with confidence interval of 99.58% - 116.96%, and coefficient of variation of 26.39%. The geometric mean of the ratio between the formulations for area under the curve of zero to infinitum as 107.12% with confidence interval of 99.11% - 115.78%),and coefficient of variation of 25.48%. CONCLUSION: According to the rate and extension of absorption, the test and reference formulations are statistically bioequivalent.

Comparative bioavailability of two oral formulations of clozapine in steady state administered in schizophrenic volunteers under individualized dose regime.

In the present study, a novel, fast, sensitive and robust method to quantify clozapine in human plasma using quetiapine as the internal standard (IS) is described. The analyte and the IS were extracted from plasma using a single protein precipitation extraction technique with methanol and analyzed by high performance liquid chromatography coupled to the electrospray ionization tandem mass spectrometric (HPLC-ESI-MS/MS). The method was linear over the range 20 to 1500 ng.mL-1. The intra-assay precisions ranged from 3.8 to 5.9%, while inter-assay precisions ranged from 4.2 to 6.0%. The intra-assay accuracies ranged from 99.3 to 107.5%, while the inter-assay accuracies ranged from 98.9 to 101.7%. This method agrees with the requirements proposed by the US Food and Drug Administration of high sensitivity, specificity and high sample throughput and was used to evaluate the pharmacokinetic profiles and bioequivalence of the two clozapine formulations in twenty six schizophrenic patients affected by refractory schizophrenia under steady-state conditions. During the hospitalization period the patients received the 100 mg clozapine formulation tablets corresponding to the same dose they were using 14 days before hospitalization. The clozapine pharmacokinetic did not differ significantly after administration of both test and the reference formulations. The Tmax and T1/2 for the test formulation were 2.26 and 10.92 h, respectively. In addition, the Tmax and T1/2 for the reference formulation were 2.44 and 11.08 h, respectively. The 90% confidence interval of the mean ratio of lnAUC0-t was within 0.80-1.25 range which indicates that the test formulation was bioequivalent to the reference formulation when orally administered to schizophrenic patients regarding both the rate and extent of absorption.

A fast, sensitive and simple method for mirtazapine quantification in human plasma by HPLC-ESI-MS/MS. Application to a comparative bioavailability study.

In the present study a simple, fast, sensitive and robust method to quantify mirtazapine in human plasma using quetiapine as the internal standard (IS) is described. The analyte and the IS were extracted from human plasma by a simple protein precipitation with methanol and were analyzed by high-performance liquid chromatography coupled to an electrospray tandem triple quadrupole mass spectrometer (HPLC-ESI-MS/MS). Chromatography was performed isocratically on a C(18), 5 µm analytical column and the run time was 1.8 min. The lower limit of quantitation was 0.5 ng/mL and a linear calibration curve over the range 0.5-150 ng/mL was obtained, showing acceptable accuracy and precision. This analytical method was applied in a relative bioavailability study in order to compare a test mirtazapine 30 mg single-dose formulation vs a reference formulation in 31 volunteers of both sexes. The study was conducted in an open randomized two-period crossover design and with a 14 day washout period. Since the 90% confidence interval for C(max) , AUC(last) and AUC(0-inf) were within the 80-125% interval proposed by the Food and Drug Administration and ANVISA (Brazilian Health Surveillance Agency), it was concluded that mirtazapine 30 mg/dose is bioequivalent to the reference formulation, according to both the rate and extent of absorption.

Budesonide quantification by HPLC coupled to atmospheric pressure photoionization (APPI) tandem mass spectrometry. Application to a comparative systemic bioavailability of two budesonide formulations in healthy volunteers.

In the present study, a novel, fast, sensitive and robust method to quantify budesonide in human plasma using 3-keto-desogestrel as the internal standard (IS) is described. The analyte and the IS were extracted from human plasma by liquid-liquid extraction (LLE) using ether. Extracted samples were analyzed by high performance liquid chromatography coupled to Atmospheric pressure photoionization tandem mass spectrometry (HPLC-APPI-MS/MS). Chromatography was performed isocratically on a C18, 5 µm analytical column. The temperature of the autosampler was kept at 6 °C and the run time was 4.00 min. A linear calibration curve over the range 7.5-1000 pg ml⁻¹ was obtained and the lowest concentration quantified was 7.5 pg ml⁻¹, demonstrating acceptable accuracy and precision. This analytical method was applied in a relative bioavailability study in order to compare a test budesonide 64 µg/dose nasal spray formulation vs. a reference 64 µg/dose nasal spray formulation (Budecort Aqua) in 48 volunteers of both sexes. The study was conducted in an open randomized two-period crossover design and with a one-week washout period. Plasma samples were obtained over a 14 h interval. Since the 90% CI for both C(max), AUC(last) and AUC(0-inf) were within the 80-125% interval proposed by the Food and Drug Administration and ANVISA, it was concluded that budesonide 64 µg/dose nasal spray was bioequivalent to Budecort Acqua® 64 µg/dose nasal spray, according to both the rate and extent of absorption.

Determination of chlorpheniramine in human plasma by HPLC-ESI-MS/MS: application to a dexchlorpheniramine comparative bioavailability study.

In the present study a fast, sensitive and robust validated method to quantify chlorpheniramine in human plasma using brompheniramine as internal standard (IS) is described. The analyte and the IS were extracted from plasma by LLE (diethyl ether-dichloromethane, 80:20, v/v) and analyzed by HPLC-ESI-MS/MS. Chromatographic separation was performed using a gradient of methanol from 35 to 90% with 2.5 mm NH(4)OH on a Gemini Phenomenex C(8) 5 microm column (50 x 4.6 mm i.d.) in 5.0 min/run. The method fitted to a linear calibration curve (0.05-10 ng/mL, R > 0.9991). The precision (%CV) and accuracy ranged, respectively: intra-batch from 1.5 to 6.8% and 99.1 to 106.6%, and inter-batch from 2.4 to 9.0%, and 99.9 to 103.1%. The validated bioanalytical procedure was used to assess the comparative bioavailability in healthy volunteers of two dexchlorpheniramine 2.0 mg tablet formulations (test dexchlorpheniramine, Eurofarma, and reference Celestamine, Schering-Plough). The study was conducted using an open, randomized, two-period crossover design with a 2 week washout interval. Since the 90% confidence interval for C(max) and AUC ratios were all within the 80-125% interval proposed by ANVISA and FDA, it was concluded that test and reference formulations are bioequivalent concerning the rate and the extent of absorption.

Cyproterone acetate quantification in human plasma by high-performance liquid chromatography coupled to atmospheric pressure photoionization tandem mass spectrometry. Application to a comparative pharmacokinetics study.

A specific, fast and sensitive high performance liquid chromatography (HPLC) coupled to atmospheric pressure photoionization (APPI) tandem mass spectrometric (LC-MS/MS) assay was developed for the determination of cyproterone (CYP) acetate (CAS 427-51-0) in human plasma. The retention times were 3.26 and 2.90 min for CYP acetate and its internal standard (I. S.) finasteride (FIN), respectively. The overall mean recovery, using liquid/liquid extraction, was found to be 109.0, 107.7 and 100.3%, for low, medium and high concentrations, respectively. Calibration curves were linear in the concentration range of 0.1-50.0 ng/ml, and the lower limit of quantification (LLOQ) was 0.1 ng/ml. The LLOQ, 0.1 ng/ml, was sensitive enough for detecting terminal phase concentrations of the drug. Inter-batch precision of the method ranged from 2.2 to 5.55%, while Inter-batch accuracy ranged from 95.5 to 100.0%. Intra-batch precision ranged from 1.8 to 5.6%, while Intra-batch accuracy ranged from 92.0 to 99.4% at concentrations of 0.3 ng/ml, 20.0 and 40.0 ng/ml. The developed method was applied to a bioequivalenc study of CYP acetate in a group of 44 female volunteers at a single oral dose of a 2 mg tablet, in a combination of ethinylestradiol/CYP acetate (0.25/2 mg). The plasma concentration of CYP acetate did not differ significantly after administration of both formulations (test formulation and the reference one). The geometric mean and respective 90% CI of CYP acetate test/reference percent ratios were 90.66% (84.39-97.40%) for Cmax and 96.20% (90.45-102.33%) for AUC0-t.

A novel and sensitive method for ethinylestradiol quantification in human plasma by high-performance liquid chromatography coupled to atmospheric pressure photoionization (APPI) tandem mass spectrometry: application to a comparative pharmacokinetics study.

In the present study, a novel, fast, sensitive and robust method to quantify ethinylestradiol in human plasma using 17alpha-ethinylestradiol-d4 as the internal standard (IS) is described. The analyte and the IS were extracted from acidified plasma by liquid-liquid extraction (LLE) using diethyl ether-hexane followed by online solid phase extraction (SPE) using online C18 cartridges. Extracted samples were analyzed by high-performance liquid chromatography coupled to atmospheric pressure photoionization tandem mass spectrometry (HPLC-APPI-MS/MS). Chromatography was performed isocratically on a C18, 5 microm analytical column. The method had a chromatographic run time of 2.50 min and a linear calibration curve over the range 5-500 pg ml(-1) (r(2)>0.9992). The lowest concentration quantified was 5 pg ml(-1), demonstrating acceptable accuracy and precision. The intra-assay precisions ranged from 2.1 to 14.6%, while inter-assay precisions ranged from 4.4 to 11.4%. The intra-assay accuracies ranged from 94.6 to 103.8%, while the inter-assay accuracies ranged from 98.9 to 101.6%. The recovery of ethinylestradiol was determined as part of the assay validation process and was 73.1 and 79.0% for the concentrations 15 and 375 pg ml(-1), respectively. Short-term stability showed that ethinylestradiol was stable in plasma for at least 19 h at room temperature or for at least 385 days when stored at -20 degrees C. In the study of bioequivalence conducted in Brazil, healthy volunteers received two ethinylestradiol 0.035 mg tablet formulations using an open, randomized, two-period crossover design with a 2-week washout interval. Since the 90% confidence interval for C(max) and area under the curve ratios were all inside the 80-125% interval proposed by the US Food and Drug Administration, it was concluded that the two ethinylestradiol formulations are bioequivalent with respect to both the rate and the extent of absorption.

Quantification of chlordesmethyldiazepam by liquid chromatography-tandem mass spectrometry: application to a cloxazolam bioequivalence study.

A rapid, sensitive and specific LC-MS/MS method was developed and validated for quantifying chlordesmethyldiazepam (CDDZ or delorazepam), the active metabolite of cloxazolam, in human plasma. In the analytical assay, bromazepam (internal standard) and CDDZ were extracted using a liquid-liquid extraction (diethyl-ether/hexane, 80/20, v/v) procedure. The LC-MS/MS method on a RP-C18 column had an overall run time of 5.0 min and was linear (1/x weighted) over the range 0.5-50 ng/mL (R > 0.999). The between-run precision was 8.0% (1.5 ng/mL), 7.6% (9 ng/mL), 7.4% (40 ng/mL), and 10.9% at the low limit of quantification-LLOQ (0.500 ng/mL). The between-run accuracies were 0.1, -1.5, -2.7 and 8.7% for the above mentioned concentrations, respectively. All current bioanalytical method validation requirements (FDA and ANVISA) were achieved and it was applied to the bioequivalence study (Cloxazolam -- test, Eurofarma Lab. Ltda and Olcadil -- reference, Novartis Biociências S/A). The relative bioavailability between both formulations was assessed by calculating individual test/reference ratios for Cmax, AUClast and AUC0-inf. The pharmacokinetic profiles indicated bioequivalence since all ratios were as proposed by FDA and ANVISA.

Verapamil quantification in human plasma by liquid chromatography coupled to tandem mass spectrometry. An application for bioequivalence study.

An analytical method based on liquid chromatography with positive ion electrospray ionization (ESI) coupled to tandem mass spectrometry detection (LC-MS/MS) was developed for the determination of Verapamil in human plasma using Metoprolol as the internal standard. The analyte and internal standard were extracted from the plasma samples by liquid-liquid extraction and chromatographed on a C(8) analytical column. The mobile phase consisted of methanol-water (70:30; v/v)+12 mM formic acid. The method had a chromatographic total run time of 3.5 min and was linear within the range 1.00-500 ng/mL. Detection was carried out on a Micromass Quattro Ultima tandem mass spectrometer by multiple reaction monitoring (MRM). The intra-run imprecision was less than 5.1% calculated from the quality control (QC) samples, and 16.3% from the limit of quantification (LOQ). The accuracy determined from QC samples were between 92.9 and 103.1%, and 95.2 and 115.3% from LOQ. Concerning the inter-batch analysis, the imprecision was less than 5.8% and 17.3% from QC samples and LOQ, respectively. The accuracy varied between 98.2 and 100.8% from QC and it was 103.1% from LOQ. The protocol herein described was employed in a bioequivalence study of two tablet formulations of Verapamil.