Sensitive LC-MS/MS method for quantification of rivaroxaban in plasma: Application to pharmacokinetic studies.

Rivaroxaban is an anticoagulant (orally active direct Xa inhibitor) considered to reduce the risk of stroke and systemic embolism and treat deep vein thrombosis, pulmonary embolism, and other cardiovascular complications. Bioanalytical methods for rivaroxaban quantification in plasma are necessary for application in pharmacokinetic studies, as well as in drug therapeutic monitoring. In this work, we developed and validated a sensitive bioanalytical method using LC-MS/MS for rivaroxaban quantification in human plasma using an one-step liquid-liquid extraction. The linear concentration range was 1-600 ng/mL. The bioanalytical method was also applied to pharmacokinetic studies in healthy volunteers under fasting and fed conditions. The results demonstrated that the method is rapid, sensitive, and adequate for application in pharmacokinetic studies.

A randomized, single-dose, two-sequence, two-period, crossover study to assess the bioequivalence between two formulations of clonazepam tablet in healthy subjects.

Clonazepam is a benzodiazepine commonly prescribed to treat panic disorder, epilepsy, anxiety, depression and certain types of seizures. This study aimed to evaluate the bioequivalence between two formulations of clonazepam tablets in order to meet regulatory requirements for marketing in Colombia and other countries in Latin America. An open-label, randomized, single-dose, two-period, two-sequence, two-treatment crossover study was conducted in 36 healthy subjects of both genders. Subjects received a single dose of clonazepam 2 mg test tablet (Sanofi-Aventis de Colombia S.A.) and reference product (Rivotril®, Produtos Roche Químicos e Farmacêuticos S.A.) under fasting conditions according to a randomly assigned order with a 21-day washout period. Serial blood samples were collected up to 96 h post-dose. Plasma concentrations of clonazepam were obtained by a validated liquid chromatography-tandem mass spectrometry method. Pharmacokinetic parameters were calculated using non-compartmental methods. A total of 36 healthy subjects were enrolled and 31 of them completed the study. Twenty-nine adverse events were reported (11 events with test product versus 18 events with reference product). There were no serious adverse events during the study. Geometric mean ratios (90% confidence intervals) for Cmax and AUC0-96h were 103.28% (98.10-108.64) and 102.50% (99.87-105.19), respectively. The test formulation of clonazepam 2 mg tablet manufactured by Sanofi-Aventis de Colombia S.A. was considered bioequivalent to reference product Rivotril® (Produtos Roche Químicos e Farmacêuticos S.A.) according to regulatory requirements. Both formulations were safe and well-tolerated during the study.

Evaluation of pantoprazole formulations in different dissolution apparatus using biorelevant medium.

PURPOSE: The study was developed to compare the in vitro dissolution profiles of pantoprazole (CAS 102625-70-7) formulations in both The United States Pharmacopeia (USP) apparatus 2 and 3 by applying biorelevant medium. Moreover, an in vitro-in vivo relationship was proposed considering in vivo data from a previously published study. METHODS: In vitro dissolution profiles were evaluated in biorelevant medium in USP apparatus 2 and 3 and the dissolution curves were either compared by the similarity factor (f2) or a model-independent approach. The fraction of drug dissolved in vitro in apparatus 2 was compared with the fraction of drug absorbed in vivo, which was obtained from a retrospective in vivo study. An in vitro-in vivo relationship analysis was then applied to elucidate the overall absorption characteristics of formulations. RESULTS: The dissolution profiles of formulations demonstrated similar disposition in biorelevant medium in both USP apparatus 2 and 3. The dissolution profiles were described by f2 model in apparatus 2 and Weibull's function in apparatus 3. The vitro-in vivo relationship analysis showed that the formulations exhibited permeability rate-limiting absorption. CONCLUSION: Biorelevant medium in both USP apparatus 2 and 3 may be used as a tool to predict in vivo disposition of formulations of pantoprazole. Furthermore, it can be argued that biowaiver can be granted for enteric coated formulations of pantoprazole on the basis of in vitro dissolution profile.

Bioequivalence of two enteric coated formulations of pantoprazole in healthy volunteers under fasting and fed conditions.

PURPOSE: To compare the bioavailability of two pantoprazole (CAS 102625-70-7) formulations (40 mg pantoprazole enteric coated tablets) under fasted and fed conditions as well as to evaluate the dissolution profile in biorelevant media. METHODS: The subjects received either 40 mg of the reference or of test formulation in fasting (n = 28) and fed (n=70) condition. The studies were conducted according to a single dose and randomized crossover design. Blood samples were collected up to 12 h after drug administration in fasting condition and up to 48 h in fed condition. Plasma concentrations of pantoprazole were determined by LC-MS/MS. Pharmacokinetic parameters were calculated from the observed plasma concentration-time profiles. Bioequivalence between the formulations in fasting and fed condition was assessed considering 90% confidence intervals for the ratio of means for lnCmax and lnAUC(0-t) within 0.8-1.25. Dissolution profiles were evaluated in biorelevant media [Fasting State Simulating Intestinal Fluid (FaSSIF) and Fed State Simulating Intestinal Fluid (FeSSIF)]. The sameness of the dissolution curves was assessed by f2 values between 50 and 100. RESULTS: Under fasting condition the 90% confidence interval for the ratio of means for the lnCmax, (0.94-1.03) and lnAUC(0-t) (0.89-0.99) was within the guideline range of bioequivalence (0.80-1.25). However, the data for lnCmax (0.51-0.76) and lnAUC(0-t) (0.68-0.90) under fed condition were not within the bioequivalence range. The postprandial study demonstrated a high intra-subject variability and in some subjects pantoprazole could not be detected for up to 24 h, although the dissolution profile of reference and test formulations presented a similar disposition in FaSSIF and FeSSIF as confirmed by the values of f2 higher than 50. CONCLUSION: The results demonstrated that the test formulation was bioequivalent to the reference in fasting condition but not in postprandial state. The dissolution profile in FaSSIF indicates that this biorelevant medium was more adequate to discriminate the in vivo disposition of pantoprazole than FeSSIF. Furthermore, the fed condition study had shown a pronounced influence of food in the absorption of pantoprazole after single oral dose administration.