Comparative bioavailability study of phenytoin in healthy Nepalese volunteers

Our study aimed to assess and compare the bioavailability of Eptoin 100 mg and Epileptin 100mg tablets in Nepalese healthy volunteers. A randomized, two-treatment cross-over study with two weeks’ wash-out period was conducted in 12 healthy non-smoker and non-alcoholic Nepalese male volunteers over a period of 6 months in the department of Clinical Pharmacology and Therapeutic at B. P. Koirala Institute of Health Sciences, Dharan, Nepal after approval from the Institutional Review Committee. The participants were randomized using sealed envelope system and received a single 100 mg oral tablet of either of the formulations with a two week washout period. Blood samples were collected predose and at regular intervals postdose upto 72 hours. Plasma phenytoin levels were estimated by reverse phase high performance liquid chromatography. The analytical method was validated prior to the start of study. Cmax (Peak Plasma Concentration), Tmax (Time to achieve maximum Plasma Concentration), AUC0-72 (Area under plasma concentration time curve 0 to 72 hours), AUC0-∞ (Area under plasma concentration time curve 0 to ∞) and T½ (Elimination half-life) and Kel (Elimination rate constant) were calculated and 80-120% margin (90% confidence interval) was used to assess bioequivalence. ANOVA test was used to analyze the data at P-value of 0.05. All volunteers completed the study. The log-transformed values of Cmax, Tmax, AUC0-t, and AUC0-∞ of the both formulations were within the specified limits and were bioequivalent according to the regulatory definition of bioequivalence based on the rate and extent of absorption. Both products can be considered equally effective in medical practice. Keywords: Bioavailability, Bioequivalence, healthy volunteer, Nepal, phenytoin sodium.