Abstract: AIM: To determine the pharmacokinetics and bioequivalence of epinastine (EPN) hydrochloride, a promising histamine H₁ receptor antagonist, in healthy Chinese volunteers under fasting conditions.METHODS: EPN hydrochloride test and reference tablets were administered as a single dose on two treatment days separated by a 1-week washout period.After dosing, serial blood samples were collected for a period of 36 h, and plasma EPN hydrochloride concentrations were determined by a validated reversed-phase HPLC method and pharmacokinetic parameters were calculated with DAS software.RESULTS: Plasma concentration-time profiles were adequately described by a two-compartment open model.The compound was rapidly absorbed and cleared slowly from plasma with a half-life of approximately 10 h.The main pharmacokinetic parameters of EPN hydrochloride test and reference tablets were as follow:t_max were (2.2 ±0.5) and (2.0 ±0.4) h, C_max were (66 ±16) and (68 ±13) μg/L, t1 2 were (10.1 ±1.3) and (10.4 ±2.4) h, AUC0-36 were (592 ±88) and (601 ±94) μg·h·L^-1, respectively.The relative bioavailability of test tablets was (99 ±13) %.CONCLUSION: The results indicate that the two formulations of EPN hydrochloride tablets are bioequivalent in the rate and extent of absorption.

Key words: epinastine hydrochloride, HPLC, pharmacokinetics, bioequivalence