Abstract: AIM:To determine ribavirin in human plasma by an LC/MS/MS method and to study the bioequivalence and pharmacokinetics of reference and test ribavirin formulations.METHODS:A double-phased stochastical crossover study design was conducted.18 healthy volunteers were given a single dose of 80 mg ribavirin of reference and test formulations.The drug was extracted from collected plasma and analyzed by LC/MS/MS.The pharmacokinetic parameters as well as relative bioavailability were measured.RESULTS:The calibration curve was linearwithin the range of 2 - 500 ng/mL (r² =0.9944).The average recovery was more than 90 %.The average RSD within 3 days and between 3 days were all less than 10 %.The major pharmacokinetic parameters t_max 、C_max 、t _1/2 、AUC_{0 -72} and AUC_0~∞ of reference and test ribavirin formulations were (1.1 ±0.5) and (1.1 ±0.4) h, (249 ±89) and (232 ±65) ng/mL, (34 ±11) and (34 ±11) h, (2828 ±1215) and (2685 ±1096) ng^。h^。mL ^-1, (3600 ±1568) and (3416 ±1379) ng^。h^。mL ^-1.The relative bioavailability of test buccal tablet was(106 ±16) %. CONCLUSION:The method is more simple, more accurate and much more sensitive.There is no significant difference between the main pharmacokinetic parmeters of two formulations of ribavirin (P >0.05), they are bioequivalent.

Key words: ribavirin, pharmacokinetics, bioequiavailability, LC-MS/MS