Pharmacokinetic Study of Modafinil in Relation to Gender and Ethnicity in Healthy Young Chinese Volunteers

Purpose. Pharmacokinetics of modafinil were investigated in relation to sex and ethnicity in healthy young volunteers from Han, Mongolian, Korean, Uygur and Hui (n = 10/group) following administration of a single 200 mg oral dose. Methods. Blood samples were collected over 48 h for the determination of plasma levels of modafinil and its acid metabolite by HPLC. Pharmacokinetic parameters were evaluated using noncompartmental methods. Results. Modafinil was well tolerated and safe at a single oral dose of 200 mg. All participants reported adverse events, none of which was serious or unexpected. The maximum plasma concentration (C(max)) and area under the curve for modafinil concentration versus time, which was extrapolated to infinity (AUC(0-8)), were higher in women compared to men (p < 0.01). No sex-based difference was noted in the total body weight-normalized modafinil oral clearance. The total body weight-normalized modafinil apparent volume of distribution and t(1/2) were found to exhibit ethnicity-based significant differences. Conclusion. There are pharmacokinetic differences based on sex and ethnicity for modafinil.