Pharmacokinetics of midazolam tablet in different Chinese ethnic groups

Abstract

Subjects of different ethnic groups may respond differently to drugs. The present study was conducted to compare the oral pharmacokinetics of midazolam among healthy volunteers from five different ethnic groups in China: Han, Mongolian, Uygur, Hui and Korean. Healthy volunteers (10 Hans, 10 Mongolians, 10 Uygurs, 10 Huis and 9 Koreans) of Chinese nationality received a single oral tablet dose of 15 mg midazolam in an open label, parallel-group study. Blood samples were collected at intervals and analysed for midazolam by high performance liquid chromatography (HPLC). Ethnic differences in pharmacokinetic parameters of midazolam using non-compartmental methods and anova and Kruskal-Wallis rank test. Midazolam maximum concentration (C(max) ) was significantly lower in Mongolians than that in Hans, Uygurs, Huis and Koreans (74·9 ± 33·7, 103·1 ± 26·4, 124·8 ± 50·0, 130·0 ± 38·3 and 189·0 ± 82·1 μg/L, respectively). C(max) for the Koreans were significantly greater, compared with Hans and Mongolians. The time to attain C(max) (t(max) ) for Hans was significantly longer as compared with Koreans and Uygurs (1·5 ± 0·7, 0·8 ± 0·5, 0·6 ± 0·7 h, respectively). Midazolam terminal half-life (t(1/2z)) were 3·0 ± 0·8, 2·2 ± 0·7, 1·9 ± 0·7, 3·5 ± 1·9, 3·8 ± 2·3 h for Hans, Mongolians, Uygurs, Huis and Koreans, respectively. The differences in half-life were significant between Koreans and Mongolians, Koreans and Uygurs, Uygurs and Huis, respectively. There were no differences between young males and females for all pharmacokinetic parameters. Double peaks in the concentration-time profiles were observed in some subjects. There were some significant differences in midazolam pharmacokinetics between the five Chinese ethnic groups. However, the wide intra-ethnic variability observed in PK parameters makes predictions of midazolam kinetics, using ethnicity as predictor, unreliable.