2010 Volume 1 Pages 24-31
Purpose: The purpose of this study is to compare the steady-state plasma levels of HAL between Japanese, Koreans and Swedes who were treated with HAL monotherapy per os.
Method: The steady-state plasma levels of haloperidol (HAL) in 75 Japanese, 120 Korean, and 50 Swedish psychiatric patients treated orally with HAL were compared.
Results: Significantly higher doses of HAL were used in the Koreans (mean dose = 21 mg/day) than in the Japanese (15 mg/day) or Swedes (9 mg/day) (one-way analysis of variance (ANOVA) (p<0.0001), Bonferroni's post test (p<0.001)). The mean concentration/daily dose ratio (C/D ratio) of HAL was 2.2 times higher in Korean patients (2.78 nmol/L/mg/day) and 1.5 times higher in Japanese patients (1.88 nmol/L/mg/day) than that in Swedish patients (1.24 nmol/L/mg/day). A significant difference in the C/D ratio was observed among the 3 ethnic groups (one-way ANOVA; p<0.0001).
Discussion: The higher C/D ratio of HAL in Asians might be partly due to the higher frequency of the CYP2D6*10 allele in Asians; however, interethnic differences in the activity of other enzymes, such as CYP3A4, might have caused the differences in the present study, especially at the higher doses of HAL.