Duloxetine pharmacokinetics are similar in Japanese and Caucasian subjects

What is already known about this subject • The pharmacokinetics of duloxetine have been assessed in a number of clinical studies. • Duloxetine is eliminated through oxidative metabolism via CYP1A2 and, to a lesser degree, CYP2D6. • There is strong evidence that the prevalence of CYP2D6 phenotypes and the activity of CYP1A2 enzyme activity differ between Japanese and Caucasians. • Given the characteristics of duloxetine metabolism, there is good reason to assess pharmacokinetic differences between Japanese and Caucasians. What this study adds • Duloxetine pharmacokinetics in Japanese or Caucasian subjects is not meaningfully different after single or multiple doses of duloxetine. • The magnitude of pharmacokinetic differences between groups is small relative to the pharmacokinetic variability in either group, and these small differences can be accounted for by differences in body weight. • The result of this study suggests that different dose recommendations for Caucasian or Japanese patients are not likely to be necessary. Aims To compare single‐ and multiple‐dose duloxetine pharmacokinetics between healthy Japanese and Caucasians. Methods Twenty‐four subjects of each race were given single oral doses of duloxetine (20, 40 and 60 mg) in a randomized, double‐blind study. Another 20 subjects of each race received 20, 40 mg or placebo (2 : 2 : 1) twice‐daily for 5 days. Results Following single doses, the mean duloxetine C max and AUC were approximately 20% greater in Japanese. This difference could be explained by the 15% lower average body weight in Japanese. Similar results were observed following multiple dosing. Conclusion Duloxetine pharmacokinetics are not meaningfully different between Japanese and Caucasians.