Multiple dose pharmacokinetics of artemether and dihydroartemisinin were investigated in chinese patients treated for malaria. They received over 2 days either 4x80 mg artemether orally (n=48) or 4x80-480 mg co-artemether (n=40), a combination of artemether and lumefantrine (benflumetol). Lag time=0.48 h (mean), C(max) after first dose=157 ng/ml, t(max)=1.73 h and elimination half-life=1.16 h. The lag and absorption times were 0.5 h longer for co-artemether compared with artemether. Dihydroartemisinin paralleled artemether pharmacokinetics. Artemether C(max) after the last dose was one-third of the C(max) after the first dose while, inversely, dihydroartemisinin C(max) increased over time. We suggest that auto-induction of gut mucosa enzymes and/or liver enzymes causes a time-dependent increase in first-pass metabolisation of artemether. Copyright (C) 1999 Elsevier Science B.V.