Pharmacokinetics and electrocardiographic pharmacodynamics of artemether-lumefantrine (Riamet®) with concomitant administration of ketoconazole in healthy subjects

Aims To evaluate whether the potent CYP3A4 inhibitor ketoconazole has any influence on the pharmacokinetic and electrocardiographic parameters of the anti-malarial co-artemether (artemether-lumefantrine) in healthy subjects. Methods Sixteen subjects were randomized in an open-label, two period crossover design study. Subjects received a single dose of co-artemether (day 1) either alone or in combination with multiple oral doses of ketoconazole (400 mg on day 1 followed by 200 mg o.d. for 4 additional days). Serial blood samples were taken and assayed for artemether and its main active metabolite dihydroartemisinin (DHA), and lumefantrine. Results The pharmacokinetics of artemether, its metabolite DHA, and lumefantrine were influenced by the presence of ketoconazole. AUC(0,infinity) was increased from 320 to 740 ng ml(-1) h (ratio 2.4, 90% CI 2.00, 2.86) for artemether, from 331 to 501 ng ml(-1) h (ratio 1.7, 90% CI 1.40, 1.98) for DHA, and from 207 to 333 mug ml(-1) h (ratio 1.7, 90% CI 1.23, 2.21) for lumefantrine in the presence of ketoconazole. C-max also increased in similar proportions for the three compounds (ratio 2.2 (90% CI 1.78, 2.83), 1.4 (90% CI 1.12, 1.74), and 1.3 (90% CI 0.96, 1.64), respectively). The terminal elimination half-life was increased for artemether (2.5 vs 1.9 h, 90% CI 1.12, 1.72) and DHA (3.1 vs 2.1 h, 90% CI 0.02, 3.36), but remained unchanged for lumefantrine (88 vs 95 h, 90% CI 0.81, 1.04). These increases in exposure to the antimalarial combination were much smaller than observed with food intake (up to 16 fold), and were not associated with increased side-effects or changes in electrocardiographic parameters. The study medications were well tolerated. Conclusions The concurrent administration of ketoconazole with co-artemether led to modest increases in artemether, DHA, and lumefantrine exposure in healthy subjects. Dose adjustment of co-artemether is probably unnecessary in falciparum malaria patients when administered in association with ketoconazole or other potent CYP3A4 inhibitors.