Recrudescence of P. falciparum in a traveller treated with artemether-lumefantrine (Riamet®, Novartis). The P. falciparum parasitaemia (% infected erythrocytes as filled circles) decreased promptly after artemether-lumefantrine treatment was initiated (day 0) and symptoms reappeared on day 21. The second episode was treated successfully with mefloquine. Plasma concentrations of artemether, dihydroartemisinin, lumefantrine and desbutyl lumefantrine were assessed on day 6 and day 25. Lumefantrine concentrations (open triangles) are shown in the graph whereas the other results are stated in the text.