Evidence of Artemisinin-Resistant Malaria in Western Cambodia

To the Editor: Although artemisinins are potent and rapidly acting antimalarial drugs, their widespread use for treating patients with Plasmodium falciparum malaria raises the question of emerging drug resistance. 1,2Artemisinin monotherapy should not be used in areas where malaria is endemic; it requires an extended administration period and may lead to treatment failure, most frequently because of problems with compliance.Recent reports of high failure rates associated with artemisinin-based combination therapy, as well as in vitro drug-susceptibility data, suggest the possibility of clinical artemisinin resistance along the Thai-Cambodian border. 3,4 We studied the potential emergence of artemisinin resistance using in vivo, in vitro, molecular, and pharmacokinetic methods specifically designed to address the question of potential artemisinin resistance.We randomly assigned, in a ratio of 2:1, 94 adults from Battambang Province presenting with uncomplicated P. falciparum malaria (100 to 100,000 parasites per microliter) to receive either highdose artesunate therapy (4 mg per kilogram of body weight per day, orally, for 7 days) (60 pa-