Artemisinin-based combination therapies and their introduction in Japan.

Artemisinin was discovered in 1971 from a herb, Artemisia annua, which had been used for more than 2,000 years in China against intermittent fever. Now, the artemisinin and its derivatives have become essential components of artemisinin-based combination therapies (ACTs). The ACTs are the recommended first-line treatments of malaria because they are effective against all four human malarias, produce rapid parasite/fever clearance, and show fewer adverse effects. Some ACTs are particularly important in cases of severe and complicated falciparum malaria, including cerebral malaria. However, neither the artemisinin and its derivatives nor any ACTs are registered in Japan. Indeed, the only licensed drugs for the treatment of malaria in Japan are quinine, mefloquine, and sulfadoxine/pyrimethamine. Although indigenous malaria has been eradicated in Japan since 1959, 60-100 imported malaria cases have been reported annually for the past decade. Some of the patients were, in fact, dying of the severe complications. Thus, the introduction of the ACTs and their application to imported malaria patients in Japan are urgently needed. A few clinical studies using the ACTs have been reported in Japan. The first application of an ACT, intramuscular artemether plus mefloquine, was reported in 1988 to be very effective against cerebral malaria with coma. Five cases with intravenous artesunate plus mefloquine were reported through 2001-2007, for severe or drug-resistant falciparum cases, resulting in successful treatment with some side effects such as hemolytic anemia or postmalaria neurological syndrome. Currently, a fixed-dose ACT, artemether-lumefantrine, is prescribed successfully for uncomplicated falciparum cases, with a limited number of recrudescences.