[A study of relapsed cases of vivax malaria after the standard primaquine therapy]

Vivax malaria is the most frequent among imported malaria in Japan, comprising about 60% of the total cases. Usually, after the acute phase therapy, e.g. with chloroquine, patients with vivax malaria are treated with the standard course of primaquine, i.e. 15 mg base/day for 14 days, as curative therapy. Recently, however, cases of relapse of vivax malaria after this standard primaquine therapy were reported from various countries and were also encountered in Japan. This report showed that the relapse after the standard primaquine therapy occurred most frequently in the cases acquired in Papua New Guinea, followed by Indonesia and Thailand. In contrast, the relapse rate of the cases acquired in India was low. Most of the relapsed cases were successfully treated with either of the regimens 1) 30 mg/ day for 7 days, 2) 2 courses of the standard primaquine therapy given 1 month apart or 3) 15 mg/ day for 21 days, without noticeable side effects. It is imperative to establish the most appropriate regimen with primaquine for the curative treatment of vivax malaria contracted in the areas mentioned above.