Long-term efficacy of primaquine in the treatment of vivax malaria in nonimmune travelers.

Fifty-six travelers presenting with vivax malaria to a German travel clinic were followed regularly for at least 18 months between 1984 and 1992 to investigate the long-term efficacy of primaquine in nonimmune patients without reinfection. All received a standard treatment of 15 mg of primaquine a day for 14 days following an initial total dose of 1,500 mg of chloroquine (base) given over a 48-hr period. None of the patients visited countries endemic for malaria during the period of observation. In seven patients (12.5%), relapses were confirmed microscopically by detection of malaria parasites in blood films. The frequency of relapses varied between one and four per patient and these occurred between 60 and 252 days after treatment. Four of these seven patients had acquired infection in Papua New Guinea or eastern Indonesia, while only five (10.2%) of the remaining 49 patients without relapses had traveled to these areas prior to referral (P < 0.01).