Higher-Dose Primaquine to Prevent Relapse of Plasmodium vivax Malaria

Background:In most of the Americas,the recommended treatment to prevent relapse of Plasmodium vivax malaria is primaquine at a total dose of 3.5 mg per kilogram of body weight,despite evidence of only moderate efficacy.Methods:In this trial conducted in Brazil,we evaluated three primaquine regimens to prevent relapse of P.vivax malaria in children at least 5 years of age and in adults with microscopy-confirmed P.vivax monoinfection.All the patients received directly observed chloroquine for 3 days(total dose,25 mg per kilogram).Group 1 received a total primaquine dose of 3.5 mg per kilogram(0.5 mg per kilogram per day)over 7 days with unobserved administration;group 2 received the same regimen as group 1 but with observed administration;and group 3 received a total primaquine dose of 7.0 mg per kilogram over 14 days(also 0.5 mg per kilogram per day)with observed administration.We monitored the patients for 168 days.