• Nathália N Chamma-Siqueira, Suiane C Negreiros, Sarah-Blythe Ballard, Sâmela Farias, Sandro P Silva, Stella M Chenet, Eduardo J M Santos, Luann W Pereira de Sena, Flávia Póvoa da Costa, Amanda G N Cardoso-Mello, Paola B Marchesini, Cássio R L Peterka, Giselle M R Viana, and Alexandre Macedo de Oliveira.
• From Instituto Evandro Chagas, Ministério da Saúde do Brasil, Ananindeua (N.N.C-.S., S.P.S., G.M.R.V.), Programa de Pós-Graduação em Biologia de Agentes Infecciosos e Parasitários (N.N.C.-S., E.J.M.S., F.P.C., G.M.R.V.) and Laboratório de Genética de Doenças Complexas (E.J.M.S., F.P.C.), Instituto de Ciências Biológicas, and Laboratório de Farmacocinética de Drogas Antimaláricas, Instituto de Ciências da Saúde (L.W.P.S., A.G.N.C.-M.), Universidade Federal do Pará, Belém, Secretaria de Saúde do Estado do Acre, Cruzeiro do Sul (S.C.N., S.F.), and Grupo Técnico da Malária, Coordenação-Geral de Vigilância de Zoonoses e Doenças de Transmissão Vetorial, Departamento de Imunização e Doenças Transmissíveis, Secretaria de Vigilância em Saúde, Ministério da Saúde (P.B.M.), and Diretoria de Vigilância Epidemiológica, Subsecretaria de Vigilância em Saúde, Secretaria Estadual de Saúde do Distrito Federal (C.R.L.P.), Brasília - all in Brazil; Epidemic Intelligence Service, Center for Surveillance, Epidemiology, and Laboratory Services (S.-B.B.), and the Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention (S.-B.B., A.M.O.) - both in Atlanta; and Instituto de Investigaciones en Ciencias Biomedicas, Universidad Ricardo Palma, Lima, and Instituto de Enfermedades Tropicales, Universidad Nacional Toribio Rodríguez de Mendoza de Amazonas, Chachapoyas (S.M.C.) - both in Peru.
• N. Engl. J. Med. 2022 Mar 31; 386 (13): 124412531244-1253.

BackgroundIn 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.MethodsIn 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.ResultsWe enrolled 63 patients in group 1, 96 in group 2, and 95 in group 3. The median age of the patients was 22.4 years (range, 5.4 to 79.8). By day 28, three P. vivax recurrences were observed: 2 in group 1 and 1 in group 2. By day 168, a total of 70 recurrences had occurred: 24 in group 1, 34 in group 2, and 12 in group 3. No serious adverse events were noted. On day 168, the percentage of patients without recurrence was 58% (95% confidence interval [CI], 44 to 70) in group 1, 59% (95% CI, 47 to 69) in group 2, and 86% (95% CI, 76 to 92) in group 3. Survival analysis showed a difference in the day 168 recurrence-free percentage of 27 percentage points (97.5% CI, 10 to 44; P<0.001) between group 1 and group 3 and a difference of 27 percentage points (97.5% CI, 12 to 42; P<0.001) between group 2 and group 3.ConclusionsThe administration of primaquine at a total dose of 7.0 mg per kilogram had higher efficacy in preventing relapse of P. vivax malaria than a total dose of 3.5 mg per kilogram through day 168. (Supported by the U.S. Agency for International Development; ClinicalTrials.gov number, NCT03610399.).Copyright © 2022 Massachusetts Medical Society.

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