Short Report: A consideration of primaquine dose adjustment for radical cure of Plasmodium vivax malaria

Relapse of Plasmodium vivax malaria following standard primaquine dosing ha s been reported from many areas, and more recently from sub-Saharan Africa. In this report we describe eight episodes tin five patients) of treatment failure in non-immune Israeli travelers returning from Ethiopia. Retrospect ive calculation of the primaquine dose per kilogram of body weight for 23 t reatment courses showed a lower total dose per kilogram in heavier patients . The mean calculated dose (95% CI) in the eight failed treatments was 2.5 +/- 0.3 mg/kg compared with 4.4 +/- 0.5 mg/kg in the 15 successful treatmen t courses. Weight-adjusted dosing regimens may prevent inadvertent subthera peutic drug failure, and thus apparent primaquine failure. In these cases, no relapses were observed in those who received > 3.5 mg/kg. Consideration should be given to adjusting the dose of primaquine according to body weigh t. For those infected by strains from Ethiopia a dose > 3.5 mg/kg is prefer able.