Management of vivax malaria with low sensitivity to primaquine.

Over the last two decades there have been numerous reports of primaquine failure in the treatment of Plasmodium vivax extending from the Western Pacific to South East Asia, India and Central and South America. In sub-Saharan Africa only five returning travellers have been reported with relapse of vivax malaria after primaquine and the absence of corroborating reports has prompted investigators to interpret their observations in terms of non-compliance. In 1997, 26 US military personnel serving in Somalia experienced attacks of P. vivax after terminal prophylaxis with primaquine. We have observed repeated relapses of P. vivax in two travellers, one to the Philippines and the other to Kenya despite both conventional and prolonged primaquine therapy. Here we report this clinical problem and propose a response to the emerging failure of the standard regimen of primaquine by considering the existing efficacy and toxicity data.