Prevention of Increasing Rates of Treatment Failure by Combining Sulfadoxine-Pyrimethamine with Artesunate or Amodiaquine for the Sequential Treatment of Malaria

Combination antimalarial therapy may delay the spread of drug resistance, but clinical data supporting this notion are limited. For 1 year, we studied Ugandan children who were treated for uncomplicated malaria with sulfadoxine-pyrimethamine (SP), SP + amodiaquine (AQ), or SP + artesunate (AS). We compared treatment responses and the prevalence of resistance-conferring mutations of new infections with those of recrudescent infections due to parasites that survived prior treatment. Recrudescent infections were associated with the selection of SP resistance–conferring mutations in all treatment groups, but responses to repeat therapy differed. Compared with initial treatments, treatment of recrudescent infections was associated with a higher rate of treatment failure (hazard ratio [HR], 2.44; P=.01), for the SP group, but with a lower rate of treatment failure (HR, 0.40; P=.08), for the SP + AS group. Treatment failure in the SP + AQ group was uncommon, limiting the analysis of recrudescent parasites. Our results suggest that the use of combination antimalarial therapy in Africa may slow the spread of drug-resistant malaria and prolong the therapeutic life span of available treatment regimens