The effect of artesunate combined with standard antimalarials against chloroquine-sensitive and chloroquine-resistant strains of Plasmodium faiciparum in vitro

The interactions of artesunate with chloroquine, mefloquine, quinine, doxyc ycline and pyrimethamine were tested in vitro against chloroquine-sensitive (D10) and chloroquine-resistant (RSA11) strains of Plasmodium falciparum. Mefloquine and quinine both showed synergism of artesunate activity against each of the strains, whilst doxycycline showed an additive interaction. Py rimethamine combinations were antagonistic, and the combination of artesuna te with chloroquine was antagonistic against RSA11, and additive against D1 0. Although weak antagonism in vitro might not indicate any clinical signif icance, synergism with artesunate may increase the clinical usefulness of e ither drug, and could potentially be of value in delaying the emergence of resistance.