Activity of azithromycin (CP-62,993) and erythromycin against chloroquine-sensitive and chloroquine-resistant strains of Plasmodium falciparum in vitro.

Several antibiotics, including the macrolide erythromycin and the azalides azithromycin (CP-62,993) and CP-63,956, that inhibit protein synthesis on 70S ribosomes demonstrated antimalarial effects in vitro against two strains of Plasmodium falciparum, one sensitive to chloroquine and the other resistant. In 48-hr incubations, erythromycin was 10-fold less potent than the azalides against the chloroquine-resistant strain. Erythromycin and the azalides were essentially equipotent against the chloroquine-sensitive strain. An additive effect occurred with the azalides in combination with chloroquine against both strains, but this was not seen with erythromycin.