The chemotherapy of rodent malaria, XXVII. Studies on mefloquine (WR 142,490).

Mefloquine (WR 142,490) is a potent blood schizontocide active against drug-sensitive and drug-resistant lines of Plasmodium berghei. The ED50 and ED90 against the P. berghei N strain in albino mice are 1.5 and 3.8 mg/kg respectively. The highly chloroquine-resistant RC line is less sensitive and mefloquine is not fully effective at the maximum tolerated dose in the '4-day test'. Mefloquine has a similar mode of action to quinine both in vitro and (as demonstrated by the morphological changes it induces in P. berghei) in vivo, but is some 100 times more potent. Unlike quinine and WR 122,455 it appears not to interact with DNA. It has no causal prophylactic effect. Mixtures of mefloquine with pyrimethamine, sulphaphenazole or primaquine have an additive effect.