Studies on the Chemotherapy of the Human Malarias. X. the Suppressive Antimalarial Effect of Paludrine.

Paludrine, N1-p-chlorphenyl-N5-isopropylbiguanide acetate, was found by British workers to be ;he most active antimalarial of a series of synthetic guanidines and biguanidines (1, 2). It possesses high activity against the erythrocytic asexual parasites of both vivax and falciparum malaria and is practically non-toxic at therapeutic doses (3, 4). Previous study of the compound has included extensive prophylactic, curative and suppressive trials by the Australian Malarial Unit at Cairns in experimental sporozoite and trophozoite induced vivax and falciparum malaria (5) and curative trials in naturally acquired relapsing Southwest Pacific vivax malaria (6). The drug has a prophylactic action in falciparum malaria which is complete in single doses as low as 25 mgm. The prophylactic action in vivax malaria is less definite, although the incubation periods of patients in the Cairns studies were systematically prolonged, and subinoculations from infected patients showed that this was due to an effect upon the initial tissue phase (cf. 7) of the disease. It is also effective in the treatment of clinical attacks of malaria, being curative in falciparum but not in vivax malaria. The response of fever and symptoms in each infection is somewhat less prompt