Antimalarial activities of hydroxypiperaquine and its phosphate against Plasmodium berghei and Plasmodium cynomolgi

Hydroxypiperaquine (HPQ) and its phosphate (HPQP) were tested for their suppressive actovities against normal and chloroquine-resistant strains of P.berghei in mice. Drugs were given intragastrically once daily for 3 consecutive days, beginning on the next day after blood inoculation. Both HPQ and HPQP possessed high suppressive activity against the 2 strains, their ED50 being lower than that of chloroquine (CQP). The cross resistance between HPQP and CQP were very slight. The suppressive effects of HPQP and CQP under various regimens were tested on rhesus monkeys infected with P.cynomolgi. No significeant difference was found between HPQP and CQP in the reduction rate of parasite and the parasite clearance time, but the recrudescence was more frequent in the monkeys treated with HPQP than those treated with CQP. The infection was cured with HPQP when the regimen was prolonged.