THE PRECISE MECHANISM OF ACTION OF QUININE IN MALARIA HAS NOT BEEN DETERMINED BUT MAY BE BASED ON ITS ABILITY TO CONCENTRATE IN PARASITIC ACID VESICLES, CAUSING AN ELEVATION OF PH IN INTRACELLULAR ORGANELLES. THIS IS THOUGHT TO DISRUPT THE INTRACELLULAR TRANSPORT OF MEMBRANE COMPONENTS AND MACROMOLECULES, AND PHOSPHOLIPASE ACTIVITY. QUININE HAS A SCHIZONTICIDAL ACTION. ITS ABILITY TO CONCENTRATE IN PARASITIZED ERYTHROCYTES MAY ACCOUNT FOR ITS SELECTIVE TOXICITY AGAINST THE ERYTHROCYTIC STAGES OF THE FOUR MALARIAL PARASITES, INCLUDING PLASMODIUM FALCIPARUM STRAINS RESISTANT TO CHLOROQUINE. THE DRUG IS ALSO GAMETOCIDAL AGAINST PLASMODIUM VIVAX AND PLASMODIUM MALARIAE