CHLOROQUINE

synthetic antimalarial drug introduced into medicine in the 1940s. Chloroquine is a member of an important series of chemically related antimalarial agents, the quinoline derivatives. Chloroquine partially displaced quinacrine, a widely used drug, as well as the earlier quinoline derivatives (such as pamaquine). Chloroquine is administered orally as chloroquine phosphate or chloroquine sulfate. It also can be given by intramuscular injection as chloroquine hydrochloride. Chloroquine is effective against susceptible strains of the malarial parasites Plasmodium vivax and P. falciparum, as well as certain parasitic worms and amoebas. Some mild side effects may occur, including headache and abdominal cramps, which are common to antimalarials. Chloroquine has also been used in the treatment of rheumatoid arthritis, but its toxicity when used over a long period limits its usefulness for that purpose.