Influence of route of administration on the pharmaco-kinetics of chloroquine and desethylchloroquine.

The pharmacokinetics of chloroquine following a single oral dose of 600 mg or an intramuscular injection of 200 mg of the drug was studied in seven healthy adult Africans. Each subject received chloroquine by both routes, with an interval of at least 4 months between them. Intramuscular injection led to rapid absorption of chloroquine, which attained a maximum concentration in plasma after 15 minutes and occasionally reached toxic levels; plasma levels fell below therapeutically useful concentrations 2-4 hours after administration. In contrast, oral administration of chloroquine produced therapeutic levels of the drug within 30 minutes and were maintained for up to 3 days. Peak levels in plasma were not high enough to produce adverse reactions. The terminal half-life and renal clearance time of chloroquine were not influenced by route of administration.