Evidence for increased metabolism of chloroquine during the early third trimester of human pregnancy.

OBJECTIVE: To examine the possibility of a different extent of chloroquine (CQ) metabolism in human pregnancy by determining blood level profiles of the drug and its major metabolite, desethylchloroquine (CQM). METHODS: Five women in the early third trimester of pregnancy and five non-pregnant women received each a single 600 mg oral dose of CQ and blood samples were collected at pre-determined intervals following drug administration. Plasma concentrations of CQ and CQM were analysed by an established HPLC method. RESULTS: The C(max) and AUC(0-48 h) of CQM were significantly higher in the pregnant than the non-pregnant group (P = 0.009). The ratio AUC(CQ)/AUC(CQM) ranged from 0.09 to 0.35 among pregnant women, and from 1.70 to 4.81 among non-pregnant women. CONCLUSION: Results from this preliminary study indicate an occurrence of induction of metabolism of CQ in the early third trimester of pregnancy. In view of toxicological importance of CQ metabolites, it is suggested that caution should be exercised in evaluation of higher dosage regimen of CQ in pregnant women.