Antibodies reacting with chloroquine in human sera.

Presence of antibodies in human sera reacting with chloroquine (CQ) was demonstrated from a malaria endemic belt. The study groups consisted of 53 healthy volunteers, receiving regular chloroquine prophylaxis [2 tablets of CQ (150 mg)/wk, single dose], 105 individuals with a history of frequent CQ intake for any febrile attack and 95 individuals from a non-endemic area who had neither a history of malaria nor of previous consumption of CQ. Sixty six per cent individuals taking regular prophylactic chloroquine and about ten per cent of those with a history of taking frequent chloroquine due to febrile illness in the malaria endemic area showed antibodies reacting to chloroquine. However, antichloroquine antibodies were either insignificant or nondetectable in serum samples collected from persons without any history of chloroquine intake. The results indicate a possible interaction of CQ in vivo.