Abstract
A 63-year-old man ingested malathion and became unconscious, and developed respiratory distress and hypotension. Electrocardiogram showed atrioventricular block and idioventricular rhythm of 10 to 35 per minute which disappeared following administration of atropine. These electrocardiographic changes in organophosphate poisoning have been observed in experimental animals but rarely noted in man. Malathion, though one of the least toxic insecticides, has caused many incidents of poisoning in man. Compared with poisoning with other organophosphate insecticides, malathion poisoning is characterized by severe manifestations and a prolonged course probably due to continuous absorption of ingested malathion. Atropine has been effective, but the effect of pralidoxime has often been unsatisfactory. The incidence of malathion poisoning is expected to increase since malathion is replacing halogenated hydrocarbon insecticides such as DDT.