An eserine-like action of chloroquine

Cholinomimetic teratogens. VI. The interaction of cholinomimetic teratogens with the antimalarial drugs chloroquine and chlorguanide

A typical syndrome of short and crooked neck together with muscular hytoplasia of the legs occurs with low incidence in chicken embryos following injection into the egg at 24 hours of incubation of the antimalarial drug chloroquine; but treatment at later stages does not have similar effects. When, however chloroquine was used in addition to carbachol or neostigmine at 96 hours of incubation the malformations caused by the two cholinomimetic compounds, i.e., carbachol and neostigmine, occurred with greatly increased frequency and tended also to be exaggerated in expression. Chlorguanide, another antimalarial drug, when used as additive, reduced the teratogenic effects of such compounds as decamethonium and neostigmine. It appears that the neuromuscular pathways to teratogenicity are for carbachol and neostigmine and for chloroquine clearly related, if at different levels of expressivity.

Dual action of chloroquine on frog's skeletal muscle contraction

Studies on the effect of chloroquine on frog's rectus abdominis muscle have been performed. Relatively low concentrations of chloroquine, 5 times 10-5 and 2 times 10-4 g/ml inhibited cholinesterase activity and potentiated acetylcholine (ACh)-induced contractions but antagonized carbachol and caffeine contractions, as well as ACh-induced contractions of eserinized muscle. High concentrations (5 times 10-4 and 2 times 10-3 g/ml) non-competitively antagonized contractions to ACh, carbachol, caffeine and potassium. It was suggested that the blocking action of chloroquine was due to its local anaesthetic property and interference with intracellular calcium movements.