Toxicity and pharmacological properties of surface-active alkyltrimethylammonium bromides in the rat

Acute intravenous toxicity and pharmacological properties of surface-active alkyltrimethylammonium bromides (C10-C20) were studied in female rats. The acute toxicity of the surfactants decreased with an increasing length of the alkyl chain length of 16 carbon atoms. Death appeared to be due to respiratory failure. The twitch responses of sciatic nerve-gastrocnemius muscle preparations were reversibly depressed at direct and indirect stimulation following intravenous injections of sublethal doses of C10-C14. Doses blocking the twitch responses of indirectly stimulated gastrocnemius corresponded to about half the LD50, and at these doses C10-C14 caused a transient decrease in respiratory rate. The C16 homologue caused respiratory arrest without affecting the twitch responses of gastrocnemius at relative low intravenous doses. Sublethal intravenous doses of C12-C20 caused, apparently due to vasodilatation, a transient fall in arterial blood pressure. The depressor response increased and the twitch response decreased with an increase in the length of the alkyl chain up to a chain length of 16 carbon atoms. Both the depression of skeletal muscle contraction and the vasodilatation is suggested to originate from a non-specific effect of the surfactants on muscle cells.