Some pharmacodynamic effects of the nematocides: methyridine, tetramisole and pyrantel

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Abstract
Methyridine, tetramisole and pyrantel affect several cholinergic mechanisms. In the rabbit, methyridine and tetramisole cause hypotension which is partially antagonized by atropine. In the cat, tetramisole causes an increase in blood pressure and causes prolonged contraction of the nictitating membrane. The evidence indicates that tetramisole may release catecholamines from the adrenal medulla. Pyrantel contracts the nictitating membrane; an effect which is abolished completely by hexamethonium. The three anthelmintics block neuromuscular transmission in a way which is characteristic of non-competitive depolarizing agents. They also inhibit cholin-esterases. These pharmacological data correlate closely with the reported clinical signs of the toxicity of these agents.