Tolpronine possesses significant analgesic properties in mice by the subcutaneous, oral and intraperitoneal routes. The compound is most active subcutaneously, having approximately 20 times the activity of metamizolum on a weight for weight basis. In addition to its analgesic activity, tolpronine also possesses local anesthetic properties, being approximately 1.5 times as active as procaine hydrochloride in the guinea pig intracutaneous wheal test. It is, however, at least twice as toxic by the subcutaneous route. It has an anti-acetylcholine action on the isolated guinea-pig ileum. Excessively large amounts constipate normal mice; a weak spasmolytic effect is seen in the isolated guinea-pig ileum and rabbit duodenum. The jejunum of the anesthetized cat shows a spasmogenic effect. Chronic administration to rats and rabbits caused a reduction in the growth rate of rats.