Effects of spasmolytics on K+-induced contraction of rat intestine in vivo

Eight spasmolytic drugs commonly used in the treatment of the irritable bowel syndrome were compared to verapamil with respect to their effects (all drugs injected i.v.) on the contraction of duodenum, ileum and colon induced by high K+ topical application in the anaesthetized rat. Verapamil greater than rociverine greater than papaverine greater than mebeverine greater than dicyclomine antagonized dose-dependently the contraction of duodenum and colon, the activity on duodenum being from 2 (rociverine) to 10 (verapamil) fold higher. Verapamil and rociverine, but not the other drugs mentioned above, were also active on ileum. N-Butylscopolammonium bromide, phloroglucinol and trimebutine were inactive against the contraction of the three intestinal tracts and prifinium bromide was inactive on duodenum and ileum, while it had remarkable activity on colon, unrelated to its antimuscarinic activity. The results are discussed briefly with reference to the pharmacological therapy of the irritable bowel syndrome.