The effects of nifedipine and verapamil on high K+ induced contractions of the rat intestinal tract in vivo.

The effects of intravenous nifedipine and verapamil against the contraction produced by topical application of 54 mM K+ on the outer surface of rat duodenum, jejunum, ileum, caecum, colon and rectum have been investigated. Both drugs exhibited a descending gradient of relaxant activity with the exception of the rectum, verapamil being 1/3-1/4 as potent as nifedipine in all the test systems studied. Since these drugs at effective spasmolytic doses significantly affect heart rate and systemic blood pressure, their use as smooth muscle relaxants in intestinal disturbances would present several drawbacks.