Assessment of potential selectivity of antispasmodics for the various sections of the gastrointestinal tract of the rat as a guideline for their clinical use.

Two spasmolytic drugs, N-butylscopolammonium bromide and octylonium bromide have been challenged against topical carbachol-induced contracture of gastric antrum, duodenum, jejunum, ileum, caecum, colon and rectum of the rat. Experimental data indicate that N-butylscopolammonium bromide, a competitive anticholinergic agent, is more effective on the upper than on the lower sections of the rat gastrointestinal tract. On the other hand octylonium bromide, which has been reported to have little if any competitive antimuscarinic properties at effective spasmolytic doses, showed a more composite spectrum of activity. Hexamethonium, a nicotinic cholinoceptor antagonist, was about equally effective in inhibiting carbachol-induced contractions of all the GIT sections under study. Data in the literature and our own findings do not support the use of competitive antimuscarinic drugs for the treatment of colonic hypermotility. In fact, at effective spasmolytic doses they are expected to produce a greater inhibition of motility of the upper sections of the GIT than at the colonic level.