Antispasmodic activity of tiropramide.

Tiropramide hydrochloride and some of its metabolites were studied in vivo for their antispasmodic activities on the following models: gastric emptying in the mouse retarded by cholecystokinin octapeptide (CCK-8) or morphine, progression of intestinal contents in the mouse, spontaneous motility of the colon in the anesthetized rabbit, diarrhea induced by castor oil in the rat, spasm of the sphincter of Oddi provoked by morphine in the guinea pig, contractions of the urinary bladder in the anesthetized rat. On these models tiropramide had an antispasmodic activity at doses of 4-40 mg/kg i.p. or i.v. and of 50-90 mg/kg orally. The potency was greater on "pathological" contractions or spasms and smaller on "physiological" movements. Tiropramide may therefore be regarded as a "eukinetic" antispasmodic agent. Tiropramide in general was more potent than reference agents such as papaverine or flavoxate and was active also after oral administration. The metabolites of tiropramide, i.e. CR 1034, CR 1098 and CR 1166 showed similar pharmacodynamic effects, but their potency was smaller than that of tiropramide. Large doses of tiropramide have depressive actions on the cardiovascular system, which can be seen especially if tiropramide is administered i.v. and are less pronounced after oral administration. The circulatory effects are therefore probably the limiting factor for increasing the parenteral doses of tiropramide in human therapy. Tiropramide was found less toxic than papaverine (LD50). The metabolites of tiropramide were less toxic than the parent compound. The toxicity of the chiralic forms of tiropramide does not differ significantly from that of the racemic substance.