Gastrointestinal Effects of Metoclopramide in Man. In Vitro Experiments with Human Smooth Muscle Preparations

Abstract

Metoclopramide (N-(diethylaminoethyl)-2-methoxy-4-amino-5-chlorobenzamide) has been investigated with human gastrointestinal smooth-muscle preparations in vitro. Small-intestinal and colonic circular muscle was contracted by metoclopramide. This effect was antagonized by atropine. Gastric and colonic longitudinal muscle was sensitized by metoclopramide to acetylcholine. Atropine acted here as a partial antagonist of metoclopramide.

The interference of acetylcholine and metoclopramide is of a hitherto undescribed pharmacological type. The effects of metoclopramide in vivo—where its action is predominantly on the stomach and pylorus—are not fully explained by these in vitro experiments in which the effect was found to be most pronounced on the colon.