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The effect of metoclopramide on gastroduodenal and gallbladder contractions in the dog has been studied. It increased the strength of antral contractions and produced stronger, more regular, duodenal contractions; these tended to follow those of the antrum, providing evidence of the dominance of antral contraction rate over that of the duodenum. In the absence of spontaneous antral activity, there was little effect on either stomach or duodenum and this was not related to the type of anaesthetic used. There was no effect on the gallbladder when it was relaxed or submaximally stimulated with cholecystokinin/pancreozymin. Further evidence has been obtained that metoclopramide acts by enhancing the local effect of acetylcholine on gastric smooth muscle. These findings provide a satisfactory mechanism for most of the observed clinical effects.

In 30 patients with gastrooesophageal reflux, intravenous metoclopramide (Maxolon) has been shown to increase the gastrooesophageal sphincter pressure. The rise is dose-related until a maximum pressure, proportional to the resting sphincter tone, is reached. The effect is reversed by atropine. Peristaltic waves are increased in pressure by metoclopramide.In 18 patients with gastrooesophageal reflux intravenous metoclopramide diminished the frequency of reflux episodes and increased the rate at which the oesophagus emptied itself of an acid load.