Naloxone and morphine inhibit gastric emptying of solids

Gastric emptying studies were performed on six healthy volunteers using a radioisotope test meal. Each subject was studied three times (control, morphine 7.5 mg, naloxone 2 mg). Both intravenous morphine and intravenous naloxone significantly delayed gastric emptying when compared with the control study. These results suggest that opiate receptors, opiate neurones, and enkephalin may regulate gastric motility and that under certain circumstances naloxone may act as an opiate agonist.