Does intravenous ondansetron affect gastric emptying of a solid meal, gastric electrical activity or blood hormone levels in healthy volunteers?

BACKGROUND: In previous studies, tropisetron has been shown to accelerate gastric emptying of a solid meal. However, it is uncertain whether other specific 5-hydroxytryptamine-3 receptor antagonists, such as ondansetron, also have a gastroprokinetic effect in humans. AIM: To evaluate the effect of ondansetron on gastric half-emptying time (T1/2) of a solid meal, gastric myoelectrical activity and hormone levels in 14 healthy volunteers. METHODS: In a placebo-controlled, randomized, crossover study, we investigated the effects of ondansetron (8 mg intravenously) on the gastric emptying of solids (by scintigraphy), gastric myoelectrical activity (by electrogastrography) and the post-prandial release of cholecystokinin, gastrin, human pancreatic polypeptide, gastric inhibitory polypeptide, vasoactive intestinal polypeptide, motilin, substance P and galanin. RESULTS: The average T1/2 values were 86 min and 85.5 min without lag time (P=0.082) and 92 min and 93 min with lag time (P=0.158) for the placebo and ondansetron treatments, respectively. The average T1/2 of female volunteers was significantly longer than that of male volunteers. The dominant gastric electrical frequency and hormone plasma concentrations were not altered by ondansetron. CONCLUSIONS: Ondansetron did not affect the gastric emptying of solids, the dominant gastric electrical frequency or the plasma concentrations of the analysed gastrointestinal peptides.

Influence of naloxone on gastric emptying of solid meals, myoelectrical gastric activity and blood hormone levels in young healthy volunteers.

There is considerable evidence that opioid mechanisms are involved in the mediation of pyloric motor responses that in turn regulate gastric emptying. The purpose of this randomized, placebo-controlled crossover study was to investigate the effect of naloxone on gastric emptying of a solid meal, gastric myoelectrical activity and the postprandial release of gastrointestinal peptides and neuropeptides in 20 healthy volunteers. Naloxone was administered as an intravenous bolus, followed by continuous infusion according to an intravenous dosing nomogram. Gastric emptying time was evaluated by scintigraphy and gastric myoelectrical activity was evaluated by cutaneous electrogastrography. Naloxone did not significantly alter gastric half-emptying time and postprandial dominant gastric electrical frequency compared with placebo. It also did not significantly change the plasma levels of several peptide hormones with the exception of neuropeptide Y, which was significantly increased (P = 0.001). In conclusion, in doses that influence human intestinal motility, naloxone had no effect on gastric motility and release of several peptide hormones in healthy male volunteers. The importance of the isolated increased neuropeptide Y plasma level needs further investigation.