A COMPARISON OF THE EFFECTS OF TRAMADOL AND MORPHINE ON GASTRIC-EMPTYING IN MAN

In a previous study using an electrical bioimpedance technique and the paracetamol absorption test, we demonstrated that 0.09 mg.kg(-1) of m orphine delayed gastric emptying in healthy human volunteers. The aim of this study was to investigate whether analgesic doses of tramadol w ould cause a delay in gastric emptying similar to conventional opioids . Using the same volunteers and techniques as in our previous study, p lacebo or tramadol (1 mg.kg(-1)) was given in a randomised, double-bli nded, cross-over placebo-controlled study. Gastric emptying was measur ed concurrently by a noninvasive epigastric bioimpedance technique and by the paracetamol absorption test. After the ingestion of 500 ml of deionised water plus paracetamol 1.5 g, the mean (SEM) time taken for gastric volume to decrease to 50% (t(0.5)) was recorded. No difference in gastric emptying rates (t(0.5)) between placebo, 7.7 (1 min), and tramadol, 9.5 (2 min), was noted. In our previous study, morphine prol onged t(0.5) to 21 (3) min (p<0.03). The maximum concentration and are a under the curve of serum paracetamol concentrations following morphi ne were significantly different from placebo (p <0.05) and tramadol (p <0.05). We conclude that tramadol at a dose of 1 mg.kg(-1) does not d elay gastric emptying in humans.