Effect of clonidine on gastric emptying of liquids

We have investigated the effects of clonidine on gastric emptying of liquids in 30 patients. In a double-blind, randomized design, clonidine 150 mu g, morphine 10 mg or saline in 1 ml was given i.m. One hour later, the patient drank a paracetamol solution (1.5 g in 50 ml water). Venous blood samples were obtained every 15 min for 90 min thereafter. Plasma paracetamol concentrations were measured using high-pressure liquid chromatography and the area under the concentration-time curve was calculated. The degree of sedation and complications were recorded. The area under the curve for 0-60 min was significantly smaller in the morphine group than in the saline group (P = 0.002; 95% confidence interval (Cl) for difference -1237 to -502 mu g min ml(-1)), whereas it was greater in the clonidine group compared with the saline group, although this was not significant (95% Cl for difference -423 to 1264 mu g min ml(-1)). Arterial pressure was significantly lower in the clonidine group compared with the saline group. Both clonidine and morphine appeared to cause mild sedation. We conclude that clonidine 150 mu g i.m. does not delay gastric emptying of liquids in a similar manner to morphine.