Effect of clonidine on gastric emptying of liquids

We have investigated the effects of clonidine on gastric emptying ofliquids in 30 patients. In a double-blind, randomized design, clonidine 150micrograms, 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). Venousblood samples were obtained every 15 min for 90 min thereafter. Plasmaparacetamol concentrations were measured using high- pressure liquidchromatography and the area under the concentration- time curve wascalculated. The degree of sedation and complications were recorded. Thearea under the curve for 0-60 min was significantly smaller in the morphinegroup than in the saline group (P = 0.002; 95% confidence interval (CI) fordifference -1237 to -502 micrograms min ml- 1), whereas it was greater inthe clonidine group compared with the saline group, although this was notsignificant (95% CI for difference - 423 to 1264 micrograms min ml-1).Arterial pressure was significantly lower in the clonidine group comparedwith the saline group. Both clonidine and morphine appeared to cause mildsedation. We conclude that clonidine 150 micrograms i.m. does not delaygastric emptying of liquids in a similar manner to morphine.