British Journal of Anaesthesia 1994; 72: 537-540 Addition of oral clonidine to postoperative patient-controlled analgesia with i.v. morphine

Using a randomized, double-blind, placebo-con-trolled design, we have investigated, in 40 patients undergoing major abdominal surgery, the effect of oral clonidine 300 fig, 1 h before and 12 h after surgery on postoperative morphine requirements (evaluated by PCA). During the 24 h of the study, pain scores measured every 6h did not differ significantly. Morphine requirements tended to be reduced in the clonidine group but the difference was not significant. There were no significant dif-ferences also in mean arterial pressure, ventilatory frequency and the incidence of pruritus and nausea. Heart rate was significantly lower until 18 h after surgery and sedation was significantly more pro-nounced in patients receiving clonidine. We cannot recommend routine oral administration of clonidine before surgery to improve postoperative analgesia