Background and Objectives The randomized, double-blind, dose-response study was designed to evaluate the effects of the addition of clonidine to epidural morphine on postoperative analgesia and side effects in patients undergoing cesarean delivery.

Methods Sixty patients, undergoing cesarean delivery under epidural anesthesia, were randomly divided in three equal groups to receive, at the end of surgery, an epidural analgesic mixture consisting of 10 mL solution containing 2 mg of morphine diluted with 0.125% bupivacaine plus 1:800,000 epinephrine and 0, 75, or 150 μg of clonidine. Duration of analgesia was assessed as the pain-free interval between the end of surgery and patient’s first analgesic request. The analgesic mixture was repeated, on patient’s request, to 36 hours after the operation. Arterial blood pressure, heart rate, respiratory rate, and side effects were noted. The total amount of morphine and clonidine delivered was also noted.

Results The addition of clonidine (0, 75, or 150 μg) to morphine significantly increased the duration of postoperative analgesia (P < .0001) (6.27 versus 13.25 and versus 21.55 hours) and reduced the mean total dose of morphine (9.40 mg versus 5.0 mg versus 3.60 mg) (P < .0001). No significant differences in side effects were noted.

Conclusions A low dose of clonidine such as 75 μg doubled the duration of analgesia produced by 2 mg of morphine and a dose of 150 μg further increased the duration of postoperative complete analgesia without increasing the incidence of side effects. The morphine requirements during the postoperative period (36 hours) was greatly reduced by the addition of clonidine to the analgesic epidural mixture.