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The rationale of this study was to compare high-dose epidural clonidine with a more commonly used agent, such as bupivacaine. This was performed to give a more objective idea of the relative analgesic potency of epidural clonidine.Sixty patients undergoing intestinal surgery during propofol anesthesia were studied. At induction, the patients received epidurally a dose of 10 mg/kg clonidine in 7 ml saline followed by an infusion of 6 mg [middle dot] kg-1 [middle dot] h-1 (7 ml/h) (group 1, n = 20), a dose of 7 ml bupivacaine, 0.5%, followed by 7 ml/h bupivacaine, 0.25% (group 2, n = 20), or a dose of 7 ml bupivacaine, 0.25%, followed by 7 ml/h bupivacaine, 0.125% (group 3, n = 20). Intraoperatively, increases in arterial blood pressure or heart rate not responding to propofol (0.5 mg/kg) were treated with intravenous alfentanil (0.05 mg/kg). Additional doses of propofol were given to maintain an adequate bispectral index. The epidural infusions were maintained for 12 h. In cases of subjective visual analogue pain scores up to 5 cm at rest or up to 8 cm during coughing, the patients were given access to a patient-controlled analgesia device.During anesthesia, patients in group 1 required less propofol than those in groups 2 and 3 (78 [36–142] mg vs. 229 [184–252] mg and 362 [295–458] mg; P < 0.05) and less alfentanil than patients in group 3 (0 [0–0] mg vs. 11 [6–20] mg; P < 0.05). Analgesia lasted 380 min (range, 180–645 min) in group 1 versus 30 min (range, 25–40 min) in group 2 and 22 min (range, 12.5–42 min) in group 3 (P < 0.05). There was no suggestion of a hemodynamic difference among the three groups except for heart rates that were significantly reduced in patients in group 1. Sedation scores were significantly higher in this group during the first 2 h postoperatively.Our results show that high doses of epidural clonidine potentiate general anesthetics and provide more efficient postoperative analgesia than the two bupivacaine dosage regimens investigated.