Patients with sleep apnea often present with cardiac diseases and breathing difficulties, with a high risk of postoperative respiratory depression. We conducted a randomized, double-blind, prospective study in 30 adult patients with obstructive sleep apnea, undergoing elective ear-nose-throat surgery. The patients were randomly assigned to receive placebo or clonidine (2 microg/kg oral) the night before and the next morning 2 h before surgery. Spo2, heart rate, mean arterial blood pressure, snoring, and oronasal airflow were monitored for 36 h. A standard anesthesia was used consisting of propofol and remifentanil. Anesthetic drug consumption, postoperative analgesics, and pain score were recorded. In the clonidine group, mean arterial blood pressures were significantly lower during induction, operation, and emergence from anesthesia. Both propofol dose required for induction (190 +/- 32.2 mg) and anesthesia (6.3 +/- 1.3 mg . kg(-1).h(-1)) during surgery were significantly reduced in the clonidine group compared with the placebo group (induction 218 +/- 32.4, anesthesia 7.70 +/- 1.5; P < 0.05). Piritramide consumption (7.4 +/- 5.1 versus 14.2 +/- 8.5 mg; P < 0.05) and analgesia scores were significantly reduced in the clonidine group. Apnea and desaturation index were not different between the groups, whereas the minimal postoperative oxygen saturation on the day of surgery was significantly lower in the placebo than in the clonidine group (76.7% +/- 8.0% versus 82.4% +/- 5.8%; P < 0.05). We conclude that oral clonidine premedication stabilizes hemodynamic variables during induction, maintenance, and emergence from anesthesia and reduces the amount of intraoperative anesthetics and postoperative opioids without deterioration of ventilation.