Intramuscular butorphanol and meperidine in postoperative pain.

Butorphanol, 1, 2, and 4 mg/70 kg, and meperidine, 40 and 80 mg/70 kg, were compared for analgesic activity and side effects in 104 hospitalized postoperative patients. Butorphanol proved to be 30 to 40 times as potent as meperidine on a weight basis. Both medications provided maximum pain relief approximately 1 hr after administration. The most common side effect in all groups was drowsiness.