Butorphanol and pentazocine in patients with severe postoperative pain.

Either butorphanol tartrate (1, 2, or 4 mg) or pentazocine (30 or 60 mg) was given intramuscularly (5 dose groups) to 262 patients, who were scheduled for major operations, if they had severe pain after full awakening in the recovery room, postoperatively under double-blind conditions. There were at least 50 patients in each of the five dosage groups. Pain intensity and relief were scored numerically for each treated patient at 1/2 1, 2, 3 and 4 hr, while under direct surveillance, and the patients were seen again for follow-ups during the first 24 hr postoperatively. Appreciable pain relief developed within 30 min at all dose levels, with a peak analgesic effect apparent at about 1 hr. Satisfactory relief persisted for 4 hr in the majority of patients in each group. With the lowest dose of butorphanol tartrate (1 mg), which gave good pain relief for only 2 to 4 hr, approximately 60% of the patients had to be remedicated within 4 hr. Vital signs were not appreciably affected, but the patients who received the high dose of analgesics (butorphanol tartrate 4 mg or pentazocine lactate 60 mg) were often quite drowsy. The incidence of other side effects was negligible. The relative potency assay showed that butorphanol was approximately 20 times as potent as pentazocine for up to 4 hr.