Butorphanol: a double-blind comparison with pentazocine in post-operative patients with moderate to severe pain.

A double-blind, randomized trial was conducted with 124 post-operative patients to compare the analgesic activity and possible side-effects of a new synthetic analgesic--butorphanol tartrate (1, 2, and 4 mg)--and pentazocine lactate (30 and 60 mg), adminstered intramuscularly. Butorphanol was determined to be 16 times more potent than pentazocine, on a weight basis. Both medications provided maximum pain relief within one hour after administration, and had comparable durations of action. Drowsiness was the most common side-effect, and it appeared to be dose related in all test groups.