Relative analgesic potencies of morphine and hydromorphone in postoperative pain.

Because of discrepancies in the estimates of the relative analgesic potencies of hydromorphone and morphine, the drugs were compared in two four-point, double-blind bioassays. In the first study, hydromorphone, 1 and 2 mg, was compared with morphine, 5 and 10 mg, in 31 postoperative patients; in the second, hydromorphone, 0.5 and 1 mg, was compared with morphine, 5 and 10 mg, in 112 postoperative patients. Subjective responses to nurse-observer questions were used to quantitate analgesia for postoperative pain. Hydromorphone is more potent than commonly believed: approximately 0.9 to 1.2 mg is equianalgesic with 10 mg of morphine, with a similar incidence of side effects.