Relative analgesic potency of oral zomepirac and intramuscular morphine in cancer patients with postoperative pain.

A twin crossover assay of oral zomepirac and intramuscular morphine was completed in 159 cancer patients with postoperative pain. Zomepirac was a surprisingly effective oral analgesic in these patients, 100 mg orally being roughly equivalent to 16 mg intramuscular morphine. Time-effect data indicate that the peak effect for oral zomepirac may occur slightly later than that for morphine but that zomepirac is relatively rapidly effective after oral administration. Side effect occurrence was roughly in the same range for both drugs, with drowsiness, nausea, dry mouth, and feelings of weakness being observed after both drugs while sweating was observed more frequently after zomepirac. The assay further provided a demonstration of the effectiveness of the twin crossover design as a clinical assay method, providing increased sensitivity of crossover data in a patient population available for only a limited number of study treatments.