A Comparison of the Analgesic Effect of Oxymorphone by Rectal Suppository and Intramuscular Injection in Patients with Postoperative Pain

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Abstract
The time-effect curves of the 2 routes of administration differed substantially; rectal administration resulted in lower and more delayed peak analgesia and a longer duration of action than intramuscular [i.m.] administration. When both duration and intensity of analgesia was considered (total effect), rectal oxymorphone was 1/10 as potent as the i.m. form; in peak effect, it was only 1/16 to 1/20 as potent. Because i.m. oxymorphone was 9-10 times as potent as i.m. morphine, 5-10 mg oxymorphone by suppository provided analgesia comparable to that provided by the usually used doses of parenteral narcotics. Rectal oxymorphone produced no more, and perhaps somewhat fewer, side-effects than doses of i.m. oxymorphone producing equivalent total analgesic effect. None of the patients objected to the rectal route of analgesic administration. The feasibility of well-controled analgesic assays employing the double-dummy technique to compare suppositories with oral or parenteral analgesic dosage forms was demonstrated. The rectal route was an acceptable and practical way of administering potent analgesics and is probably being underutilized by physicians in the control of moderate to severe pain.