DrugBuyers.Com: Gender Differences in Acute Pain Meds Responses

This study compares gender differences in the efficacy of two kinds of morphine-based meds for acute pain.
Women tend to respond better to kappa-based agonists and men to mu-based agonists; the implication being that the site of analgesic response differs between females and males.

Feb. 17, 2004 For acute pain management, women respond better to a kappa agonist than to a mu agonist, according to the results of a randomized, double-blind trial published in the January issue of the Southern Medical Journal.

"Two commonly used opioid analgesics for uncomplicated patients are morphine sulfate and butorphanol," write Penny L. Miller, MS, FNP, and Amy A. Ernst, MD, FACEP, from the University of California, Davis Medical Center, in Sacramento. "Preliminary studies suggest that there may be a sex difference in response to the site of action of these two medications."

The objective of this trial was to evaluate whether there is a sex difference in the analgesic response to the prototypical mu-receptor agonist, morphine sulfate, compared with the prototypical kappa agonist, butorphanol, in the emergency department.

Of 94 patients with acute moderate to severe traumatic pain of injury who were enrolled in this study, 49 (52%) were men and 45 (48%) were women. Subjects were randomized to receive morphine or butorphanol. Both groups were similar in demographics.

At 60 minutes, women had significantly lower visual analog scale (VAS) scores with butorphanol than with morphine (P = .046). There was a nonsignificant trend suggesting that men responded better to morphine than women did (P = .06). At 30 minutes, diastolic blood pressures were lower in women than in men.

Study limitations include use of patient self-report of pain.

"Females had better pain scores with butorphanol than morphine at 60 minutes," the authors write. "Kappa receptor agonists should be chosen preferentially for female patients with acute traumatic injury pain."

South Med J. 2004;97:35-41

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