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Study finds no differences in morphine's pain relief between women and men

Pain relief (analgesia) conferred by morphine does not appear to differ between men and women, although women suffer more related adverse effects than do men, concludes a new study of emergency department (ED) patients. Polly E. Bijur, Ph.D., M.P.H., at the Albert Einstein College of Medicine, and colleagues studied 355 patients with acute pain (211 women and 144 men) seen at a major urban ED, who received intravenous doses of morphine (0.1 mg/kg of body weight), as part of 6 clinical trials performed at the ED.

The patients were asked to rate the intensity of pain verbally on an 11-point numerical rating scale that ranged from 0 ("no pain") to 10 ("worst possible pain"), just before and 30 minutes after morphine administration. The researchers calculated the mean reduction in pain intensity and recorded the incidence of adverse events (need for the opiate antagonist naloxone, vomiting, nausea, reduced respiration, and drop in systolic blood pressure) in the period from the administration of morphine to 30 minutes later. They found that most of the predominantly Hispanic and African-American patients came into the ED with intense abdominal pain, and many had nausea before morphine was administered. Women had significantly more nausea and were more likely to suffer from abdominal pain than men. The mean decrease in pain was comparable for the men and women studied (a decrease of 3.6 pain-scale units in men and 3.7 in women).

The proportional change in pain over a 30-minute period also did not differ significantly between women and men (42 percent and 40 percent, respectively). Among the 212 patients who were not nauseated at the time of morphine administration, women had an 18 percent incidence of adverse events compared with 11 percent for men. However, this difference was not significant after controlling for the site of the pain. The study was funded in part by the Agency for Healthcare Research and Quality (HS13924).

More details are in "Response to morphine in male and female patients: Analgesia and adverse events," by Dr. Bijur, David Esses, M.D., Adrienne Birnbaum, M.D., and others, in the March/April 2008 The Clinical Journal of Pain, 24(3), pp. 192-198.

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