Background: There is little agreement about a differential response of men and women to opioid analgesics. Some experimental and clinical studies have shown that women have a better response to opioids, others have found no difference, and still others have found opioids to be more effective analgesics for men than women.
Objectives: To assess sex differences in analgesic response to morphine and incidence of adverse events in patients receiving a dose of 0.1 mg intravenous morphine/kg.
Methods: Secondary analysis of the control arms of 6 randomized clinical trials that compared 0.1 mg/kg intravenous morphine with other opioids or other doses of morphine in patients aged 21 to 65 with acute pain. The setting was an academic medical center Emergency Department serving primarily Latino and African-American patients. Change in self-reported pain intensity from baseline to 30 minutes postbaseline on a validated and reproducible 11-point numerical rating scale and count of adverse events were the primary outcomes.
Results: The sample consisted of 211 women and 144 men. The mean change in pain from baseline to 30 minutes postbaseline was 3.7 in women, 3.6 men (difference=0.04; 95% confidence interval: −0.52, 0.60). In women without nausea before administration of morphine, the incidence of adverse events was 18.3% versus 10.7% in men without initial nausea (difference=7.6%; 95% confidence interval: −2.0, 17.2).
Discussion: Men and women presenting to the Emergency Department did not have a differential response to a single weight-based dose of morphine for alleviation of acute pain. Women without baseline nausea had more adverse events than men.
Departments of *Emergency Medicine
†Family Medicine, Albert Einstein College of Medicine, Bronx, NY
Financial support information: This study was supported in part by a grant from the Agency for Healthcare Research and Quality 1 R01 HS13924.
Reprints: Polly E. Bijur, PhD, MPH, Albert Einstein College of Medicine, Rose F. Kennedy Center, 1410 Pelham Parkway South, Bronx, NY 10461 (e-mail: Bijur@aecom.yu.edu).
Received for publication September 1, 2006; revised September 7, 2007; accepted October 3, 2007