Evaluation of potential sex differences in the subjective and analgesic effects of morphine in normal, healthy volunteers.
BACKGROUND
Sex differences in the analgesic effects of mu-opioid agonists have been documented extensively in rodents and, to a lesser extent, in non-human primates. To date, there have been few experimental studies investigating this effect in humans, and the conclusions have been equivocal.


OBJECTIVE
The aims of the present study were to examine potential sex differences in the analgesic, subjective, performance, and physiological effects of morphine in human research volunteers.


METHODS
Using a double-blind outpatient procedure, the present study investigated the effects of intramuscular morphine (0, 5, and 10 mg/70 kg, i.m.) in men (N = 8) and women (N = 10). The primary dependent measure was analgesia, as assessed by the cold pressor and mechanical pressure tests. Secondary dependent measures included subjective, performance, and physiological effects of morphine, as well as plasma levels of morphine.


RESULTS
No differences in the analgesic and performance effects of morphine were observed between men and women, but significant differences in morphine's subjective effects were found. Specifically, men reported greater positive effects, whereas women reported greater negative effects after morphine administration.


CONCLUSIONS
These data suggest that, in humans, there are sex differences in the subjective mood-altering effects of morphine but, based on this limited sample, there is little evidence for sex differences in its analgesic effects.
Division on Substance Abuse, New York State Psychiatric Institute, Department of Psychiatry, College of Physicians and Surgeons of Columbia University, 1051 Riverside Dr., Unit 120, New York, NY 10032, USA. sdc10@columbia.edu
Sandra D
SD
Comer
Ziva D
ZD
Cooper
William J
WJ
Kowalczyk
Maria A
MA
Sullivan
Suzette M
SM
Evans
Adam M
AM
Bisaga
Suzanne K
SK
Vosburg
D000328:Adult; D000701:Analgesics, Opioid / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D007273:Injections, Intramuscular; D008297:Male; D008875:Middle Aged; D009020:Morphine / Q000008:administration & dosage / Q000493:pharmacokinetics / Q000494:pharmacology*; D010146:Pain / Q000188:drug therapy*; D010147:Pain Measurement; D012737:Sex Factors; D055815:Young Adult
D000701:Analgesics, Opioid; D009020:Morphine