Morphine responses in humans: a retrospective analysis of sex differences

There is increasing evidence that sex modulates the effects of opioid analg esics in nonhumans, but few studies have examined this issue in humans. Ove r the past seven years we have conducted several studies in which the subje ctive, psychomotor. and physiological effects of intravenous morphine were examined in healthy volunteers. In a retrospective analysis encompassing si x studies, we re-examined the effects of 10 mg/70 kg (iv) morphine in 57 ma les and 27 females. There were some differences in morphine's subjective ef fects as a function of sex. Females reported higher ratings of 'coasting (s paced out).' 'heavy or sluggish feeling' and 'dry mouth.' No differences in degree of psychomotor impairment or physiological effects (miosis and resp iration rate) of morphine emerged between males and females. Future studies should focus on other doses of morphine and other opioid drugs. assess mul tiple behavioral and physiological endpoints, and look at different subsamp les of humans (e.g. opioid abusers). (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.