title: Efficacy of orally administered methylnaltrexone in decreasing subjective effects after intravenous morphine.
abstract: Opioid compounds are commonly used analgesics. After opioid administration, troublesome subjective effects, such as dysphoria, dizziness, nausea, and pruritus, have been reported. While some if not all of these are believed to occur due to central nervous system effects of opioids, the anecdotal reports heard from volunteers in our other studies suggest that a peripheral opioid antagonist reduced some of these effects. In this double-blind randomized placebo-controlled study, we evaluated the efficacy of oral methylnaltrexone, a selective peripheral opioid receptor antagonist, to decrease subjective effects after administering morphine to normal human volunteers. After intravenous morphine injection (0.05 mg/kg), significant increases in subjective ratings were obtained on 'nauseous', 'skin itch', 'stimulated', and 'flushing'. Oral methylnaltrexone 19.2 mg/kg significantly decreased these four ratings. Plasma methylnaltrexone concentrations at two different oral doses were also measured to correlate between pharmacological effects of the compound and its plasma levels. Our results suggested that methylnaltrexone has a potential therapeutic value in decreasing some undesirable subjective effects associated with opioid medications.
authors.affiliation: Department of Anesthesia and Critical Care, Pritzer School of Medicine, University of Chicago, IL 60637, USA. cyuan@midway.uchicago.edu
authors.forename: C S
authors.initials: CS
authors.lastname: Yuan
authors.forename: J F
authors.initials: JF
authors.lastname: Foss
authors.forename: M
authors.initials: M
authors.lastname: O'Connor
authors.forename: J
authors.initials: J
authors.lastname: Osinski
authors.forename: M F
authors.initials: MF
authors.lastname: Roizen
authors.forename: J
authors.initials: J
authors.lastname: Moss
mesh_terms: D000284:Administration, Oral; D000328:Adult; D000339:Affect / Q000187:drug effects*; D001143:Arousal / Q000187:drug effects*; D004305:Dose-Response Relationship, Drug; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D007262:Infusions, Intravenous; D008297:Male; D009020:Morphine / Q000008:administration & dosage / Q000009:adverse effects*; D009271:Naltrexone / Q000031:analogs & derivatives* / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology*; D000644:Quaternary Ammonium Compounds; D016896:Treatment Outcome
chemical_list: D009292:Narcotic Antagonists; D000644:Quaternary Ammonium Compounds; C032257:methylnaltrexone; D009271:Naltrexone; D009020:Morphine