title: Methylnaltrexone prevents morphine-induced delay in oral-cecal transit time without affecting analgesia: a double-blind randomized placebo-controlled trial.
abstract: Methylnaltrexone is a quaternary opioid antagonist with limited ability to cross the blood-brain barrier and the potential to antagonize the peripherally mediated effects of opioids. The effectiveness of methylnaltrexone in preventing morphine-induced changes in gastrointestinal motility and transit without affecting analgesia was evaluated in humans. Twelve healthy volunteers were given intravenous placebo, placebo plus 0.05 mg/kg morphine, or 0.45 mg/kg methylnaltrexone plus 0.05 mg/kg morphine. Oral-cecal transit time was assessed by the pulmonary hydrogen measurement technique, and analgesia was measured with use of the cold-pressor test. Morphine significantly increased oral-cecal transit time from 104.6 +/- 31.1 minutes (mean +/- SD) to 163.3 +/- 39.8 minutes (p < 0.01). Methylnaltrexone prevented 97% of morphine-induced increase in oral-cecal transit time (106.3 +/- 39.8 minutes; not significant compared with baseline; p < 0.01 compared with morphine alone). Methylnaltrexone did not affect the analgesic effect of morphine on both pain intensity and pain bothersomeness ratings. At a higher dose of morphine (0.1 mg/kg), our preliminary results indicated that 0.45 mg/kg methylnaltrexone also prevented the morphine-induced delay in oral-cecal transit time, with no effect on analgesia. Methylnaltrexone may be a useful adjunct to opioids for the relief of opioid-induced constipation.
authors.affiliation: Committee on Clinical Pharmacology, University of Chicago, Chicago, IL 60637, USA.
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: A
authors.initials: A
authors.lastname: Toledano
authors.forename: M F
authors.initials: MF
authors.lastname: Roizen
authors.forename: J
authors.initials: J
authors.lastname: Moss
mesh_terms: D000293:Adolescent; D000328:Adult; D000701:Analgesics, Opioid / Q000037:antagonists & inhibitors* / Q000493:pharmacokinetics; D001944:Breath Tests; D003080:Cold Temperature; D004311:Double-Blind Method; D005260:Female; D005772:Gastrointestinal Transit / Q000187:drug effects*; D006801:Humans; D006859:Hydrogen / Q000378:metabolism; D007275:Injections, Intravenous; D008297:Male; D009020:Morphine / Q000037:antagonists & inhibitors* / Q000493:pharmacokinetics; D009271:Naltrexone / Q000031:analogs & derivatives* / Q000493:pharmacokinetics / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000493:pharmacokinetics / Q000494:pharmacology*; D010147:Pain Measurement; D011312:Pressure; D000644:Quaternary Ammonium Compounds
chemical_list: D000701:Analgesics, Opioid; D009292:Narcotic Antagonists; D000644:Quaternary Ammonium Compounds; C032257:methylnaltrexone; D009271:Naltrexone; D009020:Morphine; D006859:Hydrogen