title: Morphine or oxycodone in cancer pain?
abstract: Oxycodone is an opioid analgesic that closely resembles morphine. Oxymorphone, the active metabolite of oxycodone, is formed in a reaction catalyzed by CYP2D6, which is under polymorphic genetic control. The role of oxymorphone in the analgesic effect of oxycodone is not yet clear. In this study, controlled-release (CR) oxycodone and morphine were examined in cancer pain. CR oxycodone and morphine were administered to 45 adult patients with stable pain for 3-6 days after open-label titration in a randomized, double-blind, cross-over trial. Twenty patients were evaluable. Both opioids provided adequate analgesia. The variation in plasma morphine concentrations was higher than that of oxycodone, consistent with the lower bioavailability of morphine. Liver dysfunction affected selectively either oxycodone or morphine metabolism. Three patients with markedly aberrant plasma opioid concentrations are presented. Significant individual variation in morphine and oxycodone metabolism may account for abnormal responses during treatment of chronic cancer pain.
authors.affiliation: Pain Relief Unit, Helsinki University Hospital, Finland. tarja.heiskanen@hus.fi
authors.forename: T E
authors.initials: TE
authors.lastname: Heiskanen
authors.forename: P M
authors.initials: PM
authors.lastname: Ruismäki
authors.forename: T A
authors.initials: TA
authors.lastname: Seppälä
authors.forename: E A
authors.initials: EA
authors.lastname: Kalso
mesh_terms: D000284:Administration, Oral; D000328:Adult; D000368:Aged; D000701:Analgesics, Opioid / Q000097:blood / Q000493:pharmacokinetics* / Q000627:therapeutic use; D018592:Cross-Over Studies; D019389:Cytochrome P-450 CYP2D6 / Q000378:metabolism; D003647:Debrisoquin / Q000378:metabolism; D003692:Delayed-Action Preparations; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009019:Morphinans / Q000097:blood; D009020:Morphine / Q000097:blood / Q000493:pharmacokinetics* / Q000627:therapeutic use; D009022:Morphine Derivatives / Q000097:blood; D009369:Neoplasms / Q000097:blood / Q000150:complications / Q000378:metabolism*; D010098:Oxycodone / Q000097:blood / Q000493:pharmacokinetics* / Q000627:therapeutic use; D010146:Pain / Q000188:drug therapy* / Q000209:etiology / Q000378:metabolism*; D010147:Pain Measurement / Q000187:drug effects; D010641:Phenotype
chemical_list: D000701:Analgesics, Opioid; D003692:Delayed-Action Preparations; D009019:Morphinans; D009022:Morphine Derivatives; C035349:morphine-6-glucuronide; D009020:Morphine; C077256:noroxycodone; D010098:Oxycodone; D019389:Cytochrome P-450 CYP2D6; D003647:Debrisoquin