Relative potency of controlled-release oxycodone and controlled-release morphine in a postoperative pain model.
OBJECTIVE
The relative analgesic potency of single doses of oral controlled-release oxycodone and oral controlled-release morphine were compared in a randomized, double-blind trial using a postoperative pain model.


METHODS
Women (n = 169) with moderate to severe pain following abdominal hysterectomy received single oral doses of controlled-release oxycodone, 20 mg or 40 mg, or controlled-release morphine, 45 mg or 90 mg. Assessments were made at 30 min, 60 min, then hourly after dosing for 12 h or until remedication.


RESULTS
The most precise estimates of relative potency showed that controlled-release oxycodone was 1.8 times more potent than controlled-release morphine for total effect (95% confidence limits 1.09-2.42; lambda 0.44) and 2.2 times more potent for peak effect (95% confidence limits 0.96-4.59; lambda 0.71). Controlled-release oxycodone at doses of 20 mg or 40 mg was comparable with controlled-release morphine at doses of 45 mg or 90 mg, respectively, for total and peak analgesic effects. For the two higher doses, time to peak relief was approximately 1 h shorter with controlled-release oxycodone than with controlled-release morphine. Most patients reported onset of analgesia within 1 h with all doses. Side effects were similar with the two opioids.


CONCLUSIONS
Oral controlled-release oxycodone was twice as potent as oral controlled-release morphine in this single-dose, relative potency assay. When converting patients from oral morphine to oral oxycodone, an initial oral oxycodone dose of one-half the oral morphine dose is recommended.
Curtis
G B
GB
Alta View Hospital, Sandy, Utah 84094, USA.
Johnson
G H
GH
Clark
P
P
Taylor
R
R
Brown
J
J
O'Callaghan
R
R
Shi
M
M
Lacouture
P G
PG
D000284:Administration, Oral; D000328:Adult; D000698:Analgesia; D000701:Analgesics, Opioid / Q000008:administration & dosage / Q000009:adverse effects / Q000627:therapeutic use*; D000704:Analysis of Variance; D004311:Double-Blind Method; D005260:Female; D006801:Humans; D009020:Morphine / Q000008:administration & dosage / Q000009:adverse effects / Q000627:therapeutic use*; D010098:Oxycodone / Q000008:administration & dosage / Q000009:adverse effects / Q000627:therapeutic use*; D010149:Postoperative Pain / Q000188:drug therapy*
D000701:Analgesics, Opioid; D009020:Morphine; D010098:Oxycodone