Morphine or oxycodone for cancer-related pain? A randomized, open-label, controlled trial

Context: There is wide interindividual variation in response to morphine for cancer-related pain; 30% of patients do not have a good therapeutic outcome. Alternative opioids such as oxycodone are increasingly being used, and opioid switching has become common clinical practice.

Objectives: To compare clinical response to oral morphine vs. oral oxycodone when used as first-line or second-line (after switching) treatment in patients with cancer-related pain.

Methods: In this prospective, open-label, randomized, controlled trial (ISRCTN65155201) with a selected crossover phase, patients with cancer-related pain were randomized to receive either oral morphine or oxycodone as first-line treatment. Dose was individually titrated until the patient reported adequate pain control. Patients who did not respond to the first-line opioid (either because of inadequate analgesia or unacceptable adverse effects) were switched to the alternative opioid.

Results: Two hundred patients were recruited. On intention-to-treat analysis (n = 198, morphine 98, oxycodone 100), there was no significant difference between the numbers of patients responding to morphine (61/98 = 62%) or oxycodone (67/100 = 67%) when used as a first-line opioid. Similarly, there was no significant difference in subsequent response when patients were switched to either morphine (8/12 = 67%) or oxycodone (11/21 = 52%). Per-protocol analysis demonstrated a 95% response rate when both opioids were available. There was no difference in adverse reaction scores between morphine and oxycodone either in first-line responders or nonresponders.

Conclusion: In this population, there was no difference between analgesic response or adverse reactions to oral morphine and oxycodone when used as a first- or second-line opioid. These data provide evidence to support opioid switching to improve outcomes.