Oral morphine, oxycodone, transdermal fentanyl, and buprenorphine provided similar pain control, response rates, and safety profiles in patients with cancer pain, a study published in the journal Annals of Oncology has shown.1

Although guidelines tend to consider morphine and morphine-like opioids comparable and interchangeable in the treatment of chronic pain, individual responses can vary. Therefore, researchers sought to compare the analgesic efficacy, changes of therapy, and safety profile over time of 4 strong opioids.

For the multicenter, phase 4 trial, researchers enrolled 520 oncologic patients with moderate to severe pain requiring World Health Organization (WHO) step 3 opioids. Participants were randomly assigned to receive oral morphine, oxycodone, transdermal fentanyl, or buprenorphine for 28 days. At each visit, investigators recorded patients’ pain intensity, therapy modifications, and adverse drug reactions.

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Results showed that worst and average pain intensity decreased over the 4-week period with no significant differences between the 4 groups. Researchers found that the nonresponse rate ranged from 11.5% in the morphine group to 14.4% with buprenorphine.

The study also demonstrated that each group needed increases in the daily dose, ranging from 32.7% with morphine to 121.2% with transdermal fentanyl. The rate of adjuvant analgesic use ranged from 68.9% with morphine to 81.6% with oxycodone and the rate of drug switches ranged from 12% with oxycodone to 22.1% with morphine.

The rate of treatment discontinuation ranged from 14.5% with fentanyl to 27% with morphine.

In terms of safety, adverse drug events were similar between the 4 drugs, except morphine was significantly associated with greater neurotoxicity.


1. Corli O, Floriani I, Roberto A, et al. Are strong opioids equally effective and safe in the treatment of chronic cancer pain? A multicenter randomized phase 4 ‘real life’ trial on the variability of response to opioids [published online ahead of print March 2, 2016]. Ann Oncol. doi:10.1093/annonc/mdw097.