Transdermal opioids for cancer pain.

PURPOSE OF REVIEW: Cancer patients with moderate-to-severe pain require opioids for analgesia. Whereas early guidelines recommend oral morphine as the 'drug of choice', newer synthetic opioids can be given by a reliable and effective nonoral transdermal route. We examine the mode of action of transdermal patches and we review the evidence on two drugs, which are currently available in this formulation - buprenorphine and fentanyl - covering physicochemical characteristics and pharmacokinetics of the patches, clinical efficacy data and adverse effects.

RECENT FINDINGS: Both buprenorphine and fentanyl possess ideal characteristics for transdermal delivery, being small molecules with high lipophilicity. Studies of buprenorphine patches show benefits but there is poor randomized controlled trial evidence comparing them with oral opioids. Fentanyl patches have been used for longer and have a larger body of evidence supporting their use, with data to suggest improved pain relief and reduced opioid side effects compared with sustained release oral morphine. Patients who have used both oral morphine and transdermal fentanyl express a preference for the patch drug.

SUMMARY: Transdermal buprenorphine and fentanyl are now established for moderate-to-severe cancer pain. There is still a need for further comparative studies with other opioids, especially for buprenorphine.