Efficacy and Safety of Fentanyl Citrate Patch, Including a Low-Dose 0.5 mg Formulation, in Opioid-Naïve Patients with Cancer Pain.

BACKGROUND AND OBJECTIVE: The use of transdermal fentanyl for opioid-naïve patients is restricted, however, transdermal fentanyl is a useful opioid analgesic for patients in whom oral administration is difficult or for those with renal failure. In this study, the efficacy and safety of fentanyl citrate patches was evaluated in opioid-naïve patients suffering from cancer pain. METHODS: An open-label uncontrolled study was conducted in opioid-naïve patients with cancer pain unable to be controlled by non-opioid analgesics. Fentanyl citrate patches starting at a low dose (0.5 mg/patch, corresponding to 6.25 µg/h fentanyl delivered) were applied once/day for up to 14 days. The analgesic effect was assessed every day from the visual analogue scale pain score and the number of doses of rescue medication. When improvement of the analgesic effect was "significant" or "moderate" at a certain dose for three consecutive days, the patient was classified as a "responder" and was considered to have "completed" the study. RESULTS: A fentanyl citrate patch was administered to 208 of 209 enrolled patients. In the full-analysis set, 87.0% of the patients were "responders" (95% confidence interval 81.7-91.3%). In 148 patients, the optimum dose was low (0.5 mg in 99, and 1 mg in 49), with patients finishing the study on days 4-8. Following dose escalation to 4 mg, respiratory depression occurred in one patient; however, this was considered a mild adverse event. CONCLUSION: A low-dose fentanyl citrate patch was effective in the management of cancer pain in opioid-naïve patients and was well tolerated. STUDY REGISTRATION: JPRN-JapicCTI-173717.