• Kevin J Friesen, Cornelius Woelk, and Shawn Bugden.
• College of Pharmacy (Friesen, Bugden) Faculty of Health Sciences, University of Manitoba; Department of Family Medicine (Woelk), College of Medicine, Faculty of Health Sciences, University of Manitoba, Winnipeg, Man.
• CMAJ. 2016 Jun 14; 188 (9): 648-53.

BackgroundAlthough a convenient opioid delivery system, transdermal fentanyl patches have caused several deaths and resulted in safety warnings reminding prescribers that fentanyl patches should be prescribed only for patients who have adequate prior exposure to opioids. We conducted a longitudinal analysis of the safety of fentanyl initiation by examining past opioid exposure among patients newly prescribed fentanyl patches.MethodsWe identified all patients in the province of Manitoba who were newly prescribed fentanyl patches between Apr. 1, 2001, and Mar. 31, 2013. We converted all prior opioid use to oral morphine equivalents and determined the average daily dose in the 7-30 days before initial fentanyl patch use. Fentanyl initiation was considered unsafe if the patient's pre-fentanyl opioid exposure was below the recommended level.ResultsWe identified 11 063 patients who began using fentanyl patches during the study period. Overall, fentanyl initiation was deemed unsafe in 74.1% of cases because the patient's prior opioid exposure was inadequate. Women and patients 65 years of age and older were more likely than men and younger patients, respectively, to have inadequate prior opioid exposure (p < 0.001 for each comparison). The proportion of patients who had unsafe prescriptions for fentanyl patches decreased significantly over the study period, from 87.0% in 2001 to 50.0% in 2012 (p < 0.001).InterpretationThe safety of fentanyl initiation improved over the study period, but still half of fentanyl patch prescriptions were written for patients with inadequate prior opioid exposure. Review of prior opioid exposure may be a simple but important way to improve the safe use of fentanyl patches.© 2016 Canadian Medical Association or its licensors.

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