Fentanyl patch prescribing still not safe in 50 percent of prescriptions

Fentanyl is a highly potent opioid with potential adverse effects such as central nervous system depression, dangerously low blood pressure, impaired breathing and death. Between 1996 and 2015 in Canada, there were 284 reported deaths linked to fentanyl patches, many during the drug's initiation phase.

The fentanyl patch is recommended for people who have already used an opioid equivalent to 60 mg of morphine daily for at least a week before starting the 25 µg/h patch.

"One important safety issue, and a factor under the control of prescribers, is the recommendation that first-time users of the fentanyl patch have adequate prior exposure to opioids," writes Dr. Shawn Bugden, Associate Professor, College of Pharmacy, Faculty of Health Sciences at the University of Manitoba, with coauthors.

With the rising use of fentanyl and associated adverse events, the authors suggest it is time to look at safety issues related to the fentanyl patch.

The study examined fentanyl patch prescribing over 12 years in Manitoba, Canada, and included 11 063 people who received prescriptions for the patch. The researchers found that 74% of fentanyl prescriptions were not safe because users had not had adequate previous exposure to opioids. In 18% of cases, first-time patients started on the 50 µg/h dose or higher, rather than the 25 µg/h dose. Prescribing did improve over the study period, from 87% unsafe prescribing at the start of the study to 50%, and it was safer in women and people younger than 65 years of age.

"Of particular concern, patients 65 and older, who may be at the greatest risk, had higher levels of unsafe fentanyl initiation than younger patients," write the authors. "There was considerable improvement, with a 37.0% decrease in unsafe prescribing over the study period."

However, half of all fentanyl patch prescriptions are still unsafe. The researchers noted that although these patients had not had previous opioid exposure, most did not receive lethal doses.

The authors note several limitations to the study. They assessed safety based on product monograph recommendations and safety warnings, and could not include prescriptions obtained in other provinces.

"Considerable attention and effort have been placed into making prescribers aware of the need to ensure adequate opioid tolerance before prescribing fentanyl patches," write the authors. "Special attention should be paid to older patients, who are at greatest risk of adverse outcomes but had the lowest level of safe prescribing."

A related commentary, "Consequences of unsafe prescribing of transdermal fentanyl," discusses fentanyl patch prescribing, adverse events and potential for abuse.