Efficacy and safety of a six-hour continuous overlap method for converting intravenous to transdermal fentanyl in cancer pain.

CONTEXT: Managing cancer pain often requires opioid medications, such as fentanyl, which is frequently initiated parenterally, and then converted to transdermal form. Little evidence exists to guide this conversion.

OBJECTIVES

To observe the efficacy and safety of a six-hour continuous overlap method for converting intravenous fentanyl (IVF) to transdermal fentanyl (TF) in patients with cancer pain.

METHODS

We switched from IVF to TF using a 1:1 (IVF:TF) conversion ratio and overlapped a continuous, nontapered dose of IVF until six hours after TF placement. Pain intensity by Numeric Rating Scale, number of rescue analgesic doses, and presence and severity of opioid-related adverse events were recorded immediately before TF placement, and at six, 12, 18, and 24 hours thereafter.

RESULTS

A total of 17 consecutive patients with cancer pain controlled on IVF were converted to TF. Median age was 65 years, 10 were female, and all had Stage IV cancer. Pain intensity at six and 24 hours remained stable; a slight but statistically significant increase in Numeric Rating Scale was noted at 12 and 18 hours (P=0.01 and 0.02, respectively); however, there was no significant increase in number of rescue doses throughout the observation period. Only one patient experienced opioid-related adverse events.

CONCLUSION

A continuous six-hour overlap method is a safe and effective strategy when converting from IVF to TF in patients with cancer pain. A slight increase in pain intensity may occur, but does not lead to increased rescue doses.