Fentanyl Patches and Opioid Toxicity

As a transdermal patch, fentanyl (Duragesic®, Janssen) provides up to 72 hours of analgesia at predictable concentrations. The package insert, however, warns that fever, hot tubs, and saunas can increase the rate of drug delivery, putting patients at risk for opioid toxicity.
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One patient with a cervical carcinoma was given a heating pad. The pad was placed on her abdomen away from the patch, but at some point it shifted and covered the patch. Two hours later, she had pinpoint pupils and her breathing was shallow. After naloxone HCl was administered, she improved rapidly; after 24 hours, the fentanyl patch was applied again with no problems.

In another instance, a patient who had been wearing a transdermal fentanyl patch for three days was given a warming blanket during surgery for a stress fracture. Her breathing decreased steadily, and both pupils were pinpoint. The patch was removed, and the patient was given nalox-one HCl; within 20 minutes, she began to improve. She recovered uneventfully, with no further need for naloxone.

The third patient was wearing a trans-dermal fentanyl patch for neuropathy related to human immunodeficiency virus (HIV) infection. While he was at camp, swimming, hiking, and playing ball, he became tired and soon was unresponsive to stimuli. In the emergency department, the patch was removed and he was given naloxone. After he recovered, the patch was reapplied without further consequences.
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According to the author, transdermal fentanyl absorption depends on intra-cutaneous blood flow. A higher skin temperature, with increased perfusion, can lead to increased absorption of the drug. The manufacturer warns that serum fen-tanyl concentrations can theoretically increase by one third in patients with a body temperature of 40°C.

Although the manufacturer doesn’t give specific guidelines for restarting fen-tanyl therapy after heat-related increases, the drug was safely restarted at the same dose or at a similar dose in two patients.