fentanyl patch and heat

 Q: 78 years old male with metastatic esophageal cancer is admitted to ICU with urosepsis. The patient is on a chronic transdermal fentanyl patch from home and requested to continue it. 

Fever will __________ the systemic absorption? (select one)

A) increases

B) decreases

Answer: A

Transdermal fentanyl has some weak evidence to show reduced risk of constipation over other narcotics i.e., morphine patch. Also, it does not produce active metabolites. 

Said that any exposure of patch to heat such as fever, a heating pad, or warming blanket may increase the systemic fentanyl absorption, bearing the risk of respiratory depression.

#pharmacology

Reference:

Newshan G. Heat-related toxicity with the fentanyl transdermal patch. J Pain Symptom Manage. 1998 Nov;16(5):277-8. doi: 10.1016/s0885-3924(98)00100-6. PMID: 9846020.