Samtidig brug af stærkt virkende CYP3A4- hæmmere (fx ritonavir) og transdermalt administreret fentanyl kan give øget plasma - koncentration af fentanyl.
Concomitant use of potent CYP3A4-inhibitors (e. g. ritonavir) with transdermally administered fentanyl may result in increased plasma concentrations of fentanyl.