Does Fentanyl Have a High or Low First-Pass Effect?

SCENARIO 2

Does fentanyl have a high or low first-pass effect ? Please discuss why this is important to know and how it relates to bioavailability . What route has 100% bioavailability? In addition to parenteral, how can this medication be given to counter the first-pass effect? Write a sample prescription for this medication.

Scenario 2 SOLVED

The first pass effect of fentanyl is very high. It is extensively metabolised in the liver and the intestines by cytochrome P450 isoenzymes to the metabolite norfentanyl (Rosenthal & Burchum, 2020). This is important to know because it will determine the dose and ultimately the amount of active drug that reaches their cellular site of action. Metabolised drug does not have the same strength as the same quantity that was taken orally. Bioavailability refers to the amount of drug or its active metabolite that reaches the cellular site of action within the body and produces its effects (Rosenthal & Burchum, 2020). Knowing about first-pass effect and its extent for every drug taken orally helps in determining the optimum dose.

The route that always assures 100% bioavailability is the parenteral route, as it bypasses the liver. According to Rosenthal and Burchum (2020), transmucosal, transdermal, and sublingual routes are other ways of administering fentanyl that can avoid or reduce the first-pass effect. A sample fentanyl prescription for severe chronic cancer pain is as follows (Medscape, 2025c):

Fentanyl skin patch (Duragesic) 100 mcg/hr patches, apply 1 (one) patch q72h, #10 RF 1

Does fentanyl have a high or low first pass effect?

References

Medscape (2025c). Fentanyl transdermal . https://reference.medscape.com/drug/duragesic-fentanyl-transdermal-999646

Rosenthal, L.D., & Burchum, J.R. (2020). Lehne’s pharmacotherapeutics for advanced practice providers, 2 nd ed . Elsevier.