Fentanyl Patch Morphine Equivalence — FRCA Final MCQ

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ModeratePain MedicineFentanyl Patch Morphine EquivalenceFRCA Final

A 55-year-old man (ASA III) with chronic pain has been on a fentanyl patch 100 mcg/hr for 2 years. He requires emergency surgery and the patch must be removed. To maintain equivalent opioid cover, what is the approximate 24-hour oral morphine equivalent of fentanyl 100 mcg/hr transdermal?

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Correct answer: D — 240-360 mg

Fentanyl transdermal 100 mcg/hr is approximately equivalent to 240-360 mg oral morphine per 24 hours (conversion ratio approximately 1:100-150 when considering transdermal to oral morphine equivalence). After patch removal, fentanyl levels decline gradually over 12-24 hours due to the subcutaneous depot. Transitional analgesia with IV morphine PCA or regular oral opioids titrated to effect should be commenced, bearing in mind the residual fentanyl effect. Equianalgesic tables are guides only; individual titration is essential.

Reference: BNF – 2025 – Opioid equivalence tables; Faculty of Pain Medicine – 2022 – Opioid conversion guidelines