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Naloxegol PAMORA — SCE Medical Oncology MCQ

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ModerateSupportive & Palliative OncologyNaloxegol PAMORASCE Medical Oncology

A 65-year-old man with cancer develops acute severe constipation on opioids. His oncologist considers prescribing naloxegol. What is this drug and how does it differ from naloxone?

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Correct answer: C — Naloxegol is an oral peripherally-acting µ-opioid receptor antagonist (PAMORA) that blocks opioid receptors in the gut without crossing the blood-brain barrier — unlike oral naloxone which has low but variable systemic bioavailability

Naloxegol is an oral PAMORA specifically designed to remain peripheral (PEGylated naloxol — the PEG moiety prevents BBB penetration). This blocks opioid receptors in the gut (reversing OIC) without affecting central analgesia. It differs from oral naloxone (which has ~2-5% systemic bioavailability — usually insufficient to reverse analgesia but variable in hepatic impairment) and from subcutaneous methylnaltrexone (which is also peripheral-acting but requires injection). NICE recommends PAMORAs after failure of conventional laxative combinations.

Reference: BNF Naloxegol; NICE CG140; ESMO Supportive Care