Entacapone – COMT Inhibition Mechanism — SCE Neurology MCQ
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Correct answer: A — COMT inhibition — preventing peripheral metabolism of levodopa, increasing its bioavailability and half-life
Entacapone is a peripheral catechol-O-methyltransferase (COMT) inhibitor. It blocks the peripheral metabolism of levodopa by COMT, which normally converts levodopa to 3-O-methyldopa. This increases the bioavailability and extends the half-life of levodopa, reducing wearing-off time. It is always used in combination with levodopa/dopa decarboxylase inhibitor. Common side effects include dyskinesia (from increased levodopa exposure), diarrhoea, and orange-brown urine discolouration. A: MAO-B inhibitors are selegiline, rasagiline, and safinamide. B: Dopamine receptor agonists include ropinirole, pramipexole, and rotigotine. D: NMDA antagonism is the mechanism of amantadine. E: Anticholinergics include trihexyphenidyl.
Reference: NICE NG71 Parkinson's Disease (2017); BNF – Entacapone