A 62-year-old man with Parkinson's disease on levodopa/carbidopa develops dyskinesias during peak dose and 'wearing off' before the next dose. Which medication can be added to extend the ON time and reduce wearing off by inhibiting peripheral COMT?
- A Selegiline (MAO-B inhibitor)
- B Pramipexole (dopamine agonist)
- C Entacapone (COMT inhibitor) ✓
- D Amantadine
Correct answer: C. Entacapone (COMT inhibitor)
Explanation
Entacapone is a peripheral COMT inhibitor that blocks the conversion of levodopa to 3-O-methyldopa in the periphery, increasing levodopa bioavailability and extending ON time. It is co-formulated with levodopa/carbidopa as Stalevo. Selegiline (MAO-B inhibitor) reduces levodopa breakdown in the CNS and can help with wearing off but is a different mechanism. Pramipexole is a dopamine agonist used to smooth motor fluctuations. Amantadine is used specifically to reduce peak-dose dyskinesias by blocking NMDA receptors.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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Written and medically reviewed by the StethoPrep medical team.