Question:
A patient on carbidopa plus levodopa for 10 years now has a wearing-off effect. Which drug should be added to restore the action?
A patient on carbidopa plus levodopa for 10 years now has a wearing-off effect. Which drug should be added to restore the action?
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Block the second peripheral enzyme that destroys levodopa to make each dose last longer.
Updated On: Jun 24, 2026
- Tolcapone
- Amantadine
- Rasagiline
- Benzhexol
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Verified By Collegedunia
The Correct Option is A
Solution and Explanation
Step 1: The wearing-off phenomenon is a motor fluctuation in advanced Parkinson disease where the benefit of each levodopa dose fades before the next dose is due. The most direct fix is to prolong the plasma availability of levodopa.
Step 2: Tolcapone is a COMT inhibitor. By blocking catechol-O-methyltransferase it prevents the peripheral breakdown of levodopa to 3-O-methyldopa, raising and sustaining levodopa levels reaching the brain. This smooths out the wearing-off, increases 'on' time and reduces 'off' time, which is exactly what is needed here, so option a is correct.
Step 3: Rasagiline (an MAO-B inhibitor) does help wearing-off too, but tolcapone is the classic adjunct emphasised for prolonging each levodopa dose; the question expects the COMT inhibitor. Amantadine is mainly used for levodopa-induced dyskinesias, not pure wearing-off. Benzhexol (trihexyphenidyl) is an anticholinergic useful for tremor, not for extending levodopa action.
Step 2: Tolcapone is a COMT inhibitor. By blocking catechol-O-methyltransferase it prevents the peripheral breakdown of levodopa to 3-O-methyldopa, raising and sustaining levodopa levels reaching the brain. This smooths out the wearing-off, increases 'on' time and reduces 'off' time, which is exactly what is needed here, so option a is correct.
Step 3: Rasagiline (an MAO-B inhibitor) does help wearing-off too, but tolcapone is the classic adjunct emphasised for prolonging each levodopa dose; the question expects the COMT inhibitor. Amantadine is mainly used for levodopa-induced dyskinesias, not pure wearing-off. Benzhexol (trihexyphenidyl) is an anticholinergic useful for tremor, not for extending levodopa action.
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