Paper I — 2022 July (Supplementary) (2019 Scheme) — Q10

Paper I

2022 July (Supplementary) (2019 Scheme) · 100 marks · 180 min

Question

Pharmacotherapy of Parkinsonism.

Q104 marksShort Answers★✓

Answer

Parkinsonism results from a relative dopamine deficiency in the nigrostriatal pathway; pharmacotherapy aims to restore dopaminergic tone or rebalance the resulting cholinergic excess.

• Dopamine precursor: Levodopa (always combined with a peripheral decarboxylase inhibitor — Carbidopa or Benserazide, to reduce peripheral conversion and adverse effects while increasing CNS delivery) — the most effective agent, mainstay of therapy.
• Dopamine agonists: Pramipexole, Ropinirole (non-ergot, preferred), Bromocriptine (ergot-derived) — directly stimulate dopamine receptors; often preferred initially in younger patients to delay levodopa-related motor complications.
• MAO-B inhibitors: Selegiline, Rasagiline — reduce dopamine breakdown, mild symptomatic/possibly disease-modifying benefit.
• COMT inhibitors: Entacapone — reduce peripheral levodopa breakdown, prolonging its action, used as an adjunct for “wearing-off” fluctuations.
• Anticholinergics: Trihexyphenidyl — restore the dopamine-acetylcholine balance, particularly useful for tremor; more useful in drug-induced parkinsonism.
• Amantadine: enhances dopamine release; also has mild antiviral origin, useful early or for levodopa-induced dyskinesias.

Related Concepts

1. 1Antiparkinsonian Drugs

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