Paper I — 2020 February (Supplementary) (2010 Scheme) — Q7

Paper I

2020 February (Supplementary) (2010 Scheme) · 40 marks · 120 min

Question

Levodopa

Q73 marksShort Notes★✓

Answer

Levodopa is the metabolic precursor of dopamine, the mainstay of treatment for Parkinson’s disease.

Mechanism of action

• Crosses the blood-brain barrier (unlike dopamine itself) and is converted to dopamine by dopa decarboxylase in surviving nigrostriatal neurons, replenishing depleted striatal dopamine

Uses

• Parkinson’s disease — most effective for bradykinesia and rigidity, with lesser effect on tremor
• Always combined with a peripheral decarboxylase inhibitor (carbidopa) to reduce peripheral conversion/side effects and increase CNS bioavailability

Adverse effects

• GI: nausea, vomiting
• Cardiovascular: postural hypotension, arrhythmias
• CNS: dyskinesias with long-term use, “on-off” phenomenon, psychiatric disturbances (hallucinations)
• Mydriasis (caution in narrow-angle glaucoma)

Related Concepts

1. 1Antiparkinsonian Drugs

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