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Droxidopa – Noradrenaline Precursor for OH — SCE Neurology MCQ

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HardMovement DisordersDroxidopa – Noradrenaline Precursor for OHSCE Neurology

A 65-year-old man with Parkinson's disease presents with orthostatic hypotension causing pre-syncope. Non-pharmacological measures and midodrine have been tried. His BP drops 45 mmHg systolic on standing despite treatment. His neurologist considers droxidopa. What is the mechanism of droxidopa?

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Correct answer: D — Synthetic noradrenaline precursor — converted to noradrenaline by DOPA decarboxylase, increasing peripheral vascular resistance

Droxidopa (L-DOPS) is a synthetic amino acid precursor of noradrenaline. It is converted to noradrenaline by the enzyme aromatic L-amino acid decarboxylase (DOPA decarboxylase) — the same enzyme that converts levodopa to dopamine. This increases circulating noradrenaline levels, raising blood pressure and improving orthostatic hypotension. It is particularly useful in neurogenic orthostatic hypotension (PD, MSA, pure autonomic failure). A: Midodrine is the alpha-1 agonist. C: Beta-blockers would worsen hypotension. D: Fludrocortisone is the mineralocorticoid. E: ACE inhibitors lower BP.

Reference: EAN Autonomic Failure Guidelines; BNF