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Amantadine – NMDA Antagonism for Dyskinesia — SCE Neurology MCQ

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HardMovement DisordersAmantadine – NMDA Antagonism for DyskinesiaSCE Neurology

A 76-year-old man with Parkinson disease takes amantadine 100 mg twice daily for dyskinesia. After acute kidney injury reduces his creatinine clearance to 28 mL/min, he develops confusion, visual hallucinations, myoclonus and ataxia. His co-careldopa dose is unchanged. Which medicines plan is most appropriate?

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Correct answer: B — Withhold amantadine under supervision and reassess a renal-adjusted regimen after recovery

Amantadine is eliminated predominantly by the kidneys and can accumulate markedly when renal function falls. Confusion, hallucinations, ataxia and myoclonus are recognised manifestations of toxicity. Because toxicity is established here, amantadine should be withheld with supervised management of the withdrawal risk; after recovery, any reintroduction should use the dose or extended interval appropriate to creatinine clearance and current renal trajectory. Haemodialysis removes little amantadine. Altering co-careldopa or introducing another dopaminergic drug does not correct the accumulated amantadine exposure.

Reference: Symmetrel 100 mg Capsules SmPC: https://www.medicines.org.uk/emc/product/12143/smpc