Dopaminergic / Antiviral (Adamantane Derivative)

Amantadine Hydrochloride

Brand names: Lysovir, Symmetrel

Adult dose

Dose: Parkinson's disease: 100 mg once daily, increasing to 100 mg twice daily; max 400 mg/day (divided doses). Post-COVID fatigue/dyskinesia: specialist dosing

Route: Oral

Frequency: Once or twice daily (last dose not after 4 pm to avoid insomnia)

Clinical pearls

Used in Parkinson's disease for tremor, rigidity, and akinesia (modest effect) — also used for levodopa-induced dyskinesia
NMDA receptor antagonist mechanism in addition to dopaminergic effects
Originally developed as antiviral (influenza A) — now rarely used for this indication
Livedo reticularis is cosmetically bothersome but not harmful — reassure patients
Must taper when stopping to avoid withdrawal rebound
NICE NG71 (Parkinson's disease): amantadine can be considered for dyskinesia; limited evidence for motor symptoms alone

Contraindications

Severe renal impairment (eGFR <15) — dose accumulation risk
Epilepsy (caution — lowers seizure threshold)
History of psychosis
Closed-angle glaucoma

Side effects

Livedo reticularis (very common with chronic use — benign, reversible on stopping)
Peripheral oedema
Insomnia, nightmares
Confusion, hallucinations
Impulse control disorders
Nausea
Dry mouth

Interactions

Anticholinergics — additive confusion and hallucinations
Other dopaminergics — additive adverse effects (dyskinesia, hallucinations)
Trimethoprim / co-trimoxazole — reduced renal excretion of amantadine; toxicity risk
CNS stimulants — additive effects

Monitoring

Renal function (eGFR) — dose-adjust if impaired
Mental state / cognitive function
Impulse control behaviours
Ankle oedema

Reference: BNF; NICE NG71 (Parkinson's disease in adults, 2017 updated 2022); Parkinson's UK drug factsheet on amantadine; https://bnf.nice.org.uk/drugs/amantadine-hydrochloride/. Verify against your local formulary and the latest BNF before prescribing.

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways