Amantadine 100 mg Tablets: Prescription Antiviral (Influenza A) & Parkinson’s Disease Dyskinesia Treatment

Information last reviewed: May 2026 — for educational purposes only.

Amantadine is a prescription antiviral drug that was one of the first antivirals approved by the FDA (1966). Originally approved for prophylaxis and treatment of influenza A infections, its antiviral use has become largely obsolete because virtually all circulating influenza A strains are now resistant to amantadine. Today, amantadine’s primary clinical role is in the management of Parkinson’s disease — specifically to reduce levodopa-induced dyskinesia — and as an adjunct treatment for Parkinsonian symptoms. It requires a prescription for all uses.

Current Uses of Amantadine

Parkinson’s Disease

Amantadine is used in Parkinson’s disease for two distinct purposes:

• Immediate-release amantadine 100 mg capsules/tablets — used as monotherapy in early, mild Parkinson’s disease to improve motor symptoms; also reduces levodopa-induced dyskinesia as an add-on
• Extended-release amantadine (Gocovri 137 mg capsules, Osmolex ER 129 mg tablets) — specifically FDA-approved for the treatment of dyskinesia in patients with Parkinson’s disease receiving levodopa-based therapy (Gocovri); and as monotherapy or adjunct for Parkinson’s (Osmolex ER)

The mechanism of amantadine in Parkinson’s is multifactorial: it is an NMDA receptor antagonist (blocking glutamate-mediated excitotoxicity that contributes to dyskinesia), and also has dopaminergic effects including increasing dopamine release and blocking dopamine reuptake.

Antiviral (Historical)

Amantadine was once a first-line treatment for influenza A. It blocks the influenza A M2 ion channel protein, preventing viral uncoating inside host cells. However, the CDC and WHO no longer recommend amantadine or rimantadine for influenza treatment or prophylaxis due to nearly universal resistance among currently circulating seasonal influenza A strains, including H3N2 and H1N1. Current preferred antivirals for influenza are oseltamivir (Tamiflu) and zanamivir (Relenza), which are neuraminidase inhibitors.

Strengths and Formulations

• Immediate-release tablets / capsules 100 mg (Rx) — generic amantadine; most common form; usual dosing: 100 mg twice daily (BID) for Parkinson’s symptoms; can be taken with or without food; the last dose should be given no later than midday/early afternoon to minimise sleep disturbances
• Extended-release capsules 137 mg (Gocovri) (Rx) — taken once daily at bedtime; specifically for levodopa-induced dyskinesia
• Extended-release tablets 129/193/258 mg (Osmolex ER) (Rx) — taken once daily in the morning; Parkinson’s disease and extrapyramidal drug-induced side effects
• Oral solution 50 mg/5 ml (Rx) — for patients unable to swallow capsules

Common Side Effects

Amantadine’s side effects are largely attributable to its anti-glutamatergic and dopaminergic actions:

• Dizziness, lightheadedness
• Insomnia (hence the recommendation to avoid late afternoon/evening doses with IR formulation)
• Livedo reticularis — a distinctive net-like purplish mottling of the skin, usually on the legs; benign but notable
• Peripheral oedema
• Nausea, dry mouth
• Hallucinations (particularly in older patients or those with prior psychiatric conditions)

Frequently Asked Questions

Is amantadine still used for the flu?

Not in current clinical practice. Due to near-universal resistance among circulating influenza A strains, amantadine is no longer recommended for influenza treatment or prophylaxis by the CDC or WHO. Current influenza antiviral guidelines recommend oseltamivir (Tamiflu, oral) or zanamivir (Relenza, inhaled) as first-line options.

How quickly does amantadine work for Parkinson’s dyskinesia?

Clinical benefit for dyskinesia (involuntary movements associated with long-term levodopa therapy) may be seen within a few days to 2 weeks of starting amantadine. Extended-release formulations designed specifically for dyskinesia (Gocovri) showed significant reductions in dyskinesia scores in clinical trials at 12 weeks vs placebo.

Can amantadine be stopped suddenly?

Abrupt discontinuation of amantadine in patients with Parkinson’s disease should be avoided if possible, as sudden withdrawal can trigger worsening of Parkinsonian symptoms, and in rare cases, a neuroleptic malignant syndrome-like reaction. Doses should be tapered gradually when discontinuation is planned.

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