Amantadine

How It Works

Amantadine is a unique medication with multiple mechanisms of action relevant to Parkinson's disease: it is a weak antagonist of NMDA glutamate receptors, increases dopamine release from presynaptic neurons, blocks dopamine reuptake, and has mild anticholinergic properties. Originally developed as an antiviral medication for influenza A, its anti-parkinsonian effects were discovered serendipitously in 1968. The extended-release formulation Gocovri is specifically FDA-approved for the treatment of levodopa-induced dyskinesia (LID), the only medication with this specific indication.

Typical Dosing

Immediate release (Symmetrel): 100mg twice daily. Gocovri (ER for dyskinesia): start 137mg at bedtime, increase to 274mg at bedtime after 1 week. Osmolex ER: 129mg once daily in the morning, may increase to 322mg/day. Dose adjustment required for renal impairment.

Dosing is individualized by the prescribing physician. The information above is for general reference only.

Common Side Effects

• Livedo reticularis (mottled purple skin, particularly on legs)
• Peripheral edema (ankle swelling)
• Dizziness
• Insomnia
• Nausea
• Constipation

Serious Side Effects

Seek medical attention immediately if you experience any of the following:

• Hallucinations (especially in elderly or cognitively impaired)
• Confusion
• Suicidal ideation
• QT prolongation
• Neuroleptic malignant-like syndrome on abrupt withdrawal

Contraindications

• End-stage renal disease without dialysis
• Concurrent use of other NMDA antagonists

Food Interactions

Take immediate-release early in the day to avoid insomnia (but Gocovri ER is specifically designed for bedtime dosing). Dose adjustment is critical in patients with kidney impairment.

Drug Interactions

The following interactions have been documented with Amantadine. Always inform your healthcare provider about all medications you are taking.

How Amantadine Compares to Alternatives

Amantadine occupies a unique niche because it is the only FDA-approved treatment specifically for levodopa-induced dyskinesia. No other medication — not COMT inhibitors, not MAO-B inhibitors, not dopamine agonists — carries this specific indication. Compared to other anti-dyskinesia strategies (levodopa dose reduction, DBS), amantadine has the advantage of being a simple oral medication. However, its anti-parkinsonian effect as monotherapy (without levodopa) is modest compared to levodopa, dopamine agonists, or MAO-B inhibitors. The extended-release forms (Gocovri, Osmolex ER) provide more consistent drug levels than the immediate-release formulation.

When Is Amantadine Used by Disease Stage?

Early PD (Stages 1-2): Immediate-release amantadine may be used as initial monotherapy for mild motor symptoms, though its efficacy is modest and may wane over months. Not a preferred first-line agent. Mid-stage PD (Stage 2.5-3): Gocovri ER becomes valuable when levodopa-induced dyskinesia develops, typically after several years of levodopa therapy. This is the medication's primary clinical role. Advanced PD (Stages 4-5): Continued if tolerated and effective for dyskinesia management. Dose reduction may be needed as renal function declines with age. Watch for hallucinations and confusion, which become more likely in advanced disease.

Additional Notes

The only medication specifically approved for levodopa-induced dyskinesia (Gocovri). A landmark trial demonstrated that Gocovri reduced dyskinesia by 37% (measured by UDysRS) and simultaneously reduced off-time. Must taper slowly on discontinuation — abrupt withdrawal can cause a dangerous neuroleptic malignant-like syndrome. The immediate-release form has mild anti-parkinsonian effects and is sometimes used for early PD symptoms, though its efficacy is modest and may diminish over months.