amantadine

Adjunctive therapy

Brands: Symmetrel, Gocovri, Osmolex ER

Last reviewed 2025-12-30

Reviewed by PsychMed Editorial Team.

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Quick answers

What is amantadine?
Amantadine (brand Symmetrel; generics) is an antiparkinson medication (and historically an antiviral) that has a labeled indication for drug-induced extrapyramidal reactions, including antipsychotic-induced Parkinsonism (label).
What is Symmetrel?
Symmetrel is a brand name for amantadine (other brands: Gocovri, Osmolex ER).
What is Symmetrel (amantadine) used for?
Label indications include: Parkinson's disease; drug-induced extrapyramidal reactions; influenza A prophylaxis/treatment (label-dependent).
What drug class is Symmetrel (amantadine)?
Dopaminergic/NMDA-modulating antiparkinson agent (also historically used as an antiviral) that can treat drug-induced extrapyramidal reactions, including antipsychotic-induced parkinsonism. Not an anticholinergic; may be considered when anticholinergic cognitive burden is a concern, balancing potential benefit against neuropsychiatric adverse effects and renal-dose constraints.
What strengths does Symmetrel (amantadine) come in?
Oral capsules/tablets (often 100 mg) and syrup are available (label/manufacturer-dependent).

Snapshot

Class: Adjunctive therapy
Common US brands: Symmetrel, Gocovri, Osmolex ER
Therapeutic drug monitoring not routinely recommended.
Last reviewed: 2025-12-30

Label indications

Parkinson's disease; drug-induced extrapyramidal reactions; influenza A prophylaxis/treatment (label-dependent).

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Clinical Highlights

Amantadine (brand Symmetrel; generics) is an antiparkinson medication (and historically an antiviral) that has a labeled indication for drug-induced extrapyramidal reactions, including antipsychotic-induced Parkinsonism (label). Unlike benztropine or trihexyphenidyl, amantadine is not an anticholinergic, so it may be considered when anticholinergic cognitive burden (confusion, constipation, urinary retention) is a concern (label/clinical).

The main limitation is neuropsychiatric tolerability: insomnia, dizziness, and hallucinations/confusion can occur, particularly at higher doses or in renal impairment (label/clinical).
Because amantadine is primarily renally cleared, dosing and safety are highly dependent on kidney function and age (label).
The compare view, amantadine evidence feed, and amantadine print page support side-by-side review of EPS options and monitoring topics.

Dosing & Formulations

Oral capsules/tablets (often 100 mg) and syrup are available (label/manufacturer-dependent). For drug-induced extrapyramidal reactions, labeling commonly describes 100 mg twice daily, with some patients using 100 mg once daily depending on response and tolerability; dose adjustments are needed in renal impairment (label).

Slow titration and early follow-up can reduce insomnia and dizziness discontinuations (clinical).

Monitoring & Risks

Neuropsychiatric effects: monitor for insomnia, agitation, confusion, and hallucinations, especially in patients with psychosis risk or older adults (label/clinical). Renal impairment increases exposure and toxicity risk; reassess dosing when kidney function changes (label).

When amantadine has been used beyond short trials, clinicians often avoid abrupt discontinuation and reassess symptoms during tapering, because neuropsychiatric symptoms or rebound motor symptoms can occur during rapid changes in dose (clinical).
Peripheral edema and livedo reticularis can occur; swelling and skin changes are common follow-up topics in longer courses (label/clinical).
Orthostatic symptoms and falls risk can occur, particularly in older adults and polypharmacy (clinical).

Drug Interactions

Medications that alter urine pH can change amantadine clearance; urine acidifiers can increase elimination and alkalinizers can increase exposure (label/clinical). Other CNS-active drugs (stimulants, dopaminergic agents) can amplify insomnia or agitation; regimen review focuses on total activating burden (clinical).

Anticholinergics can be co-used but may increase confusion and other adverse effects; caution is typical in older adults (clinical).

Practice Notes

Trials comparing amantadine with anticholinergics (benztropine, trihexyphenidyl) support it as a symptomatic option for neuroleptic- induced parkinsonism, especially when anticholinergic burden is a limiting factor (Kelly 1974; AJP 1976). As with other EPS strategies, addressing the antipsychotic driver (dose reduction, switching agents) is often considered in parallel with symptomatic medication choices (Wisidagama 2021/clinical).

If hallucinations or agitation worsen, dose reduction or discontinuation is common, and clinicians often reassess whether the underlying EPS can be managed by antipsychotic adjustment instead (clinical).

References

Amantadine hydrochloride capsules prescribing information — DailyMed (2024)
A Double Blind Study OF Amantadine Hydrochloride Versus Benztropine Mesylate IN Drug Induced Parkinsonism — European Neurology (1974)
Amantadine Versus Trihexyphenidyl IN THE Treatment OF Neuroleptic Induced Parkinsonism — American Journal of Psychiatry (1976)
Recognition AND Management OF Antipsychotic Induced Parkinsonism IN Older Adults A Narrative Review — Medicines (2021)
AGNP Consensus Guidelines for Therapeutic Drug Monitoring in Neuropsychopharmacology — Pharmacopsychiatry (2018)