amantadine

General information

• Class: Adjunctive therapy
• Common US brands: Symmetrel, Gocovri, Osmolex ER
• Typical dose range: Drug-induced extrapyramidal reactions: labeling commonly describes 100 mg twice daily, with some patients using 100 mg once daily depending on response and tolerability (label).
• Therapeutic drug monitoring not routinely recommended.
• Last reviewed: 2025-12-30

Dosing & forms

• Forms/strengths: Oral capsules/tablets (often 100 mg) and syrup are available (label/manufacturer-dependent).; Extended-release amantadine products exist for specific neurologic indications; they are distinct formulations and not interchangeable without confirming equivalence (label/clinical).
• Frequency: Drug-induced extrapyramidal reactions: labeling commonly describes 100 mg twice daily, with some patients using 100 mg once daily depending on response and tolerability (label).
• Typical range: Drug-induced extrapyramidal reactions: labeling commonly describes 100 mg twice daily, with some patients using 100 mg once daily depending on response and tolerability (label).

Mechanism (brief)

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.

Metabolism & Half‑life

• Metabolism: Not extensively metabolized; an N-acetylated metabolite has been identified (label).
• Half‑life: Single-dose mean 17 h; Single-dose range 10–25 h

Therapeutic Drug Monitoring (TDM)

Recommended: No

Monitoring highlights

• Renal function and renal-dose appropriateness, especially in older adults and after intercurrent illness (label/clinical).
• Neuropsychiatric monitoring (sleep, agitation, hallucinations/confusion), particularly in patients with psychosis risk (label/clinical).
• Edema/skin monitoring (livedo reticularis) during longer courses (label/clinical).

Sources

• 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)