Amantadine has had several lives. Originally approved as an antiviral for influenza A in 1966, it was quickly noticed to relieve Parkinson's symptoms. Decades later it became part of the toolkit for managing the movement side effects of antipsychotics. More recently it has been studied for traumatic brain injury, fatigue in multiple sclerosis, and tardive dyskinesia. In schizophrenia care, it sits as a useful alternative to anticholinergics like benztropine and trihexyphenidyl.
Amantadine is a dopamine-releasing, weak NMDA-antagonist medication that can ease antipsychotic-induced parkinsonism without the cognitive and bowel side effects of anticholinergics.
How it works
Unlike benztropine, amantadine is not anticholinergic in any meaningful way. It increases dopamine release from presynaptic terminals, blocks dopamine reuptake to a small extent, and acts as a weak NMDA glutamate receptor antagonist. The net effect is to partially restore dopamine signalling in the nigrostriatal pathway, which is precisely what antipsychotics blunt when they cause parkinsonism.
What it treats
- Drug-induced parkinsonism — tremor, rigidity, bradykinesia (slowed movement)
- Some cases of akathisia, although propranolol and mirtazapine have better evidence
- Off-label, tardive dyskinesia, where some studies have shown modest benefit
For dystonic reactions, amantadine is too slow-acting to be a first-line option; injectable benztropine or diphenhydramine remain standard.
Typical dosing
The usual range is 100 to 300 mg per day in divided doses. Many clinicians start at 100 mg once daily and increase as tolerated. Because amantadine can be activating, dosing is generally avoided in the late evening to prevent insomnia. The drug is excreted almost entirely by the kidneys, so patients with reduced kidney function need a lower dose — sometimes substantially lower.
Why some clinicians prefer it
Compared to anticholinergics, amantadine has two big advantages:
- No anticholinergic burden — no dry mouth, no urinary retention, less constipation, and crucially less cognitive impact. This is particularly relevant for patients on clozapine or those with already significant cognitive symptoms.
- Possible benefit on negative symptoms — some small studies have suggested amantadine can modestly improve negative symptoms, though the evidence is inconsistent and it is not approved for this purpose.
Side effects and risks
Amantadine has a different side effect profile than anticholinergics:
- Insomnia — common, especially with evening dosing
- Lightheadedness or dizziness
- Nausea
- Livedo reticularis — a harmless purple, lacy skin pattern, usually on the legs
- Ankle swelling
- Confusion or hallucinations — particularly in older adults, at higher doses, or with kidney impairment
- Anxiety and agitation — can rarely worsen psychotic symptoms
New visual hallucinations, severe confusion, sudden agitation, suicidal thoughts, severe ankle swelling, or signs of heart failure (shortness of breath, chest discomfort).
Special populations
Older adults, patients with kidney disease, and patients with congestive heart failure need particularly careful dosing and monitoring. Pregnancy data is limited; amantadine is generally avoided in pregnancy when alternatives exist.
How long should it be used?
Like other adjunctive medications, the goal is to use the lowest effective dose for the shortest time that meaningfully helps. If the underlying antipsychotic can be adjusted — lower dose, switch to a lower-EPS agent — the need for amantadine often disappears. Some patients do stay on it long term when antipsychotic adjustment is not possible.
Discontinuation
Stopping amantadine abruptly has, in rare cases, been associated with a syndrome that looks like neuroleptic malignant syndrome, particularly in patients with Parkinson's disease. Tapering is the safer approach.
Where it fits in
For a patient with mild to moderate drug-induced parkinsonism who would do badly with anticholinergic side effects — such as someone on clozapine, an older adult, or someone whose work depends on sharp memory — amantadine is often the better choice. For acute dystonia, anticholinergics still win on speed. For akathisia, beta-blockers and mirtazapine still have stronger evidence. For more on the broader category of side effects amantadine addresses, see our overview of extrapyramidal symptoms.
This article is for educational purposes only and is not medical advice, diagnosis, or treatment. Always consult a qualified mental health professional. If you or someone you know is in crisis, call or text 988 in the US, or your local emergency number.