Amantadine (Symmetrel, Gocovri)

What it treats

Amantadine has an unusual history. It was first developed as an antiviral for influenza A, and later found to help Parkinson symptoms. Today, the FDA-approved uses in movement disorders include Parkinson disease, drug-induced extrapyramidal reactions (like antipsychotic-induced parkinsonism), and, in the extended-release Gocovri formulation, levodopa-induced dyskinesia in Parkinson disease and tardive dyskinesia.

In psychiatry, it's most often reached for when an antipsychotic is causing stiffness, slowness, or tremor and switching antipsychotics isn't the right move. It's also used for some cases of tardive dyskinesia and for antipsychotic-related sexual side effects, though the sexual-side-effect use is off-label.

How it works

Two mechanisms matter here. Amantadine enhances the release of dopamine from presynaptic terminals, which can help offset the dopamine-blocking effects of antipsychotics. It also blocks NMDA-type glutamate receptors, which is thought to be part of why it helps with dyskinesia.

Because the effect on dopamine is modest and indirect, amantadine doesn't tend to worsen psychosis at typical doses the way stronger dopaminergic drugs might. That's part of why it fits in psychiatry when a patient needs help with movement side effects but still needs their antipsychotic.

Receptor mechanism (detail)

Amantadine is a weak NMDA glutamate receptor antagonist and a presynaptic dopamine release enhancer. It also has mild anticholinergic and sigma-1 receptor activity. The NMDA piece is thought to underlie its benefit in levodopa-induced dyskinesia; the dopaminergic piece helps with parkinsonism. It's cleared largely unchanged by the kidneys, so renal function drives dosing.

Potency and typical dosing pattern

Ranges are typical framework only, not a prescription for any individual.

Immediate-release amantadine is usually started at 100 mg once daily and titrated to 100 mg twice daily. Doses up to 400 mg per day divided are used in Parkinson disease. For antipsychotic-induced parkinsonism in psychiatry, 100 to 300 mg per day divided is a typical range.

Gocovri (extended-release, taken at bedtime) starts at 137 mg at bedtime for one week, then goes to 274 mg at bedtime. Osmolex ER is a separate extended-release product with its own dosing schedule.

Renal dose adjustment: amantadine is renally cleared, and the dose must be reduced in patients with reduced kidney function. This is especially relevant in older adults.

Safety monitoring

• Kidney function (creatinine, eGFR) at baseline and periodically. Renal impairment raises blood levels at the same dose.
• Mental status, confusion, and hallucinations, especially in older adults or higher doses.
• Ankle edema (fluid in the legs) and livedo reticularis (a net-like reddish-blue skin pattern, most often on the legs) with longer use. Both are cosmetically noticeable but usually benign.
• Blood pressure and orthostatic changes.
• Sleep pattern. Amantadine can cause insomnia if taken too late in the day.
• QT interval in patients on other QT-affecting drugs or with cardiac risk factors.

What to expect

For antipsychotic-induced parkinsonism, improvement often shows up within days to about two weeks. For tardive dyskinesia with Gocovri, the benefit builds over several weeks. Because the mechanism is partly dopaminergic, some patients feel a mild mental lift; some notice a slight edginess or trouble sleeping.

Early side effects, when they show up, are usually mild: dry mouth, some lightheadedness on standing, or vivid dreams. Splitting the dose or shifting the last dose earlier in the day helps with sleep effects.

Common side effects

Most people tolerate amantadine reasonably well. The ones reported most often include:

• Insomnia (if dosed late in the day).
• Nausea.
• Dizziness.
• Dry mouth.
• Constipation.
• Ankle swelling.
• Livedo reticularis (the net-like skin pattern, usually on the legs).
• Vivid dreams.

Many of these ease as the dose stabilizes.

Serious side effects and warnings

Serious problems are uncommon, but a few need to be understood before starting.

• Confusion, hallucinations, and delirium, especially in older adults, patients with dementia, or patients on other anticholinergic medications. The risk is higher with immediate-release higher doses.
• Impulse control problems (compulsive gambling, shopping, or eating), rare but reported with dopaminergic medications, including amantadine.
• Sudden falls or postural hypotension in older adults.
• Neuroleptic malignant syndrome-like reaction if amantadine is stopped abruptly in Parkinson patients.
• Suicidal thoughts, reported rarely; any new or worsening thoughts of self-harm should prompt contact with the prescriber.

Sexual and relational effects

Amantadine isn't a common cause of sexual side effects. It's sometimes used off-label to try to counteract SSRI-related sexual dysfunction, with mixed results. If sexual function shifts either way after starting it, that's worth mentioning to the prescriber.

Weight, appetite, and sleep

Weight and appetite aren't strongly affected. Sleep can be disrupted if the dose is taken late; shifting it earlier usually fixes that. Vivid dreams are common enough that it's worth mentioning to patients ahead of time.

Starting and dosing basics

This section is general background, not a dosing instruction for any individual. The right dose is a decision for a prescriber.

Amantadine comes as immediate-release capsules and tablets (typically 100 mg), an oral solution, and two extended-release products (Gocovri, dosed at bedtime; Osmolex ER, dosed in the morning). For most psychiatric uses, immediate-release is what's used, dosed once or twice daily. Renal function is checked, and the dose is adjusted accordingly.

Missed doses and interactions

If you miss a dose, take it as soon as you remember unless the next scheduled dose is close. Don't double up.

The main interactions to know:

• Anticholinergic medications (benztropine, diphenhydramine, oxybutynin) can add up with amantadine's mild anticholinergic effect, increasing dry mouth, constipation, and confusion.
• Alcohol adds to sedation and dizziness.
• QT-prolonging medications need caution.
• Live attenuated flu vaccine can be less effective if amantadine is taken around the same time (a historical concern from its antiviral days).
• Other dopaminergic drugs can add to impulse control side effects.

Give every prescriber and pharmacist a full list of your medications and supplements.

Stopping and tapering

Don't stop amantadine abruptly, particularly if it's being used in Parkinson disease. Sudden discontinuation can precipitate a Parkinson-hyperpyrexia syndrome that looks like neuroleptic malignant syndrome. Even in psychiatry, a step-down over a week or two is generally safer than an abrupt stop.

Pregnancy and breastfeeding

Amantadine crosses the placenta and has been linked to some malformations in animal studies and case reports. Use in pregnancy is generally avoided unless the benefit is clear. It passes into breast milk. Anyone who is pregnant, planning a pregnancy, or breastfeeding should talk it through with their prescriber so specific risks and benefits can be weighed.

Cost and generic availability

Immediate-release amantadine has been generic for many years and is inexpensive. Gocovri (extended-release for Parkinson dyskinesia and tardive dyskinesia) is brand-only and expensive. Osmolex ER is also more expensive than immediate-release generic. For most psychiatric uses, generic immediate-release amantadine covers what's needed.

Common questions

Why is this in the movement disorder section instead of the antiviral section? Its antiviral use for influenza has largely been retired because of resistance. Its ongoing clinical role is in movement disorders, both drug-induced and Parkinson-related.

What's the net-like pattern on the legs? That's livedo reticularis. It's a harmless dilation of small skin vessels, more common with longer use. It can be cosmetically bothersome but isn't dangerous, and it goes away if the drug is stopped.

Will it make my psychosis worse? Usually not at typical psychiatric doses. Because the dopamine effect is indirect and mild, amantadine tends to be manageable alongside an antipsychotic. At higher doses, hallucinations and confusion can occur, especially in older adults.

Can I take it with my SSRI? Yes, generally. Amantadine is sometimes tried for SSRI-related sexual dysfunction, though evidence for that use is mixed.

Does it help with fatigue? Some patients notice a mild mental lift, and it's used off-label in a few conditions (like MS-related fatigue). The effect is variable.

Questions to ask your prescriber

• What are we hoping this treats, and how will we know it's working?
• Given my kidney function, is the dose right?
• Are any of my other medications a problem to combine with it?
• What signs should trigger a call (confusion, swelling, impulse changes)?
• If we stop it later, how would we do that safely?

Sources

This guide draws on current prescribing information and public health references. It is reviewed for clinical accuracy and updated as guidance changes, and current as of June 8, 2026.

• U.S. Food and Drug Administration. Amantadine prescribing information (Symmetrel, Gocovri, Osmolex ER).
• DailyMed, U.S. National Library of Medicine. Amantadine label.
• MedlinePlus, U.S. National Library of Medicine. Amantadine.
• National Institute of Mental Health. Mental health medications.
• American Academy of Neurology. Practice guideline on treatment of Parkinson disease motor symptoms.