Amantadine — what it does, how to use it, and what to watch for

Amantadine began life as an antiviral but most people now use it for neurological problems. Doctors commonly prescribe it for Parkinson’s symptoms, to reduce levodopa-induced dyskinesia, and sometimes for fatigue after viral illnesses. It can help movement and reduce involuntary jerks, but it also needs careful dosing and monitoring.

How amantadine works and who gets it

Amantadine affects brain chemicals involved in movement and may block certain receptors (NMDA), which helps reduce involuntary movements. Typical users are people with Parkinson’s disease or those who develop dyskinesia from Parkinson’s meds. Clinicians also use it off-label for post-viral fatigue and some drug-induced movement problems. It’s not usually the first choice for flu treatment today because many flu strains are resistant.

Practical dosing, adjustments, and common side effects

Typical adult dose: many people start at 100 mg once or twice daily. A common regimen is 100 mg twice a day (200 mg/day). Under doctor supervision the dose can be raised — some regimens go to 300 mg/day in divided doses, but higher doses raise the chance of side effects. If you have reduced kidney function, your doctor will cut the dose because the drug leaves the body through the kidneys.

Watch for these side effects: dizziness, confusion, vivid dreams or hallucinations, dry mouth, constipation, ankle swelling, and a mottled skin pattern known as livedo reticularis. Older adults and people with dementia are more likely to get confusion or hallucinations. If new mood changes, marked confusion, or swelling appear, tell your clinician right away.

A key safety tip: don’t stop amantadine suddenly without medical advice. Stopping abruptly can worsen movement problems and, rarely, cause severe withdrawal effects. Your prescriber will taper the dose if they need to stop it.

Drug interactions and monitoring: tell your doctor about other medicines that affect the brain (anticholinergics, antipsychotics, strong sedatives) because side effects add up. Because kidneys clear amantadine, drugs or conditions that change kidney function can change levels. Your provider may check kidney function and ask about balance, sleep, and mood during follow-up visits.

How to take it: take the tablet with food if stomach upset happens. Avoid driving or heavy machinery until you know how it affects you — it can cause dizziness and sleepiness. Drink enough water but mention any sudden weight gain or leg swelling to your clinician.

If you’re pregnant, breastfeeding, or have serious kidney disease, talk to your doctor before using amantadine. Always follow the prescribing information your clinician gives you and ask questions when something feels off. Simple checks — kidney tests and a quick status check about mood and walking — keep treatment safer and more effective.