Amantadine: what it treats, how to take it, side effects
Last updated September 7, 2026.
**Amantadine is a prescription medicine that acts both as a dopaminergic drug for movement symptoms and as an antiviral against influenza A.** It increases dopamine signaling in the brain and blocks NMDA glutamate receptors, which can ease stiffness, tremor, and the extra involuntary movements that come with long-term levodopa use. Your kidneys clear almost all of the drug, so the dose has to match your kidney function, and older adults usually need less. Do not stop amantadine suddenly, because abrupt withdrawal can bring back parkinsonism sharply and can trigger fever, confusion, and muscle rigidity.
What does it treat?
Amantadine is approved for parkinsonism, including idiopathic Parkinson's disease, postencephalitic parkinsonism, and parkinsonism that follows carbon monoxide poisoning or other injury to the nervous system. It is also approved for drug-induced extrapyramidal reactions, meaning the stiffness, restlessness, and abnormal movements that antipsychotic medicines can cause. Extended-release versions such as Gocovri carry a separate approval for dyskinesia and for off episodes in people with Parkinson's disease who already take levodopa, so amantadine is often layered on top of carbidopa-levodopa rather than used alone. Older immediate-release labels also list prevention and treatment of influenza A, but CDC no longer recommends amantadine for flu because circulating influenza A strains are resistant to it. Clinicians sometimes prescribe it off label for fatigue in multiple sclerosis or for arousal after brain injury, and those uses are decided case by case.
How do you take it?
Immediate-release amantadine comes as 100 mg capsules and tablets and as an oral solution or syrup containing 50 mg per 5 mL, and extended-release comes as capsules (68.5 mg and 137 mg) and tablets (129 mg, 193 mg, and 258 mg). For parkinsonism, the label starts most adults at 100 mg once daily and moves to the usual 100 mg twice daily, with a ceiling of 400 mg a day in divided doses for people who do not respond, given only under close supervision. For drug-induced extrapyramidal reactions the usual dose is 100 mg twice daily, occasionally up to 300 mg a day in divided doses. Gocovri extended-release capsules are taken at bedtime, 137 mg once daily for the first week and then 274 mg once daily; extended-release tablets start at 129 mg each morning and go no higher than 322 mg a day. Influenza A dosing in adults is 200 mg a day, taken once or split as 100 mg twice daily, and 100 mg a day if you are 65 or older. You can take any form with or without food, but take your last immediate-release dose in the afternoon or early evening so it does not keep you awake, and swallow extended-release forms whole or sprinkle the capsule contents on a spoonful of soft food. If you miss a dose, take it when you remember unless your next dose is close, then skip it and go back to schedule; never double up. If your kidney function is reduced, your prescriber will lower the dose or stretch the interval between doses. Call your prescriber before stopping, and call the same day if you develop hallucinations, new confusion, blurred vision, or ankle swelling with shortness of breath.
Side effects to know
- Common: Common effects are nausea, dizziness or lightheadedness when you stand up, trouble sleeping, vivid dreams, dry mouth, constipation, ankle swelling, and a purple lace-like mottling of the skin on the legs called livedo reticularis, which fades after the drug is stopped.
- Serious: Stop and get medical help for hallucinations, new confusion or paranoia, thoughts of suicide or self-harm, sudden episodes of falling asleep during normal daily activity, blurred or lost vision from corneal swelling, or new leg swelling with breathlessness. Fever with muscle rigidity, sweating, and confusion after a missed or stopped dose is an emergency, not a reason to wait for the next appointment.
Who should not take it?
Do not take amantadine if you have had an allergic reaction to it, and do not take the extended-release forms if you have end-stage kidney disease with a creatinine clearance below 15 mL per minute. Talk with a clinician first if you have any degree of kidney disease, a seizure disorder, heart failure or ongoing swelling, low blood pressure on standing, untreated angle-closure glaucoma, a history of psychosis or current psychiatric illness, or a history of compulsive gambling, shopping, eating, or sexual behavior, since dopamine drugs can set off those urges. Amantadine adds up with other medicines that dry you out or cloud thinking, including anticholinergics for bladder or stomach spasm, sedating antihistamines, thioridazine, quinine and quinidine, and other dopamine agonists or stimulants; triamterene with hydrochlorothiazide and trimethoprim-sulfamethoxazole can raise amantadine levels in your blood. Skip the live attenuated nasal flu vaccine within two weeks before or 48 hours after amantadine, and use the injected vaccine instead. Avoid alcohol, which sharply increases the dizziness, confusion, and drops in blood pressure this drug already causes. Human pregnancy data are limited and animal studies showed harm at high doses, so current FDA labeling says to use amantadine in pregnancy only when the benefit justifies the risk; amantadine passes into breast milk and can reduce milk supply, so breastfeeding is not recommended while you take it.
When is it an emergency?
For a known or suspected overdose, call Poison Control at 1-800-222-1222 right away, and call 911 if the person collapses, has a seizure, cannot be woken, or has trouble breathing. Amantadine overdose is dangerous in adults and in children who get into a caregiver's supply, and it shows up as agitation, hallucinations, seizures, a fast or irregular heartbeat, very high blood pressure, high body temperature, and coma. Deaths have been reported after acute overdoses as low as 1 gram. Call 911 for signs of a severe allergic reaction, including swelling of the lips, tongue, or throat, hives, wheezing, or tightness in the chest. Go to an emergency department for fever with muscle stiffness, sweating, and confusion, especially after doses were missed or the drug was stopped, and for sudden loss of vision.
What a Pymander AI doctor consult looks like
Illustrative example, not a real member's messages.
Common questions
What is the maximum amount of amantadine I can take in a day?
For immediate-release amantadine, the label allows up to 400 mg a day in divided doses for parkinsonism, and that upper range is used only under close supervision when 100 mg twice daily is not enough. Most people stay at 100 mg twice daily. For drug-induced movement reactions, the usual maximum is 300 mg a day in divided doses. Extended-release capsules top out at 274 mg once daily at bedtime, and extended-release tablets at 322 mg a day. If your kidney function is reduced, your safe daily total is lower than all of these numbers, and your prescriber sets it from your creatinine clearance.
Can I drink alcohol while taking amantadine?
No. Alcohol and amantadine both cause dizziness, confusion, poor concentration, and drops in blood pressure when you stand, and together the effect is stronger than either one alone. That combination raises your chance of falling, which matters more if you already have Parkinson's disease. The risk is highest in the first weeks and after any dose increase. If you drink regularly, tell your prescriber rather than stopping alcohol abruptly on your own, because alcohol withdrawal needs its own plan.
Is amantadine safe during pregnancy or breastfeeding?
Human data in pregnancy are limited, and animal studies showed harm to offspring at doses above those used in people. Current FDA labeling says amantadine should be used in pregnancy only if the potential benefit justifies the potential risk, so this is a decision to make with your obstetric clinician and your neurologist before you conceive if possible. Amantadine passes into breast milk and can lower prolactin, which reduces milk supply, so breastfeeding is not recommended while you take it. If you become pregnant on amantadine, do not stop it on your own; abrupt withdrawal can cause a serious rebound in symptoms. Call your prescriber the same week so the plan can be adjusted safely.
Should I take amantadine with food, and does the time of day matter?
Food does not change how well amantadine works, so you can take any form with or without meals. Taking it with food or a snack can settle nausea if that is a problem for you. Timing matters more than food: amantadine is stimulating, so take your last immediate-release dose in the afternoon or early evening rather than at bedtime, or it will keep you awake. Extended-release capsules are the exception and are designed to be taken at bedtime, while extended-release tablets are taken in the morning. Swallow extended-release forms whole, or open a capsule and sprinkle the contents onto a spoonful of soft food without chewing.
What are the signs of an amantadine overdose?
Overdose shows up as agitation, hallucinations, confusion, seizures, a fast or irregular heartbeat, very high blood pressure, high body temperature, difficulty urinating, and in severe cases coma. Deaths have been reported after acute overdoses as low as 1 gram, so the margin is narrow and children who swallow an adult's capsules are at real risk. Call Poison Control at 1-800-222-1222 immediately if too much has been taken, even if the person still seems fine. Call 911 for seizures, collapse, trouble breathing, or someone you cannot wake. Do not try to make the person vomit.
What medicines interact with amantadine?
Triamterene with hydrochlorothiazide and trimethoprim-sulfamethoxazole can raise amantadine levels in your blood and bring on confusion or hallucinations. Anticholinergic drugs, including bladder antispasmodics and sedating antihistamines, add to dry mouth, constipation, blurred vision, and mental fogginess. Thioridazine can worsen tremor, and quinine or quinidine can slow amantadine's clearance. Other dopamine agonists and stimulants stack with its stimulating effects. Avoid the live attenuated nasal influenza vaccine within two weeks before or 48 hours after amantadine and use the injected vaccine instead. Give your prescriber your full list, including over-the-counter sleep aids and cold medicines, because those often contain antihistamines.