Symmetrel (Amantadine): Uses for Parkinson's, Side Effects, and Dosage
Medically reviewed by Alan Lucks | MD, Alan Lucks MDPC Private Practice - New York on September 1st, 2026.
Published on March 9th, 2026.
Key Takeaways
Generic amantadine treats Parkinson's disease symptoms and can reduce involuntary movements caused by certain medications.
Amantadine is not recommended for the flu because circulating influenza A viruses are resistant; its main use today is Parkinson's disease.
Works by increasing dopamine levels in the brain and blocking a protein that affects nerve signals.
Common side effects include dizziness, insomnia, and dry mouth, which usually improve over time.
Must be taken exactly as prescribed and can interact with several other medications.
Doctronic's medical AI can help you understand whether amantadine fits your situation, and a licensed doctor is available by video when you want one.
Symmetrel (Amantadine) Overview
Amantadine (brand name Symmetrel) is a Parkinson's medication that was originally developed as an antiviral. It has been used for decades to treat movement disorders. Brand-name Symmetrel has been discontinued. Immediate-release amantadine is now sold as a generic alternative to brand-name drugs and typically costs less than the extended-release brands (Gocovri, Osmolex ER).
This medication works in two main ways. It increases dopamine, a chemical messenger that controls movement and mood. It also blocks a protein called NMDA, which helps calm overactive nerve signals.
Doctors prescribe amantadine mainly to manage Parkinson's symptoms such as tremors, rigidity, and slow movement. It's also used to reduce involuntary movements (called dyskinesia) that can develop with long-term levodopa use.
It was once used for influenza A, but the CDC no longer recommends it for flu because circulating influenza A viruses are resistant.
Understanding generic vs brand-name drugs can help you make informed decisions about your treatment.
Is Amantadine Used for the Flu?
No. Amantadine and the related Flumadine (rimantadine) were once used for influenza A, but circulating flu viruses are now resistant. The CDC doesn't recommend either one to treat or prevent flu.
If you have the flu, ask a licensed doctor about current flu antivirals such as Tamiflu (oseltamivir) or Xofluza (baloxavir), or get flu treatment online by video on Doctronic.
Side Effects
Amantadine is generally well tolerated, but like all medications, it can cause side effects. Most side effects are mild and improve as your body adjusts to the drug. However, it's important to know what to watch for and when to contact your doctor.
Common Side Effects
Dizziness or lightheadedness: Often happens when you stand up quickly. Moving slowly from sitting or lying down can help reduce this effect.
Insomnia or sleep disturbances: Some people have trouble falling or staying asleep. Taking the medication earlier in the day may help.
Dry mouth: Stay hydrated by drinking plenty of water, and consider sugar-free lozenges or gum.
Constipation: Eating more fiber, drinking more water, and exercising regularly can help prevent this.
Nausea: Taking amantadine with food may reduce stomach upset.
Difficulty concentrating or confusion: Mental fog is possible, especially at higher doses. Talk to your doctor if it affects your daily activities.
Serious Side Effects
Hallucinations or severe confusion: These psychiatric symptoms can happen and need immediate medical attention.
Irregular heartbeat or rapid heart rate: Contact your doctor right away if you feel your heart racing or beating irregularly.
Swelling in the legs or feet (edema): This may be a sign of fluid buildup and should be checked by a doctor.
Severe allergic reactions: Rash, hives, difficulty breathing, or facial swelling need emergency care.
Seizures: Though rare, amantadine can lower the seizure threshold in some people, especially at higher doses.
When to Seek Medical Attention
Contact your doctor if you experience confusion, hallucinations, severe dizziness, irregular heartbeat, or difficulty urinating. If you develop signs of an allergic reaction (such as rash, hives, or difficulty breathing), seek emergency care immediately. Most common side effects are mild and tend to improve within the first few weeks of treatment, but contact your doctor if you have concerns.
Dosage
Amantadine comes in immediate-release and extended-release forms, and each has its own uses and dosing.
Dose Level or Form |
Typical Dose |
Key Detail |
|---|---|---|
Parkinson's disease (initial) |
100 mg once daily |
May increase gradually every few days |
Maintenance |
100 mg twice daily |
Some patients benefit from up to 400 mg daily |
Dyskinesia reduction |
100 mg twice daily |
Often added to levodopa therapy |
Renal impairment |
Reduced doses |
Kidney function determines safe dosing |
Gocovri (extended-release capsules) |
137 mg, then 274 mg, at bedtime |
For levodopa-induced dyskinesia and OFF episodes |
Osmolex ER (extended-release tablets) |
Starts at 129 mg once daily in the morning |
For Parkinson's and drug-induced extrapyramidal reactions |
Important: Never stop taking amantadine without talking to your doctor first, as sudden withdrawal can worsen Parkinson's symptoms. Keep amantadine in a cool, dry place away from moisture and direct sunlight. Your doctor will choose the form and dose that fit your situation.
Drug Interactions
Amantadine can interact with other medications, affecting how well it works or increasing the risk of side effects. Always tell your doctor or pharmacist about all medications, supplements, and herbal products you take.
Anticholinergic Medications
Combining amantadine with anticholinergic drugs (used for overactive bladder or Parkinson's) can increase side effects like dry mouth, confusion, and constipation. Your doctor may need to adjust doses or monitor you more closely.
Levodopa (L-dopa)
Amantadine is often combined with levodopa in Parkinson's treatment, and it can lessen the involuntary movements levodopa causes. The combination can raise the risk of psychiatric side effects such as hallucinations or confusion, so your doctor will monitor you closely.
Decongestants and Stimulants
Over-the-counter decongestants containing pseudoephedrine or stimulants may increase heart rate and blood pressure when taken with amantadine. Discuss safe alternatives with your pharmacist.
Thiazide Diuretics
These blood pressure medications may reduce amantadine clearance from your body, potentially leading to higher levels and increased side effects. Your doctor may monitor kidney function more frequently.
NSAIDs and Other Pain Relievers
Combining amantadine with certain NSAIDs may affect kidney function. Acetaminophen is generally a safer choice for pain relief while taking amantadine.
Antipsychotic Medications
Some antipsychotics may interact with amantadine, increasing the risk of psychiatric side effects or reduced medication effectiveness. Your doctor will carefully balance these risks.
Pros and Cons
Pros
Effective symptom relief: Reduces Parkinson's tremors, rigidity, and slow movement in many people.
Lower cost: Generic medications provide cost savings, and immediate-release amantadine typically costs less than the extended-release brands.
Long track record: Used safely for decades, with well-understood benefits and risks.
Reduces medication side effects: Can lessen involuntary movements caused by long-term levodopa use.
Oral administration: Easy to take at home, with no injections or complex procedures.
Cons
Psychiatric side effects possible: Hallucinations and confusion can occur, especially in older adults.
Requires kidney function monitoring: Not suitable for people with significant kidney disease without a dose adjustment.
Multiple drug interactions: Must be carefully managed alongside other medications.
Insomnia and dizziness common: Can affect sleep and balance, particularly early in treatment.
Slow onset of action: May take several weeks to notice the full benefits.
Frequently Asked Questions
Get answers to common questions about amantadine.
Most people begin noticing improvements in Parkinson's symptoms within 1-2 weeks, though full benefits may take 4-8 weeks. Some symptoms, like involuntary movements from levodopa, improve more quickly. Your doctor may adjust your dose gradually to find the right balance between symptom relief and side effects. Don't increase your dose or stop the medication without medical guidance.
Yes. Amantadine is commonly added to levodopa, and it can lessen the involuntary movements levodopa causes. Your doctor will watch for psychiatric side effects and adjust doses as needed. Always take medications exactly as prescribed.
Take the missed dose as soon as you remember, unless it's almost time for your next scheduled dose. In that case, skip the missed dose and continue with your regular schedule. Never double up on doses to make up for a missed one, as this increases the risk of side effects. Consider setting phone reminders to help you remember doses.
Yes. Brand-name Symmetrel has been discontinued, so immediate-release amantadine is now dispensed as a generic. It contains the same active ingredient, and the FDA requires generics to meet strict quality and efficacy standards. The main difference between generic and brand-name drugs is the manufacturer.
Avoid alcohol, as it can increase dizziness and confusion. Be cautious with over-the-counter decongestants and stimulants, which may interact with amantadine. Don't drive or operate machinery until you know how the medication affects you. Also avoid suddenly stopping amantadine, as this can worsen Parkinson's symptoms. Always discuss any new medications or supplements with your doctor or pharmacist.
Still have questions?
Ask Doctronic's medical AI any hour, or talk to a licensed doctor by video.
The Bottom Line
Amantadine (Symmetrel) is a proven medication that helps manage Parkinson's disease symptoms. It also reduces involuntary movements caused by long-term levodopa treatment. Immediate-release amantadine is available as a generic and typically costs less than the extended-release brands.
Side effects like dizziness and insomnia are possible, but most people tolerate amantadine well, especially as their body adjusts. Take it exactly as prescribed and keep regular check-ins with your doctor. Report any concerning symptoms right away.
This information is educational and doesn't replace advice from your doctor. Have questions about your dose or side effects? Ask Doctronic's medical AI any hour, and it remembers your history.
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