Amantadine is a medication that works on the brain’s dopamine system and certain nerve receptors to treat Parkinson’s disease, reduce involuntary movements caused by other medications, and aid recovery after traumatic brain injury. It was originally approved as an antiviral drug for influenza A, but widespread resistance among flu strains has made that use obsolete. Today, amantadine is primarily a neurological medication.
How Amantadine Works in the Brain
Amantadine has a dual mechanism. First, it increases dopamine levels in the brain by blocking the reuptake of dopamine in a key movement-control region called the striatum. This means more dopamine stays active between nerve cells for longer, which helps restore the chemical signaling that Parkinson’s disease disrupts. Second, it blocks a type of receptor called NMDA, which responds to a chemical messenger involved in nerve excitability. Overactive NMDA signaling contributes to both the symptoms of Parkinson’s disease and the involuntary movements (dyskinesia) that develop as a side effect of long-term Parkinson’s treatment.
This combination of boosting dopamine and calming overexcited nerve pathways is what makes amantadine useful across several neurological conditions. Researchers have noted that while NMDA receptor blocking plays a clear role, other effects that aren’t fully understood also contribute to the drug’s benefits.
Parkinson’s Disease and Dyskinesia
Amantadine is FDA-approved for treating Parkinson’s disease itself, including cases that develop after brain infections, carbon monoxide poisoning, or age-related blood vessel changes in the brain. It can be used as an early treatment on its own or added to other Parkinson’s medications later in the disease course.
Where amantadine really stands out is in managing dyskinesia, the uncontrolled writhing or jerking movements that many Parkinson’s patients develop after years on levodopa (the main Parkinson’s drug). An extended-release form of amantadine, taken once daily at bedtime, was specifically developed for this problem. In pooled data from pivotal clinical trials, patients taking this formulation gained an average of 2.9 extra hours per day of “on” time without any dyskinesia compared to placebo. By week 12, 56% of treated patients spent more than half their waking day free of dyskinesia, up from just 5% at the start. Only 23% of patients on placebo reached the same threshold. Perhaps most striking, 16% of treated patients reported zero troublesome dyskinesia at the end of the trial, compared with just 1% on placebo.
Amantadine is also approved for drug-induced extrapyramidal reactions, which are the stiffness, tremors, and involuntary movements that certain psychiatric medications can cause.
Traumatic Brain Injury Recovery
One of amantadine’s most important uses isn’t on the FDA label at all. It’s widely prescribed to help people recover consciousness and cognitive function after severe traumatic brain injury. The logic is straightforward: by stimulating the brain’s arousal systems through dopamine activity and reducing harmful nerve overexcitation through NMDA blocking, amantadine may help “wake up” an injured brain.
A 2024 meta-analysis pooling data from six randomized controlled trials with 426 patients found that those treated with amantadine had significantly higher consciousness scores at day 7 and better cognitive test results compared to placebo. The picture isn’t entirely clear, though. Disability ratings between weeks 3 and 4 actually favored the placebo group, and there were no significant differences in overall hospital stay or long-term outcome scores. Still, the early improvements in awareness and cognition are meaningful for families waiting for signs of recovery.
Why It’s No Longer Used for the Flu
Amantadine was originally developed in the 1960s as an antiviral, approved for both preventing and treating influenza A infections. It worked by blocking a protein on the flu virus’s surface that the virus needs to release its genetic material inside cells. The CDC no longer recommends amantadine for seasonal flu because nearly all circulating influenza A strains have developed resistance to it. This resistance is so widespread that the entire class of drugs (called adamantanes) has been sidelined in favor of newer antivirals. The FDA approval technically still exists, but in practice, no one prescribes amantadine for the flu anymore.
Fatigue in Multiple Sclerosis
Amantadine is one of the most commonly prescribed medications for the crushing fatigue that affects many people with multiple sclerosis. However, the evidence supporting this use is weak. A systematic review and meta-analysis found that amantadine and similar medications showed minimal to no benefit for fatigue severity in MS patients. The small improvements measured in studies fell below the threshold considered clinically meaningful. On top of that, people taking these medications were more than twice as likely to stop treatment compared to those on placebo, largely due to side effects. Despite the thin evidence, many neurologists still try amantadine for MS fatigue because few alternatives exist.
Common Side Effects
Amantadine’s side effects range from mild annoyances to a distinctive skin change. Many people experience nausea, dizziness, insomnia, or dry mouth, particularly when starting the medication. The most visually striking side effect is livedo reticularis, a lace-like purple or reddish mottling of the skin, usually on the legs. Reported rates vary enormously, from 2% to as high as 90% depending on the study. This skin change can appear months or even years after starting the drug and typically fades within a few weeks of stopping it. Because the mottling is painless and cosmetic, it doesn’t always require stopping treatment if the medication is helping with a neurological condition.
Starting and Stopping Safely
For Parkinson’s disease, doctors typically start at a low dose and increase gradually. The standard forms (capsules, tablets, or liquid) are taken once or twice daily, while the extended-release version designed for dyskinesia is taken once at bedtime. Kidney function matters significantly with this drug because amantadine is cleared almost entirely through the kidneys. People with moderate kidney impairment receive roughly half the standard dose, those with more severe impairment get even less, and the drug is contraindicated entirely when kidney function drops below a certain threshold. It cannot be effectively removed by dialysis, so it’s not recommended for people with end-stage kidney disease.
Stopping amantadine abruptly is risky. Sudden withdrawal can trigger fever, confusion, severe mental status changes, and dangerous muscle rigidity, a constellation that resembles neuroleptic malignant syndrome. Published case reports describe acute delirium developing after abrupt discontinuation in Parkinson’s patients, with symptoms resolving only after the medication was restarted (typically within days). For this reason, the dose should always be tapered gradually under medical supervision rather than stopped all at once.