Amantadine

Key facts

• Amantadine treats the tremor, stiffness and slow movement of Parkinson's disease and drug-induced movement problems, and was historically used to prevent or treat influenza A.
• It's usually taken once or twice daily; effects on tremor and stiffness can appear within days.
• Stopping amantadine abruptly can trigger a dangerous withdrawal reaction of high fever, severe confusion and muscle rigidity, similar to neuroleptic malignant syndrome. The dose must always be tapered down.
• Seek urgent care for hallucinations, sudden severe confusion, or a fast or irregular heartbeat.

What Amantadine treats

Amantadine treats the tremor, stiffness and slow movement of Parkinson's disease, often added when other treatments aren't enough on their own. It also treats movement side effects caused by antipsychotic medicines. It was historically used to prevent and treat influenza A, though widespread viral resistance means it's rarely used for this now.

How Amantadine works

In the brain, amantadine increases the release and availability of dopamine, the chemical messenger that smooths out movement, easing Parkinson's symptoms. Against influenza A, it blocks a viral protein the virus needs to release its genetic material inside infected cells, stopping it from replicating.

Before you take it

• Tell your prescriber about seizures, heart rhythm problems, kidney disease, or a history of hallucinations or severe confusion, since amantadine can worsen all of these.
• Amantadine is cleared by the kidneys, so reduced kidney function raises the risk of confusion and hallucinations, and the dose may need lowering.
• Combining amantadine with other medicines that affect dopamine, or with drugs that prolong the heart's QT interval, raises the risk of side effects.
• Avoid alcohol, which worsens dizziness and confusion.

Side effects

Common effects include nausea, dizziness, trouble sleeping and dry mouth.

Stop and seek urgent medical care for:

• Hallucinations, severe confusion or sudden agitation.
• High fever and muscle stiffness or rigidity, especially after missed doses.
• A fast or irregular heartbeat, or fainting.

Safety essentials

• Never stop amantadine suddenly. Abrupt withdrawal can cause a fever-and-rigidity reaction resembling neuroleptic malignant syndrome, so the dose is always tapered down under medical guidance.
• Kidney function should be checked before starting and monitored during treatment, since amantadine builds up when the kidneys don't clear it properly.
• Tell your prescriber if you or your family notice new confusion, hallucinations or impulsive behaviour, which can develop gradually.

This page is educational and does not replace advice from a doctor or pharmacist who knows your health history.