amantadine hydrochloride at a glance
Medicine class
Antiparkinsonian agent with NMDA-receptor antagonist activity.
Main licensed role
Treatment of Parkinson’s disease.
What is amantadine hydrochloride used for?
Licensed uses vary between products.
Parkinson’s disease: licensed across selected capsule and liquid products to improve movement symptoms.
Herpes zoster: certain capsules and syrup are licensed to reduce prolonged pain in selected older or debilitated patients at risk of severe, painful shingles.
Influenza A: certain capsules and syrup retain licences for prevention and treatment, but amantadine is not recommended for seasonal influenza because resistance is widespread.
How does amantadine hydrochloride work?
Amantadine weakly blocks NMDA-type glutamate receptors, reducing excessive excitatory signalling implicated in parkinsonian symptoms; it also has some anticholinergic activity. Against susceptible influenza A viruses, it blocks the viral M2 proton channel and disrupts viral replication. Its action in shingles is not fully understood.
amantadine hydrochloride preparations and strengths
Capsule
Route: Oral
Strengths: 100 mg
Oral solution
Route: Oral
Strengths: 50 mg/5 mL
Syrup
Route: Oral
Strengths: 50 mg/5 mL
How to take amantadine hydrochloride
Take amantadine exactly as prescribed. It is taken by mouth.
Swallow capsules whole with water.
Shake liquid formulations before carefully measuring the prescribed amount with a suitable measuring device.
Alcohol may increase dizziness, confusion or other central nervous system effects.
Do not stop treatment suddenly; withdrawal should be supervised by the prescriber.
amantadine hydrochloride side effects
Common or expected effects
- Ankle swelling or mottled, net-like skin discolouration
- Dizziness, headache, tiredness or difficulty concentrating
- Confusion, hallucinations, anxiety, low mood, insomnia or nightmares
- Dry mouth, reduced appetite, nausea, vomiting or constipation
- Sweating, muscle pain, palpitations or dizziness on standing
Get urgent medical advice
- Seizure, severe confusion, delirium or psychosis
- Suicidal thoughts or behaviour
- Fever, sweating, muscle rigidity and altered awareness suggesting a malignant withdrawal syndrome
- New compulsive gambling, spending, eating or sexual behaviour
- Shortness of breath or worsening swelling suggesting heart failure
- Blurred vision, eye pain or reduced sight associated with possible corneal injury
amantadine hydrochloride in pregnancy
The selected products contraindicate amantadine during pregnancy and while trying to conceive because pregnancy-related complications have been reported and safety evidence is inadequate. Anyone who becomes pregnant while taking it should contact the prescriber promptly rather than stopping abruptly without advice.
amantadine hydrochloride while breastfeeding
Amantadine passes into breast milk, and adverse effects have been reported in breastfed infants. The selected products advise that breastfeeding patients should not take it; specialist assessment is needed to discuss treatment and feeding options.
amantadine hydrochloride interactions
Check all prescribed, over-the-counter and recreational substances before treatment.
Anticholinergic medicines
May increase confusion, hallucinations, nightmares, constipation, dry mouth and urinary problems.
Levodopa
May increase hallucinations, confusion and other central or anticholinergic effects.
Common questions about amantadine hydrochloride
Answers are fully visible for fast scanning and source review.
Why must amantadine hydrochloride not be stopped suddenly?
Abrupt withdrawal can worsen parkinsonism and may rarely cause confusion, delirium or a syndrome involving fever, sweating and severe muscle stiffness. Withdrawal should be planned with the prescriber.
Can amantadine hydrochloride still be used for flu?
Some products remain licensed for influenza A, but amantadine is not recommended for seasonal influenza because resistant viruses are widespread.
Sources
These sources were used to prepare and review this medicine page.
Prepared and reviewed by the iatroX editorial team.