Symmetrel (Amantadine)

Symmetrel (Amantadine) – Patient-Friendly Medicine Guide for Australia

Basic Product Information

*Oral solution may be available for paediatric use or in patients with swallowing difficulties.

Mechanism of Action

For Patients

Amantadine helps to balance chemicals in the brain involved in movement and coordination. It works by increasing levels of dopamine, an important brain chemical, making it easier for people to move and reducing shaking (tremors).

For Specialists

Amantadine is a weak, uncompetitive antagonist at the N-methyl-D-aspartate (NMDA) receptor and enhances dopaminergic transmission through presynaptic dopamine release and inhibition of dopamine reuptake. Additionally, it possesses mild anticholinergic properties. These combined actions are thought to underpin its efficacy in Parkinson's disease, levodopa-induced dyskinesias, and limiting viral replication of influenza A.

Pharmacokinetics

• Absorption: Rapid and almost complete absorption after oral administration.
• Distribution: Widely distributed, crosses the blood-brain barrier.
• Metabolism: Minimally metabolised by the liver (limited hepatic biotransformation).
• Elimination: Excreted mainly unchanged via the kidneys (urine). Dose adjustment is advised in renal impairment.
• Duration of Action: Half-life is approximately 10–15 hours in healthy adults, may extend to 24–29 hours in elderly or those with renal impairment.

Use in Everyday Life and Best Practices

• Symmetrel is most often used to treat Parkinson’s disease, symptoms caused by certain medications (such as drug-induced extrapyramidal effects), and for prevention and treatment of influenza A (less common in current Australian practice).
• Usual adult dose for Parkinson’s disease: 100 mg once or twice daily. Your doctor may adjust the dose for maximum benefit with minimum side effects. Children’s doses are based on weight and specific needs.
• Take tablets or capsules with a drink of water. If using oral solution, carefully measure each dose.
• It’s essential to take amantadine at the same times each day. Most Australians prefer breakfast and lunch time for ease and to reduce insomnia risk.
• Avoid missing or abruptly stopping the medicine without consulting your doctor, as this may worsen symptoms.

Dosing: Morning vs Evening

• Morning dosing: Reduces risk of insomnia (difficulty sleeping), as amantadine can be stimulating.
• Evening dosing: Not recommended, especially after 4pm, due to risk of sleep disturbances.
• Ensure regularity by linking doses to daily routines (e.g., with breakfast).

Taking with Food or on an Empty Stomach

• Symmetrel can be taken with or without food. Food does not significantly affect absorption.
• If you experience stomach upset, taking the medicine with a light meal or snack (such as toast or fruit, commonly eaten in Australia) may help.
• Avoid taking with large dairy-rich meals, as high-protein foods may delay some drugs’ absorption, though this effect is minor for amantadine.

Interaction Warnings

Indications

Dosing According to Clinical Indications

*Influenza A use is now rare and generally superseded by other antivirals in Australia.

Safety Profile and Side Effects

If you develop serious side effects or allergic reactions (such as trouble breathing or severe rash), stop taking amantadine and contact your doctor or call 000 for emergencies.

Guidelines for Proper Use in the Australian Context

• Store Symmetrel in a cool, dry place below 25°C and away from direct sunlight, in its original container.
• Take only the exact dose prescribed. Never give your medicine to anyone else, even if their symptoms are similar.
• Keep all medications out of reach of children. Use a daily pill organiser if memory is a concern.
• If you forget a dose, take it as soon as possible. If it’s near the time for your next dose, skip the missed dose—do not double up.
• Attend regular review appointments and report changes in movement, mood, or other medical conditions to your healthcare team.
• In Australia, your pharmacist can provide a Home Medicines Review if you have complex needs, through your GP.

Alternative Treatment Options

• Levodopa/Carbidopa (Sinemet™, Kinson™): Mainstay for Parkinson’s disease; provides stronger symptom control; may cause dyskinesia with long-term use.
• Dopamine agonists (Pramipexole, Ropinirole): Useful as add-on or alternative, can cause impulse control disorders and sleepiness.
• MAO-B inhibitors (Selegiline, Rasagiline): Mild benefit, useful for early disease or as adjuncts.
• Anticholinergics (Benztropine): Effective for tremor in younger adults; anticholinergic side effects limit use in elderly.
• NMDA antagonists (e.g., Memantine): Used off-label in some neuropsychiatric indications, but not routine for Parkinson’s.
• Influenza antivirals (Oseltamivir): Preferred over amantadine for flu prevention/treatment in Australia.

All above medications are available with a prescription and, in many cases, are subsidised under the Pharmaceutical Benefits Scheme (PBS). Some off-label uses are not subsidised.

Legal, Registration & Reimbursement Status in Australia

• Symmetrel (Amantadine) is a Schedule 4 (S4) Prescription Only Medicine, approved by the Therapeutic Goods Administration (TGA).
• It is listed on the PBS for Parkinson’s disease and drug-induced movement disorders, meaning part or all of its cost is subsidised for eligible patients.
• Off-label uses (e.g., MS-related fatigue) may not be subsidised; check with your doctor or the PBS website (pbs.gov.au).
• Not available over the counter in Australia; prescription required from a registered medical practitioner.

Latest Research and Clinical Guidance (2022–2025)

• Amantadine remains an important adjunct in the management of Parkinson’s disease, especially for dyskinesia (uncontrollable movement).
• Recent Australian and international guidelines (Movement Disorders Society, Australian Parkinson’s Guidelines 2023) recommend amantadine particularly for patients troubled by levodopa-induced dyskinesia or requiring fewer tablets per day.
• Amantadine use in influenza is now rare because of high resistance rates reported by Australian Government Department of Health 2024, CDC 2023.
• Trial evidence continues to support off-label use for fatigue in multiple sclerosis, with recent meta-analyses (European Journal of Neurology, 2023) confirming modest benefit.
• Safety alerts: Kidney impairment risk is emphasised in all recent clinical reviews — dose reductions are essential in elderly and/or those with reduced renal function.

References available upon request or via national guideline portals.

Availability and Delivery

Prices and delivery times are indicative only (check with your local PBS pharmacy).

Frequently Asked Questions (FAQ)

1. Can I drink alcohol while taking Symmetrel (Amantadine)?

Small amounts of alcohol may increase drowsiness, risk of falls, or confusion, especially in older adults. It is safer to avoid alcohol, or consult your doctor about your individual risks.

2. What should I do if I miss a dose?

Take your missed dose as soon as you remember—unless your next dose is due soon. Never double up. Resume your normal schedule the next day. If in doubt, ask your pharmacist for advice.

3. Can I stop taking Symmetrel suddenly?

No, do not stop suddenly unless directed by your doctor. Abrupt discontinuation can cause sudden worsening of movement symptoms or rarely, confusion. Discuss any plans to stop or change dose with your prescribing doctor first.

4. Is Symmetrel safe in pregnancy or breastfeeding?

Safety in pregnancy and breastfeeding has not been established. Inform your doctor immediately if you are pregnant, planning pregnancy, or breastfeeding to discuss the safest options for your health and baby.

5. How do I store my medicine?

Store Symmetrel in its original packaging, away from moisture and heat, below 25°C. Keep it out of reach of children. Do not use after the expiry date printed on the pack.