Symmetrel (Amantadine) Guide: Uses, Dosage, Side Effects & Safety

TL;DR

• Symmetrel is the brand name for amantadine, originally an antiviral now used for Parkinson’s disease and MS‑related fatigue.
• Typical adult dose for Parkinson’s is 100mg once daily; for flu prophylaxis it’s 200mg once daily for 6days.
• Common side effects include nausea, dizziness, insomnia and a dry mouth; serious effects are rare but can include heart problems.
• Never mix Symmetrel with MAO‑B inhibitors or certain anticholinergics without doctor approval.
• Always tell your doctor about kidney issues, heart disease, or pregnancy before starting.

What is Symmetrel and How It Works

Symmetrel is the trade name for the drug amantadine. It first hit the market in the 1960s as the first oral medication that could fight the flu‑A virus. Over time, doctors discovered it has a knack for affecting dopamine pathways in the brain, which makes it useful for a handful of neurological conditions.

In plain English, amantadine works in two main ways:

1. Antiviral action: It blocks a viral protein (M2) that the influenza A virus needs to get into host cells, stopping the virus from replicating.
2. Neurological modulation: It nudges dopamine release and reduces its re‑uptake, which helps smooth out the motor symptoms of Parkinson’s disease and can lift the feeling of fatigue in multiple sclerosis (MS).

Because the drug hits both the virus and the brain, the official approved uses differ by country. In Australia, the Therapeutic Goods Administration (TGA) lists the following indications:

• Prevention and early treatment of influenza A infection.
• Adjunct therapy for Parkinson’s disease (often in combination with levodopa).
• Management of fatigue in MS patients.

Off‑label doctors sometimes prescribe it for ADHD, traumatic brain injury, or even opioid withdrawal, but those uses lack robust clinical backing.

Dosage, Administration & Who Should Use It

Dosage depends heavily on why you’re taking Symmetrel. Below is a quick reference that reflects the most common regimens in 2025. Always follow your prescriber’s exact instructions-these numbers are just a baseline.

Key points on how to take the pill:

• Swallow the tablet whole with a full glass of water.
• If you experience stomach upset, taking it with food can help, but avoid high‑fat meals that might delay absorption.
• Do not crush or chew - the coating is designed for steady release.

Who should avoid it? The drug is cleared by the kidneys, so anyone with severe renal impairment (creatinine clearance <30mL/min) needs a dose cut‑back or may be advised to skip it altogether. People with a history of cardiac arrhythmias, especially atrial fibrillation, should discuss risks, as amantadine can affect heart conduction.

Pregnant or breastfeeding mothers should only use Symmetrel if the benefit outweighs the risk; animal studies have shown some fetal toxicity, though human data are limited.

Side Effects, Risks & Precautions

Like any medication, Symmetrel isn’t free of side effects. The majority are mild and resolve on their own, but a few deserve a doctor’s attention right away.

Common, usually mild reactions

• Nausea or vomiting - take with meals or a small snack.
• Dizziness or light‑headedness - avoid driving until you know how you feel.
• Insomnia - try taking the dose in the morning.
• Dry mouth - sip water or use sugar‑free lozenges.
• Loss of appetite - monitor weight, especially in older adults.

Less common but serious concerns

• Heart rhythm problems (e.g., QT prolongation, atrial fibrillation). Get an ECG if you have a cardiac history.
• Psychiatric symptoms - agitation, hallucinations, or worsening of Parkinson’s psychosis.
• Severe skin reactions like Stevens‑Johnson syndrome - stop the drug and seek emergency care if you see blistering or extensive rash.
• Liver toxicity - rare, but watch for yellowing of skin or eyes.

Drug interactions are another piece of the puzzle. The biggest red flag is combining Symmetrel with monoamine oxidase‑B (MAO‑B) inhibitors (e.g., selegiline, rasagiline). This combo can trigger a hypertensive crisis. Other meds to flag:

• Anticholinergics (e.g., benztropine) - may amplify central side effects.
• QT‑prolonging drugs (e.g., certain anti‑arrhythmics, macrolide antibiotics) - increase cardiac risk.
• Kidney‑affecting drugs - may require dose adjustment.

Before you start, give your doctor a full list of prescription, over‑the‑counter and herbal products you’re taking. A quick check can prevent a nasty surprise.

Practical Tips & Frequently Asked Questions

Thinking about starting Symmetrel? Here are some everyday pointers that make the experience smoother.

Checklist before your first dose

1. Confirm the indication with your doctor - antiviral, Parkinson’s or MS fatigue.
2. Ask whether a baseline ECG or kidney function test is needed.
3. Write down every medication you currently use, including supplements.
4. Set a daily reminder (phone alarm, pillbox) to keep the timing consistent.
5. Plan a low‑fat breakfast or snack to reduce stomach upset.

Managing side effects

• If nausea persists, your doctor may prescribe an anti‑emetic or suggest splitting the dose (e.g., 50mg twice daily).
• For insomnia, avoid caffeine after 2pm and keep the dose early in the day.
• Dry mouth? Chew sugar‑free gum, sip water, or ask about saliva substitutes.
• Dizziness? Rise slowly from sitting to standing; use a sturdy chair for support.

When to Call the Doctor

• Rapid heart beat, chest pain, or fainting.
• Hallucinations, severe agitation, or mood swings.
• Rash that spreads, especially if it blisters.
• Persistent vomiting that prevents you from staying hydrated.

Frequently Asked Questions

• Can I take Symmetrel with alcohol? A little alcohol isn’t usually a problem, but heavy drinking can worsen dizziness and liver strain.
• Does Symmetrel work for the common cold? No. It only targets influenza A; it has no impact on rhinoviruses that cause colds.
• How long does it stay in my system? The half‑life is about 15‑17hours in healthy adults, so it takes roughly 3‑4 days to clear completely after the last dose.
• Can I stop it abruptly? Generally yes for the flu indication, but for Parkinson’s you should taper under a doctor’s guidance to avoid rebound symptoms.
• Is there a generic version? Yes, amantadine hydrochloride tablets are available as a cheaper generic in most pharmacies.

Finally, if you’re unsure whether Symmetrel is the right fit, ask your health professional for a risk‑benefit discussion. The drug can be a lifesaver for flu outbreaks and a useful tool for managing neurological symptoms, but it isn’t a one‑size‑fits‑all solution.

Next Steps & Troubleshooting

• Start low, go slow: If you’re new to the medication, ask about beginning at 50mg and titrating up.
• Track symptoms: Keep a short diary of how you feel each day - energy levels, sleep quality, any side effects.
• Follow‑up labs: Schedule a kidney function test after 2‑4 weeks if you have any renal concerns.
• Switching meds: If you need to stop, discuss a taper plan especially for Parkinson’s disease.
• Ask for support: Pharmacists can advise on over‑the‑counter remedies for nausea or dry mouth without risking interactions.

With the right information and a bit of vigilance, Symmetrel can be used safely and effectively. Keep this guide handy, and don’t hesitate to reach out to your doctor if anything feels off.