Review Drug

Brand name Symmetrel

Used in the following combined preparations None

General Information

Amantadine was first used in the 1960s as an antiviral drug, originally for the prevention and treatment of influenza A. As a preventative against influenza A, it protects some 70 per cent of those not receiving vaccination. As treatment, it is effective in reducing the severity of symptoms when given within 48 hours of the onset of flu. It can also reduce pain following herpes zoster (shingles).

Information for Users

Your drug prescription is tailored for you. Do not alter dosage without checking with your doctor.

How taken

Capsules, liquid.

Frequency and timing of doses

1-2 x daily. The second dose should not be taken later than 4pm.

Adult dosage range

100-200mg daily.

Onset of effect

In parkinsonism the full effect may not be felt for up to 2 weeks. In viral infections the severity and duration of symptoms is likely to be reduced during a 1-2 week course of treatment if the drug is begun within 48 hours of the onset of symptoms. In 1969 amantadine was found to be helpful in parkinsonism, and this is now its most common use. Amantadine usually produces improvement of symptoms during the first few weeks, but its effectiveness wears off over six to eight weeks, requiring replacement by another drug. It is sometimes given with levodopa, another drug for parkinsonism.

Duration of action

Up to 24 hours.

Diet advice

None.

Storage

Keep in a closed container in a cool, dry place out of the reach of children.

Missed dose

Take as soon as you remember. If your next dose is due within 2 hours, take a single dose now and skip the next.

Stopping the drug

Do not stop taking the drug without consulting your doctor; symptoms may recur.

Exceeding the dose

An occasional unintentional extra dose is unlikely to be a cause for concern. But if you notice any unusual symptoms, or if a large overdose has been taken, notify your doctor.

Possible Adverse Effects

Adverse effects are uncommon and often wear off during continued treatment. They are rarely serious enough to require treatment to be stopped.

 

Interactions

Anticholinergic drugs.

Amantadine may add to the effects of anticholinergic drugs. In that event your doctor will probably reduce the dosage of the anticholinergic drugs.

Quick Reference

Drug group Drug for parkinsonism drug and antiviral drug

Overdose danger rating Low

Dependence rating Low

Prescription needed Yes

Available as generic No

Special Precautions

Be sure to tell your doctor if:

You have long-term liver or kidney problems.

You have a peptic ulcer.

You have had epileptic fits.

You have heart disease.

You suffer from eczema.

You are taking other medications.

 

Pregnancy

Safety in pregnancy not established. Discuss with your doctor.

 

Breast-feeding

The drug passes into the breast milk and may affect the baby. Discuss with your doctor.

 

Infants and children

Not usually prescribed. Reduced dose necessary.

 

Over 60

Increased likelihood of adverse effects. Reduced dose may therefore be necessary.

 

Driving and hazardous work

Avoid such activities until you have learned how amantidine affects you because the drug may cause blurred vision, dizziness, and confusion.

 

Alcohol

No known problems.

 

Prolonged Use

The beneficial effects of this drug usually diminish during continuous treatment for parkinsonism. When this occurs, another drug may be substituted for or given together with amantadine. Sometimes the effectiveness of amantadine can be restored if it is withdrawn by your doctor for a few weeks and later reintroduced.