Amantadine (Symmetrel)

How does it work?

This medicine contains the active ingredient amantadine hydrochloride, which is a medicine used in the treatment of Parkinson's disease. It is also used in the prevention and treatment of influenza A, and in certain cases of shingles.

Dopamine is a chemical in the brain known to be absent or reduced in people with Parkinson's disease. Amantadine is thought to increase the release of dopamine in the brain. By increasing dopamine release, amantadine has a mild effect against some of the symptoms of Parkinson's disease such as tremor and rigidity. However, after a period of time, many people observe a reduction in the effect achieved from the same dose (tolerance develops) and therefore its use may be limited. Sometimes the effectiveness can be restored if use of the drug is stopped for a period of time and then restarted. Amantadine is often used in combination with other medicines for the treatment of Parkinson's disease.

Amantadine syrup is also used in the prevention and treatment of flu caused by infection with the influenza A virus. The exact method of action in this capacity is not clear, however, amantadine is thought to inhibit the early stage of replication of the influenza A virus. It can be given to treat people suffering from flu in whom complications may develop, and to prevent flu in people at particular risk. This can include people with chronic lung disease or debilitating conditions, the elderly, the immunosuppressed and those living in crowded conditions. It can also be used to control influenza outbreaks in families where one member has been diagnosed, or in institutions, eg nursing homes, and to prevent infection of people in essential services, eg healthcare workers, who are unvaccinated or cannot be vaccinated against influenza A.Amantadine is also used to treat elderly and physically weak people with shingles (caused by the herpes zoster virus) in whom the doctor suspects that a severe and painful rash may occur. Amantadine is used to reduce the likelihood of this. It is not fully understood how amantadine works in this situation.

What is it used for?

  • Parkinson's disease
  • Prevention and treatment of influenza A (amantadine syrup only)
  • Shingles (herpes zoster)


  • This medicine must not be stopped abruptly if you are taking it for Parkinson's disease, as this can worsen the symptoms of the disease. It should also not be stopped abruptly if you are taking antipsychotic medicines, as this can increase the risk of side effects from the antipsychotic medicine.
  • This medicine may cause dizziness and blurred vision. If affected, caution is required when driving or operating machinery.

Use with caution in

  • Congestive heart failure
  • Elderly people
  • History of disease involving the heart and blood vessels (cardiovascular disease)
  • Individuals experiencing false perceptions of thing that are not really there (hallucinations)
  • Kidney disorders
  • Liver disorders
  • Psychiatric disorders
  • States of confusion

Not to be used in

  • Breastfeeding
  • History of convulsions, eg epilepsy
  • History of stomach ulcers
  • Pregnancy
  • Severe kidney disease

This medicine should not be used if you are allergic to one or any of its ingredients. Please inform your doctor or pharmacist if you have previously experienced such an allergy.If you feel you have experienced an allergic reaction, stop using this medicine and inform your doctor or pharmacist immediately.

Pregnancy and Breastfeeding

Certain medicines should not be used during pregnancy or breastfeeding. However, other medicines may be safely used in pregnancy or breastfeeding providing the benefits to the mother outweigh the risks to the unborn baby. Always inform your doctor if you are pregnant or planning a pregnancy, before using any medicine.

  • This medicine should not be used during pregnancy as it may be harmful to the unborn baby. Seek medical advice from your doctor.
  • Significant amounts of this medicine may pass into breast milk. It should not be used by breastfeeding mothers as it may be harmful to the nursing infant. Seek medical advice from your doctor.

Side effects

Medicines and their possible side effects can affect individual people in different ways. The following are some of the side effects that are known to be associated with this medicine. Because a side effect is stated here, it does not mean that all people using this medicine will experience that or any side effect.

  • Headache
  • Blurred vision
  • Difficulty in sleeping (insomnia)
  • Swelling of the legs and ankles due to excess fluid retention (peripheral oedema)
  • Depression
  • Disturbances of the gut such as diarrhoea, constipation, nausea, vomiting or abdominal pain
  • Seizures (convulsions)
  • False perceptions of things that are not really there (hallucinations)
  • Awareness of your heartbeat (palpitations)
  • Dizziness
  • Loss of appetite
  • A drop in blood pressure that occurs when going from lying down to sitting or standing, which results in dizziness and lightheadedness (postural hypotension)
  • Shaky movements and unsteady walk (ataxia)
  • Concentration difficulties
  • Nervousness
  • Slurred speech
  • Red blotchy spots on the skin (livedo reticularis)

The side effects listed above may not include all of the side effects reported by the drug's manufacturer.For more information about any other possible risks associated with this medicine, please read the information provided with the medicine or consult your doctor or pharmacist.

How can this medicine affect other medicines?

There may be an increased risk of side effects such as blurred vision, constipation, confusion, dry mouth, hallucinations and nightmares if amantadine is taken with other medicines that have anticholinergic effects, including:
- antispasmodic medicines, eg hyoscine
- antihistamines, eg meclozine
- levodopa
- anticholinergic medicines for Parkinson's disease, eg procyclidine
- certain antidepressants
- antipsychotic medicines.There may be an increased risk of side effects on the central nervous system (brain and spinal cord) if this medicine is taken with alcohol or other medicines that act on the central nervous system. If you are taking antipsychotic medicines you should not stop taking amantadine suddenly, as this can increase the risk of side effects from the antipsychotic medicine.In isolated cases, amantadine may worsen psychotic symptoms in people taking antipsychotic medicines.Combination diuretics, such as hydrochlorothiazide plus triamterene, may reduce the excretion of amantadine from the body, and so may increase the risk of amantadine side effects.

Other medicines containing the same active ingredients

Amantadine hydrochloride