How Amantadine works
Flu (influenza)
Amantadine is used against the so-called “real flu”, although it is only effective against type A influenza viruses. Amantadine is not effective against type B influenza viruses.
Influenza viruses enter the body through droplet or smear infection via the mucous membranes. There they penetrate the cells, lose their envelope (also known as “uncoating”) and multiply rapidly by using the cell’s own machinery to replicate genetic material.
The new viruses are re-enveloped and released from the cell. They can now infect body cells and force them to produce viruses.
Amantadine prevents uncoating, which means that the viruses enter the cell but cannot shed their envelope. This means that virus replication is not possible. This gives the infected person’s immune system a faster chance of bringing the infection under control, which can shorten the acute phase of the disease.
Parkinson’s disease
How amantadine can have a positive effect on Parkinson’s disease is much less well understood than its effect on influenza. It is known that the active ingredient acts on several “messenger substance networks” in the brain. This should alleviate the symptoms of the disease, above all tremors, muscle stiffness (rigor) and lack of movement (hypo/akinesia).
Overall, however, the efficacy of amantadine in the treatment of Parkinson’s disease has not been clearly proven. The active ingredient is often used in addition to drug therapy with L-DOPA in advanced Parkinson’s patients.
Absorption, breakdown and excretion
After ingestion, the active ingredient amantadine is rapidly absorbed into the bloodstream via the intestine, where it reaches its highest levels after two to eight hours. After crossing the blood-brain barrier, the active substance reaches the brain via the blood.
Amantadine is not metabolized in the body and is excreted unchanged in the urine. The rate of excretion depends on age. On average, half of the active substance has left the body 15 hours after ingestion. In older patients, this time is extended to around 30 hours.
When is amantadine used?
The areas of application (indications) for amantadine include
- Prevention and treatment of viral influenza type A
- Treatment of Parkinson’s disease (Parkinson’s disease)
The treatment of Parkinson’s disease with amantadine is long-term. The active substance is taken for up to three months to prevent influenza. For the acute treatment of influenza, it is usually taken for ten days.
How amantadine is used
For the prevention and treatment of influenza, adults receive 200 milligrams of amantadine once a day or 100 milligrams twice a day. The dosage is adjusted for children and adolescents as well as for older people or those with impaired kidney function.
Amantadine must be taken gradually to relieve Parkinson’s symptoms. This means starting with a low dosage, which is then gradually increased until optimal effectiveness is achieved. Therapy must also be discontinued gradually, i.e. gradually, as otherwise the treated symptoms may suddenly worsen.
In acute situations, such as an akinetic crisis (sudden deterioration of Parkinson’s disease to the point of complete immobility), amantadine can also be administered intravenously.
What side effects does Amantadine have?
Taking amantadine can also result in adverse drug reactions. Side effects such as sleep disorders, restlessness, urinary retention and the skin condition “livedo reticularis” (“marbled skin”) occur in one in ten to one hundred patients.
Psychoses can develop, particularly in older patients who are treated with other anti-Parkinson’s drugs in addition to amantadine.
As the active substance can prolong the QT interval in the heart, an ECG check is usually carried out before starting treatment and at regular intervals during long-term therapy.
What should I bear in mind when taking Amantadine?
Contraindications
Amantadine must not be taken if:
- Severe heart failure (cardiac insufficiency)
- Heart disease (such as grade II and III AV block, myocarditis)
- Low heart rate (less than 55 beats per minute)
- Known congenital or acquired prolonged QT interval
- Low potassium or magnesium levels in the blood
- Simultaneous therapy with Budipin (Parkinson’s medication)
Interactions
The active ingredient amantadine influences the heart rhythm in a certain way – it causes a so-called QT interval prolongation. In combination with other active substances that have this side effect, this can lead to serious interactions in the form of cardiac arrhythmia.
Examples of such drugs are
- Anti-arrhythmic agents such as quinidine, procainamide, amiodarone
- Drugs for depression such as amitryptiline, citalopram, fluoxetine
- Antibiotics such as erythromycin, clarithromycin, ciprofloxacin
There are other drugs that cause QT time prolongation. Anyone taking Amantadine should therefore always discuss any additional medication with their doctor or pharmacist.
Dehydrating agents (diuretics) such as triamterene and hydrochlorothiazide (HCT) can interfere with the excretion of amantadine. This can result in dangerously high blood levels of amantadine. Alcohol should not be consumed during treatment, as amantadine can reduce alcohol tolerance.
Age restriction
Amantadine is approved for the treatment of children aged five years and older. However, due to the lower body weight of children and the usually worsened kidney function in older patients, the dosage must be reduced in each case.
Pregnancy and lactation
Animal studies have shown that amantadine may have a harmful effect on the child during pregnancy. As it also passes into breast milk, it should not be taken by pregnant or breastfeeding women.
How to obtain medication with amantadine
In Germany, Austria and Switzerland, preparations containing the active ingredient amantadine are only available on prescription in any dosage.
How long has Amantadine been known?
As early as the 1960s, it was recognized that amantadine has a preventive effect against some influenza viruses, whereupon it was approved for this purpose in the USA in 1966. Just three years later, a positive effect on Parkinson’s symptoms was recognized, whereupon the approval was extended.
