Symmetrel (amantadine) is a medication which has been used for the prevention and treatment of infection caused by various strains of influenza A virus. While patients taking Symmetrel may avoid the signs and symptoms of flu, they can still develop appropriate immune reactions to exposure and vaccination to ensure future protection upon exposure to related viruses.

The medication is useful in treating simple respiratory tract illness, such as might arise from preexisting influenza A viral infection when administered early in the course of the illness. Symmetrel has been used as a treatment of Parkinsonism, as well as to alleviate certain Parkinsonism-drug related side effects, such as dyskinesia resultant from levodopa therapy.

Symmetrel also has moderate effects upon multiple sclerosis related fatigue.

Symmetrel for Prevention & Treatment of Influenza A

In patients between ages 13 to 64, 200 mg per day is sufficient. The 200 mg per day should be taken as a single daily dose.

Patients aged 9 to 12 or who are over age 64 should take 100 mg twice per day, with each dose as close to 12 hours apart as possible.

Patients under the age of 9 should have the dose adjusted according to weight; 2 to 4 mg per lb of body weight per day (4.4 to 8.8 mg/kg/day), not exceeding 150 mg per day.

Treatment should begin as soon as possible following exposure and continue for a minimum of 10 days or until 24 to 48 hours after the disappearance of symptoms, whichever comes latest. If not given immediately following exposure, it will ideally be administered within 24 hours of the first symptoms.

Symmetrel can be given following inactivated influenza A virus vaccine; the medication should be administered for 2 to 4 weeks following administration of the vaccine.

Symmetrel for Parkinsonism

The medication should be administered carefully for Parkinsonism, starting with 100 mg per day and after several weeks increased to 200 mg per day, if necessary. The medication should then be evaluated, and, if necessary, can again be increased to 400 mg per day, though this is rare.

In all cases more than 100 mg taken per day are given in divided doses, taken as close to 12 hours apart as possible.

Symmetrel should not be discontinued abruptly in patients with Parkinson's disease since a few patients have experienced a Parkinsonism crisis when this medication was suddenly stopped. The dose of anticholinergic drugs or of Symmetrel should be reduced if atropine-like effects appear when these drugs are used concurrently. Abrupt discontinuation may also precipitate delirium, agitation, delusions, hallucinations, paranoid reaction, stupor, anxiety, depression and slurred speech.

Neuroleptic malignant syndrome has been reported in association with dose reduction or withdrawal of Symmetrel therapy. Patients should be observed carefully when the dosage of Symmetrel is reduced abruptly or discontinued, especially if the patient is receiving neuroleptics.

Before Taking Symmetrel

The most common side effects associate with Symmetrel are:

• Nausea
• Dizziness
• Insomnia

The above are generally not cause for concern unless severe enough to be disruptive. Unfortunately, that's not all there is to this medication.

Symmetrel should be administered with central nervous stimulants only with careful observation. Taking Symmetrel in conjunction with thioridazine may worsen the tremor in elderly patients with Parkinson's disease. The effect of other phenothiazines is not known.

Taking Symmetrel with quinine or quinidine has been demonstrated to reduce kidney clearance of Symmetrel by approximately 30%.

Suicide attempts, some of which have been fatal, have been reported in patients treated with Symmetrel, many of whom received short courses for influenza treatment or prophylaxis. The incidence of suicide attempts is not known and the pathophysiologic mechanism is not understood.

Patients with a history of epilepsy or other seizures should be observed closely for possible increased seizure activity. Patients receiving Symmetrel who note central nervous system effects or blurring of vision should be cautioned against driving or working in situations where alertness and adequate motor coordination are important.