Amantadine (1-aminoadamantane, sold as Symmetrel) is an antiparkinsonic drug. In 1969 the drug was also discovered by accident to help reduce symptoms of Parkinson's disease and drug-induced extrapyramidal syndromes. It is a derivative of adamantane, like rimantadine, a similar drug.

As an antiparkinsonic it can be used as monotherapy; or together with L-DOPA to treat L-DOPA-related motor fluctuations (i.e., shortening of L-DOPA duration of clinical effect, probably related to progressive neuronal loss) and L-DOPA-related dyskinesias (choreiform movements associated with long-term L-DOPA use, probably related to chronic pulsatile stimulation of dopamine receptors).

Off-label uses
There have been anecdotal reports, based on research by Dr. William Singer of Harvard University, that low-dose amantadine has been successfully used to treat ADHD. Amantadine has been shown to relieve SSRI-induced anorgasmia in some people, though not in all people.

Amantadine has been associated with several central nervous system side effects, including nervousness, anxiety, agitation, insomnia, difficulty in concentrating, and exacerbations of pre-existing seizure disorders and psychiatric symptoms in patients with schizophrenia or Parkinson's disease. These side effects are likely due to amantadine's dopaminergic and adrenergic activity, and to a lesser extent, its activity as an anticholinergic.

The mechanism of its antiparkinsonic effect is not fully understood, but it appears to be releasing dopamine from the nerve endings of the brain cells, together with stimulation of norepinephrine response. Furthermore, it appears to be a weak NMDA receptor antagonist and an anticholinergic.

The antiviral mechanism seems to be unrelated. The drug interferes with a viral protein, M2 (an ion channel), which is needed for the viral particle to become "uncoated" once it is taken inside the cell by endocytosis.

Before taking any prescription medicine, it is important that you consult your doctor!