An antiviral drug, brand name Symmetrel, that also stimulates dopamine release. Approved for use in the United States in the 1960s, amantadine’s primary use is to prevent or shorten the course of infection with influenza A. Recent research shows promising results in treating hepatitis C as well. Doctors identified amantadine’s ability to mitigate mild motor symptoms in Parkinson’s disease when people who had the disease took the drug to treat influenza and noticed improvement in their Parkinson’s symptoms. Doctors now often prescribe amantadine as a monotherapy in the early stages of Parkinson’s disease; it usually remains effective for 18 to 24 months. In later stages of Parkinson’s, amantadine is sometimes effective as an adjunct therapy to levodopa and other ANTI-CHOLINERGIC MEDICATIONS to help offset ON-STATE and off-state fluctuations.
Researchers do not fully understand how amantadine works to neutralize the symptoms of Parkinson’s disease. It appears to stimulate dopamine production or release, although the precise mechanisms by which it does so remain a mystery. Many researchers think that amantadine’s blocking (antagonism) of NMDA-type glutamate receptors is the key to explaining its anti-dyskinetic effect. Amantadine’s side effects are similar to those of anticholinergics, and they can include visual hallucinations, swelling of the ankles and feet, and discolored skin (livido reticularis ). When amantadine ceases to be effective, it must be discontinued gradually and under a doctor‘s supervision rather than suddenly stopped. Sudden withdrawal of the drug can result in rapid and severe worsening of Parkinson symptoms.