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Amantadine (1-aminoadamantane, sold as Symmetrel) is an antiviral drug used both as an antiviral and an antiparkinsonic.It was approved by the Food and Drug Administration in October 1966 as a prophylactic agent against Asian influenza and eventually received approval for the treatment of Influenzavirus A[1][2][3][4] in adults. 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.

Side effects

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.

Mechanism of action

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.

Misuse

Recently, amantadine is reported to have been used in China poultry farming in an effort to protect the birds against avian influenza.[8] In western countries and according to international livestock regulations, amantadine is approved only for use in humans. Chickens in China have received an estimated 2.6 billion doses of amantadine.[8] Avian flu (H5N1) strains in China and southeast Asia are resistant to amantadine, but strains circulating elsewhere seem to be sensitive. If amantadine resistant strains of the virus spread, the drug of choice in an avian flu outbreak will likely be restricted to one of the scarcer and costlier oseltamivir or zanamivir, which work by a different mechanism and are less likely to trigger resistance.

Declining effectiveness

Early in the 2005/2006 flu season, the United States’ Center for Disease Control [CDC] found rates of amantadine resistance to be much higher than in previous seasons. Looking at samples from 26 states yielded the following findings:

Tags: Amantadine

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