AMANTADINE

 AMANTADINE

BRAND NAME:-AMANTREL,NEAMAN ,COMANTREL 100mg tab.

AMANTADINE as an antiviral drug for prophylaxis of influenza A2, and Glutamate (NMDA -RECEPTOR) ANTAGONIST (DOPAMINE FACILITATOR ) class of drug .

PHARMACODYNAMIC & MECHANISM OF ACTION:-

it was found serendipitiously to benefit parkinosonism. It acts rapidly but has lower efficacy than levodopa , which is equivalent to or higher than ANTI- cholinergic. About 2/3rd patients derive some benefit. However, tolerance develops over months and the efficacy is gradually lost. 

Amantadine promotes presynaptic synthesis and release of DNA  in the brain and has anticholinergic property. These were believed to explain all its beneficial effects in Parkinosonism. However,an antagonistic action on  NMDA type of glutamate receptors, through which the striatal dopaminergic system exerts its influence is now considered to be more important.

CHEMICALLY,it is unique Tricycle amine unrelated to any nucleic acid precursor, but inhibits replication of influenza A virus . The antiviral activity of amantadine is strain specific; influenza B is not affected. Moreover,H5N1(bird flu,avian influenza) and H1N1 (swine flu) strains of influenza A are resistant in most areas. It appears to act at an early step( possibly uncoating) as well as at a late step( viral assembly) in viral replication. A protein designated 'M2' which acts as an ion channels has been identified as one of its targets of action. Resistance to amantadine develops by mutation causing amino acid substitutions in the M2 protein. Amantadine is well absorbed orally and excreted unchanged in urine over 2-3 days (t½ 16hr).

ADVERSE EFFECTS:-

Generally well tolerated; nausea, anorexia, insomnia, dizziness, nightmares,lack of mental concentration,rarely hallucinations have been reported. Ankle edema occurs due to local vasoconstriction.

USED :- Parkinson's, prophylaxis of influenza A2 illness, prophylaxis of influenza A2 during an epidemic or seasonal influenza, especially in High risk patients.

DOSE:-100mg BD, elderly —half dose , children 5mg/kg /day; 100mg OD may be used for prophylaxis.

CONTRAINDICATIONS: epilepsy and other CNS disease; gastric ulcer, PREGNANCY.