Amantadine hydrochloride is designated chemically as 1-adamantanamine hydrochloride. Its molecular weight is 187.71 with a molecular formula C10H18NCl. Amantadine has been shown to relieve SSRI-induced anorgasmia in some people, though not in all people.
Amantadine is effective in reducing severity or abolishing drug-induced extrapyramidal reactions including parkinsonism syndrome, dystonia and akathisia. It is not effective in the management of tardive dyskinesia. Amantadine is useful as an adjunct in patients who do not tolerate optimal doses of levodopa alone or in combined therapy with a decarboxylase inhibitor. In these patients, the addition of amantadine may result in better control of Parkinson's syndrome and may help to smooth out fluctuations in performance.
While the mechanism of action of amantadine in the treatment of Parkinson's syndrome and drug-induced extrapyramidal reactions is not known, it is believed to release brain dopamine from nerve endings making it more available to activate dopaminergic receptors. The drug does not possess anticholinergic activity in animal tests at doses similar to those used clinically.
Possible use of amantadine in depression
Amantadine, originally used in the treatment and prophylaxis of influenza infection, has also proved beneficial in drug-induced Parkinsonism, Parkinson's disease, traumatic head injury, dementia, multiple sclerosis and cocaine withdrawal. Amantadine appears to act through several pharmacological mechanisms, none of which has been identified as the one chief mode of action. It is a dopaminergic, noradrenergic and serotonergic substance, blocks monoaminoxidase A and NMDA receptors, and seems to raise beta-endorphin/beta-lipotropin levels.
Amantadine should not be discontinued abruptly since a few patients with Parkinson's syndrome experienced a parkinsonian crisis, i.e., sudden marked clinical deterioration, when this medication was suddenly stopped.
Amantadine has been shown to be embryotoxic and teratogenic in rats at 50 mg/kg/day, approximately 12 times the recommended human dose, but not at 37 mg/kg/day. Embryotoxic and teratogenic drug effects were not seen in rabbits that received up to 25 times the recommended human dose.
The dose of anticholinergic drugs or of amantadine should be reduced if atropine-like effects appear when these drugs are used concurrently.
Careful observation is required when amantadine is administered concurrently with CNS stimulants.