From the Guidelines
Symmetrel (Amantadine) is indeed considered to have dopaminergic properties, making it useful in treating Parkinson's disease and drug-induced extrapyramidal symptoms. According to the evidence from 1, amantadine is classified as a mild dopaminergic agent, which is used to treat symptoms of Parkinson's disease, such as bradykinesia, tremors, and rigidity, induced by antidopaminergic agents. This is further supported by 1, which mentions that drug-induced Parkinsonism syndrome can be treated by adding a dopaminergic agonist, such as amantadine.
Key Points
- Amantadine works by increasing dopamine release and blocking dopamine reuptake in the brain, effectively enhancing dopaminergic neurotransmission 1.
- Typical dosing for Parkinson's disease starts at 100 mg daily, potentially increasing to 100 mg twice daily, with a maximum of 400 mg daily in divided doses.
- Common side effects include nausea, dizziness, insomnia, and hallucinations.
- Patients with renal impairment require dose adjustment as the drug is primarily excreted unchanged in urine.
- Symmetrel is less potent than levodopa for Parkinson's treatment but may be used as monotherapy in early disease or as an adjunct to other antiparkinsonian medications when symptoms are not adequately controlled.
Clinical Considerations
When using amantadine to treat Parkinson's disease or drug-induced extrapyramidal symptoms, it is essential to monitor patients for potential side effects and adjust the dose accordingly. Additionally, patients with renal impairment require close monitoring and dose adjustment to prevent adverse effects. The evidence from 1 highlights the importance of early diagnosis and rapid withdrawal of the antipsychotic drug in cases of drug-induced Parkinsonism to improve the possibility of complete recovery.
Treatment Approach
The use of amantadine as a dopaminergic agent should be considered in the treatment of Parkinson's disease and drug-induced extrapyramidal symptoms, taking into account the patient's individual needs and medical history. The dosing and administration of amantadine should be guided by the evidence from 1 and 1, with careful monitoring of patients for potential side effects and adjustment of the dose as needed.
From the Research
Mechanism of Action of Amantadine
- Amantadine is primarily known as an NMDA receptor antagonist 2, 3, 4.
- It has been shown to reduce dyskinesia scores and improve motor complications in patients with Parkinson's disease when given adjunctively with levodopa 2, 4.
- The mechanism of action of amantadine in reducing dyskinesias is thought to be related to its ability to block NMDA receptors, although some studies suggest that this may not be the only mechanism by which it exerts its effects 5.
Comparison with Dopamine Agonists
- Dopamine agonists are a class of medications that directly stimulate dopamine receptors and are used to treat Parkinson's disease 2.
- Amantadine is not classified as a dopamine agonist, but rather as an NMDA receptor antagonist with possible neuroprotective effects 2, 5.
- While dopamine agonists can improve motor response and decrease 'off' time in patients with Parkinson's disease, amantadine has been shown to reduce dyskinesia severity and improve motor fluctuations without altering the antiparkinsonian effect of levodopa 4.
Clinical Use of Amantadine
- Amantadine is used as an adjunctive treatment to levodopa in patients with Parkinson's disease to reduce dyskinesias and motor fluctuations 2, 4, 6.
- It has been shown to be effective in reducing dyskinesia severity and improving motor response complications in patients with advanced Parkinson's disease 4.
- An extended-release formulation of amantadine has been developed, which provides higher and more continuous brain delivery of the medication and has been shown to be effective in reducing dyskinesias and 'OFF' intervals in fluctuating orally levodopa-treated patients 6.