Symmetrel: Effective Antiviral and Parkinson's Symptom Management
Symmetrel
| Product dosage: 100mg | |||
|---|---|---|---|
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| 360 | $0.85
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Synonyms | |||
Symmetrel (amantadine hydrochloride) is a well-established antiviral and antiparkinsonian agent with a unique dual mechanism of action. As a synthetic tricyclic amine, it demonstrates clinical efficacy against influenza A virus while providing symptomatic relief for Parkinson’s disease. This medication represents a valuable therapeutic option with decades of clinical evidence supporting its appropriate use in neurology and infectious disease management. Healthcare professionals appreciate its predictable pharmacokinetics and established safety profile when administered according to guidelines.
Features
- Contains amantadine hydrochloride as the active pharmaceutical ingredient
- Available in 100 mg capsule and syrup formulations (50 mg/5 mL)
- Demonstrated activity against influenza A virus strains
- Exhibits dopaminergic and anticholinergic properties
- Standardized manufacturing under current Good Manufacturing Practices
- Stable shelf life of 24 months when stored properly
Benefits
- Reduces duration and severity of influenza A symptoms when initiated within 48 hours of onset
- Provides symptomatic improvement in Parkinson’s disease, particularly for rigidity and bradykinesia
- May help manage drug-induced extrapyramidal symptoms in certain psychiatric treatments
- Offers flexible dosing options with both solid and liquid formulations
- Established safety profile with extensive clinical experience spanning decades
- Cost-effective therapeutic option compared to newer antiviral agents
Common use
Symmetrel is primarily indicated for the prophylaxis and treatment of respiratory illness caused by influenza A virus strains. In neurological practice, it is employed as monotherapy or adjunctive treatment for Parkinson’s disease, particularly in early-stage management or to address specific symptoms like rigidity and tremor. Off-label applications include management of fatigue in multiple sclerosis and treatment of certain drug-induced movement disorders. The medication requires careful patient selection and monitoring based on the specific indication and patient comorbidities.
Dosage and direction
For influenza A treatment in adults: 200 mg daily as a single dose or divided as 100 mg twice daily. For prophylaxis: 200 mg daily or 100 mg twice daily. For Parkinson’s disease: Initial dose of 100 mg daily, increasing to 100 mg twice daily after one week if necessary. Maximum daily dose should not exceed 400 mg in divided doses. For patients with renal impairment (creatinine clearance <80 mL/min), dosage reduction is mandatory. Elderly patients often require lower initial doses and careful titration. Administration with food may minimize gastrointestinal discomfort.
Precautions
Patients with history of seizure disorders require careful monitoring as Symmetrel may lower seizure threshold. Those with congestive heart failure, peripheral edema, or orthostatic hypotension need cardiovascular assessment before initiation and during treatment. Psychiatric history, particularly of psychosis or confusion, warrants cautious use. Renal function must be assessed before prescribing and monitored periodically during treatment. Patients should avoid abrupt discontinuation to prevent rebound Parkinsonian symptoms or neuroleptic malignant syndrome-like reactions.
Contraindications
Hypersensitivity to amantadine or any component of the formulation. Severe renal impairment (creatinine clearance <15 mL/min) without appropriate dosage adjustment. History of angle-closure glaucoma. Concurrent use with live attenuated influenza vaccine. Patients with uncontrolled psychosis or severe psychoneurosis not adequately managed by antipsychotic medication. Pregnancy unless potential benefit justifies potential risk to fetus.
Possible side effect
Common reactions include nausea (5-10%), dizziness (5-8%), insomnia (5-7%), and dry mouth (5-6%). Less frequently, patients may experience livedo reticularis (mottling of skin), peripheral edema, orthostatic hypotension, or confusion. Neuropsychiatric effects including anxiety, irritability, hallucinations, and depression occur in approximately 5% of patients. Rare but serious adverse effects include suicidal ideation, seizures, and neuroleptic malignant syndrome. Most side effects are dose-dependent and often diminish with continued therapy or dosage reduction.
Drug interaction
Concomitant use with anticholinergic agents may potentiate adverse effects. Alcohol may increase risk of central nervous system effects. Co-administration with stimulants may exacerbate sympathetic nervous system activation. Quinidine and quinine reduce renal clearance of amantadine. Thiazide diuretics may decrease renal elimination. Concurrent use with memantine should be avoided due to similar mechanisms. Careful monitoring required when used with drugs affecting dopamine systems or those with central nervous system effects.
Missed dose
If a dose is missed, it should be taken as soon as remembered unless it is nearly time for the next scheduled dose. Patients should not double the dose to make up for a missed administration. Consistent dosing is important for maintaining therapeutic levels, particularly for antiviral prophylaxis. For Parkinson’s disease management, missed doses may result in return of symptoms. Patients should maintain a regular dosing schedule and contact their healthcare provider if multiple doses are missed.
Overdose
Symptoms may include agitation, hallucinations, cardiac arrhythmias, hyperthermia, and seizures. Serious overdose can lead to respiratory distress, pulmonary edema, and renal failure. Management includes gastric lavage if presentation is early, activated charcoal, and supportive care. Acidification of urine may enhance elimination but is controversial due to risk of renal crystal formation. Hemodialysis may be effective in severe cases. Cardiac monitoring and symptomatic treatment of central nervous system effects are essential. Specific antidotes are not available.
Storage
Store at controlled room temperature (20-25°C/68-77°F). Protect from light and moisture. Keep container tightly closed. Do not freeze the syrup formulation. Keep out of reach of children and pets. Discard any unused medication after the expiration date. Do not transfer capsules to other containers without proper labeling. The syrup formulation should be used within the specified period after opening as directed in the package insert.
Disclaimer
This information is for educational purposes only and does not constitute medical advice. Symmetrel is a prescription medication that requires professional medical supervision. Individual response to therapy may vary. Patients should consult their healthcare provider for personalized medical advice, diagnosis, and treatment. The complete prescribing information should be reviewed before initiating therapy. Safety and efficacy in pediatric patients have not been fully established.
Reviews
Clinical studies demonstrate Symmetrel’s efficacy in reducing influenza A symptom duration by 1-2 days when initiated within 48 hours of symptom onset. In Parkinson’s disease, approximately 60-70% of patients show moderate to significant improvement in motor symptoms. Long-term use may be limited by developing tolerance in some patients. The medication is generally well-tolerated, with most adverse effects being mild and transient. Healthcare professionals value its established role in specific clinical scenarios despite the availability of newer agents.