Nurses Compass
Drug Guide
Amantadine Hydrochloride
Classification
Therapeutic: Antiviral and antiparkinsonian agent
Pharmacological: NPDA (N-methyl-D-aspartate) receptor antagonist, Dopamine releaser
FDA Approved Indications
- Prevention and treatment of influenza A virus infections
- Parkinson's disease (adjunct therapy)
- Drug-induced extrapyramidal symptoms
Mechanism of Action
Amantadine inhibits viral replication by blocking the M2 protein of the influenza A virus, impairing uncoating of viral RNA. In Parkinson's disease, it increases dopamine release and blocks dopamine reuptake, providing antiparkinsonian effects.
Dosage and Administration
Adult: 200 mg per day in divided doses (e.g., 100 mg twice daily); adjust based on response and tolerance
Pediatric: Typically 3-12 years old: 7 mg/kg/day in divided doses (maximum 200 mg/day); use with caution
Geriatric: Start at lower doses (e.g., 100 mg once daily), increase gradually based on response and tolerability
Renal Impairment: Adjust dose according to renal function; e.g., for creatinine clearance <50 mL/min, dose reduction recommended
Hepatic Impairment: No specific adjustments; caution advised
Pharmacokinetics
Absorption: Well absorbed from gastrointestinal tract
Distribution: Widely distributed; crosses blood-brain barrier
Metabolism: Minimal hepatic metabolism
Excretion: Primarily renal excretion unchanged in urine
Half Life: 15-20 hours in healthy adults; longer in renal impairment
Contraindications
- Hypersensitivity to amantadine
- History of seizure disorder
Precautions
- Use with caution in patients with renal impairment, history of psychiatric disorders, or cardiovascular disease. Monitor for confusion, hallucinations, and orthostatic hypotension. Caution during pregnancy and lactation; consult risk-benefit ratio.
Adverse Reactions - Common
- Nausea (Most common)
- Insomnia (Common)
- Dizziness (Common)
- Constipation (Common)
Adverse Reactions - Serious
- Livedo reticularis (skin discoloration) (Rare)
- Neuropsychiatric effects (hallucinations, agitation, confusion) (Rare)
- Seizures (Rare)
- Anaphylaxis (Rare)
Drug-Drug Interactions
- Anticholinergics (may enhance anticholinergic side effects)
- centrally acting agents (additive CNS effects)
- Other drugs affecting renal function
Drug-Food Interactions
N/ADrug-Herb Interactions
N/ANursing Implications
Assessment: Monitor renal function, neurological status, and mental health status regularly.
Diagnoses:
- Risk for falls related to dizziness or orthostatic hypotension
- Risk for confusion or altered mental status
Implementation: Administer with food to reduce gastrointestinal upset. Educate patients about potential neuropsychiatric side effects.
Evaluation: Assess therapeutic response (e.g., symptom control in Parkinson's), monitor for adverse effects, and adjust dose accordingly.
Patient/Family Teaching
- Take medication exactly as prescribed.
- Report any neuropsychiatric symptoms or skin discoloration.
- Do not stop medication abruptly without consulting your healthcare provider.
- Maintain adequate hydration and report any signs of urinary retention or hallucinations.
Special Considerations
Black Box Warnings:
- Neuropsychiatric adverse reactions, including hallucinations, agitation, and depression, may occur, particularly in elderly patients or those with preexisting psychiatric conditions.
Genetic Factors: None specifically identified.
Lab Test Interference: May cause false positives in certain laboratory tests (e.g., urinary catecholamine tests).
Overdose Management
Signs/Symptoms: CNS stimulation (agitation, hallucinations), orthostatic hypotension, urinary retention, seizures in severe cases.
Treatment: Supportive care, activated charcoal if within 1 hour of ingestion, and symptomatic treatment. Hemodialysis may be considered in severe cases, especially with renal failure.
Storage and Handling
Storage: Store at room temperature, away from moisture and light.
Stability: Stable under recommended conditions; check manufacturer’s instructions for expiration date.