General

Pronunciation
a-MAN-ta-deen

Trade Name(s)

• Symmetrel

Indications

• Symptomatic initial and adjunct treatment of Parkinson's disease

• Prophylaxis and treatment of influenza A viral infections

Action

• Potentiates the action of dopamine in the CNS

• Prevents penetration of influenza A virus into host cell

• Relief of Parkinson's symptoms

• Prevention and decreased symptoms of influenza A viral infection

Pharmacokinetics

Absorption: Well absorbed from the GI tract

Distribution: Distributed to various body tissues and fluids. Crosses blood-brain barrier and enters breast milk

Metabolism and Excretion: Excreted unchanged in the urine

Half-life: 10–28 hr

TIME/ACTION PROFILE (antiparkinson effect)

Contraindication/Precautions

Contraindicated in:
Hypersensitivity

Use Cautiously in:

• Seizure disorders

• Liver disease

• Psychiatric problems

• Congestive heart failure

• Renal impairment (dosage reduction/increased dosing interval required if CCr <=50 ml/min)

• May increase susceptibility to rubella infections

• OB: Lactation: Safety not established

• Geri: Increased sensitivity to adverse effects

Adverse Reactions/Side Effects

CNS: ataxia, dizziness, insomnia, anxiety, confusion, depression, drowsiness, psychosis, seizures.

GI: nausea, vomiting, anorexia, constipation.

EENT: blurred vision, dry mouth.

Resp: dyspnea.

CV: hypotension, CHF, edema.

GU: urinary retention.

Derm: mottling, livedo reticularis, rashes.

Hemat: leukopenia, neutropenia.

*CAPITALS indicates life-threatening.
*italic indicates most frequent.

Interactions

Drug-Drug

• Concurrent use of antihistamines, phenothiazines, quinidine, disopyramide, and tricyclic antidepressants may increase anticholinergic effects (dry mouth, blurred vision, constipation)

• Increased risk of adverse CNS reactions with alcohol

• Increased risk of CNS stimulation with other CNS stimulants

Route/Dosage

Parkinson's Disease

• PO (Adults): 100 mg 1–2 times daily (up to 400 mg/day).

• PO (Adults and Children >12 yr):
Treatment—200 mg/day as a single dose or 100 mg bid (not >100 mg/day in geriatric patients);
Prophylaxis—100 mg/day in 1–2 divided doses.

• PO (Children 10–12 yr): 100 mg q 12 hr
or 5 mg/kg/day in 1–2 divided doses; not to exceed 200 mg/day.

• PO (Children 1–9 yr): 5 mg/kg/day in 1–2 divided doses; not to exceed 150 mg/day.

• PO (Adults):
CCr 30–50 ml/min—200 mg on the first day, then 100 mg once daily;
CCr 15–29 ml/min—200 mg on the first day, then 100 mg every other day;
<15 ml/min or hemodialysis patients—200 mg once every 7 days.

Availability

• Liquid-filled capsules: 100 mg

• Tablets: 100 mg

• Syrup (raspberry flavor): 50 mg/5 ml

Assessment

• Monitor blood pressure periodically. Assess patient for drug-induced orthostatic hypotension

» Monitor vital signs and mental status periodically during first few days of dosage adjustment in patients receiving >200 mg daily; side effects are more likely

» Assess for CHF (peripheral edema, weight gain, dyspnea, rales/crackles, jugular venous distention), especially in patients on chronic therapy or with a history of CHF

» Assess patient for the appearance of a diffuse red mottling of the skin (livedo reticularis), especially in the lower extremities or on exposure to cold. Disappears with continued therapy but may not completely resolve until 2–12 wk after therapy has been discontinued

» Geri: Monitor intake and output closely in geriatric patients. May cause urinary retention. Report significant discrepancy or bladder distention

• Assess akinesia, rigidity, tremors, and gait disturbances before and throughout therapy

• Monitor respiratory status (rate, breath sounds, sputum) and temperature periodically. Supportive treatment is indicated if symptoms occur

• Symptoms of toxicity include CNS stimulation (confusion, mood changes, tremors, seizures, arrhythmias, and hypotension). There is no specific antidote, although physostigmine has been used to reverse CNS effects

Potential Nursing Diagnoses

• Impaired physical mobility

• Risk for infection (Indications)

Implementation

• Do not confuse amantadine with rimantidine or ranitidine

• PO: Do not administer last dose of medication near bedtime; may produce insomnia in some patients

» Administering amantadine in divided doses may decrease CNS side effects

» The contents of capsules may be mixed with food or fluids if the patient has difficulty swallowing

• Antiviral Prophylaxis: Treatment should be started in anticipation of contact or as soon as possible after exposure and continue for at least 10 days following exposure. Infectious period is just before onset of symptoms to up to 1 wk after. If vaccine is unavailable or contraindicated, may be administered up to 90 days to protect from repeated exposures

» May be used with inactivated influenza A virus vaccine until protective antibody response develops. Administer for 2–3 wk after vaccine has been given

• Antiviral Treatment: Administer as soon as possible after onset of symptoms and continue for 24–48 hr after symptoms disappear

Patient/Family Teaching

• Advise patient to take medication around the clock as directed and not to skip doses or double up on missed doses. If a dose is missed, do not take within 4 hr of the next dose

» May cause dizziness or blurred vision. Advise patient to avoid driving or other activities that require alertness until response to the drug is known

» Advise patient to make position changes slowly to minimize orthostatic hypotension

» Inform patient that frequent mouth rinses, good oral hygiene, and sugarless gum or candy may decrease dry mouth. Consult health care professional if dry mouth persists for >2 wk

» Advise patient to confer with health care professional before taking OTC medications, especially cold remedies, or drinking alcoholic beverages

» Instruct patient to notify health care professional if confusion, mood changes, difficulty with urination, edema and shortness of breath, or worsening of Parkinson's disease symptoms occurs

• Antiviral: Instruct patient and family to notify health care professional if influenza symptoms occur when amantadine is used as prophylaxis or if symptoms do not improve in a few days when product is used for treatment

• Parkinson's Disease: Advise patient that up to 2 wk of therapy may be needed for full benefit of medication. Notify health care professional if medication gradually loses its effectiveness. Amantadine should be tapered gradually; abrupt withdrawal may precipitate a parkinsonian crisis

Evaluation/Desired Outcomes

• Decrease in akinesia and rigidity. Full therapeutic effects may require 2 wk of therapy

• Absence or reduction of influenza A symptoms

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