amantadine hydrochloride

a·man·ta·dine hydrochloride (-mnt-dn)

n.

An antiviral drug used also in the treatment of Parkinson's disease.

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amantadine hydrochloride

[əman′tədēn]

an antiviral and antiparkinsonian agent.

indications It is prescribed in the prophylaxis and early treatment of influenza virus A and in the treatment of parkinsonian symptoms and drug-induced extrapyramidal reactions.

contraindications It is used with caution in patients with congestive heart failure and in women who are pregnant and lactating. Known hypersensitivity to this drug prohibits its use.

adverse effects Among the most serious adverse reactions are central nervous system effects and livedo reticularis. Nausea, dizziness, insomnia, nervousness, blurred vision, and slurred speech also may occur.

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amantadine hydrochloride

an antiviral agent which prevents penetration and uncoating of several RNA viruses.

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amantadine hydrochloride

Symmetrel, Lysovir (UK)

Pharmacologic class: Anticholinergic-like agent

Therapeutic class: Antiviral, antiparkinsonian

Pregnancy risk category C

Action

Antiviral action unclear; may prevent penetration of influenza A virus into host cell. Antiparkinsonian action unknown; may ease parkinsonian symptoms by increasing dopamine release, preventing dopamine reuptake into presynaptic neurons, stimulating dopamine receptors, or enhancing dopamine sensitivity.

Availability

Capsules (liquid-filled): 100 mg

Syrup: 50 mg/5 ml

Tablets: 100 mg

⊘Indications and dosages

➣ Symptomatic treatment or prophylaxis of influenza type A virus in patients with respiratory conditions

Adults older than age 65 with normal renal function: 100 mg P.O. once daily

Adults to age 64 with normal renal function: 200 mg (tablets) or 4 tsp of syrup P.O. daily in a single dose, or 100 mg tablet or 2 tsp of syrup P.O. b.i.d.

Children ages 9 to 12: 100 mg P.O. q 12 hours

Children ages 1 to 9 or weighing less than 45 kg (99 lb): 4.4 to 8.8 mg/kg/day of syrup P.O. q 12 hours, not to exceed 150 mg daily

➣ Parkinson's disease

Adults: Initially, 100 mg P.O. daily, increased to 100 mg b.i.d. if needed. If patient doesn't respond adequately, give 200 mg b.i.d., up to 400 mg/day.

➣ Drug-induced extrapyramidal reactions

Adults: 100 mg to 300 mg P.O. daily in divided doses

Dosage adjustment

• Renal impairment

Contraindications

• Hypersensitivity to drug
• Untreated closed-angle glaucoma

Precautions

Use cautiously in:
• cardiac disease, hepatic disease, renal impairment, seizure disorder, psychiatric problems
• elderly patients
• pregnant or breastfeeding patients.

Administration

• For antiviral use, start therapy within 24 to 48 hours of symptom onset and continue for 24 to 48 hours after symptoms resolve.
• When giving as prophylactic antiviral, start therapy as soon as possible and continue for at least 10 days after exposure to virus.
• When giving with influenza vaccine, continue drug for 2 to 3 weeks while patient develops antibody response to vaccine.

Route	Onset	Peak	Duration
P.O.	48 hr	2 wk	Unknown

Adverse reactions

CNS: depression, dizziness, drowsiness, insomnia, light-headedness, anxiety, irritability, hallucinations, confusion, ataxia, headache, nervousness, abnormal dreams, agitation, fatigue, delusions, aggressive behavior, manic reaction, psychosis, slurred speech, euphoria, abnormal thinking, amnesia, increased or decreased motor activity, paresthesia, tremor, abnormal gait, delirium, stupor, coma

CV: orthostatic hypotension, tachycardia, peripheral edema, heart failure, cardiac arrest, arrhythmias

EENT: blurred vision, mydriasis, keratitis, photosensitivity, optic nerve palsy, nasal congestion

GI: nausea, vomiting, diarrhea, constipation, dry mouth, dysphagia, anorexia

GU: urine retention, decreased libido

Hematologic: leukocytosis

Musculoskeletal: involuntary muscle contractions

Respiratory: tachypnea, acute respiratory failure, pulmonary edema

Skin: purplish skin discoloration, rash, pruritus, diaphoresis

Other: edema, fever, allergic reactions including anaphylaxis

Interactions

Drug-drug. Anticholinergics, antihistamines, phenothiazines, quinidine, tricyclic antidepressants: increased atropine-like adverse effects

CNS stimulants: increased CNS stimulation

Hydrochlorothiazide, triamterene: increased amantadine effects

Drug-diagnostic tests. Alanine aminotransferase, alkaline phosphatase, aspartate aminotransferase, bilirubin, blood urea nitrogen, creatine kinase, creatinine, gamma-glutamyltransferase, lactate dehydrogenase: increased levels

Drug-herbs. Angel's trumpet, jimsonweed, scopolia: increased cardiac and anticholinergic-like effects

Drug-behaviors. Alcohol use: increased CNS adverse reactions

Patient monitoring

☞ Monitor patient for depression and suicidal ideation.
• Watch for mental status changes, especially in elderly patients.
• Stay alert for worsening of psychiatric problems if patient has a history of such problems or substance abuse.
• Monitor for orthostatic hypotension.
• Evaluate for signs and symptoms of fluid overload.
• Monitor kidney and liver function test results.

Patient teaching

☞ Caution patient that taking more than prescribed dosage may lead to serious adverse reactions or even death.
• Advise patient to establish effective bedtime routine and to take drug several hours before bedtime to minimize insomnia.
• Caution patient to avoid driving and other hazardous activities until he knows how drug affects concentration and alertness.
• Advise patient to minimize GI upset by eating small, frequent servings of foods and drinking plenty of fluids.
• Instruct patient to contact prescriber if he develops signs or symptoms of depression.
• As appropriate, review all other significant and life-threatening adverse reactions and interactions, especially those related to the drugs, tests, herbs, and behaviors mentioned above.