Amantadine

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Amantadine is a dopaminergic drug. It has the ability to increase dopamine levels.

Amantadine is used to treat Parkinson’s disease and Drug-induced extrapyramidal reactions

Contents

[edit] BRAND NAMES

[edit] STRUCTURE

Amantadine.jpg

[edit] MECHANISM OF ACTION

Amantadine has an indirectly agonistic effect at the striatal dopamine receptor

Animal studies have shown that amantadine increases the extracellular dopamine concentration both by increased dopamine release and through blockade of re-uptake into the presynaptic neurons. At therapeutic concentrations, amantadine inhibits the release of acetylcholine mediated by NMDA receptors and can thus trigger anticholinergic effects.

Amantadine has synergistic effects with L-dopa (Levodopa)

[edit] INDICATIONS

  • Amantadine is no longer recommended for treatment of influenza A infection
  • Treatment of symptoms of Parkinson's disease by improving muscle control and reducing stiffness, shakiness and shuffling. Amantadine is usually combined with L-DOPA when L-DOPA responses decline (probably due to tolerance). Amantadine can also be given alone for initial therapy or combined with anticholinergic drugs.
  • Drug-induced extrapyramidal reactions (movement disorder)
  • Treatment of chronic fatigue often experienced by patients with multiple sclerosis (Off-label)

[edit] DOSAGE

Dosage for Parkinsonism:

Adults up to 65 years old:

The usual dose of Amantadine is 100 mg twice a day when used alone. Amantadine has an onset of action usually within 48 hours.

The initial dose of Amantadine is 100 mg daily for patients with serious associated medical illnesses or who are receiving high doses of other antiparkinson drugs. After one to several weeks at 100 mg once daily, the dose may be increased to 100 mg twice daily, if necessary.

Occasionally, patients whose responses are not optimal with Amantadine at 200 mg daily may benefit from an increase up to 400 mg daily in divided doses. However, such patients should be supervised closely by their physicians.


Dosage for Concomitant Therapy

Some patients who do not respond to anticholinergic antiparkinson drugs may respond to Amantadine. When Amantadine or anticholinergic antiparkinson drugs are each used with marginal benefit, concomitant use may produce additional benefit.

When Amantadine and levodopa are initiated concurrently, the patient can exhibit rapid therapeutic benefits. Amantadine should be held constant at 100 mg daily or twice daily while the daily dose of levodopa is gradually increased to optimal benefit.

When Amantadine is added to optimal well-tolerated doses of levodopa, additional benefit may result, including smoothing out the fluctuations in improvement which sometimes occur in patients on levodopa alone. Patients who require a reduction in their usual dose of levodopa because of development of side effects may possibly regain lost benefit with the addition of Amantadine.


Adults over 65 years old:

Since patients in this age group tend to have lower renal clearance and consequently higher plasma concentrations (see "Pharmacokinetics"), the recommended dose is 100 mg daily.


Note: Patients deriving benefit initially from Amantadine not uncommonly experience a reduction in effectiveness after a few weeks. Temporary discontinuation of Amantadine for several weeks, followed by re-introduction of therapy, may result in regaining of benefit in some patients. The use of other anti-Parkinson drugs may be necessary. Treatment with Amantadine must be reduced gradually because abrupt discontinuation may exacerbate Parkinson's syndrome, regardless of the patient's response to therapy

[edit] CONTRAINDICATIONS

  • Known hypersensitivity to amantadine

[edit] WARNINGS and PRECAUTIONS

  • Closely observe patients with history of epilepsy and reduce dosage in patients with renal function impairment

[edit] INTERACTIONS

  • Careful observation is required when Amantadine is administered concurrently with central nervous system stimulants.
  • Agents with anticholinergic properties may potentiate the anticholinergic-like side effects of amantadine.

[edit] PREGNANCY AND LACTATION

  • Pregnancy Category C (US). Amantadine should be used during pregnancy only if the potential benefit justifies the potential risk to the embryo or fetus.
  • Nursing Mothers: Amantadine is excreted in human milk. Use is not recommended in nursing mothers.

[edit] SIDE EFFECTS

The adverse reactions reported most frequently at the recommended dose of Amantadine (5-10%) are: nausea, dizziness (lightheadedness), and insomnia.

Less frequently (1-5%) reported adverse reactions are: depression, anxiety and irritability, hallucinations, confusion, anorexia, dry mouth, constipation, ataxia, livedo reticularis, peripheral edema, orthostatic hypotension, headache, somnolence, nervousness, dream abnormality, agitation, dry nose, diarrhea and fatigue.

Infrequently (0.1-1%) occurring adverse reactions are: congestive heart failure, psychosis, urinary retention, dyspnea, skin rash, vomiting, weakness, slurred speech, euphoria, thinking abnormality, amnesia, hyperkinesia, hypertension, decreased libido, and visual disturbance, including punctate subepithelial or other corneal opacity, corneal edema, decreased visual acuity, sensitivity to light, and optic nerve palsy.

Rare (less than 0.1%) occurring adverse reactions are: instances of convulsion, leukopenia, neutropenia, eczematoid dermatitis, oculogyric episodes, suicidal attempt, suicide, and suicidal ideation

[edit] RELATED LINKS

Medications for the Treatment of Parkinson's Disease

[edit] BIBLIOGRAPHY

[edit] REFERENCES