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Amantadine

Medical and Pharmacy Editor:

Brand Name: Symmetrel

Generic Name: amantadine

Drug Class: Antivirals, Influenza; Antiparkinson Agents, Dopamine Agonists

What Is Amantadine and How Does It Work?

Amantadine is used to prevent or treat a certain type of flu (influenza A). If you have been infected with the flu, this medication may help make your symptoms less severe and shorten the time it will take you to get better. Taking amantadine if you have been or will be exposed to the flu may help to prevent you from getting the flu. This medication is an antiviral that is believed to work by stopping growth of the flu virus. This medication is not a vaccine. To increase the chance that you will not get the flu, it is important to get a flu shot once a year at the beginning of every flu season, if possible.

Based on the recommendation from the Centers for Disease Control (CDC) in the U.S., amantadine should not be used to treat or prevent influenza A because the current influenza A virus in the United States and Canada is resistant to this medication. For more details, talk to your doctor or pharmacist.

Amantadine is also used to treat Parkinson's disease, as well as side effects caused by drugs (e.g., drug-induced extrapyramidal symptoms), chemicals, and other medical conditions. In these cases, this medication may help to improve your range of motion and ability to exercise. For the treatment of these conditions, amantadine is believed to work by restoring the balance of natural chemicals (neurotransmitters) in the brain.

Dosages of Amantadine:

Adult and Pediatric Dosage Forms and Strengths

Capsule/Tablet

Syrup

  • 50 mg/5mL

Dosage Considerations – Should be Given as Follows:

Parkinson Disease

  • Serious illness or high dose of other antiparkinson agents: 100 mg/day orally initially; may be increased to 100 mg every 12 hours after at least 1 week
  • Up to 400 mg/day, but only in special circumstances
  • Geriatric: Adults over 65 years: Therapy should be based on renal function

Drug-Induced Extrapyramidal Symptoms

  • 100 mg orally every 12 hours; not to exceed 300 mg/day

Influenza A Treatment, Pediatric

  • NOTE: Because of resistance, amantadine is no longer recommended for prophylaxis or treatment of influenza A; refer to current Advisory Committee on Immunization Practices (ACIP) recommendations
  • Children 1-9 years or less than 40 kg (any age): 5 mg/kg/day orally in single dose or divided every 12 hours; not to exceed 150 mg/day
  • Children 10 years and older and less than 40 kg: 5 mg/kg/day orally divided every 12 hours
  • Children 10 years and older and 40 kg or more: 100 mg orally every 12 hours

What Are Side Effects Associated with Using Amantadine?

Side effects of amantadine include:

Less common side effects of amantadine include:

This document does not contain all possible side effects and others may occur. Check with your physician for additional information about side effects.

What Other Drugs Interact with Amantadine?

If your doctor has directed you to use this medication, your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor, health care provider or pharmacist first.

Amantadine has no known severe interactions with other drugs.

Serious Interactions of amantadine include:

  • mefloquine

Mild Interactions of amantadine include:

This information does not contain all possible interactions or adverse effects. Therefore, before using this product, tell your doctor or pharmacist of all the products you use. Keep a list of all your medications with you, and share this information with your doctor and pharmacist. Check with your health care professional or doctor for additional medical advice, or if you have health questions, concerns or for more information about this medicine.

What Are Warnings and Precautions for Amantadine?

Warnings

  • Amantadine and metabolites are inhibitors of phosphodiesterase III; such activity has been shown to decrease survival of patients with class III-IV congestive heart failure (CHF); contraindicated in patients with CHF of any severity
  • This medication contains amantadine. Do not take Pletal if you are allergic to amantadine or any ingredients contained in this drug

Contraindications

Effects of Drug Abuse

  • No information available

Short-Term Effects

  • See "What Are Side Effects Associated with Using Amantadine?"

Long-Term Effects

  • See "What Are Side Effects Associated with Using Amantadine?"

Cautions

  • Since 2008-09 influenza season, Centers for Disease Control and Prevention (CDC) advises against use for treatment or prophylaxis of influenza in U.S.
  • Congestive heart failure, swelling of extremities (peripheral edema), low blood pressure and dizziness upon standing (orthostatic hypotension)
  • Renal impairment, liver disease
  • Advanced age
  • History of seizures, eczematoid rash, severe psychosis or psychoneurosis
  • Dosages greater than 200 mg/day
  • Consider reducing anticholinergic dosages before initiating amantadine therapy
  • Avoid abrupt withdrawal
  • Risk of neuroleptic malignant syndrome (NMS) with dosage reduction or withdrawal
  • May impair ability to perform hazardous tasks
  • Possibility of reduced effectiveness after several months; may regain efficacy if dosage is increased
  • Parkinson patients
    • Risk of uncontrollable sexual, gambling, or other urges
    • May be linked to higher melanoma risk

Pregnancy and Lactation

  • Use amantadine with caution during pregnancy if benefits outweigh risks. Animal studies show risk and human studies are not available or neither animal nor human studies were done
  • Amantadine enters breast milk; it is not recommended for use while breastfeeding
Reviewed on 5/1/2017

Medscape. Amantadine.
https://reference.medscape.com/drug/endantadine-symmetrel-amantadine-342604
RxList. Symmetrel Side Effects Center.
https://www.rxlist.com/symmetrel-side-effects-drug-center.htm

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