Amantadine

Parkinson's Disease and Movement Disorders

Amantadine is primarily prescribed to manage the symptoms of Parkinson's disease. It helps improve muscle control and reduce issues such as:

• Tremors or shaking
• Muscle stiffness or rigidity
• Slowed physical movement
• Loss of muscle control

It is also used to treat extrapyramidal reactions. These are involuntary muscle movements or spasms that can occur as a side effect of certain medications, such as those used to treat mental or emotional conditions.

Influenza A Virus

This medication is used to prevent and treat respiratory tract infections caused by various strains of the influenza A virus. It may be used in the following situations:

• To reduce the severity and duration of symptoms if started shortly after the onset of illness.
• As a preventive measure for individuals who have been exposed to the virus or are at high risk.

Amantadine is specifically for influenza A and is not effective against other types of viral infections, such as the common cold or influenza B.

Amantadine works in different ways depending on the condition being treated. While its exact mechanism for movement disorders is not fully known, its antiviral actions are well-documented.

Parkinson's Disease and Movement Disorders

For Parkinson's disease and movement-related side effects caused by certain medications, amantadine is thought to increase the amount of dopamine available in the brain. Dopamine is a chemical messenger responsible for smooth and controlled muscle movements. Amantadine may help by:

• Increasing dopamine release: It may encourage nerve cells to release more dopamine.
• Slowing reabsorption: It may prevent dopamine from being absorbed back into the cells too quickly, keeping it active for longer.
• Blocking receptors: It may block certain brain receptors, known as NMDA receptors, which can help reduce involuntary movements.

Influenza A Treatment

As an antiviral, amantadine specifically targets the influenza A virus. It works by preventing the virus from uncoating once it enters a host cell. By blocking a specific viral protein, the medication stops the virus from releasing its genetic material into the cell. This prevents the virus from replicating and spreading the infection throughout the body. Amantadine does not work against the common cold or other types of flu viruses, such as influenza B.

Common Side Effects

• Dizziness or lightheadedness
• Nausea
• Difficulty sleeping (insomnia)
• Dry mouth
• Constipation
• Nervousness or anxiety
• Blurred vision
• Headache
• Loss of appetite

Serious Side Effects

Contact a healthcare provider immediately if you experience any of the following:

• Hallucinations or confusion
• Swelling in the hands, legs, or feet
• Difficulty urinating
• Livedo reticularis (a purplish, lace-like pattern on the skin)
• Shortness of breath
• Fainting or extreme drowsiness
• New or worsening depression or suicidal thoughts
• Unusual or intense urges, such as gambling or increased sexual desires
• Seizures

Stopping amantadine suddenly can cause a serious reaction. Always consult a doctor before changing your dose or discontinuing the medication.

Mental Health and Behavior

Amantadine has been associated with an increased risk of suicidal thoughts and behaviors. It is important to monitor for signs of depression, anxiety, or changes in mood. Some people may experience intense urges, such as compulsive gambling, increased sexual urges, or binge eating, while taking this medication.

Central Nervous System Effects

This medication can cause dizziness, confusion, and hallucinations, particularly in older adults. It may also cause sudden sleep onset during daily activities, which can be dangerous when driving or operating machinery.

Abrupt Discontinuation

Stopping amantadine suddenly can lead to serious complications, including a condition similar to neuroleptic malignant syndrome. Symptoms may include high fever, muscle stiffness, and mental status changes. Dosage should be reduced gradually under medical supervision.

Physical Precautions

• Blood Pressure: Amantadine may cause orthostatic hypotension, a drop in blood pressure when standing up, which can lead to fainting.
• Kidney Function: Because the drug is cleared by the kidneys, individuals with renal impairment require lower doses to avoid toxicity.
• Heart Health: It may worsen congestive heart failure or cause swelling in the legs (peripheral edema).
• Skin Changes: Some patients develop livedo reticularis, a purplish, lace-like pattern on the skin.

Pre-existing Conditions

Caution is advised for individuals with a history of seizures, as amantadine may increase the frequency of episodes. It should also be used carefully in those with narrow-angle glaucoma or a history of eczema.

Pregnancy

The safety of amantadine during pregnancy has not been fully established in humans. Research in animals has shown that high doses of the medication may lead to birth defects. Consequently, amantadine should be used during pregnancy only if the potential benefit to the mother justifies the potential risk to the fetus.

Individuals who are pregnant or planning to become pregnant should discuss their treatment options and the potential risks with their healthcare provider.

Breastfeeding

Amantadine is excreted into breast milk. Additionally, the medication may lower prolactin levels, which can decrease the amount of breast milk a person produces. Due to the risk of side effects in the nursing infant and the potential for reduced milk supply, caution is advised.

Patients should consult with a healthcare professional to weigh the benefits of breastfeeding against the potential risks to the infant while taking this medication.

Available Forms

Amantadine is primarily administered by mouth and comes in the following forms:

• Immediate-release capsules
• Immediate-release tablets
• Oral solution (syrup)
• Extended-release capsules
• Extended-release tablets

The specific form prescribed depends on the condition being treated and the patient's individual needs. Extended-release versions are designed to release the medication slowly into the body over time.

FDA Approval Status

Amantadine is approved by the U.S. Food and Drug Administration (FDA) for the treatment of specific neurological and viral conditions. It was originally approved as an antiviral agent and later received approval for managing symptoms of Parkinson's disease.

Approved Indications

The FDA has approved amantadine for the following uses:

• Parkinson's Disease: It is indicated for the treatment of idiopathic Parkinson's disease, including the management of tremors, stiffness, and slow movement.
• Drug-Induced Extrapyramidal Reactions: It is used to treat movement disorders that occur as side effects of certain medications, such as antipsychotics.
• Influenza A: It is approved for the prevention and treatment of respiratory infections caused by influenza A virus strains. However, its use for this purpose has become limited due to widespread viral resistance.

Boxed Warnings and REMS

There are currently no FDA boxed warnings associated with amantadine. A boxed warning is the most serious type of warning required by the FDA for certain medications. Additionally, there is no Risk Evaluation and Mitigation Strategy (REMS) required for this drug.

Regulatory Safety Information

While approved for use, the FDA requires the drug's labeling to include warnings regarding potential central nervous system effects, such as suicidal ideation, depression, and hallucinations. It also includes precautions for patients with kidney disease, as the dosage must be adjusted to prevent toxicity.

Risks of Abrupt Discontinuation

Stopping amantadine suddenly can cause serious side effects and may lead to a significant worsening of the condition being treated. It is important to talk to a healthcare provider before stopping the medication, as they will likely recommend a gradual reduction in dosage to prevent withdrawal reactions.

Potential Withdrawal Symptoms

Abruptly ending treatment may result in symptoms such as:

• High fever
• Severe muscle stiffness
• Confusion or hallucinations
• Agitation or anxiety
• Slurred speech

In rare cases, stopping amantadine suddenly can trigger a dangerous condition similar to neuroleptic malignant syndrome (NMS) or a parkinsonian crisis. These conditions require immediate medical attention and are characterized by very high fever, rapid heart rate, and extreme muscle rigidity.