Amantadine Full Prescribing Information
Brand Name: Symmetrel
Amantadine (Symmetrel) is also used to treat Parkinson's disease (paralysis agitans or shaking palsy) and to treat stiffness and shaking caused by medicines used to treat nervous, mental, and emotional conditions. By improving muscle control and reducing stiffness, this medicine allows more normal movements of the body as the disease symptoms are reduced. It may also be used for other conditions as determined by your doctor.
While the mechanism of action of amantadine in the treatment of Parkinson's syndrome and drug-induced extrapyramidal reactions is not known, it is believed to release brain dopamine from nerve endings making it more available to activate dopaminergic receptors.
After oral administration of a single dose of 100 mg, maximum blood levels are reached in approximately 4 hours.
Amantadine is useful in the treatment of Parkinson's syndrome and in the short-term management of drug-induced extrapyramidal symptoms.
Amantadine is effective in reducing severity or abolishing drug-induced extrapyramidal reactions including parkinsonism syndrome, dystonia and akathisia.
Patients hypersensitive to amantadine should not be given the drug.
A small number of suicidal attempts, some of which have been fatal, have been reported in patients treated with amantadine. The incidence of suicidal attempts is not known and the pathophysiologic mechanism is not understood. Suicidal attempts and suicidal ideation have been reported in patients with and without prior history of psychiatric illness. Amantadine can exacerbate mental problems in patients with a history of psychiatric disorders or substance abuse.
Patients who attempt suicide may exhibit abnormal mental states which include disorientation, confusion, depression, personality changes, agitation, aggressive behavior, hallucinations, paranoia, other psychotic reactions, and somnolence or insomnia. Because of the possibility of serious adverse effects, caution should be observed when prescribing amantadine to patients being treated with drugs having CNS effects, or for whom the potential risks outweigh the benefit of treatment. Because some patients have attempted suicide by overdosing with amantadine, prescriptions should be written for the smallest quantity consistent with good patient management.
Patients with a history of epilepsy or other seizures should be observed closely for possible increased seizure activity.
Patients with a history of congestive heart failure (CHF) or peripheral edema should be followed closely as there are patients who developed congestive heart failure while receiving amantadine.
Patients with Parkinson's disease improving on amantadine should resume normal activities gradually and cautiously, consistent with other medical considerations, such as the presence of osteoporosis or phlebothrombosis.
Usage in Pregnancy
Safe use of amantadine during pregnancy and lactation has not been established; therefore, when the drug is administered to pregnant patients, nursing mothers, or women of childbearing potential, the potential benefits must be weighed against the possible hazards.
Usage in Children: The safety and efficacy of use of amantadine in infants less than 1 year old have not been established.
Amantadine should not be discontinued abruptly since a few patients with Parkinson's syndrome experienced a parkinsonian crisis, i.e., sudden marked clinical deterioration, when this medication was suddenly stopped.
Neuroleptic Malignant Syndrome (NMS):
Sporadic cases of possible Neuroleptic Malignant Syndrome (NMS) have been reported in association with dose reduction or withdrawal of amantadine therapy. NMS is an uncommon but life-threatening syndrome characterised by fever or hyperthermia; neurologic findings including muscle rigidity, involuntary movements, altered consciousness; other disturbances such as autonomic dysfunction, tachycardia, tachypnea, hyper- or hypotension; laboratory findings such as creatinine phosphokinase elevation, leukocytosis, and increased serum myoglobin.
Cardiac & Renal Impairment: The dose of amantadine should be reduced in patients with renal impairment and in patients who are 65 years of age or older. The dose of amantadine may need careful adjustment in patients with congestive heart failure, peripheral edema, or orthostatic hypotension.
Care should be exercised when administering amantadine to patients with liver disease, a history of recurrent eczematoid rash, or to patients with psychosis or severe psychoneurosis not controlled by chemotherapeutic agents. Rare instances of reversible elevation of liver enzyme levels have been reported in patients receiving amantadine, though a specific relationship between the drug and such changes has not been established.
Interference with Cognitive or Motor Performance: This drug may cause dizziness and impaired vision, and impair judgment, thinking, or motor skills. Patients should be advised to avoid driving a car or operating hazardous machinery until they are reasonably certain that the drug treatment does not affect them adversely.
Careful observation is required when amantadine is administered concurrently with CNS stimulants.
BEFORE USING THIS MEDICINE: Some medicines or medical conditions may interact with this medicine. Inform your doctor or pharmacist of all prescription and over-the-counter medicine that you are taking. DO NOT take this medicine if you are also taking astemizole or terfenadine. Inform your doctor of any other medical conditions, allergies, pregnancy, or breast-feeding. Contact your doctor or pharmacist if you have any questions or concerns about taking this medicine.
Check with your doctor as soon as possible if you experience fainting, difficulty urinating, or swelling of legs, feet, or ankles. Other concerns would include euphoria, thinking abnormality, amnesia, hyperkinesia, hypertension. If you notice other effects not listed above, contact your doctor, nurse, or pharmacist.
Other side effects, that may go away during treatment, include nausea, dizziness or lightheadedness, difficulty sleeping, decreased appetite, anxiety, confusion, dry mouth, headache, or constipation. If they continue or are bothersome, check with your doctor.
Deaths have been reported from overdose with amantadine. Symptoms of overdose may include nausea, vomiting, slurred speech, blurred vision, drowsiness, memory loss, depression, excessive excitability, increased sensitivity to the sun, and loss of consciousness.
If you or someone you know may have used more than the recommended dose of this medicine, contact your local poison control center or emergency room immediately.
No specific antidote is known. General supportive measures are indicated, with gastric lavage and administration of i.v. fluids if necessary.
If you are taking this medicine for Parkinson's disease, do not stop taking this medicine without first checking with your doctor.
Improvement in the symptoms of Parkinson's disease usually occurs in about 2 days. However, in some patients this medicine must be taken for up to 2 weeks before full benefit is seen.
- Follow the directions for using this medicine provided by your doctor.
- Store this medicine at room temperature, in a tightly-closed container, away from heat and light.
- If you miss a dose of this medicine, take it as soon as possible. If it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not take 2 doses at once.
Additional Information: Do not share this medicine with others for whom it was not prescribed. Do not use this medicine for other health conditions. Keep this medicine out of the reach of children.
IF USING THIS MEDICINE FOR AN EXTENDED PERIOD OF TIME, obtain refills before your supply runs out.
For patients taking amantadine for Parkinson's disease or movement problems caused by certain medicines used to treat nervous, mental, and emotional conditions:
The dose of amantadine will be different for different patients. Follow your doctor's orders or the directions on the label. The following information includes only the average doses of amantadine. Your dose may be different if you have kidney disease. If your dose is different, do not change it unless your doctor tells you to do so.
Older Adults: 100 milligrams once a day to start. The dose may be increased slowly over time, if needed.
Adults: 100 milligrams one or two times a day.
Children: Dose has not been determined.
Amantadine HCl 100 mg is available in capsules.
Syrup: each 5 mL of clear colorless syrup contains Amantadine HCl 50 mg.
The information in this monograph is not intended to cover all possible uses, directions, precautions, drug interactions or adverse effects. This information is generalized and is not intended as specific medical advice. If you have questions about the medicines you are taking or would like more information, check with your doctor, pharmacist, or nurse. Last updated 3/03.
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