Symmetrel

GENERIC AVAILABLE: No

Your pharmacist can provide more information about amantadine.

Remember, keep this and all other medicines out of the reach of children, never share your medicines with others, and use this medication only for the indication prescribed.

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Symmetrel is part of the drug class:

• Adamantane derivatives

Tell your doctor if you are pregnant or plan to become pregnant.

The FDA categorizes medications based on safety for use during pregnancy. Five categories - A, B, C, D, and X, are used to classify the possible risks to an unborn baby when a medication is taken during pregnancy.

Symmetrel falls into category C. In animal studies, pregnant animals were given this medication and had some babies born with problems. No well-controlled studies have been done in humans. Therefore, this medication may be used if the potential benefits to the mother outweigh the potential risks to the unborn child.

Amantadine is an antiviral medicine that blocks the actions of viruses in your body.

Amantadine is used to treat and prevent influenza A (a viral infection). Amantadine may not be effective during every flu season because certain strains of influenza virus may be resistant to this medicine.

Amantadine should not be used in place of getting a yearly flu shot. The Centers for Disease Control recommends an annual flu shot to help protect you each year from new strains of influenza virus.

Amantadine is also used to treat Parkinson's disease and "Parkinson-like" symptoms such as stiffness and shaking that may be caused by the use of certain drugs.

Amantadine may also be used for purposes not listed in this medication guide.

In the U.S.

• Symmetrel

Available Dosage Forms:

• Capsule, Liquid Filled
• Solution
• Tablet
• Capsule
• Syrup

Therapeutic Class: Antiparkinsonian

Pharmacologic Class: Anticholinergic

Chemical Class: Adamantane

It is important that your doctor check your progress at regular visits to allow changes in your dose and to check for any unwanted effects.

Amantadine may cause some people to be agitated, irritable, or display other abnormal behaviors. It may also cause some people to have suicidal thoughts and tendencies or to become more depressed. If you, your child, or your caregiver notice any of these adverse effects, tell your doctor or your child's doctor right away.

Some people who have used this medicine had unusual changes in their behavior. Talk with your doctor right away if you start having problems with gambling or an increased interest in sex while using this medicine.

Drinking alcoholic beverages while taking this medicine may cause increased side effects, such as circulation problems, dizziness, lightheadedness, fainting, or confusion. Do not drink alcoholic beverages while you are taking this medicine.

This medicine may cause some people to become dizzy, confused, or lightheaded, or to have blurred vision or trouble concentrating. Make sure you know how you react to this medicine before you drive, use machines, or do anything else that could be dangerous if you are dizzy or are not alert or able to see well. If these reactions are especially bothersome, check with your doctor.

Dizziness, lightheadedness, or fainting may occur with this medicine, especially when you get up from a lying or sitting position suddenly. These symptoms are more likely to occur when you begin taking this medicine, or when the dose is increased. Getting up slowly may help. If this problem continues or gets worse, check with your doctor.

Patients with Parkinson's disease must be careful not to overdo physical activities when their condition improves and body movements become easier since injuries resulting from falls may occur. Such activities must be gradually increased to give your body time to adjust to a change in balance, circulation, and coordination.

Amantadine may cause dryness of the mouth, nose, and throat. For temporary relief of mouth dryness, use sugarless candy or gum, melt bits of ice in your mouth, or use a saliva substitute. However, if your mouth continues to feel dry for more than 2 weeks, check with your doctor or dentist. Continuing dryness of the mouth may increase the chance of dental disease, including tooth decay, gum disease, and fungus infections.

This medicine may cause purplish red, net-like, blotchy spots on the skin. This problem occurs more often in females and usually occurs on the legs and/or feet after this medicine has been taken regularly for a month or more. Although the blotchy spots may remain as long as you are taking this medicine, they usually go away gradually within 2 to 12 weeks after you stop taking the medicine. If you have any questions about this, check with your doctor.

Check with your doctor right away if you are having convulsions (seizures); difficulty with breathing; a fast heartbeat; a high fever; high or low blood pressure; increased sweating; loss of bladder control; severe muscle stiffness; unusually pale skin; or tiredness. These could be symptoms of a serious condition called neuroleptic malignant syndrome (NMS).

If you are using this medicine for Parkinson's disease, do not stop taking this medicine suddenly without first checking with your doctor. Your doctor may want you to gradually reduce the amount you are using before stopping it completely.

If you are using this medicine for Parkinson's disease, it is important that your doctor check your skin regularly for signs of a skin cancer called melanoma. If you notice any unusual red, brown, or black spots on your skin, talk to your doctor right away.

If your Parkinson's symptoms do not improve within a few days, if they become worse, or if this medicine appears less effective after a few weeks, check with your doctor.

Along with its needed effects, a medicine may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if any of the following side effects occur:

• Blurred vision
• confusion
• difficult urination
• dizziness or lightheadedness
• fainting
• seeing, hearing, or feeling things that are not there
• swelling of the hands, feet, or lower legs

• Convulsions (seizures)
• decreased vision or any change in vision
• difficulty in coordination
• fever, chills, or sore throat
• increased blood pressure
• increase in body movements
• irritation and swelling of the eye
• loss of memory
• mental depression
• severe mood or mental changes
• skin rash
• slurred speech
• thoughts of suicide or attempts at suicide
• unexplained shortness of breath

Some side effects may occur that usually do not need medical attention. These side effects may go away during treatment as your body adjusts to the medicine. Also, your health care professional may be able to tell you about ways to prevent or reduce some of these side effects. Check with your health care professional if any of the following side effects continue or are bothersome or if you have any questions about them:

• Agitation, anxiety, or nervousness
• difficulty concentrating
• headache
• irritability
• loss of appetite
• nausea
• purplish red, net-like, or blotchy spots on the skin
• trouble in sleeping or nightmares

• Constipation
• decrease in sexual desire
• diarrhea
• drowsiness
• dryness of the mouth, nose, and throat
• false sense of well-being
• vomiting
• unusual tiredness or weakness

Other side effects not listed may also occur in some patients. If you notice any other effects, check with your healthcare professional.

Call your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.

Deaths

Deaths have been reported from overdose with Symmetrel. The lowest reported acute lethal dose was 1 gram. Acute toxicity may be attributable to the anticholinergic effects of amantadine. Drug overdose has resulted in cardiac, respiratory, renal or central nervous system toxicity. Cardiac dysfunction includes arrhythmia, tachycardia and hypertension (see OVERDOSAGE).

Suicide Attempts

Suicide attempts, some of which have been fatal, have been reported in patients treated with Symmetrel, many of whom received short courses for influenza treatment or prophylaxis. The incidence of suicide attempts is not known and the pathophysiologic mechanism is not understood. Suicide attempts and suicidal ideation have been reported in patients with and without prior history of psychiatric illness. Symmetrel 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 Symmetrel to patients being treated with drugs having CNS effects, or for whom the potential risks outweigh the benefit of treatment.

CNS Effects

Patients with a history of epilepsy or other “seizures” should be observed closely for possible increased seizure activity.

Patients receiving Symmetrel who note central nervous system effects or blurring of vision should be cautioned against driving or working in situations where alertness and adequate motor coordination are important.

Other

Patients with a history of congestive heart failure or peripheral edema should be followed closely as there are patients who developed congestive heart failure while receiving Symmetrel.

Patients with Parkinson’s disease improving on Symmetrel should resume normal activities gradually and cautiously, consistent with other medical considerations, such as the presence of osteoporosis or phlebothrombosis.

Because Symmetrel has anticholinergic effects and may cause mydriasis, it should not be given to patients with untreated angle closure glaucoma.

Deaths have been reported from overdose with Symmetrel. The lowest reported acute lethal dose was 1 gram. Because some patients have attempted suicide by overdosing with amantadine, prescriptions should be written for the smallest quantity consistent with good patient management.

Acute toxicity may be attributable to the anticholinergic effects of amantadine. Drug overdose has resulted in cardiac, respiratory, renal or central nervous system toxicity. Cardiac dysfunction includes arrhythmia, tachycardia and hypertension. Pulmonary edema and respiratory distress (including adult respiratory distress syndrome - ARDS) have been reported; renal dysfunction including increased BUN, decreased creatinine clearance and renal insufficiency can occur. Central nervous system effects that have been reported include insomnia, anxiety, agitation, aggressive behavior, hypertonia, hyperkinesia, ataxia, gait abnormality, tremor, confusion, disorientation, depersonalization, fear, delirium, hallucinations, psychotic reactions, lethargy, somnolence and coma. Seizures may be exacerbated in patients with prior history of seizure disorders. Hyperthermia has also been observed in cases where a drug overdose has occurred.

There is no specific antidote for an overdose of Symmetrel. However, slowly administered intravenous physostigmine in 1 and 2 mg doses in an adult2 at 1- to 2-hour intervals and 0.5 mg doses in a child3 at 5- to 10-minute intervals up to a maximum of 2 mg/hour have been reported to be effective in the control of central nervous system toxicity caused by amantadine hydrochloride. For acute overdosing, general supportive measures should be employed along with immediate gastric lavage or induction of emesis. Fluids should be forced, and if necessary, given intravenously. The pH of the urine has been reported to influence the excretion rate of Symmetrel. Since the excretion rate of Symmetrel increases rapidly when the urine is acidic, the administration of urine acidifying drugs may increase the elimination of the drug from the body. The blood pressure, pulse, respiration and temperature should be monitored. The patient should be observed for hyperactivity and convulsions; if required, sedation, and anticonvulsant therapy should be administered. The patient should be observed for the possible development of arrhythmias and hypotension; if required, appropriate antiarrhythmic and antihypotensive therapy should be given. Electrocardiographic monitoring may be required after ingestion, since malignant tachyarrhythmias can appear after overdose.

Care should be exercised when administering adrenergic agents, such as isoproterenol, to patients with a Symmetrel overdose, since the dopaminergic activity of Symmetrel has been reported to induce malignant arrhythmias.

The blood electrolytes, urine pH and urinary output should be monitored. If there is no record of recent voiding, catheterization should be done.

Applies to amantadine: compounding powder, oral capsule, oral syrup, oral tablet

General

The adverse effects of amantadine (the active ingredient contained in Symmetrel) are generally mild and, when they occur, may diminish or cease after a week or more on the medication. The most commonly reported side effects have included nausea, dizziness/lightheadedness, and insomnia in 5% to 10% of patients. All side effects, particularly those involving the central nervous system, may be more likely and more severe in patients with renal dysfunction and/or advanced age. Close monitoring for undue adverse effects is highly recommended.[Ref]

Nervous system

Nervous system side effects have included dizziness/lightheadedness and insomnia in 5% to 10% of patients. Hallucinations, confusion, ataxia, headache, somnolence, agitation, and fatigue have been reported in 1% to 5% of patients. Weakness, slurred speech, and hyperkinesia have been reported in 0.1% to 1% of patients and instances of convulsion have been reported in less than 0.1% of patients. At least one case of dropped head syndrome (associated with unbalanced contraction of the neck muscles) has been reported. Neuroleptic malignant syndrome, involuntary muscle contractions, coma, stupor, hypokinesia, hypertonia, gait abnormalities, paresthesia, EEG changes, and tremor have been reported during postmarketing experience. Agitation, hallucinations, stupor, and slurred speech have also occurred after abrupt discontinuation.[Ref]

Most cases of CNS toxicity have occurred in patients with renal insufficiency, seizure disorders, or psychiatric illnesses, and in elderly patients receiving 200 mg/day for influenza prophylaxis.[Ref]

Psychiatric

A case report describes a psychotic episode consisting of abnormal behavior in a young woman following a week of concomitant therapy with Naldecon. The patient had no personal or family history of psychiatric illness and no history of recreational substance use. It is not clear whether the episode was due to the amantadine (the active ingredient contained in Symmetrel) the phenylpropanolamine in the Naldecon, or an interaction between the two.

An exacerbation of panic occurred in one patient approximately 2 weeks after the initiation of amantadine therapy for Parkinson's disease. The causal relationship is unclear.

Severe CNS adverse effects have most often been associated with dosages greater than approximately 2 mg/kg/day and/or amantadine blood levels exceeding 1 mcg/mL. Most cases of CNS toxicity have occurred in patients with renal insufficiency, seizure disorders, or psychiatric illnesses, and in elderly patients receiving 200 mg/day for influenza prophylaxis.[Ref]

Psychiatric side effects have included depression, anxiety, irritability, nervousness, and dream abnormality in 1% to 5% of patients. Psychosis, euphoria, thinking abnormality, amnesia, and decreased libido have been reported in 0.1% to 1% of patients and suicidal attempt, suicidal ideation, and suicide have been reported in less than 0.1% of patients. Aggressive behavior, delirium, delusions, manic reaction, paranoid reaction, delusions of parasitosis, pathological gambling, increased libido (including hypersexuality), and impulse control symptoms have been reported during postmarketing experience. Delirium, delusions, paranoid reaction, anxiety, and depression have also occurred after abrupt discontinuation.[Ref]

Gastrointestinal

Gastrointestinal side effects have included nausea in 5% to 10% of patients; diarrhea, constipation, anorexia, and dry mouth in 1% to 5% of patients; and vomiting in 0.1% to 1% of patients. Dysphasia has been reported during postmarketing experience.[Ref]

Cardiovascular

Cardiovascular side effects have included orthostatic hypotension in 1% to 5% of patients, and congestive heart failure and hypertension in 0.1% to 1% of patients. Cardiac arrest, arrhythmias (including malignant arrhythmias), hypotension, and tachycardia have been reported during postmarketing experience.[Ref]

Congestive heart failure with severe lower limb edema was diagnosed in one patient receiving amantadine, but resolved following drug discontinuation. A positive correlation with amantadine therapy could not be established, although no other cause for this patient's heart failure was found.[Ref]

Ocular

At least two cases of decreased visual acuity have been reported following approximately three weeks of amantadine (the active ingredient contained in Symmetrel) therapy. Both resolved after drug discontinuation. In one case, the visual disturbance was related to a corneal edema similar to that seen with amiodarone.[Ref]

Ocular side effects have included visual disturbance, including punctuate subepithelial or other corneal opacity, corneal edema, decreased visual acuity, sensitivity to light, and optic nerve palsy in 0.1% to 1% of patients and oculogyric episodes in less than 0.1% of patients. Keratitis and mydriasis have been reported during postmarketing experience.[Ref]

Other

Other side effects have included peripheral edema (1% to 5%). Edema and fever have been reported during postmarketing experience.[Ref]

Respiratory

Respiratory side effects have included dry nose (1% to 5%) and dyspnea (0.1% to 1%). Acute respiratory failure, pulmonary edema, and tachypnea have been reported during postmarketing experience.[Ref]

Hematologic

Hematologic side effects have included leukopenia and neutropenia in less than 0.1% of patients. Leukocytosis and agranulocytosis have been reported during postmarketing experience.[Ref]

Dermatologic

Livedo reticularis occurs mainly on the legs. It is generally reversible over weeks to months following drug discontinuation.[Ref]

Dermatologic side effects have included livedo reticularis (1% to 5%), skin rash (0.1% to 1%), and eczematoid dermatitis (less than 0.1%). Pruritus and diaphoresis have been reported during postmarketing experience.[Ref]

Hypersensitivity

Hypersensitivity side effects have included allergic reactions including anaphylactic reactions during postmarketing experience.[Ref]

Genitourinary

Genitourinary side effects have included urinary retention (0.1% to 1%).[Ref]

Renal

Renal side effects have included elevations in BUN and serum creatinine during postmarketing experience.[Ref]

Hepatic

Hepatic side effects have included elevations in bilirubin, GGT, SGOT, and SGPT during postmarketing experience.[Ref]

Metabolic

Metabolic side effects have included elevated alkaline phosphatase and lactate dehydrogenase during postmarketing experience.

Musculoskeletal

Musculoskeletal side effects have included elevated creatine kinase during postmarketing experience.[Ref]

Endocrine

A 66-year-old female patient with Parkinson disease developed syndrome of inappropriate antidiuretic hormone secretion nine days after starting amantadine (the active ingredient contained in Symmetrel) and entacapone. The patient did not recover following discontinuation of entacapone. Five days after entacapone was stopped, amantadine was discontinued. The patient gradually improved following amantadine discontinuation.[Ref]

Endocrine side effects have included at least one case of syndrome of inappropriate antidiuretic hormone secretion.[Ref]

Some side effects of Symmetrel may not be reported. Always consult your doctor or healthcare specialist for medical advice. You may also report side effects to the FDA.