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Does Symmetrel (amantadine) cause side effects?
Symmetrel (amantadine) is an antiviral drug used to prevent and treat infections with influenza A. Symmetrel is also used to control the symptoms of Parkinson’s disease and for the treatment of drug-induced extrapyramidal symptoms.
Symmetrel can inhibit the replication of viruses in cells. It was initially used to prevent influenza A during flu season, and, if given within 24 to 48 hours of the onset of flu symptoms, to decrease the severity of the flu. Later Symmetrel was found to cause improvement in the symptoms of Parkinson’s disease.
Symmetrel's mechanism of action in Parkinson's disease is not fully understood. Symmetrel is less effective than levodopa in Parkinson's disease but can offer additional benefit when taken with levodopa. The brand name Symmetrel is discontinued.
Common side effects of Symmetrel include:
- loss of coordination,
- slurred speech,
- loss of appetite, and
- discolorations in the eye.
Serious side effects of Symmetrel include:
- extreme drowsiness,
- falling asleep suddenly,
- shortness of breath,
- swelling in hands or feet,
- painful or difficult urination,
- behavior changes,
- thoughts of hurting yourself,
- seizures, and
- severe nervous system reactions (very stiff muscles, high fever, sweating, confusion, fast or uneven heartbeats, and tremors).
- tricyclic antidepressants,
- certain antihistamines,
- opiate agonists,
- certain antihypertensive medications, which, when combined with Symmetrel can cause dizziness, confusion, lightheadedness, fainting, or dizziness upon standing (orthostatic hypotension).
No well-controlled studies have been done in pregnant women to evaluate Symmetrel’s safety. Physicians may choose to use Symmetrel during pregnancy when the potential benefits outweigh the potential but unknown risks to the fetus.
Symmetrel is excreted into breast milk in low concentrations. Although no information is available on the effects in infants, the manufacturer recommends Symmetrel be used cautiously in breastfeeding women.
What are the important side effects of Symmetrel (amantadine)?
The most frequent side effects associated with amantadine that can appear after a few hours or several days of therapy include:
Less common side effects include:
Symmetrel (amantadine) side effects list for healthcare professionals
The adverse reactions reported most frequently at the recommended dose of Symmetrel (amantadine hydrochloride) (5-10%) are:
- dizziness (lightheadedness), and
Less frequently (1-5%) reported adverse reactions are:
- anxiety and irritability,
- dry mouth,
- livedo reticularis,
- peripheral edema,
- orthostatic hypotension,
- dream abnormality,
- dry nose,
- diarrhea and
Infrequently (0.1-1%) occurring adverse reactions are:
- congestive heart failure,
- urinary retention,
- skin rash,
- slurred speech,
- thinking abnormality,
- decreased libido, and
- visual disturbance, including
Rare (less than 0.1%) occurring adverse reactions are:
- instances of convulsion,
- eczematoid dermatitis,
- oculogyric episodes,
- suicidal attempt,
- suicide, and
- suicidal ideation.
Other adverse reactions reported during postmarketing experience with Symmetrel (amantadine hydrochloride) usage include:
coma, stupor, delirium, hypokinesia, hypertonia, delusions, aggressive behavior, paranoid reaction, manic reaction, involuntary muscle contractions, gait abnormalities, paresthesia, EEG changes, and tremor. Abrupt discontinuation may also precipitate delirium, agitation, delusions, hallucinations, paranoid reaction, stupor, anxiety, depression and slurred speech;
acute respiratory failure, pulmonary edema, and tachypnea;
keratitis and mydriasis;
Skin and Appendages
pruritus and diaphoresis;
What drugs interact with Symmetrel (amantadine)?
- Careful observation is required when Symmetrel (amantadine hydrochloride) is administered concurrently with central nervous system stimulants.
- Agents with anticholinergic properties may potentiate the anticholinergic-like side effects of amantadine.
- Coadministration of thioridazine has been reported to worsen the tremor in elderly patients with Parkinson's disease, however, it is not known if other phenothiazines produce a similar response.
- Coadministration of Dyazide (triamterene/hydrochlorothiazide) resulted in a higher plasma amantadine concentration in a 61-year-old man receiving Symmetrel (Amantadine Hydrochloride, USP) 100 mg TID for Parkinson's disease.
- It is not known which of the components of Dyazide contributed to the observation or if related drugs produce a similar response.
- Coadministration of quinine or quinidine with amantadine was shown to reduce the renal clearance of amantadine by about 30%.
- The concurrent use of Symmetrel (amantadine hydrochloride) with live attenuated influenza vaccine (LAIV) intranasal has not been evaluated. However, because of the potential for interference between these products, LAIV should not be administered within 2 weeks before or 48 hours after administration of Symmetrel (amantadine hydrochloride), unless medically indicated.
- The concern about possible interference arises from the potential for antiviral drugs to inhibit replication of live vaccine virus. Trivalent inactivated influenza vaccine can be administered at any time relative to use of Symmetrel (amantadine hydrochloride).
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Parkinson's disease is a slowly progressive neurological disease characterized by a fixed inexpressive face, a tremor at rest, slowing of voluntary movements, a gait with short accelerating steps, peculiar posture and muscle weakness, caused by degeneration of an area of the brain called the basal ganglia, and by low production of the neurotransmitter dopamine. Most patients are over 50, but at least 10 percent are under 40.
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Medications & Supplements
Report Problems to the Food and Drug Administration
You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.
Professional side effects and drug interactions sections courtesy of the U.S. Food and Drug Administration.