"Flu viruses are constantly changing so it's not unusual for new flu virus strains to appear each year. For more information about how flu viruses change, visit How the Flu Virus Can Change www.cdc.gov/flu/about/viruses/change.htm.
Less frequently (1-5%) reported adverse reactions are: depression, anxiety and irritability, hallucinations, confusion, anorexia, dry mouth, constipation, ataxia, livedo reticularis, peripheral edema, orthostatic hypotension, headache, somnolence, nervousness, dream abnormality, agitation, dry nose, diarrhea and fatigue.
Infrequently (0.1-1%) occurring adverse reactions are: congestive heart failure, psychosis, urinary retention, dyspnea, skin rash, vomiting, weakness, slurred speech, euphoria, thinking abnormality, amnesia, hyperkinesia, hypertension, decreased libido, and visual disturbance, including punctate subepithelial or other corneal opacity, corneal edema, decreased visual acuity, sensitivity to light, and optic nerve palsy.
Rare (less than 0.1%) occurring adverse reactions are: instances of convulsion, leukopenia, neutropenia, eczematoid dermatitis, oculogyric episodes, suicidal attempt, suicide, and suicidal ideation (see WARNINGS).
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;
Skin and Appendages
pruritus and diaphoresis;
neuroleptic malignant syndrome (see WARNINGS), allergic reactions including anaphylactic reactions, edema, fever, pathological gambling, increased libido including hypersexuality, and impulse control symptoms.
Read the Symmetrel (amantadine hydrochloride) Side Effects Center for a complete guide to possible side effects
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.1 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) .
1. W.W. Wilson and A.H. Rajput, Amantadine-Dyazide Interaction, Can. Med. Assoc. J. 129:974- 975, 1983.
Read the Symmetrel Drug Interactions Center for a complete guide to possible interactions
Last reviewed on RxList: 3/12/2009
This monograph has been modified to include the generic and brand name in many instances.
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