The adverse reactions reported most frequently at the recommended dose of SYMMETREL (5-10%) are: nausea, dizziness (lightheadedness), and insomnia.

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 usage include:

Nervous System/Psychiatric

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;

Cardiovascular

cardiac arrest, arrhythmias including malignant arrhythmias, hypotension, and tachycardia;

Respiratory

acute respiratory failure, pulmonary edema, and tachypnea;

Gastrointestinal

dysphagia;

Hematologic

leukocytosis; agranulocytosis

Special Senses

keratitis and mydriasis;

Skin and Appendages

pruritus and diaphoresis;

Miscellaneous

neuroleptic malignant syndrome (see WARNINGS), allergic reactions including anaphylactic reactions, edema, and fever;

Laboratory Test

elevated: CPK, BUN, serum creatinine, alkaline phosphatase, LDH, bilirubin, GGT, SGOT, and SGPT.

Careful observation is required when SYMMETREL 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 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, 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.

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