warnings
WARNINGS Deaths Deaths have been reported from overdose with amantadine. 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 ). Deaths due to drug accumulation (overdosage) have been reported in patients with renal impairment, who were prescribed higher than recommended doses of amantadine hydrochloride for their level of renal function (see DOSAGE AND ADMINISTRATION; Dosage for Impaired Renal Function and OVERDOSAGE ). Suicide Attempts Suicide attempts, some of which have been fatal, have been reported in patients treated with amantadine, 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. 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 hydrochloride capsules 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 amantadine hydrochloride capsules 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 amantadine hydrochloride capsules. Patients with Parkinson’s disease improving on amantadine hydrochloride capsules should resume normal activities gradually and cautiously, consistent with other medical considerations, such as the presence of osteoporosis or phlebothrombosis. Because amantadine hydrochloride capsules have anticholinergic effects and may cause mydriasis, it should not be given to patients with untreated angle closure glaucoma. Corneal Edema Corneal edema has been reported in patients taking amantadine. Symptoms include sudden onset of blurry vision, or progressive vision loss, with or without eye pain. Corneal involvement is usually bilateral. Onset can occur from a few weeks to several years after starting amantadine. Resolution of symptoms typically begins within weeks of amantadine cessation. However, corneal grafts have been required in some patients when the condition is not recognized. Permanent damage can occur if amantadine is continued. Ask patients if their vision has changed and obtain ophthalmologic examinations to rule out corneal edema should vision changes occur after initiation of therapy with amantadine. If corneal edema occurs, taper and discontinue amantadine [see Dosage and Administration ] .