Adverse Effects of amantadine 

Amantadine may cause anorexia, nausea, peripheral edema and, particularly in the elderly, minor CNS effects such as nervousness, anxiety, insomnia, lethargy, difficulty concentrating, and light-headedness. These effects usually diminish after the first week of use and rapidly disappear after the drug is stopped. Serious CNS effects (confusion, hallucinations, seizures) can occur, especially with old age, renal insufficiency, seizure disorders, concomitant CNS stimulant or anti- cholinergic drug therapy and underlying psychiatric illness. Amantadine is excreted mainly in urine, and dosage must be reduced for creatinine clearance below 50 mL/min.