We report a case with disturbed consciousness and myoclonus, diagnosed as amantadine intoxication. Amantadine is widely used in the treatment of Parkinson's syndrome. However, in elderly patients and those with renal dysfunction, amantadine overdose is a rare complication, resulting in symptoms of intoxication such as impaired consciousness and myoclonus. In the present case, multiple amantadines prescribed by several medical institutions may have resulted in the observed intoxication. Our pharmacists and nurses checked the medications and found duplicate amantadine prescriptions.