We report the case of a 69-year-old woman with seizures and acute renal failure with hyperkalemia. She presented with bladder turgescence and hydronephrosis on admission and was diagnosed as obstructive acute renal failure. Urethral catheterization was performed after a single-session hemodialysis. It resulted in immediate improvement of renal function and consciousness, and subsequent disappearance of seizures. Improvement of serum creatinine level to 0.7 from 10.6 mg/dL was associated with a fall in blood level of amantadine hydrochloride from 4.40 to 0.47 microg/mL. Physicians should be aware of urinary retention in patients treated with amantadine as a first sign of intoxication that could lead if untreated to obstructive acute renal failure. And we recommend to check the overdose symptoms, even those with normal renal function, treated with amantadine.