Encephalopathy from unintentional donepezil and memantine ingestion.

Donepezil and memantine are commonly prescribed antidementia drugs. There is a paucity of literature concerning pediatric ingestions of these drugs. We describe a case of a 2-year-old child who developed encephalopathy after an unintentional ingestion of donepezil and memantine. A 2-year-old girl was found by her family members agitated and reporting visual hallucinations. In the emergency department, she became sedated and had rightward eye deviation. She was hospitalized and had extensive neurological and infectious disease testing that was unremarkable, except for an electroencephalogram, which showed a nonspecific encephalopathy. She recovered with supportive care for 72 hours. Serum concentrations of donepezil and memantine measured on arrival were 470 ng/mL (therapeutic range, 25-50 ng/mL) and 32 ng/mL (therapeutic range, 70-150 ng/mL), respectively. This case demonstrates that unintentional ingestions of memantine and donepezil can potentially cause significant and prolonged neurological symptoms in pediatric patients.

A memantin HCL intoxication responsive to plasmapheresis therapy.

Memantin HCL (Ebixa) is a drug which antagonizes the effects of N-methyl-D-aspartat receptors and which is used for the treatment of acute Alzheimer patients. Plasmapheresis is a method of cleaning nonspecific extracorporeal blood and it is applied in many immunologic and toxicologic diseases. Female patient at the age of 35 was admitted to the emergency department with complaints of tendency to sleep and sensory loss. About 12 hours before her history she had taken 200 tablets of 10 mg memantin HCL (Ebixa) (2000 mg) and she was transferred to an intensive care department with the diagnosis of drug toxicity (400 mg toxic dose). Her memantin HCL (Ebixa) level in blood was 12,000 ng/mL. It was reported in her physical examination that she was unconscious, her general condition was bad, there were no cooperation and orientation, ahe hadmydriasis and reflexes of light, cornea and eyelash were bilaterally positive and she had horizontal nystagmus. Glascow Coma Scale of the patient was 6, body temperature was 37.5 degrees C and she had tachycardia (130/min) and hypertension (160/90 mmHg). Intravenous Diazepam was effective aginst recurring convulsions. Sinusoidal tachycardia was detected with electrocardiography (EKG) and respiratory alkalosis in arterial blood gases. Six cysles of plasmapheresis were aplied and in the sixth cycle the memantin HCL (Ebixa) level turned to normal. As a result of the sixth plasmapheresis the findings were normal and that is why she was discharged from the hospital. Plasmapheresis should be taken into consideration in case of drug overdose or high doses of plasmatic proteinous drug toxicities (Ref. 11).

Postmortem memantine concentrations.

Postmortem fluid and tissue concentrations of memantine (Namenda), a drug recently approved for the treatment of Alzheimer's Disease by the FDA, are reported in a suspicious death. In addition, memantine concentrations considered to be incidental findings in three other cases are included to aid in the interpretation in future toxicological investigations. Memantine was extracted from biological samples by a standard liquid-liquid basic drug method followed by analysis utilizing a gas chromatograph-mass spectrometer operated in SIM mode. Blood concentrations ranged from 0.03 to 1.8 mg/L, and the liver concentration was 6.1 mg/kg.