Plasmapheresis as an Adjunctive Therapy in Phenytoin Poisoning

Abstract

Phenytoin is frequently used as an anticonvulsant. Phenytoin has saturable metabolic kinetics in overdose circumstances, making therapy challenging. Because of its high protein binding property, the usual hemodialysis and hemoperfusion are not usually preferred. We report a case of a chronic overdose in which an attempt was made to decrease the toxicity and lower plasma levels of phenytoin using plasmapheresis. A 60-year-old female with a history of seizure disorder on phenytoin for the last 25 years and asthma for 15 years on salbutamol when needed presented with a sudden onset of vomiting followed by altered sensorium in the form of drowsiness and decreased responsiveness. She was suspected of having phenytoin toxicity and given a stomach elsewhere. Her phenytoin level after admission to our center was 46 mg/mL (therapeutic range: 10–20 mg/mL). The initial assessment of the patient was done by the treating physician. As the patient did not improve with supportive management, the transfusion medicine department received the request to conduct a therapeutic plasmapheresis. The first session of plasmapheresis was performed using the Haemonetics MCS machine. After the procedure, her phenytoin level decreased by 43% from the baseline, and she was shifted out of the intensive care unit to the ward and discharged after 2 weeks.

Keywords

• phenytoin
• plasma exchange
• toxicity