A Rare Case of Hemodialysis as an Extracorporeal Treatment for Severe Phenytoin Overdose

Phenytoin is a well-known anticonvulsant medication that is useful in the management of most seizure disorders. Given the narrow therapeutic index of 10-20 mg/mL, acute phenytoin overdose can occur with either oral or intravenous administration. There is no distinct antidote to phenytoin, and therefore supportive care is the treatment of choice. Various methods to enhance the elimination have been discussed controversially and have shown a limited effect. We discuss a case in which intermittent hemodialysis was shown to significantly enhance the elimination of phenytoin in an acute overdose and drastically improve the clinical outcome. A 46-year-old male presented to the emergency department after a fall in which he injured his head and left knee. The patient admitted to ingesting 60 tablets of 100 mg extended-release phenytoin directly preceding the fall. He presented lethargic with slurred speech and ataxia. The patient was admitted to the ICU for observation with an initial phenytoin level of 50.1 mg/L. Phenytoin levels peaked at 68.7 mg/L on day two and continued to fluctuate. On day seven of admission, the level remained high at 62.6 mg/L, and at this point, the hospitalist, nephrologist, and poison control agreed to proceed with a trial of intermittent hemodialysis. After a four-hour dialysis session, phenytoin levels declined 27% to 45.6 mg/L and continued to fall. The patient's symptoms of slurred speech, drowsiness, and agitation remained throughout the hospital course but improved each day after hemodialysis. Phenytoin levels reached a therapeutic level of 19.5 mg/L on day 14 of admission, and the patient was alert, talkative, and asymptomatic. Intermittent hemodialysis was shown to be an effective elimination method in those with severe phenytoin toxicity and should be considered as a therapeutic option. Even with significant albumin binding, a single session of hemodialysis lowered the phenytoin levels by 27%. We also suspect the removal of additional toxins, and the desaturation of hepatic metabolism could have aided in the patient's clinical improvement, further supporting therapeutic hemodialysis.