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Phenytoin poisoning

Mark Su, MD, MPH
Allon Amitai, MD
Section Editors
Stephen J Traub, MD
Michele M Burns, MD, MPH
Deputy Editor
Jonathan Grayzel, MD, FAAEM


Phenytoin (eg, Dilantin) is an anticonvulsant medication used to treat many seizure disorders. It is also a Vaughan-Williams class IB antiarrhythmic agent, although it is now infrequently used for that indication.

Phenytoin toxicity is rarely fatal, but can cause neurologic symptoms ranging from nystagmus to ataxia to coma. Intravenous phenytoin administration may rarely be complicated by Purple Glove Syndrome.

The basic pharmacology, presentation, and management of phenytoin toxicity will be reviewed here. The clinical use of phenytoin to treat epilepsy and general issues concerning management of the poisoned patient are discussed elsewhere. A summary table to facilitate emergent management is provided (table 1). (See "Overview of the management of epilepsy in adults" and "General approach to drug poisoning in adults".)


Phenytoin toxicity is associated with few serious adverse events or fatalities. According to the 2011 Annual Report of the American Association of Poison Control Centers (AAPCC) National Poison Data System, 1971 single-substance phenytoin exposures resulted in only 46 major outcomes and one death [1]. There were four reported fatalities in cases of multiple-substance exposures in which phenytoin or fosphenytoin was deemed contributory, but in none of these cases was phenytoin determined to be the primary cause of death. This low incidence of major outcomes and deaths is similar to that seen in previous years [2].

Fosphenytoin, a prodrug of phenytoin, is believed to have fewer adverse effects than phenytoin. However, there were 29 cases of cardiac events related to fosphenytoin infusion reported to the US Food and Drug Administration (FDA) between 1997 and 2002 [3]. Ten of these resulted in death. Arrhythmias included bradycardia, high degree AV block, and sinus arrest. It is unclear how many of these dysrhythmias can be directly attributed to fosphenytoin, since many of these patients had significant preexisting cardiac pathology or were presumed to be in a state of cardiac stress from status epilepticus.


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Literature review current through: Sep 2016. | This topic last updated: Oct 27, 2015.
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