Clinical Features and Management of Poisoning Due to Phenytoin

The widespread use of phenytoin results in frequent accidental and intentional toxicity. Metabolism is enzymatic and can be described by Michaelis-Menten kinetics. This results in an increased half-life in overdose situations and a protracted clinical course which may last a week or more. The primary toxicity is on the central nervous system. The most common initial finding in mild toxicity is nystagmus. As concentrations increase ataxia, decreased coordination, hyper-reflexia, slurred speech and diplopia may develop. Progressive increases result in confusion, lethargy and coma.