Adverse effects of phenytoin on peripheral nerves and neuromuscular junction: a review

Review of the literature shows that long-term phenytoin therapy is associated with peripheral neuropathy and neuromuscular disorder that rarely can be symptomatic. The usual manifestations of the peripheral neuropathy are lower extremity areflexia, sensory deficits, and reduced conduction velocities. The risk for these peripheral nerve abnormalities is greater with increased serum levels or long duration of therapy (usually more than 5 years). The relative risks according to age groups or number and kinds of antiepileptic drugs used are undetermined. It is not known if detected abnormalities are static or slowly progressive. Isolated case reports have claimed the resolution of signs and symptoms after discontinuance of therapy or correction of a state of intoxication. Appropriate measures to prevent the appearance or progression of the complications are discussed in light of the available evidence.