Diverse presentations of phenytoin toxicity-presenile cataract, encephalopathy and peripheral neuropathy: a case series

One of the most commonly used antiepileptic drugs, phenytoin, has a narrow therapeutic index, high plasma protein binding, non-linearpharmacokinetics and inter-individual variability. It can also present with adverse drug reactions due to phenytoin toxicity with diverse presentations mimicking symptoms of other diseases thus causing diagnostic predicament. This case series reports three such cases of uncommon presentation of phenytoin toxicity like presenile cataract, fluctuating encephalopathy with diurnal variation and peripheral neuropathy. Monitoring of serum drug levels in such cases aids in confirming drug toxicity. Adverse drug reaction monitoring helps in early detection and appropriate management of drug related morbidity.