Phenytoin intoxication associated with omeprazole administration in a child with defective CYP2C9.

Adverse drug reactions occur at a high rate in hospitalized children, frequently due to antiepileptic drug administration. Phenytoin is a commonly used drug, and its metabolism is mediated by a specific cytochrome-P450 isoform, CYP2C9, which is encoded by a polymorphic gene. It is worth noting that very frequently administered drugs, such as proton pump inhibitors, compete with phenytoin for CYP2C19-mediated metabolism. Here we describe a case of phenytoin intoxication in a child with defective CYP2C9, after omeprazole administration.