A nurse is caring for a client who has a new prescription for phenytoin to treat seizures. Which of the following laboratory findings should the nurse monitor?

The correct answer is B: Liver function tests. Phenytoin is known to have hepatotoxic effects, potentially leading to liver damage. Monitoring liver function tests like AST, ALT, and bilirubin levels is crucial to detect any signs of liver dysfunction early on. Platelet count (A) is not specifically associated with phenytoin use. Blood urea nitrogen (C) is more relevant for kidney function monitoring. Sodium levels (D) are not typically affected by phenytoin. In summary, monitoring liver function tests is essential to detect and manage potential liver damage caused by phenytoin.