A patient who has been taking phenobarbital for epilepsy begins taking valproic acid [Depakote] as adjunct therapy. The nurse notes that the patient is very drowsy. What will the nurse do?

Question

Quizplus · Accepted Answer

Valproic acid competes with phenobarbital for drug-metabolizing enzymes and can increase plasma levels of phenobarbital by approximately 40%. When this combination is used, the dose of phenobarbital should be reduced. Increasing the dose of valproic acid would compound the problem. Patients taking phenobarbital alone experience sedation, which diminishes as tolerance develops. Liver toxicity is a rare adverse effect of valproic acid and is marked by symptoms of nausea, vomiting, and malaise, not drowsiness.

A Patient Who Has Been Taking Phenobarbital for Epilepsy Begins