A nurse is caring for a patient who has been taking an anticonvulsant drug for 4 weeks. The nurse asks the patient if the therapy is effective. The patient reports little change in seizure frequency. What is the priority intervention?

A. Contact the provider to request an order for serum drug levels: Measuring serum drug levels helps determine whether the anticonvulsant concentration is within the therapeutic range. Subtherapeutic levels may explain persistent seizures, while toxic levels would indicate overdose risk. B. Reinforce the need to take the medications as prescribed: While adherence is essential, the client has already been on therapy for 4 weeks, and reinforcement alone will not clarify whether the drug is reaching effective blood concentrations. This step is supportive but not the immediate priority. C. Request an order to increase the dose of the antiepileptic drug: Dose adjustments should not be made without knowing the current serum drug level. Increasing the dose blindly risks toxicity without addressing whether the issue is poor absorption, nonadherence, or drug interactions. D. Encourage the client to start a seizure diary to log frequency of seizures: A seizure diary is useful for long-term monitoring, but it does not address the immediate concern of ineffective therapy. The priority is determining whether drug levels are therapeutic before considering changes to treatment.