A nurse in a primary care clinic is caring for a 28-year-old female client who was diagnosed with epilepsy during childhood. For each finding, indicate whether it is a contraindication to phenytoin or requires immediate follow-up.

Requires Immediate Follow-Up Alcohol use While not a strict contraindication, alcohol can interfere with phenytoin metabolism, increasing the risk of toxicity or subtherapeutic levels. It also lowers the seizure threshold. This pattern of alcohol use warrants counseling and follow-up. Amenorrhea (last menstrual period 3 months ago) This may indicate pregnancy, which is critical to assess because phenytoin is teratogenic (FDA Pregnancy Category D). Immediate follow-up is needed to evaluate for pregnancy and consider alternative treatment options or additional supplementation (e.g., folic acid). Diazepam use Diazepam and phenytoin are both central nervous system depressants and can interact pharmacokinetically. Diazepam may increase phenytoin levels and vice versa, requiring close monitoring for sedation or toxicity. Not Concerning Vegetarian diet and multivitamin use This is not a contraindication and does not require immediate follow-up. However, long-term phenytoin use can affect folate and vitamin D metabolism, so continued multivitamin use may be beneficial. Take-home points Phenytoin has a narrow therapeutic index and interacts with many substances, including alcohol and benzodiazepines. Women of childbearing age should be screened for pregnancy before initiating phenytoin due to its teratogenic potential. Amenorrhea in a client on antiseizure medication should prompt evaluation for pregnancy or endocrine dysfunction. Nutritional status and supplementation should be monitored in clients on long-term phenytoin, especially for folate and vitamin D.