Monitoring Phenytoin Levels

Introduction to Phenytoin Monitoring

• The American Journal of Respiratory and Critical Care Medicine notes that ethionamide can increase phenytoin (Dilantin) levels, requiring more frequent monitoring when starting or stopping medications that interact with phenytoin 1

Patient Populations Requiring Special Consideration

• Elderly patients may require lower doses and are more susceptible to toxicity at lower serum concentrations, necessitating closer monitoring 1
• Patients with renal or hepatic impairment, as well as those on multiple medications with potential interactions, require more frequent monitoring 1

Medication Interactions

• The American Journal of Respiratory and Critical Care Medicine recommends particular attention when adding drugs that may displace phenytoin from protein binding, inhibit or induce phenytoin metabolism, with ethionamide being an example of a drug that can increase phenytoin levels 1