What is the therapeutic level range for phenytoin?

The therapeutic range for phenytoin is generally accepted to be between 10 to 20 mg/L. Within this range, phenytoin is effective in controlling seizures with a lower risk of toxicity. Levels below 10 mg/L may not provide adequate seizure control, while levels above 20 mg/L can increase the risk of serious side effects and toxicity. Monitoring phenytoin levels is crucial due to its nonlinear pharmacokinetics and potential for narrow therapeutic index, which means that small increases in dose can lead to significant increases in serum levels, raising the risk for adverse effects. Thus, maintaining serum phenytoin levels within this therapeutic range is essential for effective management of seizure disorders.