Standards of Laboratory Practice: Antiepileptic Drug Monitoring (Nacb Symposium‪)‬

Epilepsy is one of most common dysfunctions of the nervous system, with a prevalence of 2 million affected individuals in the US (1). Patients with epilepsy are often noncompliant or incompletely compliant with their medication regimens for a variety of reasons. The effects of antiepileptic therapy can be assessed only through evaluation of the patient's seizure frequency, a sometimes time-consuming process, especially if seizures are infrequent. Drugs for which relationships between blood concentration and therapeutic effect have been established can be evaluated through use of therapeutic drug monitoring, which can quickly determine whether the patient has achieved the desired drug concentration. This helps expedite the process of establishing a drug regimen for an individual patient. Monitoring is also helpful in this class of drugs because it is sometimes difficult to differentiate between drug toxicity and uncontrolled disease. When monitoring is performed, the therapeutic ranges that have been established for the drugs in this class should be used only as guides. Several articles indicate that a strict use of the therapeutic range cutoffs to classify patients as subtherapeutic, therapeutic, or toxic will result in considerable numbers of misclassifications (2, 3). A therapeutic concentration is one that stops seizures or decreases seizure frequency with acceptable side effects in an individual patient.