Therapeutic Drug Monitoring of Second- and Third-Generation Antiepileptic Drugs Insights From a College of American Pathologists Proficiency Testing Survey

center dot Context.-Therapeutic drug monitoring has traditionally been widely used for first-generation antiepileptic drugs (AEDs) such as carbamazepine and phenytoin. The last 2 decades have seen the introduction of second-and third generation AEDs (eg, lamotrigine, levetiracetam, and topiramate) into clinical practice. Objective.-To use data from the College of American Pathologists Therapeutic Drug Monitoring, Extended Proficiency Testing Survey to determine the performance of assays used for therapeutic drug monitoring of newer AEDs, including comparison of enzyme immunoassay and chromatographic techniques. Design.-Six years of proficiency testing surveys were reviewed (2013-2018). Results.-Steady growth was seen in participant volumes for newer AEDs. The analytical performance of automated enzyme immunoassays for lamotrigine, levetiracetam, and topiramate was similar to that of chromatographic methods, consistent with published literature using patient samples for comparisons. The majority of participating laboratories now use enzyme immunoassays to measure levetiracetam. Conclusions.-Survey results reflect steadily growing interest in therapeutic drug monitoring of newer AEDs. The increasing availability of robust immunoassays for new AEDs should facilitate their clinical utility, especially for clinical laboratories that do not perform chromatographic assays for therapeutic drug monitoring.