Author response: Clinical utility of therapeutic drug monitoring of antiepileptic drugs

I appreciated Dr. Sethi's commentary on our recently published article as he raises a number of interesting points.¹ Certainly, intraindividual variability is another complicating aspect of therapeutic drug monitoring (TDM) in epilepsy care and, while outside the scope of our review, should be taken into account by all clinicians who choose to incorporate serum antiepileptic drug levels into their clinical decision-making. For my personal practice, I tend to agree that the clinical utility of serum antiepileptic drug levels is limited and that dosing adjustments are best made based on clinical response (seizure control and reported adverse effects). Although our systematic review did identify some studies showing evidence for TDM, the higher quality studies did not show convincing evidence supporting a clinical benefit. In general, we clinicians now have a wealth of diagnostic options available to us, and it is easy to forget that the patient's reported symptoms and clinical examination are almost always the most important outcome measures.