Why ICU patients may need different antiseizure medication strategies

Antiseizure medications (ASMs) are commonly used in the intensive care unit (ICU) and often exhibit pharmacokinetics that differ substantially from those in healthy volunteers or in the outpatient setting. Organ dysfunction, polypharmacy, exogenous devices, and greater severity of illness all influence ASM pharmacokinetics, dosing decisions, and monitoring parameters. It is essential for critical care clinicians to familiarize themselves with the pharmacokinetics, dosing considerations, effects of exogenous devices, and therapeutic drug monitoring (TDM)-all covered in this narrative review-to incorporate in their approach to ASMs in the critical care setting. We identified relevant literature from MEDLINE from inception to March 2026 related to ASMs in the ICU. Data on pharmacokinetics, dosing in the ICU, the effect of renal replacement therapy, extracorporeal membrane oxygenation (ECMO), and plasmapheresis (PLEX) on ASM exposure, and the role of TDM in the ICU were collected and summarized. Considerations for 15 ASMs (brivaracetam, cannabidiol, carbamazepine, cenobamate, clobazam, lacosamide, lamotrigine, levetiracetam, oxcarbazepine, perampanel, phenobarbital, phenytoin, topiramate, valproate, and zonisamide) were included in the review. Dosing considerations for TDM, including indications and target reference ranges, and specific settings such as organ dysfunction, illness severity, renal replacement therapy, ECMO, and PLEX are discussed. The use of ASMs in the ICU require a distinct approach from outpatient settings. Severity of illness, organ dysfunction and replacement devices, and frequent drug-drug interactions warrant tailored agent selection, dosing, and monitoring.