Therapeutic Drug Monitoring of Levetiracetam in Select Populations

Purpose: Levetiracetam (LEV) is a broad spectrum antiepileptic drug (AED) that has a more favorable side effect profile compared to older AEDs. Therapeutic drug monitoring (TDM) of LEV is generally unnecessary given its linear and predictable dose-serum concentration relationship, lack of drug-drug interactions, and broad therapeutic window. However, there is growing evidence showing that alteration of LEV pharmacokinetics (PK) may occur in special populations calling for the need for TDM. The purpose of this review was to summarize current literature surrounding altered LEV PK in special patient populations and determine if there is a need for levetiracetam TDM. Methods: A literature search of MEDLINE (1946 - November 2017) database of available evidence pertaining to altered LEV PK in humans was conducted. Results: A total of 51 articles were found. There has not been a positive correlation shown between LEV levels and efficacy or toxicity. Variable LEV levels are reported in the literature with respect to adverse effects, seizures and efficacy occurring below, within and above the supposed reference ranges. Age is a major contributor to altered pharmacokinetics of LEV as shown in elderly patients and pediatric patients. Compared to adults, clearance of LEV has been shown to be decreased by almost half in patients over 65 and increased by 30-40% in pediatric patients. LEV pharmacokinetics varied further when data from its use in neonates was explored. LEV clearance declined in a linear fashion with declining estimates of creatinine clearance but was variable in patients with end-stage renal failure or those requiring renal replacement therapy. In patients who were critically ill, LEV clearance may be augmented and these patients may require higher doses of medications to maintain drug levels. In patients who are pregnant, LEV levels are likely to decline as pregnancy progresses due to changes in glomerular filtration rate and remain variable in the post-partum period. Conclusion: Routine TDM of levetiracetam is not recommended for all populations, however, it may be beneficial to maintain an individual therapeutic range in patients where the PK of LEV may be altered, such as in patients who are critically ill patients, pregnant, pediatrics or elderly.