Therapeutic drug monitoring of daptomycin in a critically ill patient cohort

Background Pharmacokinetics of antimicrobial agents are altered in critically ill patients. Therefore, therapeutic drug monitoring (TDM) has gained much attention in recent years. Specifically, the role of TDM for daptomycin, its potential influence on dose adaptations and subsequent daptomycin levels, as well as daptomycin-related side effects is so far unclear in the critical care setting. Methods This was a retrospective study including critically ill, adult patients from January 2010 to July 2023. No criteria for TDM were predefined and the decision to perform TDM was left to the discretion of the treating physician. The primary outcome was the evaluation of baseline daptomycin trough levels in patients undergoing TDM, and how subsequent levels were affected by potential dose adaptations. Further outcomes included daptomycin-free days alive over 14 days and the occurrence of side effects between patients with and without daptomycin TDM. Results Two hundred seventy patients were included. The patient group was heterogeneous regarding elective or emergency admissions and had surgical and medical underlying conditions. Over the ICU stay, median daptomycin trough levels were 9 mg/L (IQR 5.8–16.4 mg/L) and median peak levels were 29. 8 mg/L (IQR 14.8 – 46 mg/L). The first measured daptomycin trough level was too low (