Therapeutic drug monitoring (TDM) is increasingly relevant for an individualized antibiotic therapy and subsequently a necessary tool to reduce multidrug-resistant pathogens, especially in light of diminishing antimicrobial capabilities. Critical illness is associated with profound pharmacokinetic and pharmacodynamic alterations, which challenge dose finding and the application of particularly hydrophilic drugs such as β-lactam antibiotics. Methods: Implementation strategy, potential benefit, and practicability of the developed standard operating procedures were retrospectively analyzed from January to December 2020. Furthermore, the efficacy of the proposed dosing target of piperacillin in critically ill patients was evaluated. Results: In total, 160 patients received piperacillin/tazobactam therapy and were subsequently included in the study. Of them, 114 patients received piperacillin/tazobactam by continuous infusion and had at least one measurement of piperacillin serum level according to the standard operating procedure. In total, 271 measurements were performed with an average level of 79.0 ± 46.0 mg/L. Seventy-one piperacillin levels exceeded 100 mg/L and six levels were lower than 22.5 mg/L. The high-level and the low-level group differed significantly in infection laboratory parameters (CRP (mg/dL) 20.18 ± 11.71 vs. 5.75 ± 5.33) and renal function [glomerular filtration rate (mL/min/1.75 m2) 40.85 ± 26.74 vs. 120.50 ± 70.48]. Conclusions: Piperacillin levels are unpredictable in critically ill patients. TDM during piperacillin/tazobactam therapy is highly recommended for all patients. Although our implementation strategy was effective, further strategies implemented into the daily clinical workflow might support the health care staff and increase the clinicians’ alertness.
Oral valganciclovir and intravenous ganciclovir are used for prophylaxis, treatment, and pre-emptive treatment of cytomegalovirus and human herpesvirus 6. It is important to estimate the exposure to these antivirals, as deviating levels can cause adverse events or induce acquired drug resistance, which can both lead to treatment failure. Therapeutic drug monitoring (TDM) is a good tool to estimate drug exposure in these patients. With this observational study we aimed to evaluate which patients would benefit most from TDM.
An observational study was performed in adult solid-organ and stem cell transplant recipients on routine (val)ganciclovir (dosed according to renal function, weight and indication). As valganciclovir is a prodrug of ganciclovir, only the latter was measured. Ganciclovir trough (Ctrough) and peak (Cpeak) concentrations were measured with a validated LC-MS/MS assay. The target concentrations defined for the study were 1–2 mg/L and 2–4 mg/L for prophylaxis and treatment, respectively, and over 5 mg/L toxic.
From June 2018 to April 2019, 66 patients were included. Within this timeframe, 236 Ctrough and 52 Cpeak were measured with median of 4 samples per patient. The median Ctrough was 1.1 mg/L and 2.3 mg/L for prophylaxis and treatment, respectively. Over 50% of the concentrations were out of the therapeutic window. The median creatinine for all measurements was 100 µmol/L. Observational analysis showed patients with kidney failure and on continuous renal replacement therapy (CVVH) had more concentrations measured out of the predefined range (Figures 1 and 2). For one individual with augmented renal clearance we observed significantly lower concentrations during routine dosing. 6 toxic concentrations were measured (5 subjects); creatinine concentrations ranged 71–527 µmol/L in these individuals. A preliminary linear-mixed model analysis did not show drug formulation, age or gender as a significant predictor for ganciclovir concentrations.
We believe that patients with decreased renal function, on CVVH or showing changes in renal function might benefit from TDM to guide therapy. TDM of ganciclovir for patients without renal failure remains debatable. Further studies with specific patient groups are needed to confirm these results.
All authors: No reported disclosures.