Are Standard Dosing Regimens of Ceftriaxone Adapted for Critically Ill Patients with Augmented Creatinine Clearance?

The objective of the present study was to determine whether augmented renal clearance (ARC) impacts negatively on ceftriaxone pharmacokinetic (PK)/pharmacodynamic (PD) target attainment in critically ill patients. Over a 9-month period, all critically ill patients treated with ceftriaxone were eligible. During the first 3 days of antimicrobial therapy, every patient underwent 24-h creatinine clearance (CLCR) measurements and therapeutic drug monitoring of unbound ceftriaxone. ARC was defined by a CLCR of ≥150 ml/min. Empirical underdosing was defined by a trough unbound ceftriaxone concentration under 2 mg/liter (percentage of the time that the concentration of the free fraction of drug remained greater than the MIC [fT>MIC], 100%). Monte Carlo simulation (MCS) was performed to determine the probability of target attainment (PTA) of different dosing regimens for various MICs and three groups of CLCR (<150, 150 to 200, and >200 ml/min). Twenty-one patients were included. The rate of empirical ceftriaxone underdosing was 62% (39/63). A CLCR of ≥150 ml/min was associated with empirical target underdosing with an odds ratio (OR) of 8.8 (95% confidence interval [CI] = 2.5 to 30.7; P < 0.01). Ceftriaxone PK concentrations were best described by a two-compartment model. CLCR was associated with unbound ceftriaxone clearance (P = 0.02). In the MCS, the proportion of patients who would have failed to achieve a 100% fT>MIC was significantly higher in ARC patients for each dosage regimen (OR = 2.96; 95% CI = 2.74 to 3.19; P < 0.01). A dose of 2 g twice a day was best suited to achieve a 100% fT>MIC When targeting a 100% fT>MIC for the less susceptible pathogens, patients with a CLCR of ≥150 ml/min remained at risk of empirical ceftriaxone underdosing. These data emphasize the need for therapeutic drug monitoring in ARC patients.

Higher than standard dosing regimen are needed to achieve optimal antibiotic exposure in critically ill patients with augmented renal clearance receiving piperacillin-tazobactam administered by continuous infusion.

PURPOSE: To determine whether augmented renal clearance (ARC) impacts negatively on piperacillin-tazobactam unbound concentrations in critically ill patients receiving 16 g/2 g/day administered continuously. MATERIAL AND METHODS: Fifty nine critically ill patients without renal impairment underwent 24-h creatinine clearance (CrCL) measurement and therapeutic drug monitoring during the first three days of antimicrobial therapy by piperacillin-tazobactam. The main outcome was the rate of piperacillin underexposure, defined by at least one of three samples under 16 mg/L. Monte Carlo simulation was performed to predict the distribution of piperacillin concentrations for various CrCL and minimal inhibitory concentration (MIC) values. RESULTS: The rate of piperacillin underexposure was 19%, significantly higher in ARC patients (0 vs. 31%, p = .003). A threshold of CrCL ≥ 170 mL/min had a sensitivity and specificity of 1 (95%CI: 0.79-1) and 0.69 (95%CI: 0.61-0.76) to predict piperacillin underexposure. In ARC patients, a 20 g/2.5 g/24 h PTZ dosing regimen was associated with the highest probability to reach the 16 mg/L empirical target, without risk of excessive dosing. CONCLUSIONS: When targeting a theoretical MIC at the upper limit of the susceptibility range, the desirable target (100%fT>16) may not be achieved in patients with CrCL ≥ 170 mL/min receiving PTZ 16 g/2 g/day administered continuously.

Association between augmented renal clearance, antibiotic exposure and clinical outcome in critically ill septic patients receiving high doses of ß-lactams administered by continuous infusion: a prospective observational study.

This study assessed whether augmented renal clearance (ARC) impacts negatively on antibiotic concentrations and clinical outcomes in patients treated by high-dose ß-lactams administered continuously. Over a 9-month period, all critically ill patients without renal impairment treated by one of the monitored ß-lactams for a documented infection were eligible. During the first 3 days of antibiotic therapy, every patient underwent 24-h CLCr measurements and therapeutic drug monitoring. The main outcome was the rate of ß-lactam underdosing, defined as a free drug concentration <4 × MIC of the known pathogen. Secondary outcomes were rates of subexposure for ß-lactams and therapeutic failure. The performance of CLCr in predicting underdosing was assessed by a ROC curve, and multivariable logistic regression was performed to determine risk factors for subexposure and therapeutic failure. A total of 79 patients were included and 235 samples were analysed. The rate of underdosing<4×MIC was 12%, with a significant association with CLCr (P <0.0001). A threshold of CLCr ≥ 170 mL/min had a sensitivity and specificity of 0.93 (95% CI 0.77-0.99) and 0.65 (95% CI 0.58-0.71) for predicting ß-lactam underdosing<4×MIC. Mean CLCr values ≥170 mL/min were significantly associated with subexposure<4xMIC [OR = 10.1 (2.4-41.6); P = 0.001]. Patients with subexposure<4×MIC presented higher rates of therapeutic failure [OR = 6.3 (1.2-33.2); P = 0.03]. Mean CLCr values ≥170 mL/min remain a risk factor for subexposure to ß-lactams despite high doses of ß-lactams administered continuously. ß-Lactam subexposure was associated with higher rates of therapeutic failure in septic critically ill patients.