When More is Still Not Enough: A Case of Ceftazidime-Avibactam Resistance in a Burn Patient

Pharmacokinetic Analysis of Intravenous Push Cefepime in Burn Patients with Augmented Renal Clearance

Patients with augmented renal clearance (ARC) are a subset of critically ill patients including burn patients that exhibit increased renal elimination of medications beyond that of similarly injured patients. Currently approved maximum regimens of medications primarily eliminated by the kidney, such as cefepime (>90% unchanged in the urine), may be inadequate (eg, compromising the bactericidal activity of cefepime) in patients with ARC. Due to recent resource limitations, centers have changed infusion practices of commonly prescribed medications to intravenous push (IVP), potentially exacerbating the problem of maintaining bactericidal cefepime concentrations. The hypothesis of the study was patients with ARC are not currently achieving adequate target attainment, when receiving cefepime 2 g every 8 h IVP. Eight blood samples were collected from each patient, and concentrations measured via LC-MS/MS. WinNonlin (version 8.3) was used to estimate the pharmacokinetic parameters of cefepime and simulate plasma concentrations of cefepime in each of the ten subjects. Simulations of cefepime plasma concentrations produced by a 2 g dose given every 8 h and a 1 g dose given every 4 h were performed and the time above a MIC of 4 mg/L, 8 mg/L, and 16 mg/L compared. The 2 g every 8 h regimen remained above the breakpoints for 92%, 85%, and 71% of the dosing interval, respectively. The 1 g every 4 h regimen remained above the same breakpoints at a frequency of 100%, 99%, and 92% of the dosing interval. Giving cefepime 1 g every 4 h is a simple approach to increase the likelihood of maintaining the optimal bactericidal activity of cefepime in patients with ARC.

Analysis of Ceftazidime/Avibactam Use for Treating Carbapenem-Resistant Infections in Critically Ill Patients With Thermal or Inhalation Injuries

Rising antimicrobial resistance is a pressing public health concern. An increase in carbapenem-resistant organisms has led to increased use of novel antibiotics, such as ceftazidime/avibactam (CZ/AV). However, recent studies have shown increasing treatment failures and resistance rates associated with ceftazidime/avibactam use. The efficacy of CZ/AV has not been studied in patients with thermal or inhalation injuries, where pharmacokinetic derangements are common and patients are often subject to longer lengths of stay and several antimicrobial courses that may lead to higher resistance rates. The objective of this study was to evaluate the outcomes of patients with thermal and inhalation injuries including clinical success, the frequency of adverse effects, and emergence of resistance. In the 17 courses of CZ/AV evaluated, clinical success occurred in 71% (12/17) of courses. Enterobacter cloacae was the most commonly treated pathogen. Resistance developed in 18% (3/17) of courses, but follow-up sensitivities were not evaluable for every case. Although lower than desired, clinical success rates in this sample were similar to other reported populations treated with CZ/AV. However, the emergence of resistance occurred more frequently and was likely underreported in this sample. Although limited by its small sample size, this study emphasizes the concern of growing antimicrobial resistance among even novel antibiotics. Resistance can develop during the initial course, stressing the importance of infection prevention and antimicrobial stewardship. Furthermore, attention and resources should be given to proper pharmacokinetic analysis of medications given in severely ill, hypermetabolic populations.