Pharmacokinetics of meropenem in burn patients with infections caused by Gram-negative bacteria: Are we getting close to the right treatment?

Which Are the Best Regimens of Broad-Spectrum Beta-Lactam Antibiotics in Burn Patients? A Systematic Review of Evidence from Pharmacology Studies

BACKGROUND

Burn injury causes profound pathophysiological changes in the pharmacokinetic/pharmacodynamic (PK/PD) properties of antibiotics. Infections are among the principal complications after burn injuries, and broad-spectrum beta-lactams are the cornerstone of treatment. The aim of this study was to review the evidence for the best regimens of these antibiotics in the burn patient population.

METHODS

We performed a systematic review of evidence available on MEDLINE (from its inception to 2023) of pharmacology studies that focused on the use of 13 broad-spectrum beta-lactams in burn patients. We extracted and synthetized data on drug regimens and their ability to attain adequate PK/PD targets.

RESULTS

We selected 35 studies for analysis. Overall, studies showed that both high doses and the continuous infusion (CI) of broad-spectrum beta-lactams were needed to achieve internationally-recognized PK/PD targets, ideally with therapeutic drug monitoring guidance. The most extensive evidence concerned meropenem, but similar conclusions could be drawn about piperacillin-tazobactam, ceftazidime, cefepime, imipenem-clinastatin and aztreonam. Insufficient data were available about new beta-lactam-beta-lactamase inhibitor combinations, ceftaroline, ceftobiprole and cefiderocol.

CONCLUSIONS

Both high doses and CI of broad-spectrum beta-lactams are needed when treating burn patients due to the peculiar changes in the PK/PD of antibiotics in this population. Further studies are needed, particularly about newer antibiotics.

Does Prolonged Infusion Time Really Improve the Efficacy of Meropenem Therapy? A Prospective Study in Critically Ill Patients

Introduction

Meropenem is a carbapenem antibiotic, which has demonstrated excellent antimicrobial activity against gram-negative clinical isolates. It is also commonly used in critically ill patients. This study aimed to determine the pharmacokinetics/pharmacodynamics of meropenem in critically ill patients and whether prolonged injection duration is really beneficial to meropenem therapy.

Methods

We included 209 samples in 64 patients in this prospective study. PPK analysis and Monte Carlo dosing simulations were developed using Phoenix.

Results

A two-compartment model described the data adequately. Clearance (CL), volume (V), clearance of peripheral compartment (CL₂), and volume of peripheral compartment (V₂) were 6.15 l/h, 2.83 l/h, 17.40 l, and 17.48 l, respectively. Creatinine clearance and uric acid were significant covariates. Patients with creatinine clearance ≤ 60 ml/min and uric acid > 400 μmol/l could achieve the target > 90% under the minimum inhibitory concentration (MIC) of 8 mg/l, even with the administration dose of 500 mg/8 h with a 2-h infusion. Prolonging the infusion time significantly improved the therapeutic effect when MIC < 4. However, for the pharmacodynamic (PD) effects of 100% fT > MIC and 100% fT > 4 MIC, no significant statistical difference was observed in critically ill patients.

Conclusions

Critically ill patients with lower creatinine clearance and higher uric acid levels tended to need a lower dosage of meropenem. Prolonged infusion time was not always beneficial for those who needed a higher therapeutic target (100% fT > MIC, 100% fT > 4 MIC) or with MIC > 4 mg/l. Increasing dose or alternative therapeutic strategies may be required for critically ill patients with drug-resistant or severe infections. The study is of great significance to guide the rational use of meropenem in critically ill patients.

Trial Registration

The trial was registered in the China Clinical Trial (ChiCTR1900020672). Registered on 12 January 2019.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40121-021-00551-2.

Meropenem is commonly used empirically or targeted in critically ill patients for bacterial infection. Many studies have reported that prolonged infusion time can improve the efficacy of meropenem therapy. However, we are skeptical about that. Meanwhile, prolonged injections can sometimes cause mobility problems for patients. A quantitative method is used to evaluate meropenem use. It is called the population pharmacokinetic model or pharmacodynamic study. Using this method, we found two significant influencing factors of meropenem metabolism: creatinine clearance and uric acid level. It is likely that patients with a lower level of creatinine clearance and a high uric acid level tend to require lower dosages of meropenem. As for the effect of infusion time, Monte Carlo simulation was used, which can do 3000 simulations on an individual. The result was complex. We found infusion time was beneficial only when bacteria were sensitive to meropenem. The evidence suggests that prolonged injection duration sometimes does not significantly improve the outcome of antimicrobial therapy.

Evaluation of Voriconazole and Posaconazole Dosing in Patients with Thermal Burn Injuries

Fungal infections are a recognized cause of increased morbidity and mortality in thermal burn patients. Adequate treatment regimens remain a challenge due to unpredictable pharmacokinetic/pharmacodynamic changes caused by a hypermetabolic state and individual patient factors. A retrospective evaluation of adult thermal burn patients from April 2014 to April 2020 was conducted to assess voriconazole and posaconazole antifungal dosing regimens. The primary outcome was the incidence of attaining a therapeutic steady-state trough level on the patient's initial voriconazole or posaconazole regimen. Of the 35 patients analyzed, 28 (80.0%) patients achieved a therapeutic level during azole therapy. However, only 13 (46.4%) patients achieved a therapeutic level on their first azole regimen. The median time to therapeutic level was 8.0 + 21.1 days from the start of azole therapy. Optimal dosing strategies for azole therapy in patients with thermal burns remains undefined. Further assessment is needed to delineate patient-specific factors that can contribute to subtherapeutic azole levels in thermal burn patients and the overall clinical impact of population-specific dosing regimens.

Acute respiratory failure and burn patient outcomes

PURPOSE OF REVIEW

Advances in the care of inhalational injuries have not kept pace with advances that have been seen in the treatment of cutaneous burns. There is not yet a standard of care for best outcomes for airway management of patients with known or suspected inhalational injuries. Clinicians must decide if to intubate the patient, and if so, whether to intubate early or late in their presentation. Unnecessary intubation affects morbidity and mortality. This review will summarize literature that highlights present practices in the treatment of patients with inhalation injuries.

RECENT FINDINGS

There have been promising investigations into biomarkers that can be used to quantify a patient's risk and better target therapies. Grading systems serve to better stratify the burn victim's prognosis and then direct their care. Special ventilator modes can assist in ventilating burn patients with inhalation injuries that experience difficulties in oxygenating.

SUMMARY

Inhalational injuries are a significant source of morbidity and mortality in thermally injured patients. Treatment modalities, such as modified ventilator settings, alteration in fluid resuscitation, and a standardized grading system may improve morbidity and mortality.

Pharmacokinetics and Pharmacodynamics of Antimicrobial Agents in Burn Patients

Background: Infection is common after burn injury and accounts for the most frequent complications of burn injury. This review describes the effects of burn injury on pharmacokinetics, focusing on the impact of these changes on antimicrobial therapy. Methods: The published literature on pharmacokinetics and pharmacodynamics in burn injury of antibiotic use was reviewed. Results: Physiologic and metabolic changes of burn injury can alter pharmacokinetic parameters, leading to larger volumes of distribution, faster hepatic metabolism, and increased renal clearance. Changes in pharmacokinetics may lead to subtherapeutic doses of commonly used antibiotic and antifungal agents. Conclusions: Although not all antimicrobial agents are well studied in the burn population, dose recommendations exist for some agents. Additional research is needed to cover the systemic antimicrobial agents used in the care of burn patients so that appropriate dosing adjustments can be made to optimize outcomes.

Microbiome in the setting of burn patients: implications for infections and clinical outcomes

Burn damage can lead to a state of immune dysregulation that facilitates the development of infections in patients. The most deleterious impact of this dysfunction is the loss of the skin’s natural protective barrier. Furthermore, the risk of infection is exacerbated by protracted hospitalization, urinary catheters, endotracheal intubation, inhalation injury, arterial lines and central venous access, among other mainstays of burn care. Currently, infections comprise the leading cause of mortality after major burn injuries, which highlights the improvements observed over the last 50 years in the care provided to burn victims. The need to implement the empirical selection of antibiotic therapy to treat multidrug-resistant bacteria may concomitantly lead to an overall pervasiveness of difficult-to-treat pathogens in burn centres, as well as the propagation of antimicrobial resistance and the ultimate dysregulation of a healthy microbiome. While preliminary studies are examining the variability and evolution of human and mice microbiota, both during the early and late phase burn injury, one must consider that abnormal microbiome conditions could influence the systemic inflammatory response. A better understanding of the changes in the post-burn microbiome might be useful to interpret the provenance and subsequent development of infections, as well as to come up with inferences on the prognosis of burn patients. This review aims to summarise the current findings describing the microbiological changes in different organs and systems of burn patients and how these alterations affect the risks of infections, complications, and, ultimately, healing.