Antibiotic dosing in obesity: the search for optimum dosing strategies

Evaluation and implementation of optimized antimicrobial dosing strategies in obese and underweight patients

PURPOSE

We aimed to develop and implement dosing recommendations for antimicrobials in obese and underweight patients within an academic hospital, and assess their impact on antibiotic prescribing.

METHODS

A multi-step approach project was performed. First, obese and underweight patient prevalence and antimicrobial prescription frequency was determined in a point prevalence study. Second and third, a literature review and e-survey provided dosing evidence. Fourth, a consensus meeting was organized to formulate dosing recommendations. Fifth, these were implemented in our clinical validation service as six clinical rules continuously screening patients' records for potentially inappropriate prescriptions (PIPs). Uptake was evaluated by documenting the number of advices and acceptance rate. Last, an interrupted time series analysis (ITS) compared pre- and post-implementation periods to measure the impact of the intervention on residual PIPs/day. A residual PIP was defined as a PIP which persisted up to 48 h.

RESULTS

First, 41% of 15.896 hospitalized patients received antimicrobials over 20 days; of which 12% were obese and 9% underweight. Antibiotics were predominantly prescribed according to standard dosing regimens, adjusted to renal function. Next, six dosing recommendations, derived from literature, survey, and consensus, were implemented. In the fifth step, during an 18-week period, 219 advices were given, with 86% acceptance rate. Last, in the ITS analysis, at preintervention, a median of 75% residual PIPs/day existed, reduced to 0% postintervention. Use of clinical rules resulted in a significant immediate 84% relative reduction in residual PIPs (95% CI 0.55-0.94).

CONCLUSION

After conducting a literature review, e-survey, and seeking consensus from a panel of experts, dosing recommendations for antimicrobial treatment in both obese and underweight patients were developed. These recommendations have been successfully implemented into clinical practice, addressing the specific needs of these patient populations.

[An online tool to personalize the drug-doses for obese adults]

BACKGROUND

Between 1975 and 2014, the number of people suffering from obesity tripled, reaching 17% of the adult population in France and more than 35% in the United States. Obesity is defined by a Body Mass Index (BMI)>30kg/m2 and characterized by a significant accumulation of adipose tissue responsible for the increase in weight. This accumulation leads to physiological changes capable of modifying the pharmacokinetics of drugs, which can lead to the administration of inappropriate doses. For this reason, some significant dosage adjustments are necessary for obese patients. However, data on these adaptations are not easily accessible and sometimes complex to implement in practice.

AIM

To perform a new online tool allowing to calculate and propose an adjusted dose of a drug that should be administered to an obese patient.

METHOD

(i) carrying out an extensive bibliographic research according to the PRISMA methodology; and (ii) the development of a new website site proposing an adjusted dose for obese patients.

RESULTS

Firstly, 49 reviews concerning the dose adaptation have been evaluated and, secondly, 319 articles have been selected. Among them, 204 articles have been included in the database to justify the adjusted dose of 84 drugs and administration methods including antibiotics, antifungals, anticoagulants or even cancer drugs. This database is available online through a calculator on the website named Adapt'Obese. Thus, with the sex, height and weight of an obese patient, Adapt'Obese proposes a personalized and adjusted dose of the drug to administer.

PERSPECTIVES

Other drugs will be added soon, and functional improvements are planned, with the aim of adapting the dosages in obese patients, as for patients with renal insufficiency.

Pharmacokinetics of obese adults: Not only an increase in weight

Obesity is a pathophysiological state defined by a body mass index > 30 kg/m2 and characterized by an adipose tissue accumulation leading to an important weight increased. Several pathologies named comorbidities such as cardiovascular disease, type 2 diabetes and cancer make obesity the fifth cause of death in the world. Physiological changes impact the four main phases of pharmacokinetics of some drugs and leads to an inappropriate drug-dose. For absorption, the gastrointestinal transit is accelerated, and the gastric empty time is shortened, that can reduce the solubilization and absorption of some oral drugs. The drug distribution is probably the most impacted by the obesity-related changes because the fat mass (FM) increases at the expense of the lean body weight (LBW), leading to an important increase of the volume of distribution for lipophilic drugs and a low or moderately increase of this parameter for hydrophilic drugs. This modification of the distribution may require drug-dose adjustments. By various mechanisms, the metabolism and elimination of drugs are impacted by obesity and should be considered as similar or lower than that non-obese patients. To better understand the necessary drug-dose adjustments in obese patients, a narrative review of the literature was conducted to highlight the main elements to consider in the therapeutic management of adult obese patients.

A Multidisciplinary Approach to Improvements in Perioperative Antibiotic Prophylaxis at a Military Treatment Facility

INTRODUCTION

Surgical site infections complicate 2%-5% of surgeries. According to the Centers for Disease Control and Prevention, half of all surgical site infections are preventable. Adherence to published recommendations regarding perioperative antibiotic administration decreases the incidence of surgical site infections. Members of the Department of Anesthesia noticed casual observations of inaccurate prescribing of antibiotics at our institution, Brooke Army Medical Center, and approached the Antimicrobial Stewardship Program to collaborate on this issue.

MATERIALS AND METHODS

A team of anesthesiologists, clinical pharmacists, and infectious disease specialists collaborated with the Department of Surgery to improve this effort as part of a multiyear project from 2018 to 2021. We first assessed adherence to recommended perioperative antibiotic use to establish a baseline and next, noticing gaps, created a project with the goal to improve compliance to >90% across surveyed measures. Our key interventions included educational initiatives, creation of facility-specific guidelines, peer benchmarking, updating order sets, interdisciplinary collaboration, creation of intraoperative reminders and visual aids, and tailored presentations to selected services.

RESULTS

Of 292 charts (2.3% of cases from January to October 2018) reviewed pre-intervention, compliance rates were 84% for antibiotic choice, 92% for dose, 65% for redosing, and 71% for postoperative administration. Of doses, 100% were timed correctly, and thus, this variable was not targeted. Post-intervention, our review of 387 charts (10% of cases from May to November 2020) showed no change in correct antibiotic choice (84%) and statistical improvement to 96% for correct dose, 95% for correct redosing, and 85% for correct postoperative administration (P < .05 for all).

CONCLUSIONS

Our multidisciplinary approach of collaboration with multiple departments, creating guidelines and providing feedback, improved compliance with perioperative antibiotic administration recommendations.

Relationship Between Multidrug-Resistant Enterobacterales and Obesity in Older Adults

Purpose

The objective of our study was to determine if obesity is associated with the presence of multidrug-resistant (MDR) bacteria among Enterobacterales.

Patients and Methods

This two-center cohort study included adult hospitalized patients with at least one specimen sampled from any site for bacterial culture yielding an Enterobacterales bacterial species from November 2016 to May 2017. Study groups were stratified by obesity status based on body mass index <30 kg/m² (non-obese) and ≥30 kg/m² (obese). The primary outcome was the presence of gram-negative MDR bacteria defined as presumptive extended-spectrum beta-lactamase (ESBL)-producing Enterobacterales (ceftriaxone resistance) or carbapenem-resistant Enterobacterales (CRE). A multivariable logistic regression model was fit to estimate the adjusted odds ratio while controlling for potential confounders.

Results

A total of 366 patients, 238 non-obese and 128 obese, were included. The most common gram-negative bacterial species identified was Escherichia coli (64.2%). There was a higher proportion of gram-negative MDR bacteria in obese versus non-obese patients (18.8 versus 11.3%, P=0.057). Obesity was independently associated with gram-negative MDR bacteria after controlling for confounders (adjusted odds ratio, 1.92; 95% CI 1.03–3.60). The association did not significantly vary by diabetes status (interaction term P=0.792).

Conclusion

Among older adult hospitalized patients, obesity was independently associated with the presence of a gram-negative MDR bacteria (presumptive ESBL or CRE) in a culture.

Efficacy and Safety of Eravacycline in Obese Patients: A Post Hoc Analysis of Pooled Data From the IGNITE1 and IGNITE4 Clinical Trials

Background

The increasing prevalence of obesity worldwide merits an examination of the efficacy and safety profiles of agents dosed by weight.

Methods

Data for patients (n = 1037) were obtained from the pooled IGNITE1 and IGNITE4 randomized double-blind trials in which patients with complicated intra-abdominal infections received eravacycline 1 mg/kg (actual body weight [ABW]) every 12 hours or comparator (ertapenem 1 g every 24 hours or meropenem 1 g every 8 hours) intravenously. This post hoc analysis evaluated clinical cure rates, adverse events, and drug discontinuation rates stratified by body mass index (BMI) categories of BMI >40 kg/m² (Obese, Class III), BMI 35–39.9 kg/m² (Obese, Class II), BMI 30–34.9 kg/m² (Obese, Class I), BMI 25–29.9 kg/m² (Overweight), BMI 18.5–24.9 kg/m² (Healthy weight), and BMI <18.5 kg/m² (Underweight).

Results

Clinical cure rates were high across BMI categories and ranged from 82% to 94% in the eravacycline group and 88.5%–100% in the comparator group. Similar cure rates were observed among eravacycline-treated healthy weight (126/134; 94%), overweight (127/146; 87%), and obese (BMI ≥30 kg/m²; 110/129; 85.3%) patients. In the comparator group, a similar proportion of patients demonstrated clinical response (healthy weight [132/145; 91%], overweight [130/144; 90.3%], and obese [115/129; 89.1%]). Of the treatment-emergent adverse events that occurred in eravacycline-treated obese patients, a larger proportion were gastrointestinal-related (ie, nausea and vomiting); however, discontinuation rates were low and similar between eravacycline and carbapenems.

Conclusions

This post hoc analysis demonstrates the therapeutic utility and acceptable safety profile of eravacycline dosed by ABW in obese patients (BMI ≥30 kg/m²).

Evaluation of a modified vancomycin nomogram for obese adults

PURPOSE

The purpose of this study was to compare therapeutic vancomycin trough levels in obese adults when using an original nomogram (phase I) versus a modified nomogram (phase II).

METHODS

This study compared a vancomycin nomogram with a modified vancomycin nomogram for obese adults over 100 kg. The primary endpoint compared the percentage of sub-therapeutic, therapeutic, and supra-therapeutic vancomycin trough concentrations between the nomograms. Patients were included if they were at least 18 years of age, had a total body weight of 100-299 kg, and had an initial vancomycin trough level collected. Patients were excluded if they had end-stage renal disease or were on continuous renal replacement therapy.

RESULTS

Therapeutic trough levels occurred in 85 out of 171 patients (50%) in phase I and 98 out of 149 patients (66%) in phase II. The incidence of both sub-therapeutic and supra-therapeutic troughs was less in phase II (p = 0.013). In the subgroup of adults aged 18 to 49 with a normalized creatinine clearance of greater than 90 mL/min, there was a trend in more therapeutic levels with the modified nomogram and less chance of sub-therapeutic levels (p = 0.088). In the subgroup of adults with a normalized creatinine clearance of 60-90 mL/min, there was significant improvement in therapeutic levels and a decrease in supra-therapeutic levels without increasing the percent of sub-therapeutic levels (p = 0.001).

CONCLUSION

The modified vancomycin nomogram at Cone Health showed significant improvement in therapeutic trough concentrations while reducing the rates of under and over dosing obese adults. The Cone Health-modified vancomycin nomogram could be a useful tool for initial dosing of vancomycin in the obese population.

Tubo-Ovarian Abscesses: Epidemiology and Predictors for Failed Response to Medical Management in an Asian Population

Pelvic inflammatory disease (PID) complicated by tubo-ovarian abscesses (TOA) has long-term sequelae in women of reproductive age. Consensus on the optimal treatment of TOA remains lacking. Most clinicians utilize antibiotics as a first-line conservative approach, failing which invasive intervention is adopted. Our aim is to identify risk factors predicting failed response to conservative medical management for TOA in an Asian population. A retrospective cohort study of 136 patients admitted to a tertiary hospital in Singapore for TOA between July 2013 and December 2017 was performed. Patients were classified into 2 groups: successful medical treatment with intravenous antibiotics and failed medical treatment requiring invasive intervention. 111 (81.6%) of patients were successfully treated with conservative medical approach using intravenous antibiotics; 25 (18.4%) required invasive intervention having failed medical therapy. Multivariate logistic regression model adjusted for age, ethnicity, C-reactive Protein (CRP), TOA size, and body mass index (BMI) showed the odds ratio (OR) of each centimetre increase in TOA size to be 1.28 (95% confidence interval (CI) 1.03-1.61; P=0.030) and every kg/m2 increase in BMI to be 1.10 (95% CI 1.00-1.21; P=0.040). Failed medical management was predicted by a cutoff of TOA size ≥ 7.4 cm and ≥ BMI 24.9 kg/m2. Patients who failed medical treatment received a mean of 4.0±2.1 days of antibiotics before a decision for invasive intervention was made, with a significantly longer intravenous antibiotic duration (9.4±4.3 versus 3.6±2.2 days; P <0.001) and prolonged hospitalization (10.8± 3.6 versus 4.5 ± 2.0 days; P <0.001) compared to the medical group. Patients with higher BMI and larger TOA size were associated with failed response to conservative medical management in our study population. Early identification of these patients for failed medical therapy is imperative for timely invasive intervention to avoid prolonged hospitalization, antibiotic usage, and patient morbidity.

Antimicrobials: a global alliance for optimizing their rational use in intra-abdominal infections (AGORA)

Intra-abdominal infections (IAI) are an important cause of morbidity and are frequently associated with poor prognosis, particularly in high-risk patients. The cornerstones in the management of complicated IAIs are timely effective source control with appropriate antimicrobial therapy. Empiric antimicrobial therapy is important in the management of intra-abdominal infections and must be broad enough to cover all likely organisms because inappropriate initial antimicrobial therapy is associated with poor patient outcomes and the development of bacterial resistance. The overuse of antimicrobials is widely accepted as a major driver of some emerging infections (such as C. difficile), the selection of resistant pathogens in individual patients, and for the continued development of antimicrobial resistance globally. The growing emergence of multi-drug resistant organisms and the limited development of new agents available to counteract them have caused an impending crisis with alarming implications, especially with regards to Gram-negative bacteria. An international task force from 79 different countries has joined this project by sharing a document on the rational use of antimicrobials for patients with IAIs. The project has been termed AGORA (Antimicrobials: A Global Alliance for Optimizing their Rational Use in Intra-Abdominal Infections). The authors hope that AGORA, involving many of the world's leading experts, can actively raise awareness in health workers and can improve prescribing behavior in treating IAIs.

Obesity: impact of infections and response to vaccines

Obesity is a common condition that has rapidly increased in both the industrialised and developing world in recent decades. Obese individuals show increased risk factors for severe infections and significant immune system dysregulation that may impair the immune response to vaccines. The main aim of this paper was to review the current knowledge regarding the association between obesity and the risk and outcome of infections as well as immune response to vaccines. The results showed that obesity is a highly complex clinical condition in which the functions of several organ and body systems, including the immune system, are modified. However, only a small minority of the biological mechanisms that lead to reduced host defences have been elucidated. Relevant efforts for future research should focus on obese children, as the available data on this population are scarce compared with the adult population. Even if most vaccines are given in the first months of life when obesity is rare, some vaccines require booster doses at preschool age, and other vaccines, such as the influenza vaccine, are recommended yearly in the obese population, but it is not known whether response to vaccines of obese patients is impaired. The reduced immune response of obese patients to vaccination can be deleterious not only for the patient but also for the community.