Cefepime pharmacokinetics in adult extracorporeal membrane oxygenation patients

BACKGROUND

The impact of extracorporeal membrane oxygenation (ECMO) on the pharmacokinetics/dynamics (PK/PD) of beta-lactam antibiotics have not been well studied in general, but cefepime specifically has the least amount of data. We aimed to investigate whether ECMO alters the PK of cefepime in adult intensive care unit (ICU) patients.

METHODS

This single-center, retrospective case-control study evaluated cefepime therapeutic drug monitoring (TDM) results from ECMO patients that were matched 1:1 with TDM results in non-ECMO patients for drug regimen and renal function. The primary outcome was the difference in PK/PD of cefepime in ECMO compared with non-ECMO ICU patients. Secondary outcomes included hospital length of stay, treatment failure, superinfection, bacterial resistance, and survival to discharge.

RESULTS

Eighty-two patients were included with 44 matched cefepime concentrations in each group. ECMO patients had higher free maximum concentrations (fCmax) (p = 0.003), lower free minimum concentration (fCmin)/1x minimum inhibitory concentration (MIC) ratios (p = 0.040), and lower attainment of free Cmin/4x MIC (p = 0.010). There were no differences between the groups for free Cmin, time above 1xMIC or 4x MIC, and pharmacokinetic parameters (ke, half-life, and Vd). Of those who survived to discharge, hospital length of stay was longer in the ECMO group (p < 0.001). Patients on ECMO were more likely to experience treatment failure (p = 0.036). The incidence of bacterial resistance, superinfection, or survival were similar among the groups.

CONCLUSION

These data suggest that more aggressive empiric dosing may be warranted in patients on ECMO. Therapeutic drug monitoring and future prospective studies would provide more evidence to guide decision making regarding dose adjustments.

A Randomized Clinical Trial of Bayesian-Guided Beta-Lactam Infusion Strategy and Associated Bacterial Resistance and Clinical Outcomes in Patients With Severe Pneumonia

BACKGROUND

Antimicrobial resistance is a growing health concern worldwide. The objective of this study was to evaluate the effect of beta-lactam infusion on the emergence of bacterial resistance in patients with severe pneumonia in the intensive care unit.

METHODS

Adult intensive care patients receiving cefepime, meropenem, or piperacillin-tazobactam for severe pneumonia caused by Gram-negative bacteria were randomized to receive beta-lactams as an intermittent (30 minutes) or continuous (24 hours) infusion. Respiratory samples for culture and susceptibility testing, with minimum inhibitory concentrations (MIC), were collected once a week for up to 4 weeks. Beta-lactam plasma concentrations were measured and therapeutic drug monitoring was performed using Bayesian software as the standard of care.

RESULTS

The study was terminated early owing to slow enrollment. Thirty-five patients were enrolled in this study. Cefepime (n = 22) was the most commonly prescribed drug at randomization, followed by piperacillin (n = 8) and meropenem (n = 5). Nineteen patients were randomized into the continuous infusion arm and 16 into the intermittent infusion arm. Pseudomonas aeruginosa was the most common respiratory isolate (n = 19). Eighteen patients were included in the final analyses. No differences in bacterial resistance were observed between arms ( P = 0.67). No significant differences in superinfection ( P = 1), microbiological cure ( P = 0.85), clinical cure at day 7 ( P = 0.1), clinical cure at end of therapy ( P = 0.56), mortality ( P = 1), intensive care unit length of stay ( P = 0.37), or hospital length of stay ( P = 0.83) were observed. Achieving 100% ƒT > MIC ( P = 0.04) and ƒT > 4 × MIC ( P = 0.02) increased likelihood of clinical cure at day 7 of therapy.

CONCLUSIONS

No differences in the emergence of bacterial resistance or clinical outcomes were observed between intermittent and continuous infusions. Pharmacokinetic/pharmacodynamic target attainment may be associated with a clinical cure on day 7.

Impact of Beta-Lactam Target Attainment on Resistance Development in Patients with Gram-Negative Infections

BACKGROUND

The objective was to identify associations between beta-lactam pharmacokinetic/pharmacodynamic (PK/PD) targets and Gram-negative bacteria resistance emergence in patients.

METHODS

Retrospective data were collected between 2016 to 2019 at the University of Florida Health-Shands Hospital in Gainesville, FL. Adult patients with two Gram-negative isolates receiving cefepime, meropenem, or piperacillin-tazobactam and who had plasma beta-lactam concentrations were included. Beta-lactam exposures and time free drug concentrations that exceeded minimum inhibitory concentrations (ƒT > MIC), four multiples of MIC (ƒT > 4× MIC), and free area under the time concentration curve to MIC (ƒAUC/MIC) were generated. Resistance emergence was defined as any increase in MIC or two-fold increase in MIC. Multiple regression analysis assessed the PK/PD parameter impact on resistance emergence.

RESULTS

Two hundred fifty-six patients with 628 isolates were included. The median age was 58 years, and 59% were males. Cefepime was the most common beta-lactam (65%) and Pseudomonas aeruginosa the most common isolate (43%). The mean daily ƒAUC/MIC ≥ 494 was associated with any increase in MIC (p = 0.002) and two-fold increase in MIC (p = 0.004). The daily ƒAUC/MIC ≥ 494 was associated with decreased time on antibiotics (p = 0.008). P. aeruginosa was associated with any increase in MIC (OR: 6.41, 95% CI [3.34-12.28]) or 2× increase in MIC (7.08, 95% CI [3.56-14.07]).

CONCLUSIONS

ƒAUC/MIC ≥ 494 may be associated with decreased Gram-negative resistance emergence.

Effect of HIV infection on plasma exposure to first-line TB drugs and target attainment in children

BACKGROUND: Whether HIV infection adversely affects exposure to first-line TB drugs in children is debatable. It is also not known whether HIV infection increases the risk of plasma underexposure or overexposure to TB drugs. This study sought to address these questions.DESIGN/METHODS: Children on TB treatment were enrolled. After 4 weeks on therapy, blood samples were collected at pre-dose, 1, 2, 4, 8, and 12 h post-dose for pharmacokinetic analysis. Plasma drug exposure below and above the lower and upper bounds of the 95% confidence intervals of the reference mean for children were considered underexposure and overexposure, respectively. The effect of HIV infection on drugs exposure and risk of underexposure were examined using multivariate analysis.RESULTS: Of 86 participants (median age: 4.9 years), 45 had HIV coinfection. HIV coinfection was associated with lower pyrazinamide (PZA) and ethambutol exposures in adjusted analysis. Patients with TB-HIV coinfection were three times more likely to have PZA underexposure than those with TB only. Underexposure of rifampin was common irrespective of HIV coinfection status.CONCLUSIONS: HIV coinfection was associated with a higher risk for PZA underexposure in children. This effect should be accounted for in models and simulations to determine optimal PZA dose for children.

Utilization of cefepime therapeutic drug monitoring in febrile neutropenia patients with hematologic malignancies

INTRODUCTION

Cefepime is a fourth-generation cephalosporin and is a workhorse for the empiric treatment of febrile neutropenia (FN). Beta-lactam therapeutic drug monitoring (TDM) has emerged as a dose optimization strategy in patient populations with altered kinetics. Prior literature has demonstrated that patients with FN exhibit augmented renal clearance which may lead to subtherapeutic drug concentrations with standard dosing regimens. The aim of this study was to evaluate pharmacokinetic/pharmacodynamic (PK/PD) target attainment and clinical outcomes in patients with hematologic malignancies and FN who were treated empirically with cefepime.

METHODS

This was a prospective, single-center study of adults with hematologic malignancies and FN admitted to the inpatient unit. The primary outcome was PK/PD target attainment (defined as 100% free time greater than minimum inhibitory concentration (100% fT > MIC)). Secondary clinical outcomes were time to defervescence, time to ANC recovery, in-hospital mortality, and cefepime failure.

RESULTS

There were 55 patients in our study. Forty-three (78%) patients achieved the primary outcome of PK/PD target attainment. The mean time to defervescence was similar between those that achieved PK/PD target attainment and those that did not (95% CI -0.75 to 1.25, p = 0.62).

CONCLUSIONS

This study showed that standard cefepime dosing in patients with hematologic malignancies and FN does not result in achievement of 100% fT > MIC in all patients. Patients in the group that did not achieve PK/PD target attainment were younger with increased creatinine clearance, indicating that cefepime TDM may be especially beneficial in these patients.

Cefepime Daily Exposure and the Associated Impact on the Change in Sequential Organ Failure Assessment Scores and Vasopressors Requirement in Critically Ill Patients Using Repeated-Measures Mixed-Effect Modeling

IMPORTANCE

Sepsis and septic shock are major healthcare problems that need early and appropriate management.

OBJECTIVES

To evaluate the association of daily cefepime pharmacokinetic/pharmacodynamic (PK/PD) parameters with change in Sequential Organ Failure Assessment (SOFA) score and vasopressors requirement.

DESIGN SETTING AND PARTICIPANTS

This is a retrospective study. Adult ICU patients who received cefepime for Gram-negative pneumonia or bloodstream infection (BSI) and had cefepime concentrations measured were included. Daily cefepime exposure was generated and PK/PD parameters calculated for patients. Repeated-measures mixed-effect modeling was used to evaluate the impact of PK/PD on the outcomes.

MAIN OUTCOMES AND MEASURES

Change in daily SOFA score and vasopressors requirement.

RESULTS

A total of 394 and 207 patients were included in the SOFA and vasopressors analyses, respectively. The mean (±sd) age was 55 years (19) and weight 81 kg (29). For the change in SOFA score, daily SOFA score, mechanical ventilation, renal replacement therapy, and number of vasopressors were included. In the vasopressors analysis, daily SOFA score, day of therapy, and hydrocortisone dose were significant covariates in the final model. Achieving cefepime concentrations above the minimum inhibitory concentration (MIC) (T>MIC) for 100% of the dosing interval was associated with 0.006 µg/kg/min decrease in norepinephrine-equivalent dose. Cefepime PK/PD did not have an impact on the daily change in SOFA score.

CONCLUSIONS AND RELEVANCE

Achieving 100% T>MIC was associated with negligible decrease in vasopressors requirement in ICU patients with Gram-negative pneumonia and BSI. There was no impact on the change in SOFA score.

The effect of anti-tuberculosis drug pharmacokinetics on QTc prolongation

BACKGROUND

Implementation of newer anti-tuberculosis (TB) drugs may prolong the QT interval, increasing the risk of arrythmias and sudden cardiac death. The potential for cardiac adverse events has prompted recommendations for frequent cardiac monitoring during treatment. However, unknowns remain, including the association between drug concentrations and QT interval.

METHODS

An observational prospective cohort study design was used. Patients undergoing treatment for drug-resistant TB in Georgia were assessed. Serial blood samples were collected at 4-6 weeks for pharmacokinetics. Electrocardiograms were recommended to be performed monthly. A generalized estimating equation spline model was used to investigate (1) the effect difference between bedaquiline and delamanid, (2) the cumulative effect of number of anti-TB drugs, and (3) the relationship between serum drug concentrations on QTc interval.

RESULTS

Among 94 patients receiving either bedaquiline (n = 64) or delamanid (n = 30)-based treatment, most were male (82%), and the mean age was 39 years. The mean maximum QTc increase during the first six months was 37.5 ms (IQR: 17.8-56.8). Bedaquiline- and delamanid-based regimens displayed similar increased mean QTc change from baseline during drug administration (P = 0.12). Increasing number of anti-TB drugs was associated with an increased QTc (P = 0.01), but participants trended back towards baseline after drug discontinuation (P = 0.25). A significant association between AUC, Cmin, Cmax, and increased QTc interval was found for bedaquiline (months 1-6) and levofloxacin (months 1-12).

CONCLUSION

Bedaquiline- and delamanid-based regimens and increasing number of QT prolonging agents led to modest increases in the QTc interval with minimal clinical effect.

Making the case for precision dosing: visualizing the variability of cefepime exposures in critically ill adults

OBJECTIVE

To investigate and describe the variability in cefepime exposures among 'real-world', critically ill patients by using population pharmacokinetic modelling and simulations, and with translation of these findings to visualizations.

METHODS

A cohort of adult medical ICU patients who received cefepime with therapeutic drug monitoring was studied. Two compartment models were developed to estimate cefepime clearance (Model 1) and simulate cefepime exposures among 1000 patients, each with identical creatinine clearance of 60 mL/min and receiving a regimen of cefepime 1 gram IV over 30 minutes, every 8 hours (Model 2). Variability in the relationship between cefepime clearance and creatinine clearance (CrCL) was visualized, and a random, representative sample of 10 simulated patients was utilized to illustrate variability in cefepime exposures.

RESULTS

A total of 75 adult medical ICU patients (52% female) and 98 serum cefepime samples were included in the study. Population parameter estimates for cefepime displayed a wide range of variation in Model 1 (CV: 45% to 95%), with low bias at the individual level at 0.226 mg/L but high bias in the population model 10.6 mg/L. Model 2 displayed similar fits, demonstrating that correcting for individual patient creatinine clearance slightly improves the bias of the population model (bias = 4.31 mg/L). Among 10 simulated patients that a clinician would deem similar from a dosing perspective (i.e. equivalent creatinine clearance), maximum concentrations after three simulated doses varied more than 8-fold from 41.2 to 339 mg/L at the 5th and 95th percentiles, and clearance profiles were highly different.

CONCLUSION

Creatinine clearance estimates alone are inadequate for predicting cefepime exposures. Wide variations in cefepime exposure exist among ICU patients, even for those with similar kidney function estimates. Current population adjustment schemes based solely on creatinine clearance will result in unintended high and low exposures leading to safety and efficacy concerns, respectively.

International consensus recommendations for the use of prolonged-infusion beta-lactam antibiotics: Endorsed by the American College of Clinical Pharmacy, British Society for Antimicrobial Chemotherapy, Cystic Fibrosis Foundation, European Society of Clinical Microbiology and Infectious Diseases, Infectious Diseases Society of America, Society of Critical Care Medicine, and Society of Infectious Diseases Pharmacists

Intravenous β-lactam antibiotics remain a cornerstone in the management of bacterial infections due to their broad spectrum of activity and excellent tolerability. β-lactams are well established to display time-dependent bactericidal activity, where reductions in bacterial burden are directly associated with the time that free drug concentrations remain above the minimum inhibitory concentration (MIC) of the pathogen during the dosing interval. In an effort to take advantage of these bactericidal characteristics, prolonged (extended and continuous) infusions (PIs) can be applied during the administration of intravenous β-lactams to increase time above the MIC. PI dosing regimens have been implemented worldwide, but implementation is inconsistent. We report consensus therapeutic recommendations for the use of PI β-lactams developed by an expert international panel with representation from clinical pharmacy and medicine. This consensus guideline provides recommendations regarding pharmacokinetic and pharmacodynamic targets, therapeutic drug-monitoring considerations, and the use of PI β-lactam therapy in the following patient populations: severely ill and nonseverely ill adult patients, pediatric patients, and obese patients. These recommendations provide the first consensus guidance for the use of β-lactam therapy administered as PIs and have been reviewed and endorsed by the American College of Clinical Pharmacy (ACCP), the British Society for Antimicrobial Chemotherapy (BSAC), the Cystic Fibrosis Foundation (CFF), the European Society of Clinical Microbiology and Infectious Diseases (ESCMID), the Infectious Diseases Society of America (IDSA), the Society of Critical Care Medicine (SCCM), and the Society of Infectious Diseases Pharmacists (SIDP).

International consensus recommendations for the use of prolonged-infusion beta-lactam antibiotics: Endorsed by the American College of Clinical Pharmacy, British Society for Antimicrobial Chemotherapy, Cystic Fibrosis Foundation, European Society of Clinical Microbiology and Infectious Diseases, Infectious Diseases Society of America, Society of Critical Care Medicine, and Society of Infectious Diseases Pharmacists: An executive summary

Intravenous β-lactam antibiotics remain a cornerstone in the management of bacterial infections due to their broad spectrum of activity and excellent tolerability. β-lactams are well established to display time-dependent bactericidal activity, where reductions in bacterial burden are directly associated with the time that free drug concentrations remain above the minimum inhibitory concentration (MIC) of the pathogen during the dosing interval. In an effort to take advantage of these bactericidal characteristics, prolonged (extended and continuous) infusions (PI) can be applied during the administration of intravenous β-lactams to increase time above the MIC. PI dosing regimens have been implemented worldwide, but implementation is inconsistent. We report consensus therapeutic recommendations for the use of β-lactam PI developed by an expert international panel with representation from clinical pharmacy and medicine. This consensus guideline provides recommendations regarding pharmacokinetic and pharmacodynamic targets, therapeutic drug monitoring considerations, and the use of PI β-lactam therapy in the following patient populations: severely ill and nonseverely ill adult patients, pediatric patients, and obese patients. These recommendations provide the first consensus guidance for the use of β-lactam therapy administered as PIs and have been reviewed and endorsed by the American College of Clinical Pharmacy (ACCP), the British Society for Antimicrobial Chemotherapy (BSAC), the Cystic Fibrosis Foundation (CFF), the European Society of Clinical Microbiology and Infectious Diseases (ESCMID), the Infectious Diseases Society of America (IDSA), the Society of Critical Care Medicine (SCCM), and the Society of Infectious Diseases Pharmacists (SIDP).

Adequacy of WHO weight-band dosing and fixed-dose combinations for the treatment of TB in children

BACKGROUND: We examined whether the updated WHO weight-band dosing recommendations and fixed-dose combination tablets for the treatment of TB in children achieves recommended calculated dosages and adequate drug plasma exposure.DESIGN/METHODS: Children on first-line TB treatment per WHO guidelines were enrolled. Blood sampling at pre-dose, 1, 2, 4, 8, and 12 h post-dose after at least 4 weeks of treatment was performed. Drugs concentrations were measured using validated liquid chromatography tandem with mass spectrometry and pharmacokinetic parameters calculated using noncompartmental analysis. Plasma drug exposure below the lower limit of the 95% confidence interval of the mean for children was considered low and above the upper limit was high.RESULTS: Of 71 participants, 34 (47.9%) had HIV coinfection. The median calculated dose for isoniazid (INH), rifampin (RIF), pyrazinamide (PZA), and ethambutol (EMB) was 10.0 (range 4.3-13.3), 15.0 (range 8.6-20.0), 30.0 (range 21.0-40.0), and 20.4 (range 14.3-26.7) mg/kg, respectively. Overall, most patients had under-exposure for RIF and PZA and over-exposure for INH and EMB. Drug dose and weight-for-age Z-score were associated with area under the curve from time 0-24 h for all drugs.CONCLUSIONS: Despite adherence to WHO dosing guidelines, low PZA and RIF plasma exposures were frequent in our study population. Higher than currently recommended dosages of RIF and PZA may be needed in children.

Therapeutic drug monitoring in cystic fibrosis and associations with pulmonary exacerbations and lung function

BACKGROUND

Cystic fibrosis transmembrane conductance regulator (CFTR) modulator therapy have resulted in longer life expectancies, yet pulmonary exacerbations remain a leading cause of morbidity. Intravenous antibiotics is the mainstay treatment, however achieving adequate concentrations remains challenging. The effect of therapeutic drug monitoring (TDM) of beta-lactams on exacerbations and lung function has not been studied.

METHODS

Patient demographics, antibiotic regimens, forced expiratory volume 1 second (FEV1), and exacerbation history was obtained from 32 patients with cystic fibrosis admitted for exacerbations. All patients were colonized with Pseudomonas aeruginosa, received CFTR therapy for at least one year, and had 3-month interval follow ups. Plasma concentrations, FEV1, and exacerbation history was obtained before and after therapeutic drug monitoring. This included peak and trough plasma concentrations of piperacillin-tazobactam and cefepime using liquid chromatography with mass spectrometry. T-test and Mann-Whitney U test were used to compare medians/means of FEV1 and pulmonary exacerbations pre and post-TDM as well as free trough-to-minimum inhibitory concentration ratio (fC_min/MIC) ≥1 and ≥ 4.

RESULTS

TDM was associated with decreased exacerbations/year from 1.91 to 1.31 (p = 0.04) and among the cohort with >/ = 2 exacerbations per year, there was a longer exacerbation free interval after TDM (196.2 vs 103.7 days, p = 0.02). The decline in FEV1% predicted after therapeutic drug monitoring to the first exacerbation was -4.9 compared to -9.7 prior (p = 0.03).

CONCLUSIONS

TDM for cystic fibrosis pulmonary exacerbations results in decreased pulmonary exacerbations, longer intervals to pulmonary exacerbation, and lower decline in FEV1% predicted.

Why is the Implementation of Beta-Lactam Therapeutic Drug Monitoring for the Critically Ill Falling Short? A Multicenter Mixed-Methods Study

BACKGROUND

Beta-lactam therapeutic drug monitoring (BL TDM; drug level testing) can facilitate improved outcomes in critically ill patients. However, only 10%-20% of hospitals have implemented BL TDM. This study aimed to characterize provider perceptions and key considerations for successfully implementing BL TDM.

METHODS

This was a sequential mixed-methods study from 2020 to 2021 of diverse stakeholders at 3 academic medical centers with varying degrees of BL TDM implementation (not implemented, partially implemented, and fully implemented). Stakeholders were surveyed, and a proportion of participants completed semistructured interviews. Themes were identified, and findings were contextualized with implementation science frameworks.

RESULTS

Most of the 138 survey respondents perceived that BL TDM was relevant to their practice and improved medication effectiveness and safety. Integrated with interview data from 30 individuals, 2 implementation themes were identified: individual internalization and organizational features. Individuals needed to internalize, make sense of, and agree to BL TDM implementation, which was positively influenced by repeated exposure to evidence and expertise. The process of internalization appeared more complex with BL TDM than with other antibiotics (ie, vancomycin). Organizational considerations relevant to BL TDM implementation (eg, infrastructure, personnel) were similar to those identified in other TDM settings.

CONCLUSIONS

Broad enthusiasm for BL TDM among participants was found. Prior literature suggested that assay availability was the primary barrier to implementation; however, the data revealed many more individual and organizational attributes, which impacted the BL TDM implementation. Internalization should particularly be focused on to improve the adoption of this evidence-based practice.

Use of therapeutic drug monitoring to characterize cefepime-related neurotoxicity

STUDY OBJECTIVES

Data evaluating cefepime thresholds associated with neurotoxicity remain limited. The objectives of this study were to evaluate the incidence of cefepime-related neurotoxicity (CRN) in patients with plasma cefepime concentrations, assess the relationship between cefepime exposure and CRN, investigate clinical factors associated with CRN, and describe electroencephalogram (EEG) abnormalities in CRN.

DESIGN

This was a retrospective study of adult inpatients admitted between 2016 and 2018 who received cefepime therapeutic drug monitoring (TDM). Potential CRN cases were identified utilizing a standard definition. The primary outcomes of the study were to determine the incidence of CRN and evaluate the relationship between cefepime trough concentrations, the average daily AUC, and neurotoxicity. Bayesian posteriors were generated for each patient using a cefepime pharmacokinetic (PK) model, and the mean daily area under the concentration-time curve (AUC) was calculated. Multiple regression was performed to assess the association between CRN, cefepime PK, and clinical predictors of neurotoxicity.

MAIN RESULTS

Four hundred eighty-one patients with 503 hospital encounters received cefepime TDM and were included in the analysis. The incidence of CRN was 4.4% (22/503). Patients with CRN had a higher incidence of renal dysfunction, hypertension, and diabetes mellitus compared to patients without CRN (non-NT). The mean cefepime trough concentration was significantly greater in the CRN patients than in the non-NT group (61.8 ± 33.7 vs. 30 ± 27.7 mg/L, respectively, p = 0.0002). Cefepime trough concentration and renal dysfunction were independently associated with increased risk of CRN in the adjusted multiple regression model. Moderate generalized slowing of the background rhythm was the most common EEG pattern associated with CRN. Delaying cefepime TDM greater than 72 h after the initiation of cefepime was associated with a 3-fold increased risk of CRN.

CONCLUSION

Cefepime should be used cautiously in hospitalized patients with renal dysfunction due to the risk of neurotoxicity. Dose optimization utilizing TDM early in cefepime treatment may minimize adverse effects and improve patient safety.

743. Implementation of Beta-Lactam Therapeutic Drug Monitoring Programs in the Critically Ill: A Multicenter Mixed-Methods Study

Background

Beta-lactam therapeutic drug monitoring (BL TDM; drug level testing) can facilitate improved outcomes in critically ill patients. Yet less than 20% of hospitals have implemented BL TDM. The purpose of this study was to characterize provider perceptions and key considerations for successful implementation of BL TDM.

Methods

This was a sequential mixed methods study from 2020 to 2021 of stakeholders at three academic medical centers with varying degrees of BL TDM implementation - Mayo Clinic (BL TDM not implemented), University of Florida Health Shands (partially implemented), and Royal Brisbane and Women’s Hospital (fully implemented). Stakeholders completed a survey to characterize their knowledge, perceptions, and experience with BL TDM. A diverse group of 30 respondents were then purposively sampled for semi-structured interviews. Results from the two strands were integrated, themes were identified, and findings were situated within implementation science frameworks.

Results

Among the 138 survey respondents (22% response rate), the majority were physicians (38%) and pharmacists (33%). 71% practiced in critical care and 21% in infectious diseases. The majority of respondents felt BL TDM was relevant to their practice and improved medication effectiveness and safety (Figure 1). Two implementation themes were identified: individual internalization and organizational features. Individuals needed to internalize, make sense of, and agree to BL TDM implementation which was positively influenced by repeated exposure to evidence and expertise. The process of internalization seemed more complex with BL TDM than with other antibiotics (i.e., vancomycin). Organizational considerations relevant to BL TDM implementation included adequate physical and informational infrastructure, access to trained personnel, supportive governance/leadership, and robust process and workflow development.

Conclusion

We found broad enthusiasm about the relevance and potential benefits of BL TDM among stakeholders. Prior literature suggested the primary barrier to implementation was assay availability, but we identified many more individual and organizational attributes which impacted the scale and spread of BL TDM.

Disclosures

Sara Ausman, PharmD, Gilead: Honoraria Christina G. Rivera, PharmD, Gilead: Grant/Research Support|Gilead: Honoraria|Insmed: Honoraria Jason Roberts, BPharm(Hons), PhD, FSHP, FISAC, British Society of Chemotherapy: Grant/Research Support|Cipla: Honoraria|Gilead: Advisor/Consultant|MSD: Advisor/Consultant|MSD: Honoraria|Pfizer: Board Member|Pfizer: Honoraria|Qpex: Grant/Research Support|Sandoz: Board Member|Summit: Advisor/Consultant|Wolters Kluwer: Advisor/Consultant Marc H. Scheetz, PharmD, MSc, Abbvie: Advisor/Consultant|Allecra: Grant/Research Support|Merck: Advisor/Consultant|Nevakar: Advisor/Consultant|Nevakar: Grant/Research Support|Premier Healthcare Solutions: Honoraria|Spero: Advisor/Consultant|SuperTrans Medical: Advisor/Consultant|SuperTrans Medical: Grant/Research Support|Takeda: Advisor/Consultant|Third Pole Therapeutics: Advisor/Consultant.

604. Effect of rifabutin in dolutegravir dosing: a case series

Background

Tuberculosis (TB) is the leading cause of death in human immunodeficiency virus (HIV) infected people worldwide. Patients with HIV who have latent TB are 20-30 times more likely to develop active TB. Integrated antiretroviral therapy (ART) early in the treatment for tuberculosis is recommended due to improved morbidity and mortality, however, there can be serious drug interactions.

Rifamycins are potent inducers of the CYP3A4 isoform, which can cause sub-therapeutic concentrations of anti-retroviral drugs, among these, rifabutin (RBN) is a less potent inducer of CYP3A4. Pharmacokinetic (PK) studies done on healthy adults showed that rifampin decreased dolutegravir (DTG) concentrations by more than 50 % whereas RBN decreased it by 30%. RBN has been preferred given that its favorable pharmacokinetic and toxicity profile. Currently there are no studies examining the use of RBN and DTG in co-infected persons. This is a case series of 4 co-infected patients receiving both agents who underwent PK analysis.

Methods

Retrospective analysis of patients in the respiratory care unit (RCU) at Jackson Memorial Hospital in Miami. We included adult patients, admitted to the RCU, with a concomitant diagnosis of HIV and active TB disease who received DTG and RBN, and for which DTG and RBN plasma concentrations were measured for therapeutic drug monitoring (TDM). A non-compartmental analysis was performed and the area under the concentration-time curve (AUC) was calculated for DTG and RBN.

Results

We report 4 patients (Figure 1) that met criteria and underwent PK analysis. All patients with TB who were treated with RBN had low concentrations of DTG, requiring higher doses of DTG (Table 1 & 2). After adjustments based on PK analysis, there was evidence of a favorable response to treatment in 2 patients, with a less than robust in the 2 others. Adequate suppression of viral load could not be determined for 3 of the patients because of the short observation time. Figure 1:Timelines of patients describing admission and HIV and tuberculosis treatment providedDTG, dolutegravir. RFB, rifabutin. VL, viral load. AFB, Acid fast bacilli. LAD, lymphadenopathy. TAF, Tenofovir alafenamide. FTC, Emtricitabine. TDF, Tenofovir Disoproxil Fumarate. INH, Isoniazid. PYZ, Pyrazinamide. BID, twice a day. QD, daily. IRIS, Immune reconstitution inflammatory syndrome. GU, genitourinary. TB, tuberculosis.Table 1:Patients’ pharmacokinetics of DTGAUCX-Y, area under the concentration-time curve from time X to Y hours; AUC0-tau, area under the concentration-time curve from time zero to the end of the dosing interval; DTG, dolutegravir; TDM, therapeutic drug monitoring. a) AUC0-6 was calculated.Table 2:Patients’ pharmacokinetics of RBNAUCX-Y, area under the concentration-time curve from time X to Y hours; AUC0-tau, area under the concentration-time curve from time zero to the end of the dosing interval; RBN, Rifabutin; TDM, therapeutic drug monitoring. a) All RBN doses given every 24 hours, b) RBN value was trace and AUC was not calculated.

Conclusion

All patients with HIV and TB who were treated with RBN had low concentrations of DTG. This case series demonstrates that for optimal concomitant use of rifabutin and dolutegravir it is highly recommended to use TDM. Prospective clinical studies are needed to further determine the PK interactions between RBN and DTG and virologic response to treatment.

Disclosures

All Authors: No reported disclosures.

Cerebrospinal fluid concentrations of fluoroquinolones and carbapenems in tuberculosis meningitis

Background: Tuberculosis meningitis (TBM) is the most lethal form of TB. It is difficult to treat in part due to poor or uncertain drug penetration into the central nervous system (CNS). To help fill this knowledge gap, we evaluated the cerebrospinal fluid (CSF) concentrations of fluoroquinolones and carbapenems in patients being treated for TBM. Methods: Serial serum and CSF samples were collected from hospitalized patients being treated for TBM. CSF was collected from routine lumbar punctures between alternating timepoints of 2 and 6 h after drug administration to capture early and late CSF penetration. Rich serum sampling was collected after drug administration on day 28 for non-compartmental analysis. Results: Among 22 patients treated for TBM (8 with confirmed disease), there was high use of fluoroquinolones (levofloxacin, 21; moxifloxacin, 10; ofloxacin, 6) and carbapenems (imipenem, 11; meropenem, 6). Median CSF total concentrations of levofloxacin at 2 and 6 h were 1.34 mg/L and 3.36 mg/L with adjusted CSF/serum ratios of 0.41 and 0.63, respectively. For moxifloxacin, the median CSF total concentrations at 2 and 6 h were 0.78 mg/L and 1.02 mg/L with adjusted CSF/serum ratios of 0.44 and 0.62. Serum and CSF concentrations of moxifloxacin were not affected by rifampin use. Among the 76 CSF samples measured for carbapenem concentrations, 79% were undetectable or below the limit of detection. Conclusion: Fluoroquinolones demonstrated high CSF penetration indicating their potential usefulness for the treatment of TBM. Carbapenems had lower than expected CSF concentrations.

Linezolid Exposure Is Associated with Cytopenias in Patients Treated for Multidrug-Resistant Tuberculosis

Although linezolid is effective for multidrug-resistant TB (MDR-TB) tuberculosis treatment, it is associated with cytopenias after 4 weeks of administration. Data on toxicities with long-term use of linezolid and drug pharmacodynamics in MDR-TB treatment are limited, and concerns about toxicity present barriers to wider implementation. This was a secondary analysis of a prospective cohort study of patients treated for MDR-TB in the country of Georgia from 2015 to 2017. Intensive blood sampling 4 to 6 weeks after treatment initiation with linezolid 600 mg daily was performed for pharmacokinetic (PK) analysis, including linezolid trough concentration (Cmin) and area under the curve from 0 to 24 hours (AUC0-24). Linezolid exposure was defined using literature-reported thresholds. Cytopenias were defined using an NIH adverse event (AE) scale. Logistic regression was used to evaluate the relationship between linezolid exposure and cytopenias. Among 76 patients receiving linezolid in their baseline treatment regimen and who had PK data available, cytopenia AEs occurred in 30 (39.5%) for an incidence rate of 46 per 100 person-years. The median duration of linezolid therapy was 526 days. No patients required dose reduction or interruption due to cytopenias. Median linezolid Cmin was 0.235 mg/L (interquartile range [IQR], 0.069 to 0.529), and median AUC0-24 was 89.6 mg·h/L (IQR, 69.2 to 116.2). Cytopenias were associated with linezolid PK parameters (Cmin > 2 mg/L and AUC0-24 > 160 mg·h/L). Cytopenias occurred frequently with long-term use of linezolid 600 mg/day and were associated with PK parameters but did not result in the need for treatment interruption in the management of a cohort of patients with MDR-TB.

Cycloserine and Linezolid for Tuberculosis Meningitis: Pharmacokinetic Evidence of Potential Usefulness

BACKGROUND

The ability of antituberculosis drugs to cross the blood-brain barrier and reach the central nervous system is critical to their effectiveness in treating tuberculosis meningitis (TBM). We sought to fill a critical knowledge gap by providing data on the ability of new and repurposed antituberculosis drugs to penetrate into the cerebrospinal fluid (CSF).

METHODS

We conducted a clinical pharmacology study among patients treated for TBM in Tbilisi, Georgia, from January 2019 until January 2020. Serial serum and CSF samples were collected while patients were hospitalized. CSF was collected from routine lumbar punctures with the timing of the lumbar puncture alternating between 2 and 6 hours to capture early and late CSF penetration.

RESULTS

A total of 17 patients treated for TBM (8 with confirmed disease) were included; all received linezolid, with a subset receiving cycloserine (5), clofazimine (5), delamanid (4), and bedaquiline (2). All CSF measurements of bedaquiline (12), clofazimine (24), and delamanid (19) were below the limit of detection. The median CSF concentrations of cycloserine at 2 and 6 hours were 15.90 and 15.10 µg/mL with adjusted CSF/serum ratios of 0.52 and 0.66. CSF concentrations of linezolid were 0.90 and 3.14 µg/mL at 2 and 6 hours, with adjusted CSF/serum ratios of 0.25 and 0.59, respectively. CSF serum linezolid concentrations were not affected by rifampin coadministration.

CONCLUSIONS

Based on moderate to high CSF penetration, linezolid and cycloserine may be effective drugs for TBM treatment, whereas the utility of bedaquiline, delamanid, and clofazimine is uncertain given their low CSF penetration.

Clinical Pharmacokinetics and Pharmacodynamics of Cefepime

Cefepime is a broad-spectrum fourth-generation cephalosporin with activity against Gram-positive and Gram-negative pathogens. It is generally administered as an infusion over 30-60 min or as a prolonged infusion with infusion times from 3 h to continuous administration. Cefepime is widely distributed in biological fluids and tissues with an average volume of distribution of ~ 0.2 L/kg in healthy adults with normal renal function. Protein binding is relatively low (20%), and elimination is mainly renal. About 85% of the dose is excreted unchanged in the urine, with an elimination half-life of 2-2.3 h. The pharmacokinetics of cefepime is altered under certain pathophysiological conditions, resulting in high inter-individual variability in cefepime volume of distribution and clearance, which poses challenges for population dosing approaches. Consequently, therapeutic drug monitoring of cefepime may be beneficial in certain patients including those who are critically ill, have life-threatening infections, or are infected with more resistant pathogens. Cefepime is generally safe and efficacious, with a goal exposure target of 70% time of the free drug concentration over the minimum inhibitory concentration for clinical efficacy. In recent years, reports of neurotoxicity have increased, specifically in patients with impaired renal function. This review summarizes the pharmacokinetics, pharmacodynamics, and toxicodynamics of cefepime contemporarily in the setting of increasing cefepime exposures. We explore the potential benefits of extended or continuous infusions and therapeutic drug monitoring in special populations.

Pharmacokinetic-Pharmacodynamic Determinants of Clinical Outcomes for Rifampin-Resistant Tuberculosis: A Multisite Prospective Cohort Study

BACKGROUND

Rifampin-resistant and/or multidrug-resistant tuberculosis (RR/MDR-TB) treatment requires multiple drugs, and outcomes remain suboptimal. Some drugs are associated with improved outcome. It is unknown whether particular pharmacokinetic-pharmacodynamic relationships predict outcome.

METHODS

Adults with pulmonary RR/MDR-TB in Tanzania, Bangladesh, and the Russian Federation receiving local regimens were enrolled from June 2016 to July 2018. Serum was collected after 2, 4, and 8 weeks for each drug's area under the concentration-time curve over 24 hours (AUC0-24). Quantitative susceptibility of the M. tuberculosis isolate was measured by minimum inhibitory concentrations (MICs). Individual drug AUC0-24/MIC targets were assessed by adjusted odds ratios (ORs) for favorable treatment outcome, and hazard ratios (HRs) for time to sputum culture conversion. K-means clustering algorithm separated the cohort of the most common multidrug regimen into 4 clusters by AUC0-24/MIC exposures.

RESULTS

Among 290 patients, 62 (21%) experienced treatment failure, including 30 deaths. Moxifloxacin AUC0-24/MIC target of 58 was associated with favorable treatment outcome (OR, 3.75; 95% confidence interval, 1.21-11.56; P = .022); levofloxacin AUC0-24/MIC of 118.3, clofazimine AUC0-24/MIC of 50.5, and pyrazinamide AUC0-24 of 379 mg × h/L were associated with faster culture conversion (HR >1.0, P < .05). Other individual drug exposures were not predictive. Clustering by AUC0-24/MIC revealed that those with the lowest multidrug exposures had the slowest culture conversion.

CONCLUSIONS

Amidst multidrug regimens for RR/MDR-TB, serum pharmacokinetics and M. tuberculosis MICs were variable, yet defined parameters to certain drugs-fluoroquinolones, pyrazinamide, clofazimine-were predictive and should be optimized to improve clinical outcome.

CLINICAL TRIALS REGISTRATION

NCT03559582.

Effect of Rifabutin in Dolutegravir Dosing: A Case Series

Background: Tuberculosis (TB) is the leading cause of death in human immunodeficiency virus (HIV)-infected people worldwide. Currently there are no studies examining the use of Rifabutin (RBN) and Dolutegravir (DTG) in co-infected persons. This is a case series of 4 co-infected patients receiving both agents who underwent Pharmacokinetic (PK) analysis. Methods and Results: This is a retrospective chart review study of four patients diagnosed with both HIV and TB, receiving RBN and DTG and undergoing therapeutic drug monitoring. All 4 cases had lower than expected DTG concentrations at least once, including those on the current recommended dose of DTG with RBN, and even those receiving higher doses. Conclusions: Given the frequency of low DTG and RBN concentrations, therapeutic drug monitoring (TDM) for these drugs is advisable. Prospective clinical studies are needed to further determine the PK interactions between RBN and DTG, and virologic response to treatment.

Provider perspectives on beta-lactam therapeutic drug monitoring programs in the critically ill: a protocol for a multicenter mixed-methods study

Background

Beta-lactams (i.e., penicillins, cephalosporins, carbapenems, monobactams) are the most widely used class of antibiotics in critically ill patients. There is substantial interpatient variability in beta-lactam pharmacokinetics which renders their effectiveness and safety largely unpredictable. One strategy to ensure achievement of therapeutic concentrations is drug level testing (“therapeutic drug monitoring”; TDM). While studies have suggested promise with beta-lactam TDM, it is not yet widely available or implemented. This protocol presents a mixed-methods study designed to examine healthcare practitioners’ perspectives on the use and implementation of beta-lactam TDM in the critically ill.

Methods

An explanatory sequential mixed-methods design will be used [QUANT → qual]. First, quantitative data will be collected through a web-based questionnaire directed at clinicians at three academic medical centers at different phases of beta-lactam TDM implementation (not yet implemented, partially implemented, fully implemented). The sampling frame will include providers from a variety of disciplines that interact with drug level testing and interpretation in the critical care environment including pharmacists, intensivists, infectious diseases experts, medical/surgical trainees, and advanced practice providers. Second, approximately 30 individuals will be purposively sampled from survey respondents to conduct in-depth qualitative interviews to explain and expand upon the results from the quantitative strand. Normalization Process Theory and the Consolidated Framework for Implementation Science will be used to guide data analysis.

Discussion

These data will be used to answer two specific questions: “What are ICU practitioners’ perspectives on implementing beta-lactam TDM?” and “What factors contribute to the success of beta-lactam TDM program implementation?” Results of this study will be used to design future implementation strategies for beta-lactam TDM programs in the critically ill.

Trial registration

NCT04755777.

Supplementary Information

The online version contains supplementary material available at 10.1186/s43058-021-00134-9.