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Tebipenem pivoxil hydrobromide (TBP-PI-HBr) is an oral carbapenem prodrug being developed for the treatment of serious bacterial infections. The active moiety, tebipenem, has broad-spectrum activity against common Enterobacterales pathogens, including extended-spectrum-β-lactamase (ESBL)-producing multidrug-resistant strains. This study evaluated the intrapulmonary pharmacokinetics (PK) and epithelial lining fluid (ELF) and alveolar macrophage (AM) concentrations of tebipenem relative to plasma levels in nonsmoking, healthy adult subjects. Thirty subjects received oral TBP-PI-HBr at 600 mg every 8 h for five doses. Serial blood samples were collected following the last dose. Each subject underwent one standardized bronchoscopy with bronchoalveolar lavage (BAL) 1, 2, 4, 6, or 8 h after the fifth dose of TBP-PI-HBr. The tebipenem area under the concentration-time curve for the 8-h dosing interval (AUC(0–8)) values in plasma, ELF, and AMs were calculated using the mean concentration at each BAL sampling time. Ratios of AUC(0–8) values for total ELF and AMs to those for unbound plasma were determined, using a plasma protein binding value of 42%. Mean values ± standard deviations (SD) of tebipenem maximum (C(max)) and minimum (C(min)) total plasma concentrations were 11.37 ± 3.87 mg/L and 0.043 ± 0.039 mg/L, respectively. Peak tebipenem concentrations in plasma, ELF, and AMs occurred at 1 h and then decreased over 8 h. Ratios of tebipenem AUC(0–8) values for ELF and AMs to those for unbound plasma were 0.191 and 0.047, respectively. Four (13.3%) subjects experienced adverse events (diarrhea, fatigue, papule, and coronavirus disease 2019 [COVID-19]); all resolved, and none were severe or serious. Tebipenem is distributed into the lungs of healthy adults, which supports the further evaluation of TBP-PI-HBr for the treatment of lower respiratory tract bacterial infections caused by susceptible pathogens. (This study has been registered at ClinicalTrials.gov under identifier NCT04710407.)

Background SPR206 is a novel intravenously (IV)-administered next-generation polymyxin being developed for the treatment of multi-drug resistant (MDR) Gram-negative (GN) infections. A Phase 1 bronchoalveolar lavage (BAL) study was conducted to evaluate SPR206 safety and PK in plasma and pulmonary matrices (ELF and AM) in healthy volunteers. Methods Subjects received 100 mg SPR206 administered intravenously over 1 h q8h for 3 consecutive doses. Blood samples were collected pre-dose (second and third dose) and at 2, 3, 4, 6, and 8 h after the start of the last dose. Each subject underwent one standardized bronchoscopy with BAL at 2, 3, 4, 6 or 8 hours after the start of the third IV infusion. Concentrations of SPR206 in plasma, BAL, and cell pellet were measured with a validated LC-MS/MS assay. Plasma, ELF, and AM PK parameters were determined by noncompartmental analysis. SPR206 AUC0–8 in ELF and AM were calculated using the mean concentration values at the BAL sampling times. SPR206 AUC0–8 ratios of ELF and AM to unbound plasma were determined using plasma protein binding value of 8.6%. Results Thirty-four subjects were enrolled and completed the study and 30 of 34 completed bronchoscopy. The mean SPR206 Cmax concentrations in plasma, ELF, and AM were 4395.0, 735.5, and 860.6 ng/mL, respectively. Mean AUC0-8 h values in plasma, ELF, and AM concentrations were 20120.7, 4859.8, and 6026.4 ng*h/mL, respectively--leading to a free ELF to plasma concentration ratio of 0.264 and free AM to plasma ratio of 0.328. Importantly, mean concentrations of SPR206 in the ELF achieved lung exposures above its minimum inhibitory concentration for the targeted gram-negative pathogens for the entire 8-hour dosing interval. Figure 1 displays the mean (±SD) SPR206 total and unbound plasma, ELF, and AM concentrations at the BAL sampling times. Overall, SPR206 was well tolerated; 22 subjects (64.7%) experienced at least 1 TEAE, mostly mild with a few moderate. The most frequently reported TEAEs were oral paresthesia [10 subjects (29.4%)] and nausea [2 subjects (5.9%)], which were reversible. Conclusion This study demonstrates pulmonary penetration of SPR206 and supports further development of SPR206 for the treatment of patients with pneumonia caused by MDR GN infections. Figure 1.Mean (±SD) plasma (total and unbound), epithelial lining fluid (ELF), and alveolar macrophage (AM) concentrations of SPR206 in healthy adult subjects. This study was conducted in collaboration with, and with financial support from, the United States Department of Defense (Award No. W81XWH1910295). Disclosures Keith A. Rodvold, PharmD, Spero Therapeutics: Advisor/Consultant|Spero Therapeutics: Honoraria Justin Bader, n/a, Spero Therapeutics: Employee Vipul K. Gupta, Ph.D., Spero Therapeutics: Employee Troy Lister, Ph.D., Spero Therapeutics: Employee Praveen Srivastava, Ph.D., Spero Therapeutics: Employee Jon Bruss, M.D., Spero Therapeutics: Employee.

A comprehensive review of drug penetration into pulmonary epithelial lining fluid (ELF) was previously published in 2011. Since then, an extensive number of studies comparing plasma and ELF concentrations of antibacterial agents have been published and are summarized in this review. The majority of the studies included in this review determined ELF concentrations of antibacterial agents using bronchoscopy and bronchoalveolar lavage, and this review focuses on intrapulmonary penetration ratios determined with area under the concentration-time curve from healthy human adult studies or pharmacokinetic modeling of various antibacterial agents. If available, pharmacokinetic/pharmacodynamic parameters determined from preclinical murine infection models that evaluated ELF concentrations are also provided. There are also a limited number of recently published investigations of intrapulmonary penetration in critically ill patients with lower respiratory tract infections, where greater variability in ELF concentrations may exist. The significance of these changes may impact the intrapulmonary penetration in the setting of infection, and further studies relating ELF concentrations to clinical response are needed. Phase I drug development programs now include assessment of initial pharmacodynamic target values for pertinent organisms in animal models, followed by evaluation of antibacterial penetration into the human lung to assist in dosage selection for clinical trials in infected patients. The recent focus has been on β-lactam agents, including those in combination with β-lactamase inhibitors, particularly due to the rise of multidrug-resistant infections. This manifests as a large portion of the review focusing on cephalosporins and carbapenems, with or without β-lactamase inhibitors, in both healthy adult subjects and critically ill patients with lower respiratory tract infections. Further studies are warranted in critically ill patients with lower respiratory tract infections to evaluate the relationship between intrapulmonary penetration and clinical and microbiological outcomes. Our clinical research experience with these studies, along with this literature review, has allowed us to outline key steps in developing and evaluating dosage regimens to treat extracellular bacteria in lower respiratory tract infections.

ObjectivesLung penetration of cefiderocol, a novel siderophore cephalosporin approved for treatment of nosocomial pneumonia, has previously been evaluated in healthy subjects. This study assessed the intrapulmonary pharmacokinetic profile of cefiderocol at steady state in hospitalized, mechanically ventilated pneumonia patients.MethodsPatients received cefiderocol 2 g (or ≤1.5 g if renally impaired), administered IV q8h as a 3 h infusion, or 2 g q6h if patients had augmented renal function (estimated CLCR > 120 mL/min). After multiple doses, each patient underwent a single bronchoalveolar lavage (BAL) procedure either at the end of the infusion or at 2 h after the end of infusion. Plasma samples were collected at 1, 3, 5 and 7 h after the start of infusion. After correcting for BAL dilution, cefiderocol concentrations in epithelial lining fluid (ELF) for each patient and the ELF/unbound plasma concentration ratio (RC, E/P) were calculated. Safety was assessed up to 7 days after the last cefiderocol dose.ResultsSeven patients received cefiderocol. Geometric mean ELF concentration of cefiderocol was 7.63 mg/L at the end of infusion and 10.40 mg/L at 2 h after the end of infusion. RC, E/P was 0.212 at the end of infusion and 0.547 at 2 h after the end of infusion, suggesting delayed lung distribution. There were no adverse drug reactions.ConclusionsThe results suggest that cefiderocol penetrates the ELF in critically ill pneumonia patients with concentrations that are sufficient to treat Gram-negative bacteria with an MIC of ≤4 mg/L.

Background Recent vancomycin PK/PD and toxicodynamic studies enable a reassessment of the current dosing and monitoring guideline in an attempt to further optimize the efficacy and safety of vancomycin therapy. The area-under-the-curve to minimum inhibitory concentration (AUC/MIC) has been identified as the most appropriate pharmacokinetic/pharmacodynamic (PK/PD) target for vancomycin. The 2009 vancomycin consenus guidelines recommended specific trough concentrations as a surrogate marker for AUC/MIC. However, more recent toxicodynamic studies have reported an increase in nephrotoxicity associated with trough monitoring. Methods and results This is the executive summary of the new vancomycin consensus guidelines for dosing and monitoring vancomycin therapy and was developed by the American Society of Health-Systems Pharmacists, Infectious Diseases Society of America, Pediatric Infectious Diseases Society and the Society of Infectious Diseases Pharmacists vancomycin consensus guidelines committee. Conclusions The recommendations provided in this document are intended to assist the clinician in optimizing vancomycin for the treatment of invasive MRSA infections in adult and pediatric patients. An AUC/MIC by broth microdilution (BMD) ratio of 400 to 600 (assuming MICBMD of 1 mg/L) should be advocated as the target to achieve clinical efficacy while improving patient safety for patients with serious MRSA infections. In such cases, AUC-guided dosing and monitoring is the most accurate and optimal way to manage vancomycin therapy.

Background Recent vancomycin PK/PD and toxicodynamic studies enable a reassessment of the current dosing and monitoring guideline in an attempt to further optimize the efficacy and safety of vancomycin therapy. The area-under-the-curve to minimum inhibitory concentration (AUC/MIC) has been identified as the most appropriate pharmacokinetic/pharmacodynamic (PK/PD) target for vancomycin. The 2009 vancomycin consenus guidelines recommended specific trough concentrations as a surrogate marker for AUC/MIC. However, more recent toxicodynamic studies have reported an increase in nephrotoxicity associated with trough monitoring. Methods and results This is the executive summary of the new vancomycin consensus guidelines for dosing and monitoring vancomycin therapy and was developed by the American Society of Health-Systems Pharmacists, Infectious Diseases Society of America, Pediatric Infectious Diseases Society and the Society of Infectious Diseases Pharmacists vancomycin consensus guidelines committee. Conclusions The recommendations provided in this document are intended to assist the clinician in optimizing vancomycin for the treatment of invasive MRSA infections in adult and pediatric patients. An AUC/MIC by broth microdilution (BMD) ratio of 400 to 600 (assuming MICBMD of 1 mg/L) should be advocated as the target to achieve clinical efficacy while improving patient safety for patients with serious MRSA infections. In such cases, AUC-guided dosing and monitoring is the most accurate and optimal way to manage vancomycin therapy.

Tebipenem pivoxil hydrobromide (TBP-PI-HBr) is an oral carbapenem prodrug antimicrobial agent with broad-spectrum activity that includes multidrug-resistant (MDR) Enterobacterales . This study evaluated the safety, tolerability, and pharmacokinetics of TBP-PI-HBr in healthy subjects with normal renal function (cohort 1) and subjects with various degrees of renal impairment (RI [cohorts 2 to 4]) or end-stage renal disease (ESRD) receiving hemodialysis (HD) (cohort 5). Subjects in cohorts 1 to 4 received a single oral dose of TBP-PI-HBr (600 mg).

Omadacycline is a novel aminomethylcycline antibiotic (antibacterial). Omadacycline has had chemical structure modifications at the C9 and C7 positions of the core tetracycline rings that allow stability in the efflux pump and ribosomal protection protein mechanisms of tetracycline resistance. The systemic exposure (i.e., maximum plasma concentrations [Cmax] and area under the plasma concentration–time curve [AUC]) after intravenous (IV) administration were linear and predictable over the dose range of 25 and 600 mg in healthy subjects. The oral bioavailability of omadacycline was 34.5% under fasted conditions (no food intake 6 h before and 4 h after dosing). Both AUC and Cmax values significantly decreased (41–61%) when a high-fat meal, with and without dairy, were administered 2 h before oral dosing of omadacycline. Similar to other tetracyclines, it is advisable to avoid concurrent administration of divalent- or trivalent cation-containing products (e.g., antacids and iron-containing preparations) for at least 4 h after oral administration of omadacycline. Omadacycline has a large volume of distribution (190 L) and low plasma protein binding (21.3%) that was concentration independent. Systemic exposure of omadacycline in epithelial lining fluid (ELF) and alveolar macrophages was greater than in plasma in healthy adult subjects. Omadacycline is excreted unchanged in the feces (81.1%) and urine (14.4%), and has a low potential for drug–drug interactions since it was not a substrate, inhibitor, or inducer of major cytochrome-metabolizing enzymes or organic anion transporters (OATs). No clinically significant differences in the pharmacokinetics of omadacycline have been observed for age, sex, and renal or hepatic impairment. Pharmacokinetic–pharmacodynamic studies have confirmed that the AUC from time zero to 24 h (AUC24)/minimum inhibitory concentration (MIC) ratio was the best index for correlating unbound plasma and total-drug ELF concentrations with the efficacy of omadacycline. A population pharmacokinetic model was developed with data from healthy subjects and infected patients and used to establish interpretive criteria for in vitro susceptibility testing and dosing regimens of omadacycline for treating acute bacterial skin and skin structure infections and community-acquired bacterial pneumonia.

Oral and intravenous (IV) omadacycline formulations are approved in the United States for treating acute bacterial skin and skin structure infections and community-acquired bacterial pneumonia in adults. Oral omadacycline bioavailability is 34.5%; similar exposures are obtained following 300 mg oral and 100 mg IV doses. Oral administration should be in a fasted state, with dairy products, antacids, or multivitamins avoided for ≥4 hours after dosing. Low protein binding (21%), large volume of distribution (190 L), low systemic clearance (10 L/hour), and long elimination half-life (16–17 hours) support once-daily dosing. Omadacycline is excreted unchanged in feces (81.1%) and urine (14.4%), with low potential for drug–drug interactions. Dose adjustments are unnecessary for age, sex, and renal or hepatic impairment. Pharmacokinetic–pharmacodynamic studies identify fAUC0–24/MIC ratio as the parameter that correlates with in vivo efficacy. Systemic exposure of omadacycline in epithelial lining fluid is greater than/equal to plasma concentrations in healthy adults.

Tetracyclines have come a long way since they became available almost seven decades ago, with numerous enhancements allowing new agents to overcome bacterial mechanisms of resistance. However, these enhancements come with toxicities and pharmacokinetic disadvantages such as the gastrointestinal side-effects and poor oral bioavailability seen with the glycylcylcines. Omadacycline, a new and improved tetracycline, has demonstrated a broad spectrum of in vitro activity, has oral and intravenous formulations, improved safety compared to glycylcyclines, as well as clinical efficacy and safety for two types of infections: acute bacterial skin and skin structure infections and community-acquired bacterial pneumonia. This review will summarize salient points about its pharmacologic properties, available clinical efficacy, and safety data and omadacycline's place in therapy.

BACKGROUND: Vancomycin is the most commonly administered antibiotic in hospitalized patients, but optimal exposure targets remain controversial. To clarify the therapeutic exposure range, this study evaluated the association between vancomycin exposure and outcomes in patients with methicillin-resistant Staphylococcus aureus (MRSA) bacteremia. METHODS: This was a prospective, multicenter (n = 14), observational study of 265 hospitalized adults with MRSA bacteremia treated with vancomycin. The primary outcome was treatment failure (TF), defined as 30-day mortality or persistent bacteremia ≥7 days. Secondary outcomes included acute kidney injury (AKI). The study was powered to compare TF between patients who achieved or did not achieve day 2 area under the curve to minimum inhibitory concentration (AUC/MIC) thresholds previously found to be associated with lower incidences of TF. The thresholds, analyzed separately as co-primary endpoints, were AUC/MIC by broth microdilution ≥650 and AUC/MIC by Etest ≥320. RESULTS: Treatment failure and AKI occurred in 18% and 26% of patients, respectively. Achievement of the prespecified day 2 AUC/MIC thresholds was not associated with less TF. Alternative day 2 AUC/MIC thresholds associated with lower TF risks were not identified. A relationship between the day 2 AUC and AKI was observed. Patients with day 2 AUC ≤515 experienced the best global outcomes (no TF and no AKI). CONCLUSIONS: Higher vancomycin exposures did not confer a lower TF risk but were associated with more AKI. The findings suggest that vancomycin dosing should be guided by the AUC and day 2 AUCs should be ≤515. As few patients had day 2 AUCs

Background Infections caused by antibiotic-resistant bacteria, including carbapenem-resistant Enterobacteriaceae, have increased in frequency, resulting in significant patient morbidity and mortality. The Infectious Diseases Society of America continues to propose legislative, regulatory, and funding solutions to address this escalating crisis. This report updates the status of development and approval of systemic antibiotics in the United States as of late 2018. Methods We performed a review of the published literature and on-line clinical trials registry at www.clinicaltrials.gov to identify new systemically acting orally and/or intravenously administered antibiotic drug candidates in the development pipeline, as well as agents approved by the US Food and Drug Administration since 2012. Results Since our 2013 pipeline status report, the number of new antibiotics annually approved for marketing in the United States has reversed its previous decline, likely influenced by new financial incentives and increased regulatory flexibility. Although our survey demonstrates progress in development of new antibacterial drugs that target infections caused by resistant bacterial pathogens, the majority of recently approved agents have been modifications of existing chemical classes of antibiotics, rather than new chemical classes. Furthermore, larger pharmaceutical companies continue to abandon the field, and smaller companies face financial difficulties as a consequence. Conclusions Unfortunately, if 20 × '20 is achieved due to efforts embarked upon in decades past, it could mark the apex of antibiotic drug development for years to come. Without increased regulatory, governmental, industry, and scientific support and collaboration, durable solutions to the clinical, regulatory, and economic problems posed by bacterial multidrug resistance will not be found.

Recent vancomycin PK/PD and toxicodynamic studies enable a reassessment of the current dosing and monitoring guideline in an attempt to further optimize the efficacy and safety of vancomycin therapy. The area-under-the-curve to minimum inhibitory concentration (AUC/MIC) has been identified as the most appropriate pharmacokinetic/pharmacodynamic (PK/PD) target for vancomycin. The 2009 vancomycin consenus guidelines recommended specific trough concentrations as a surrogate marker for AUC/MIC. However, more recent toxicodynamic studies have reported an increase in nephrotoxicity associated with trough monitoring.This is the executive summary of the new vancomycin consensus guidelines for dosing and monitoring vancomycin therapy and was developed by the American Society of Health-Systems Pharmacists, Infectious Diseases Society of America, Pediatric Infectious Diseases Society and the Society of Infectious Diseases Pharmacists vancomycin consensus guidelines committee.The recommendations provided in this document are intended to assist the clinician in optimizing vancomycin for the treatment of invasive MRSA infections in adult and pediatric patients. An AUC/MIC by broth microdilution (BMD) ratio of 400 to 600 (assuming MICBMD of 1 mg/L) should be advocated as the target to achieve clinical efficacy while improving patient safety for patients with serious MRSA infections. In such cases, AUC-guided dosing and monitoring is the most accurate and optimal way to manage vancomycin therapy.

Meropenem/vaborbactam (M/V) represents the first carbapenem and β-lactamase inhibitor combination approved for treatment of complicated urinary tract infections (cUTIs), including pyelonephritis. Vaborbactam is a novel boronic acid, β-lactamase inhibitor with a high affinity for serine β-lactamases, including Klebsiella pneumoniae carbapenemase (KPC). This combination, Vabomere™, was approved in August 2017 by the United States Food and Drug Administration for the treatment of cUTIs in patients 18 years or older, including pyelonephritis, caused by the following susceptible microorganisms: Escherichia coli, K. pneumoniae, and Enterobacter cloacae species complex. Areas covered: Relevant literature regarding microbiology, pharmacokinetics, pharmacodynamics, and clinical trials evaluating efficacy, safety, and tolerability will be discussed. Expert opinion: Current treatment options for KPC-producing infections such as aminoglycosides, polymyxins, fosfomycin, and tigecycline are associated with concerns regarding efficacy, toxicities, optimal dosing, and/or development of resistance. Additionally, resistance to the new combination product of ceftazidime/avibactam has also emerged. Current clinical evidence supporting the use of M/V for KPC-producing infections is limited to an open-label, randomized, phase III study in a small number of patients with serious infections due to carbapenem-resistant Enterobacteriaceae. Although M/V is not approved for KPC-producing infections, we believe that M/V will become a preferred agent for KPC-producing Enterobacteriaceae infections.

Lefamulin is the first semisynthetic pleuromutilin being developed for oral and intravenous administration. The drug selectively inhibits prokaryotic ribosomal protein synthesis by binding to the peptidyl transferase centre via four H-bonds and other interactions, resulting in an ‘induced fit’ that tightens the binding pocket around lefamulin. This unique mechanism of action has been associated with a low probability of cross-resistance to other antimicrobial classes commonly used to treat community-acquired bacterial pneumonia (CABP). This Supplement, entitled ‘Pharmacokinetic and pharmacodynamic analyses and dose rationale for lefamulin, a novel pleuromutilin antibiotic, for the treatment of community-acquired bacterial pneumonia’, is intended to be a valuable resource for both clinicians and researchers. It provides the essential pharmacokinetic and pharmacodynamic data on lefamulin that were used to support the optimal dose selection of lefamulin for the safe and effective treatment of CABP in adults.

BackgroundSevere infections of the respiratory tracts of critically ill patients are common and associated with excess morbidity and mortality. Piperacillin is commonly used to treat pulmonary infections in critically ill patients. Adequate antibiotic concentration in the epithelial lining fluid (ELF) of the lung is essential for successful treatment of pulmonary infection.ObjectivesTo compare piperacillin pharmacokinetics/pharmacodynamics in the serum and ELF of healthy volunteers and critically ill patients.MethodsPiperacillin concentrations in the serum and ELF of healthy volunteers and critically ill patients were compared using population methodologies.ResultsMedian piperacillin exposure was significantly higher in the serum and the ELF of critically ill patients compared with healthy volunteers. The IQR for serum piperacillin exposure in critically ill patients was six times greater than for healthy volunteers. The IQR for piperacillin exposure in the ELF of critically ill patients was four times greater than for healthy volunteers. The median pulmonary piperacillin penetration ratio was 0.31 in healthy volunteers and 0.54 in critically ill patients.ConclusionsGreater variability in serum and ELF piperacillin concentrations is observed in critically ill patients compared with healthy adult subjects and must be considered in the development of dosage regimens. Pulmonary penetration of antimicrobial agents should be studied in critically ill patients, as well as healthy volunteers, during drug development to ensure appropriate dosing of patients with pneumonia.

Methicillin-resistant Staphylococcus aureus (MRSA), while decreasing in overall incidence, is still a prominent concern world-wide. New agents coming to market in the last 10 years allow practitioners to optimize treatment for MRSA infections. Ceftobiprole is a cephalosporin agent with MRSA activity, currently approved in selected countries for the treatment of community-acquired pneumonia and hospital-acquired pneumonia. Areas covered: Relevant literature regarding spectrum of activity, pharmacokinetics, pharmacodynamics, and clinical trials will be discussed. Expert opinion: Ceftobiprole is an addition to a growing number of antimicrobials with activity against MRSA. Concern for appropriate dosing in critically ill patients remains due to its ineffectiveness for the treatment of ventilator-associated pneumonia (VAP). While ceftobiprole has activity against gram-negative organisms, the allowance for use of an additional agent for gram-negative infections in clinical trials limits recommendations for monotherapy for empirical treatment of HAP. Ceftobiprole's place in therapy will lie in its activity against gram positive organisms, such as Streptococcus spp. and Staphylococcus spp.

The ex vivo bactericidal activity and pharmacodynamics of fosfomycin in urine were evaluated in 18 healthy subjects. Subjects received 3 g every other day (QOD) for 3 doses and then every day (QD) for 7 doses or vice versa. Serial urine samples were collected before and up to 24 h after dosing on days 1 and 5. Eight bacterial strains with various genotypic and phenotypic susceptibilities to fosfomycin were used for all experiments (5 Escherichia coli, 2 Klebsiella pneumoniae, and 1 Proteus mirabilis). MICs were performed via agar dilution. Urinary bactericidal titers (UBTs) were performed via modified Schlichter test using participant's drug-free urine as the diluent. Urinary time-kill analyses were performed on pooled 24-h urine aliquots from days 1 and 5. All experiments were performed in triplicate with and without the addition of 25 mg/liter of glucose-6-phosphate (G6P). Mean 24-h urine concentrations of fosfomycin ranged from 324.7 to 434.6 mg/liter regardless of study day or dosing regimen. The urinary antibacterial activity of fosfomycin was also similar across study days and dosing regimens. UBT values did not correlate with MICs determined in the presence of G6P. Fosfomycin was reliably bactericidal in urine only against the 5 E. coli strains, regardless of genotype or MIC value. Together, these data do not support the use of oral fosfomycin tromethamine for pathogens other than E. coli or at a dosing frequency higher than QOD. Fosfomycin MICs determined in the presence of G6P may not accurately reflect the in vivo activity given the lack of G6P in human urine. (This study has been registered at ClinicalTrials.gov under identifier NCT02570074.).

Omadacycline is a novel aminomethylcycline antibiotic (antibacterial). Omadacycline has had chemical structure modifications at the C9 and C7 positions of the core tetracycline rings that allow stability in the efflux pump and ribosomal protection protein mechanisms of tetracycline resistance. The systemic exposure (i.e., maximum plasma concentrations [C

The polymyxins are important agents for carbapenem-resistant Gram-negative bacilli. The United States Committee on Antimicrobial Susceptibility Testing breakpoint recommendations for colistin and polymyxin B are that isolates of Pseudomonas aeruginosa , Acinetobacter baumannii , and Enterobacteriaceae are considered susceptible at MIC values of ≤2 mg/liter. These recommendations are contingent upon dosing and testing strategies that are described in this commentary.

BACKGROUND: The need for antimicrobial therapies effective against multidrug resistant organisms for children remains unmet. Tigecycline shows antibacterial activity across a broad spectrum of bacteria and is approved for treating complicated skin and skin-structure infections, complicated intra-abdominal infections and, in the United States, community-acquired bacterial pneumonia for adult patients. No blinded, randomized phase 3 tigecycline clinical trials on neonates or children have been completed or planned. This review aimed to provide a comprehensive synthesis of all the existing data sources, both on-label and off-label, for tigecycline use in children. METHODS: Data on tigecycline use in children were identified from published and unpublished sources including clinical trials, expanded access and compassionate use programs, databases of healthcare records and patient safety monitoring. RESULTS: Pharmacokinetic simulations predicted that tigecycline 1.2 mg/kg (maximum dose 50 mg) every 12 hours (q12h) in children 8-11 years and 50 mg q12h in children 12 to

Fosfomycin is a bactericidal antibiotic available since the 1970s whose intravenous formulation has been available in many countries outside the USA. Given the rise in drug-resistant bacteria, its introduction into the US market has become a necessity for addressing these organisms. This review provides an overview of the microbiology, clinical pharmacology and initial clinical experiences of the intravenous fosfomycin product (ZTI-01) that is undergoing clinical development in the USA for the treatment of complicated urinary tract infections and acute pyelonephritis.

Background Cefiderocol (CFDC), a novel siderophore cephalosporin, has potent in vitro activity against Gram-negative bacteria causing nosocomial pneumonia (NP). The non-inferiority of CFDC to meropenem in Day 14 all-cause mortality in NP was previously demonstrated. In this study, we assessed the intrapulmonary pharmacokinetics of CFDC in hospitalized and ventilated patients with bacterial pneumonia receiving standard of care (SOC) antibiotics. Methods A multicenter, single-arm, open-label study was conducted to assess epithelial lining fluid (ELF) and plasma concentrations of CFDC at steady state in mechanically ventilated patients with bacterial pneumonia receiving SOC antibiotics (NCT03862040). Seven patients received 2 g doses of CFDC (or renally adjusted doses), infused over 3 hours, q8h, or q6h for patients with augmented renal function (creatinine clearance estimated by Cockcroft-Gault equation >120 mL/min). One bronchoalveolar lavage (BAL) sample per patient was collected to determine ELF concentration at 3 or 5 hours after at least 3 CFDC doses (or ≥6 doses in patients with severe renal impairment). Four blood samples were collected per patient for plasma concentrations at 1, 3, 5, and 7 hours after the start of the infusion used for BAL sampling. Urea concentrations in blood and BAL were measured to calculate CFDC concentrations in ELF. Results Geometric mean (minimum, maximum) ELF concentration of CFDC was 7.63 (3.10, 20.7) µg/mL at the end of infusion (3 h after the start of infusion) (N=4) and 10.4 (7.19, 15.9) µg/mL at 2 hours after the end of infusion (5 h after the start of infusion) (N=3). ELF/free plasma concentration ratios were estimated to be 0.212 at the end of infusion and 0.547 at 2 hours after the end of infusion based on the in vitro unbound fraction of 0.422. Conclusion The individual ELF concentrations of CFDC were close to, or higher than, 4 µg/mL in pneumonia patients. Compared with the ELF/free plasma area under the curve ratio in healthy subjects (0.239), the ELF/free plasma concentration ratio at the end of infusion (0.212) was comparable, and at 2 hours after the end of infusion (0.422) was higher in pneumonia patients. These findings suggest delayed distribution and sustained exposure of CFDC in the ELF of pneumonia patients. Disclosures Takayuki Katsube, PhD, Shionogi & Co., Ltd. (Employee) Toshihiro Wajima, PhD, Shionogi & Co., Ltd. (Employee) Roger Echols, MD, Shionogi Inc. (Consultant) Simon Portsmouth, MD, Shionogi Inc. (Employee) Mari Ariyasu, BPharm, Shionogi & Co., Ltd. (Employee) Keith Rodvold, PharmD, FCCP, FIDSA, Shionogi Inc. (Consultant) David P. Nicolau, PharmD, Cepheid (Other Financial or Material Support, Consultant, speaker bureau member or has received research support.)Merck & Co., Inc. (Consultant, Grant/Research Support, Speaker’s Bureau)Wockhardt (Grant/Research Support)

ETX2514 is a novel β-lactamase inhibitor that broadly inhibits Ambler class A, C, and D β-lactamases. ETX2514 combined with sulbactam (SUL) in vitro restores sulbactam activity against Acinetobacter baumannii. ETX2514-sulbactam (ETX2514SUL) is under development for the treatment of A. baumannii infections. The objective of this study was to determine and compare plasma, epithelial lining fluid (ELF), and alveolar macrophage (AM) concentrations following intravenous (i.v.) ETX2514 and sulbactam. Plasma, ELF, and AM concentrations of ETX2514 and sulbactam were measured by liquid chromatography-tandem mass spectrometry (LC-MS/MS) in 30 healthy adult subjects following repeated dosing (ETX2514 [1 g] and sulbactam [1 g] every 6 h [q6h], as a 3-h i.v. infusion, for a total of 3 doses). A bronchoalveolar lavage (BAL) was performed once in each subject at either 1, 2.5, 3.25, 4, or 6 h after the start of the last infusion. Penetration ratios were calculated from area under the concentration-time curve from 0 to 6 h (AUC(0–6)) values for total plasma and ELF using mean and median concentrations at the BAL fluid sampling times. Respective ELF AUC(0–6) values, based on mean and median concentrations, were 40.1 and 39.4 mg · h/liter for ETX2514 and 34.7 and 34.5 mg · h/liter for sulbactam. Respective penetration ratios of ELF to total/unbound plasma concentrations, based on mean and median AUC(0–6) values, of ETX2514 were 0.37/0.41 and 0.36/0.40, whereas these same ratio values were 0.50/0.81 and 0.50/0.80 for sulbactam. ETX2514 and sulbactam concentrations in AM were measurable and fairly constant throughout the dosing interval (median values of 1.31 and 1.01 mg/liter, respectively). These data support further study of ETX2514SUL for the treatment of pneumonia caused by multidrug-resistant A. baumannii. (This study has been registered at ClinicalTrials.gov under identifier NCT03303924.)

WCK 5222 is a combination of cefepime and the novel β-lactam enhancer zidebactam being developed for the treatment of serious Gram-negative bacterial infections. The objective of this study was to compare plasma (total), epithelial lining fluid (ELF), and alveolar macrophage (AM) concentrations of cefepime and zidebactam in healthy adult subjects. The WCK 5222 dosing regimen was 2 g cefepime/1 g zidebactam administered as a 1-h intravenous infusion every 8 h for a total of 7 doses. Subjects were assigned to one bronchoalveolar lavage (BAL) sampling time at 0.5, 1.25, 3, 6, 8, or 10 h after the seventh dose. Noncompartmental pharmacokinetic parameters were determined from serial plasma concentrations collected over 8-hour and 10-hour intervals following the first and seventh doses, respectively. Penetration ratios were calculated from the area under the plasma concentration-time curve from 0 to 8 h (AUC0-8) for plasma, ELF, and AM using mean and median concentrations at each BAL sampling time. The plasma maximum concentration of drug (Cmax) and AUC values of cefepime and zidebactam increased by 8% to 9% after the seventh versus the first dose of WCK 5222. The respective AUC0-8 values based on mean concentrations of cefepime and zidebactam in ELF were 127.9 and 52.0 mg · h/liter, and 87.9 and 13.2 mg · h/liter in AM. The ELF to total plasma penetration ratios of cefepime and zidebactam based on mean AUC0-8 values were 0.39 and 0.38, respectively. The AM to total plasma ratios were 0.27 and 0.10, respectively. The observed plasma, ELF, and AM concentrations of cefepime and zidebactam support studies of WCK 5222 for treatment of pneumonia caused by susceptible pathogens.

The pharmacokinetics (PK), safety, and tolerability of two repeated dosing regimens of oral fosfomycin tromethamine were evaluated in 18 healthy adult subjects. Subjects received 3 g every other day (QOD) for 3 doses and then every day (QD) for 7 doses, or vice versa, in a phase I, randomized, open-label, two-period-crossover study. Serial blood (n = 11) and urine (n = 4 collection intervals) samples were collected before and up to 24 h after dosing on days 1 and 5, along with predose concentrations on days 3 and 7. PK parameters were similar between days 1 and 5 within and between dosing regimens. The mean (± standard deviation [SD]) PK parameters for fosfomycin in plasma on day 5 during the respective QOD and QD dosing regimens were as follows: maximum concentration of drug in serum (Cmax) = 24.4 ± 6.2 versus 23.8 ± 5.6 μg/ml, time to Cmax (Tmax) = 2.2 ± 0.7 versus 2.0 ± 0.4 h, apparent volume of distribution (V/F) = 141 ± 67.9 versus 147 ± 67.6 liters, apparent clearance (CL/F) = 21.4 ± 8.0 versus 20.4 ± 5.3 liters/h, renal clearance (CLR) = 7.5 ± 4.1 versus 7.3 ± 3.5 liters/h, area under the concentration-time curve from 0 to 24 h (AUC0-24) = 151.6 ± 35.6 versus 156.6 ± 42.5 μg · h/ml, and elimination half-life (t1/2) = 4.5 ± 1.1 versus 5.0 ± 1.7 h. Urine concentrations peaked at approximately 600 μg/ml through the 0- to 8-h urine collection intervals but displayed significant interindividual variability. Roughly 35 to 40% of the 3-g dose was excreted in the urine by 24 h postdose. No new safety concerns were identified during this study. The proportion of diarrhea-free days during the study was significantly lower with the QD regimen than with the QOD regimen (61% versus 77%; P < 0.0001). Further studies to establish the clinical benefit/risk ratio for repeated dosing regimens of oral fosfomycin tromethamine are warranted. (This trial is registered at ClinicalTrials.gov under registration no. NCT02570074.).

Antibiotic renal dose adjustments are determined in patients with stable chronic kidney disease and may not translate to patients in late-phase trials and practice. Ceftolozane/tazobactam, ceftazidime/avibactam, and telavancin all carry precautionary statements for reduced clinical response in patients with baseline creatinine clearance of 30-50 mL/min, potentially due to unnecessary dose reduction in the setting of acute kidney injury (AKI). In this review, we discuss the regulatory landscape for antibiotics eliminated by the kidney and highlight the importance of the first 48 hours of therapy. Using a clinical database, we identified AKI on admission in a substantial proportion of patients with pneumonia (27.1%), intraabdominal (19.5%), urinary tract (20.0%), or skin and skin structure infections (9.7%) that resolved by 48 hours in 57.2% of cases. We suggest that deferred renal dose reduction of wide therapeutic index antibiotics could improve outcomes in patients with infectious diseases.

Alalevonadifloxacin (WCK 2349) is a novel l -alanine ester prodrug of levonadifloxacin that is being developed as an oral fluoroquinolone antibiotic. The primary objective of this study was to determine and compare plasma, epithelial lining fluid (ELF), and alveolar macrophage (AM) concentrations of levonadifloxacin following oral administration of alalevonadifloxacin to healthy adult subjects. Levonadifloxacin concentrations in plasma, ELF, and AM samples from 30 healthy subjects were measured by liquid chromatography-tandem mass spectrometry (LC-MS/MS) following oral dosing of alalevonadifloxacin (1,000 mg twice daily for 5 days). Six subjects were assigned to each bronchoalveolar lavage (BAL) fluid sampling time, i.e., 2, 4, 6, 8, or 12 h after the ninth oral dose. Noncompartmental pharmacokinetic (PK) parameters were determined from serial total plasma concentrations collected over a 12-h interval following the first and ninth oral doses. Penetration ratios were calculated from the areas under the concentration-time curves from 0 to 12 h (AUC 0–12 ) for plasma, ELF, and AM by using mean (and median) concentrations at each BAL sampling time. Unbound plasma concentrations (∼85% plasma protein binding) were used to determine site-to-plasma penetration ratios. Plasma PK parameter values for levonadifloxacin were similar after the first and ninth doses. The respective AUC 0–12 values based on mean ELF and AM concentrations were 172.6 and 35.3 mg · h/liter, respectively. The penetration ratios for ELF and AM levonadifloxacin concentrations to unbound plasma levonadifloxacin concentrations were 7.66 and 1.58, respectively. Similar penetration ratios were observed with median concentrations. The observed plasma, ELF, and AM concentrations of levonadifloxacin support further studies of alalevonadifloxacin for treatment of lower respiratory tract bacterial infections caused by susceptible pathogens. (This study has been registered at ClinicalTrials.gov under identifier NCT02253342.)

The pharmacokinetic profile of ceftaroline has not been well characterized in obese adults. The purpose of this study was to evaluate the pharmacokinetics of ceftaroline in 32 healthy adult volunteers aged 18 to 50 years in the normal, overweight, and obese body size ranges. Subjects were evenly assigned to 1 of 4 groups based on their body mass index (BMI) and total body weight (TBW) (ranges, 22.1 to 63.5 kg/m 2 and 50.1 to 179.5 kg, respectively). Subjects in the lower-TBW groups were matched by age, sex, race/ethnicity, and serum creatinine to the upper-BMI groups. Serial plasma and urine samples were collected over 12 h after the start of the infusion, and the concentrations of ceftaroline fosamil (prodrug), ceftaroline, and ceftaroline M-1 (inactive metabolite) were assayed. Noncompartmental and population pharmacokinetic analyses were used to evaluate the data. The mean plasma ceftaroline maximum concentration and area under the curve were ca. 30% lower in subjects with a BMI of ≥40 kg/m 2 compared to those 2 . A five-compartment pharmacokinetic model with zero-order infusion and first-order elimination optimally described the plasma concentration-time profiles of the prodrug and ceftaroline. Estimated creatinine clearance (eCL CR ) and TBW best explained ceftaroline clearance and volume of distribution, respectively. Although lower ceftaroline plasma concentrations were observed in obese subjects, Monte Carlo simulations suggest the probability of target attainment is ≥90% when the MIC is ≤1 μg/ml irrespective of TBW or eCL CR . No dosage adjustment for ceftaroline appears to be necessary based on TBW alone in adults with comparable eCL CR . Confirmation of these findings in infected obese patients is necessary to validate these findings in healthy volunteers. (This study has been registered at ClinicalTrials.gov under registration no. NCT01648127.)

Over 1000 new molecular entities (NMEs) have been introduced into the marketplace since the end of World War II. These therapeutic innovations have contributed to an increase in life expectancy but have also increased the prevalence of polypharmacy and the risk for adverse drug-drug interactions. The economic burden associated with adverse drug events is estimated to exceed $100 billion in the United States alone. These adverse events are most often associated with chronic medications used to manage hypercholesterolemia, diabetes, asthma, and depression that are widely prescribed in more economically developed countries. Acute infections most often lead to the short-term prescription of antimicrobials that can increase the risk for adverse events and or therapeutic failure when co-prescribed with these agents. Likewise combination antimicrobial therapies used to manage chronic or deep-seated infections carry a high potential for drug-drug interactions. The large number of NMEs and continued influx of new agents limits the design of a comprehensive resource that can accurately predict the extent and clinical implications of pharmacokinetic and pharmacodynamic interactions. This chapter provides a broad overview of clinical pharmacology from the perspective of systems that influence absorption, distribution, metabolism, and excretion of drugs that can lead to pharmacokinetic drug interactions.

A recommended total-body-weight (TBW) dosing strategy for telavancin may not be optimal in obese patients. The primary objective of this study was to characterize and compare the pharmacokinetics (PK) of telavancin across four body size groups: normal to overweight and obese classes I, II, and III. Healthy adult subjects ( n = 32) received a single, weight-stratified, fixed dose of 500 mg ( n = 4), 750 mg ( n = 8), or 1,000 mg ( n = 20) of telavancin. Noncompartmental PK analyses revealed that subjects with a body mass index (BMI) of ≥40 kg/m 2 had a higher volume of distribution (16.24 ± 2.7 liters) than subjects with a BMI of 2 (11.71 ± 2.6 liters). The observed area under the concentration-time curve from time zero to infinity (AUC 0–∞ ) ranged from 338.1 to 867.3 mg · h/liter, with the lowest exposures being in subjects who received 500 mg. AUC 0–∞ values were similar among obese subjects who received 1,000 mg. A two-compartment population PK model best described the plasma concentration-time profile of telavancin when adjusted body weight (ABW) was included as a predictive covariate. Fixed doses of 750 mg and 1,000 mg had similar target attainment probabilities for efficacy as doses of 10 mg/kg of body weight based on ABW and TBW, respectively. However, the probability of achieving a target area under the concentration-time curve from time zero to 24 h of ≥763 mg · h/liter in association with acute kidney injury was highest (19.7%) with TBW-simulated dosing and lowest (0.4%) at the 750-mg dose. These results suggest that a fixed dose of 750 mg is a safe and effective alternative to telavancin doses based on TBW or ABW for the treatment of obese patients with normal renal function and Staphylococcus aureus infections. (This study has been registered at ClinicalTrials.gov under identifier NCT02753855.)

Bronchoalveolar lavage (BAL) and microdialysis have become the most reliable and relevant methods for measuring lung concentrations of antibiotics, with the majority of BAL studies involving either healthy adult subjects or patients undergoing diagnostic bronchoscopy. Emphasis on the amount of drug that reaches the site of infection is increasingly recognized as necessary to determine whether a dose selection will translate to good clinical outcomes in the treatment of patients with pneumonia. Observed concentrations and/or parameters of exposure (e.g. area-under-the-curve) need to be incorporated with pharmacokinetic-pharmacodynamic indices so that rational dose selection can be identified for specific pathogens and types of pneumonic infection (community-acquired vs hospital-acquired bacterial pneumonia, including ventilator-associated bacterial pneumonia). Although having measured plasma or lung concentration-time data from critically ill patients to incorporate into pharmacokinetic-pharmacodynamic models is very unlikely during drug development, it is essential that altered distribution, augmented renal clearance, and renal or hepatic dysfunction should be considered. Notably, the number of published studies involving microdialysis and intrapulmonary penetration of antibiotics has been limited and mainly involve beta-lactam agents, levofloxacin, and fosfomycin. Opportunities to measure in high-resolution effect site spatial pharmacokinetics (e.g. with MALDI-MSI or PET imaging) and in vivo continuous drug concentrations (e.g. with aptamer-based probes) now exist. Going forward these studies could be incorporated into antibiotic development programs for pneumonia in order to further increase the probability of candidate success.

The pharmacokinetics, safety, and tolerability of intravenous (i.v.) fosfomycin disodium (ZTI-01) and oral fosfomycin tromethamine were evaluated after a single dose in 28 healthy adult subjects. Subjects received a single 1-h i.v. infusion of 1 g and 8 g fosfomycin disodium and a single dose of 3 g oral fosfomycin tromethamine in a phase I, randomized, open-label, three-period crossover study. Serial blood and urine samples were collected before and up to 48 h after dosing. The mean pharmacokinetic parameters ± standard deviations of fosfomycin in plasma after 1 g and 8 g i.v., respectively, were the following: maximum clearance of drug in serum ( C max ), 44.3 ± 7.6 and 370 ± 61.9 μg/ml; time to maximum concentration of drug in serum ( T max ), 1.1 ± 0.05 and 1.08 ± 0.01 h; volume of distribution ( V ), 29.7 ± 5.7 and 31.5 ± 10.4 liters; clearance (CL), 8.7 ± 1.7 and 7.8 ± 1.4 liters/h; renal clearance (CL R ), 6.6 ± 1.9 and 6.3 ± 1.6 liters/h; area under the concentration-time curve from 0 to infinity (AUC 0–∞ ), 120 ± 28.5 and 1,060 ± 192 μg·h/ml; and half-life ( t 1/2 ), 2.4 ± 0.4 and 2.8 ± 0.6 h. After oral administration, the parameters were the following: C max , 26.8 ± 6.4 μg/ml; T max , 2.25 ± 0.4 h; V /F, 204 ± 70.7 liters; CL/F, 17 ± 4.7 liters/h; CL R , 6.5 ± 1.8 liters/h; AUC 0–∞ , 191 ± 57.6 μg · h/ml; and t 1/2 , 9.04 ± 4.5 h. The percent relative bioavailability of orally administered fosfomycin was 52.8% in relation to the 1-g i.v. dose. Approximately 74% and 80% of the 1-g and 8-g i.v. doses were excreted unchanged in the urine by 48 h compared to 37% after oral administration, with the majority of this excretion occurring by 12 h regardless of dosage form. No new safety concerns were identified during this study. The results of this study support further investigation of i.v. fosfomycin in the target patient population, including patients with complicated urinary tract infections and pyelonephritis.

The nafithromycin concentrations in the plasma, epithelial lining fluid (ELF), and alveolar macrophages (AM) of 37 healthy adult subjects were measured following repeated dosing of oral nafithromycin at 800 mg once daily for 3 days. The values of noncompartmental pharmacokinetic (PK) parameters were determined from serial plasma samples collected over a 24-h interval following the first and third oral doses. Each subject underwent one standardized bronchoscopy with bronchoalveolar lavage (BAL) at 3, 6, 9, 12, 24, or 48 h after the third dose of nafithromycin. The mean ± standard deviation values of the plasma PK parameters after the first and third doses included maximum plasma concentrations ( C max ) of 1.02 ± 0.31 μg/ml and 1.39 ± 0.36 μg/ml, respectively; times to C max of 3.97 ± 1.30 h and 3.69 ± 1.28 h, respectively; clearances of 67.3 ± 21.3 liters/h and 52.4 ± 18.5 liters/h, respectively, and elimination half-lives of 7.7 ± 1.1 h and 9.1 ± 1.7 h, respectively. The values of the area under the plasma concentration-time curve (AUC) from time zero to 24 h postdosing (AUC 0–24 ) for nafithromycin based on the mean or median total plasma concentrations at BAL fluid sampling times were 16.2 μg · h/ml. For ELF, the respective AUC 0–24 values based on the mean and median concentrations were 224.1 and 176.3 μg · h/ml, whereas for AM, the respective AUC 0–24 values were 8,538 and 5,894 μg · h/ml. Penetration ratios based on ELF and total plasma AUC 0–24 values based on the mean and median concentrations were 13.8 and 10.9, respectively, whereas the ratios of the AM to total plasma concentrations based on the mean and median concentrations were 527 and 364, respectively. The sustained ELF and AM concentrations for 48 h after the third dose suggest that nafithromycin has the potential to be a useful agent for the treatment of lower respiratory tract infections. (This study has been registered at ClinicalTrials.gov under registration no. NCT02453529.)

The steady-state concentrations of omadacycline and tigecycline in the plasma, epithelial lining fluid (ELF), and alveolar cells (AC) of 58 healthy adult subjects were obtained. Subjects were administered either omadacycline at 100 mg intravenously (i.v.) every 12 h for two doses followed by 100 mg i.v. every 24 h for three doses or tigecycline at an initial dose of 100 mg i.v. followed by 50 mg i.v. every 12 h for six doses. A bronchoscopy and bronchoalveolar lavage were performed once in each subject following the start of the fifth dose of omadacycline at 0.5, 1, 2, 4, 8, 12, or 24 h and after the start of the seventh dose of tigecycline at 2, 4, 6, or 12 h. The value of the area under the concentration-time curve (AUC) from time zero to 24 h postdosing (AUC 0–24 ) (based on mean concentrations) in ELF and the ratio of the ELF to total plasma omadacycline concentration based on AUC 0–24 values were 17.23 mg · h/liter and 1.47, respectively. The AUC 0–24 value in AC was 302.46 mg · h/liter, and the ratio of the AC to total plasma omadacycline concentration was 25.8. In comparison, the values of the AUC from time zero to 12 h postdosing (AUC 0–12 ) based on the mean concentrations of tigecycline in ELF and AC were 3.16 and 38.50 mg · h/liter, respectively. The ratio of the ELF and AC to total plasma concentrations of tigecycline based on AUC 0–12 values were 1.71 and 20.8, respectively. The pharmacokinetic advantages of higher and sustained concentrations of omadacycline compared to those of tigecycline in plasma, ELF, and AC suggest that omadacycline is a promising antibacterial agent for the treatment of lower respiratory tract bacterial infections caused by susceptible pathogens.

Ceftazidime-avibactam administered at 1.25 g every 8 h was used to treat multidrug-resistant Pseudomonas aeruginosa bacteremia in a critically ill patient on continuous venovenous hemofiltration (CVVH). Prefiltration plasma drug concentrations of ceftazidime and avibactam were measured at 0, 1, 2, 4, 6, and 8 h along with postfiltration and ultrafiltrate concentrations at h 2 and h 6. Plasma pharmacokinetic parameters of ceftazidime and avibactam, respectively, were as follows: maximum plasma concentration ( C max ), 61.10 and 14.54 mg/liter; minimum plasma concentration ( C min ), 31.96 and 8.45 mg/liter; half-life ( t 1/2 ), 6.07 and 6.78 h; apparent volume of distribution at the steady state ( V ss ), 27.23 and 30.81 liters; total clearance at the steady state (CL ss ), 2.87 and 2.95 liters/h; area under the concentration-time curve from 0 to 8 h (AUC 0–8 ), 347.87 and 85.69 mg · h/liter. Concentrations of ceftazidime in plasma exceeded the ceftazidime-avibactam MIC (6 mg/liter) throughout the 8-h dosing interval. Mean CVVH extraction ratios for ceftazidime and avibactam were 14.44% and 11.53%, respectively, and mean sieving coefficients were 0.96 and 0.93, respectively. The calculated mean clearance of ceftazidime by CVVH was 1.64 liters/h and for avibactam was 1.59 liters/h, representing 57.1% of the total clearance of ceftazidime and 54.3% of the total clearance of avibactam. Further data that include multiple patients and dialysis modes are needed to verify the optimal ceftazidime-avibactam dosing strategy during critical illness and CVVH.

Ceftaroline fosamil is a 5th generation cephalosporin with an in vitro spectrum of activity including Streptococcus agalactiae, penicillin- and cephalosporin-resistant S. pneumoniae, S. pyogenes, methicillin-susceptible S. aureus and methicillin-resistant S. aureus, Haemophilus influenzae, Klebsiella oxytoca, K. pneumoniae and Moraxella catarrhalis. It is currently approved by the FDA for the treatment of acute bacterial skin and skin structure infections (ABSSSI) and community-acquired bacterial pneumonia (CABP) in adults.This review covers the mechanism of action; bacterial resistance; pharmacokinetic characteristics in various patient populations; pharmacodynamic data in animal and in vitro models as well as human studies; efficacy observed in clinical trials for ABSSSI and CABP; and adverse effects.Ceftaroline provides in vitro bactericidal activity against methicillin-, vancomycin-, daptomycin-, and linezolid-resistant Gram-positive organisms and select Gram-negative pathogens. The pharmacodynamics of ceftaroline is similar to other β-lactam agents. Ceftaroline exhibits a favorable adverse effect profile and is generally well tolerated. There is little data on clinical success of ceftaroline in patients with bacteremia or endocarditis other than what has been published in a small series of case reports. Randomized-control studies are needed to establish clinical outcomes and safety in these patient populations.

Background Polymyxins are important antimicrobial agents for the treatment of infections due to carbapenem-resistant and other multidrug-resistant organisms. Recently, the CLSI and EUCAST have set breakpoints for colistin (EUCAST and CLSI) and polymyxin B (CLSI) with slight differences in recommendations. However, there are issues unique to the polymyxin class that warrant additional guidances. Herein, we assess data related to breakpoint setting and make additional recommendations for polymyxin AST interpretive criteria. Methods Data sources included longitudinal (2011–2017) US surveillance reference broth microdilution (BMD) MIC distributions (128,573 isolates) for colistin and polymyxin B (PB), published data on accuracy of various AST methodologies, in vivo pharmacokinetic/pharmacodynamic (PK-PD) models, prior polymyxin guidelines and agency package insert dosing recommendations, and population PK-PD and toxicodynamic (TD) data. Epidemiological cut-off, PK-PD (and TD), and clinical data were all considered for susceptible (S) breakpoint determinations. Results Data demonstrate that the most commonly utilized AST methodologies (disk diffusion, Etest, and automated MIC susceptibility panels), as well as agar dilution testing cannot reliably detect resistance; and BMD is the preferred AST. Importantly, colistin S is a reliable surrogate for PB S with cross-S accuracy at > 99% of isolates in each pathogen group. Breakpoint recommendations can be found in the Table with emphasis on applying combination therapy. Key recommendations include an S breakpoint of ≤2 mg/L for each pathogen (both colistin and PB). However, based on a lack of preclinical efficacy in murine pneumonia models, PK/PD concerns, and poor clinical outcome data, we strongly suggest that no breakpoints are applied for pneumonia and that alternative therapies should be used where available. Additionally, due to a lack of significant renal excretion, PB will also have no S breakpoint recommendation for lower urinary tract infections. Conclusion The polymyxins have compromising characteristics that make them suboptimal antimicrobials when used alone, and additional caveats are required for AST breakpoint interpretive criteria and stewardship programs. Disclosures All authors: No reported disclosures.

GSK1322322 is a potent peptide deformylase inhibitor with in vitro and in vivo activity against multidrug-resistant skin and respiratory pathogens. This report provides plasma and intrapulmonary pharmacokinetics, safety, and tolerability of GSK1322322 after repeat (twice daily intravenous dosing for 4 days) dosing at 1,500 mg. Plasma samples were collected over the last 12-hour dosing interval of repeat dosing following the day 4 morning dose (the last dose). Bronchoalveolar lavage samples were collected once in each subject, either before or at 2 or 6 h after the last intravenous dose. Plasma area under the concentration-time curve (AUC 0–τ ) was 66.7 μg · h/ml, and maximum concentration of drug in serum (C max ) was 25.4 μg/ml following repeat doses of intravenous GSK1322322. The time course of epithelial lining fluid (ELF) and alveolar macrophages (AM) mirrored the plasma concentration-time profile. The AUC 0–τ for ELF and AM were 78.9 μg · h/ml and 169 μg · h/ml, respectively. The AUC 0–τ ratios of ELF and AM to total plasma were 1.2 and 2.5, respectively. These ratios increased to 3.5 and 7.4, respectively, when unbound plasma was considered. These results are supportive of GSK1322322 as a potential antimicrobial agent for the treatment of lower respiratory tract bacterial infections caused by susceptible pathogens. (This study has been registered at ClinicalTrials.gov under registration number NCT01610388.)

Labetalol is frequently prescribed for the treatment of hypertension during pregnancy; however, the influence of pregnancy on labetalol pharmacokinetics is uncertain, with inconsistent findings reported by previous studies. This study examined the population pharmacokinetics of oral labetalol during and after pregnancy in women receiving labetalol for hypertension. Data were collected from 57 women receiving the drug for hypertension from the 12th week of pregnancy through 12 weeks postpartum using a prospective, longitudinal design. A sparse sampling strategy guided collection of plasma samples. Samples were assayed for labetalol by high-performance liquid chromatography. Estimation of population pharmacokinetic parameters and covariate effects was performed by nonlinear mixed effects modeling using NONMEM. The final population model was validated by bootstrap analysis and visual predictive check. Simulations were performed with the final model to evaluate the appropriate body weight to guide labetalol dosing. Lean body weight (LBW) and gestational age, i.e. weeks of pregnancy, were identified as significantly influencing oral clearance (CL/F) of labetalol, with CL/F ranging from 1.4-fold greater than postpartum values at 12 weeks’ gestational age to 1.6-fold greater at 40 weeks. Doses adjusted for LBW provide more consistent drug exposure than doses adjusted for total body weight. The apparent volumes of distribution for the central compartment and at steady-state were 1.9-fold higher during pregnancy. Gestational age and LBW impact the pharmacokinetics of labetalol during pregnancy and have clinical implications for adjusting labetalol doses in these women.

Purpose A national survey was conducted to evaluate the use of continuous and extended infusions for administering β-lactams and vancomycin. Methods The survey was sent to a random sample of 1000 acute care hospital pharmacists in the United States to evaluate the use of continuous and extended infusions of antibiotics. In addition, the same survey was sent to members of the Society of Infectious Diseases Pharmacists (SIDP) to assess the adoption of these infusion strategies. Results In the random-sample survey, 29 (11.2%) and 15 (5.8%) hospitals reported using continuous and extended infusions, respectively. Common rationales for adopting continuous and extended infusions were greater efficacy, equal or less toxicity, and cost savings. The SIDP survey revealed that 30 (50%) and 21 (35%) of responding pharmacists have initiated continuous and extended infusions, respectively. Common rationales for adopting continuous and extended infusions were greater efficacy, equal or less toxicity, and cost savings. Both surveys found that penicillins were the antibiotics most frequently administered as continuous and extended infusions. Conclusion The results of a survey sent to a random sample of hospital pharmacists and to SIDP members indicated that the majority did not use either continuous or extended infusions of antibiotics. SIDP survey respondents more frequently reported the use of both continuous and extended infusions than the respondents of the random-sample survey, and the percentage of time above the minimum inhibitory concentration was the most frequently assessed pharmacokinetic–pharmacodynamic parameter for both groups. Am J Health-Syst Pharm. 2012; 69:1895-904