Simplified Aztreonam Dosing in Patients with End-Stage Renal Disease: Results of a Monte Carlo Simulation.

The manufacturer-recommended aztreonam dosing for patients with creatinine clearance values of <10 ml/min/1.73 m2 is complex. It is not known whether simpler posthemodialysis dosing administered once daily or thrice weekly can reliably achieve pharmacodynamic goals. We found that 1 or 2 g administered once daily after hemodialysis had >90% probability of target attainment up to MICs of 4 or 8 mg/liter, respectively. Thrice-weekly dosing should generally be avoided, except in nonsevere infections with MICs of ≤0.5 mg/liter.

Effects of i.v. push administration on ß-lactam pharmacodynamics.

PURPOSE: The effects of i.v. push administration on the pharmacodynamic exposures of meropenem, cefepime, and aztreonam were evaluated. METHODS: Pharmacokinetic and pharmacodynamic analyses were conducted using previously published pharmacokinetic data for meropenem, cefepime, and aztreonam. The probability of target attainment (PTA) was assessed using Monte Carlo simulations for 30-minute and 5-minute infusions of approved dosing regimens and alternative dosing schemes often used in clinical practice, including 500 mg every 6 hours and 1 g every 8 hours for meropenem, 1 g every 6 hours and 2 g every 8 hours for cefepime, and 2 g every 8 hours for aztreonam. For each regimen examined, means and standard deviations for the percentage of the dosing interval that the free drug concentration remained above the minimum inhibitory concentration (MIC) were calculated and reported. RESULTS: No or only minor differences were noted between 30-minute and 5-minute infusions. The largest differences were observed at an MIC of 4 mg/L for meropenem and an MIC of 16 mg/L for aztreonam. At an MIC of 4 mg/L, meropenem 500 mg every 6 hours as a 30-minute infusion had an 8% greater PTA compared with the 5-minute infusion. At an MIC of 16 mg/L, a 30-minute infusion of aztreonam 2 g every 8 hours had a 12% greater PTA compared with the 5-minute infusion. CONCLUSION: Simulations of meropenem, cefepime, and aztreonam by i.v. push over 5 minutes indicated that there would be minimal or no effect on pharmacodynamic exposures compared with the effect when administered by 30-minute infusions.

Evaluation of Aztreonam Dosing Regimens in Patients With Normal and Impaired Renal Function: A Population Pharmacokinetic Modeling and Monte Carlo Simulation Analysis.

Aztreonam is a monocyclic ß-lactam antibiotic often used to treat infections caused by Enterobacteriaceae or Pseudomonas aeruginosa. Despite the long history of clinical use, population pharmacokinetic modeling of aztreonam in renally impaired patients is not yet available. The aims of this study were to assess the impact of renal impairment on aztreonam exposure and to evaluate dosing regimens for patients with renal impairment. A population model describing aztreonam pharmacokinetics following intravenous administration was developed using plasma concentrations from 42 healthy volunteers and renally impaired patients from 2 clinical studies. The final pharmacokinetic model was used to predict aztreonam plasma concentrations and evaluate the probability of pharmacodynamic target attainment (PTA) in patients with different levels of renal function. A 2-compartment model with first-order elimination adequately described aztreonam pharmacokinetics. The population mean estimates of aztreonam clearance, intercompartmental clearance, volume of distribution of the central compartment, and volume of distribution of the peripheral compartment were 4.93 L/h, 9.26 L/h, 7.43 L, and 6.44 L, respectively. Creatinine clearance and body weight were the most significant variables to explain patient variability in aztreonam clearance and volume of distribution, respectively. Simulations using the final pharmacokinetic model resulted in a clinical susceptibility break point of 4 and 8 mg/L, respectively, based on the clinical use of 1- and 2-g loading doses with the same or reduced maintenance dose every 8 hours for various renal deficiency patients. The population pharmacokinetic modeling and PTA estimation support adequate PTAs (>90% PTA) from the aztreonam label for dose adjustment of aztreonam in patients with moderate and severe renal impairment.

Continuous alternating inhaled antibiotics for chronic pseudomonal infection in cystic fibrosis.

BACKGROUND: Inhaled antibiotics are standard of care for treating chronic pseudomonal respiratory infections in cystic fibrosis patients, initially approved for intermittent administration. However, use of continuous inhaled antibiotic regimens of differing combinations is growing. METHODS: This double-blind trial compared continuous alternating therapy (CAT) to an intermittent treatment regimen. Subjects were treated with 3cycles of 28-days inhaled aztreonam (AZLI) or placebo 3-times daily alternating with 28-days open-label tobramycin inhalation solution (TIS). RESULTS: 90 subjects were randomized over 18months. Study enrollment was limited, in part because of evolving practices by clinicians of adopting a CAT regimen in clinical practice; consequently the study was underpowered. AZLI/TIS treatment reduced exacerbation rates by 25.7% (p=0.25; primary endpoint) and rates of respiratory hospitalizations by 35.8% compared with placebo/TIS (p=0.14). AZLI/TIS CAT therapy was well tolerated. CONCLUSIONS: This trial illustrates challenges with studying treatment regimens in a constantly evolving CF care environment. Nonetheless, the results of this trial indicate that AZLI/TIS CAT is well tolerated and may provide additional clinical benefit in CF patients compared with intermittent use of TIS alone. Clinicaltrials.gov: NCT01641822.

Inhaled aztreonam lysine versus inhaled tobramycin in cystic fibrosis. An economic evaluation.

RATIONALE: Pseudomonas aeruginosa infection is a significant cause of morbidity and mortality in patients with cystic fibrosis and is associated with a high economic burden. A recently published comparator trial demonstrated that outcomes in patients with cystic fibrosis with chronic P. aeruginosa infections switched from tobramycin solution for inhalation to aztreonam lysine for inhalation were better than those of patients who continued on tobramycin. OBJECTIVES: To compare overall costs of treatment of chronic inhaled tobramycin and aztreonam lysine in patient with cystic fibrosis who have chronic Pseudomonas infection, taking differences in outcomes into account. METHODS: A cost-effectiveness analysis with a 3-year time horizon was performed to simulate the economic consequences of either treatment from the perspective of a third party payer in the United States. We extrapolated results from the comparator trial and used data regarding clinical outcomes, quality of life, and costs from published literature and proprietary databases. A Markov structure was used to consider transitions between health states, defined principally by levels of percent predicted of FEV1. Extensive scenario and probabilistic sensitivity analyses were performed. MEASUREMENTS AND MAIN RESULTS: Use of aztreonam lysine for inhalation was associated with an average cost saving of $41,947 per patient over 3 years, as well as greater quality-adjusted life-years and total life-years. Scenario analyses demonstrated that these findings were robust to changes in key assumptions. CONCLUSIONS: It appears, with high likelihood, that the use of aztreonam solution for inhalation is associated with cost savings, an increase in quality-adjusted life-years, and improved clinical outcomes among patients with extensive prior use of tobramycin solution for inhalation who are naive to inhaled aztreonam lysine.

Inhaled aztreonam lysine: an evidence-based review.

INTRODUCTION: Chronic airway infection in cystic fibrosis (CF) is linked with progressive loss of pulmonary function and is the primary cause of mortality. Treatment regimens have generally focused on the use of chronic antibiotic therapy to target Pseudomonas aeruginosa (PA), a major pathogen associated with a decline in FEV1%. Specifically, inhaled antibiotic therapy provides high antibiotic sputum concentrations and decreases bacterial burden. AREAS COVERED: This article describes the pharmacology, pharmacodynamics/pharmacokinetics, clinical efficacy, microbiology and safety of aztreonam lysine (AZLI, Cayston), an inhaled antibiotic indicated for use in CF patients with PA. Articles were identified using MEDLINE (1966 - June 13, 2013) and EMBASE (1947 - June 13, 2013). Abstracts from the annual meeting (2011 - 2012) of the North American Cystic Fibrosis Conference were searched to identify additional publications. EXPERT OPINION: AZLI is an additional product that can be used in the management of CF and will likely play a major role in the suppression of PA. Clinical trials have demonstrated improvements in pulmonary function and patient reported symptoms. AZLI may therefore be used as an alternative to traditional inhaled antibiotics in patients with moderate-to-severe CF and PA colonization. Further investigation is warranted into use of AZLI in mild lung disease and for PA eradication.

Ceftaroline fosamil use in hospitalized patients with acute bacterial skin and skin structure infections: Budget impact analysis from a hospital perspective.

PURPOSE: The budgetary impact of adding ceftaroline fosamil to a hospital formulary for the treatment of acute bacterial skin and skin structure infections (ABSSSIs) was evaluated. METHODS: A three-year hospital budget impact model was constructed with three initial treatment options for ABSSSIs: ceftaroline fosamil, vancomycin plus aztreonam, and other vancomycin-containing regimens. The target population was hospitalized adult patients with an ABSSSI. Clinical cure rates with initial treatment were assumed to be similar to those from ceftaroline fosamil clinical trials. Patients who did not respond to initial treatment were assumed to be treated successfully with second-line antimicrobial therapy. Length of stay and cost per hospital day (by success or failure with initial treatment) were estimated based on a large database from more than 100 U.S. hospitals. Other model inputs included the annual number of ABSSSI admissions, projected annual case growth rate, proportion of ABSSSI target population receiving vancomycin-containing regimen, expected proportion of ABSSSI target population to be treated with ceftaroline fosamil, drug acquisition cost, cost of antibiotic administration, and cost of vancomycin monitoring. Sensitivity analysis using 95% confidence limits of clinical cure rates was also performed. RESULTS: The estimated total cost of care for treating a patient with an ABSSSI was $395 lower with ceftaroline fosamil ($15,087 versus $15,482) compared with vancomycin plus aztreonam and $72 lower ($15,087 versus $15,159) compared with other vancomycin-containing regimens. CONCLUSION: Model estimates indicated that adding ceftaroline fosamil to the hospital formulary would not have a negative effect on a hospital's budget for ABSSSI treatment.

Comparison of the pharmacokinetics and pharmacodynamic profile of carumonam in cystic fibrosis patients and healthy volunteers.

Our objectives were to compare the pharmacokinetics (PK) of carumonam, a monobactam, between cystic fibrosis (CF) patients and healthy volunteers and assess its pharmacodynamic profile. We studied 10 adult CF patients and 18 healthy volunteers of similar body size (dose: 2.166 g of carumonam as 15-min intravenous infusion). High performance liquid chromatography with ultraviolet detection (HPLC-UV) was used for drug analysis and NONMEM (ICON, Ellicot City, MD) for population PK and Monte Carlo simulation with targets between > or =20% and 100% free time above MIC (fT > MIC). Unscaled renal clearance was 24% higher in CF patients. Lean body mass and creatinine clearance explained the difference in average clearance and volume of distribution between both subject groups. For a daily dose of 6 g per 70 kg of total body weight, 15-min infusions q8h achieved robust (>90%) probabilities of target attainment (PTAs) (target, 60% fT > MIC) for MICs < or =3 mg/L in CF patients and < or =6 mg/L in healthy volunteers. At the same dose, 4-h infusions q8h achieved robust PTAs up to markedly higher MICs < or =8 to 12 mg/L in CF patients and < or =16 mg/L in healthy volunteers.

Outpatient treatment of febrile episodes in low-risk neutropenic patients with cancer.

BACKGROUND: Hospitalization and intravenous (IV) broad-spectrum antibiotics are the standard of care for all febrile neutropenic patients with cancer. Recent work suggests that a low-risk population exists who might benefit from an alternate approach. METHODS: A prospective randomized clinical trial was performed comparing oral ciprofloxacin 750 mg plus clindamycin 600 mg every 8 hours with IV aztreonam 2 g plus clindamycin 600 mg every 8 hours for the empiric outpatient treatment of febrile episodes in low-risk neutropenic patients with cancer. RESULTS: The oral regimen cured 35 of 40 episodes (88% response rate), whereas the IV regimen cured 41 of 43 episodes (95% response rate, P = 0.19). Although the cost of the oral regimen was significantly less than that of the IV regimen (P < 0.0001), it was associated with significant renal toxicity (P < 0.05), which led to early termination of the study. Overall, combining its safety and efficacy, the IV regimen was superior (P = 0.03). CONCLUSIONS: This prospective study suggested that outpatient antibiotic therapy for febrile episodes in low-risk neutropenic patients with cancer is safe and effective. Better oral regimens are needed.

Pathophysiology and management of postcesarean endomyometritis.

Endomyometritis is the most common complication associated with cesarean delivery. The incidence varies from 5 to 85%, depending upon the patient population surveyed. The major risk factors for postcesarean endomyometritis are young age, low socioeconomic status, and extended duration of labor and ruptured membranes. The principal microorganisms responsible for infection are group B streptococci, aerobic gram-negative bacilli, anaerobic gram-positive cocci, and anaerobic gram-negative bacilli. The mean incidence of bacteremia in patients with endomyometritis is 10%. Less than 2% of infected patients develop life-threatening complications such as septic shock, pelvic abscess, or septic pelvic thrombophlebitis. Antibiotics of proved value in treatment of postcesarean endomyometritis include the newer broad-spectrum cephalosporins and ureidopenicillins and the combination regimen of clindamycin plus aminoglycoside.