Evaluating biapenem dosage regimens in intensive care unit patients with Pseudomonas aeruginosa infections: a pharmacokinetic/pharmacodynamic analysis using Monte Carlo simulation.

This study was conducted to identify optimal dosage regimens and estimate pharmacokinetic/pharmacodynamic (PK/PD) characteristics of short-infusion (SI) versus extended-infusion (EI) biapenem against Pseudomonas aeruginosa infections in Chinese intensive care unit (ICU) patients. A total of 85 strains of P. aeruginosa were collected, and the minimum inhibitory concentration (MIC) of biapenem was measured by the serial two-fold agar dilution method. We designed four frequently used clinical regimens: biapenem 300 mg I.V. q12h, q8h, and q6h, and 600 mg q12h. The Monte Carlo Simulation (MCS) was performed using previously published pharmacokinetic data to calculate the probability of target attainment (PTA) and the cumulative fraction of response (CFR) of these regimens as an SI (0.5 h) and an EI (1 h, 2 h, 3 h, and 4 h). For a target of 40%fT>MIC (serum drug concentration remains above the MIC for a dosing period), none of the regimens achieved any CFRs>90% for P. aeruginosa, multidrug-resistant P. aeruginosa (MDR-PA) and even non-MDR-PA. The traditional biapenem SI regimens most commonly seen in clinical practice were insufficient in treating both MDR and non-MDR P. aeruginosa in ICU patients. However, biapenem 600 mg q12h over 2-4 h EI regimens could achieve CFR>90% with 20%fT>MIC. Clinical trials should aim to validate the potentially greater PK/PD index with higher, more frequent doses and longer extended infusions.

Antibiotic Dosing in Continuous Renal Replacement Therapy.

Appropriate antibiotic dosing is critical to improve outcomes in critically ill patients with sepsis. The addition of continuous renal replacement therapy makes achieving appropriate antibiotic dosing more difficult. The lack of continuous renal replacement therapy standardization results in treatment variability between patients and may influence whether appropriate antibiotic exposure is achieved. The aim of this study was to determine if continuous renal replacement therapy effluent flow rate impacts attaining appropriate antibiotic concentrations when conventional continuous renal replacement therapy antibiotic doses were used. This study used Monte Carlo simulations to evaluate the effect of effluent flow rate variance on pharmacodynamic target attainment for cefepime, ceftazidime, levofloxacin, meropenem, piperacillin, and tazobactam. Published demographic and pharmacokinetic parameters for each antibiotic were used to develop a pharmacokinetic model. Monte Carlo simulations of 5000 patients were evaluated for each antibiotic dosing regimen at the extremes of Kidney Disease: Improving Global Outcomes guidelines recommended effluent flow rates (20 and 35 mL/kg/h). The probability of target attainment was calculated using antibiotic-specific pharmacodynamic targets assessed over the first 72 hours of therapy. Most conventional published antibiotic dosing recommendations, except for levofloxacin, reach acceptable probability of target attainment rates when effluent rates of 20 or 35 mL/kg/h are used.

[The reliability of using impenem, meropenem, cefoperazone-sulbactam and piperacillin-tazobactam to treat nosocomial Gram-negative bacterial infections with Monte Carlo simulation].

Objective: To evaluate the reliability of using imipenem, meropenem, cefoperazone-sulbactam, piperacillin-tazobactam in the treatment of hospital-acquired Gram-negative bacterial infections with Monte Carlo simulation(MCS). Methods: The MIC of the four agents collected from hospital-acquired infections were detected in accordance with broth dilution method of Clinical and Laboratory Standard Institute (CLSI). MCS were conducted with MICs and the pharmacokinetics parameters of the four agents based on conventional dose regimens.The cumulative fraction of response (CFR) of time over MIC target attainment in different dosing regimen were generated. Results: A total of 2 541 strains, including 2 093 strains of Enterobacteriaceae and 448 strains of glucose non-fermentative bacilli were collected.The MIC(90) of imipenem and meropenem against Enterobacteriaceae were less than 1 mg/L in general, whereas MIC(90) of two agents with ß-lactamase inhibitors was around 64 mg/L.As to glucose non-fermenting bacteria, MICs of all the four agents were very high, especially to Acinetobacter baumannii, which indicated MIC(50) more than 32 mg/L.MCS revealed that carbapenems had significantly higher CFR than those with ß-lactamase inhibitors.Imipenem and meropenem (1 g, q8 h) obtained CFRs of 74.69% and 81.42%, respectively.The CFR of cefoperazone-sulbactam (2 g, q8 h) and piperacillin-tazobactam (4 g, q6 h) (both excluding ß-lactamase inhibitors) were just 49.59% and 27.66% respectively, which increased after excluding A. baumannii in piperacillin-tazobactam. Conclusions: The conventional dose regimens of imipenem and meropenem are reliable for the empiric therapy of Gram-negative hospital-acquired bacterial infections.Piperacillin-tazobactam is suggested to use with higher doses or prolonged infusion time to satisfy the time of drug concentration exceeded the MIC(T>MIC)requirement.More clinical studies of cefoperazone-sulbactam should be conducted to optimize its regimen and guarantee its efficacy.

Pharmacokinetic/Pharmacodynamic Analysis of Meropenem for the Treatment of Nosocomial Pneumonia in Intracerebral Hemorrhage Patients by Monte Carlo Simulation.

BACKGROUND: Nosocomial pneumonia (NP) is a frequent complication among patients with intracerebral hemorrhage (ICH). However, there are currently no pharmacokinetic (PK) and pharmacodynamic (PD) data to guide meropenem dosing in these patients. OBJECTIVE: To investigate the PK/PD properties of meropenem in these patients and whether the usual dosing regimens of meropenem (2-hour infusion, 1 g, every 8 hours) was suitable. METHODS: A total of 11 patients with a diagnosis of ICH complicated with NP were selected in the emergency internal medicine and treated with a 1-g/2-hours extended infusion model. The plasma concentrations of meropenem were determined by high-performance liquid chromatography. PK parameters were estimated by plasma concentration versus time profile using WinNonlin software. The probability of target attainments (PTAs) of meropenem at different minimum inhibitory concentrations (MICs) based on percentage time that concentrations were above the minimum inhibitory concentration (%T>MIC) value were performed by Monte Carlo simulation. RESULTS: The volume of distribution and total body clearance of meropenem were 55.55 L/kg and 22.89 L/h, respectively. Using 40%T>MIC, PTA was >90% at MICs ≤4 µg/mL. Using 80% or 100%T>MIC, PTA was >90% only at MICs ≤1 µg/mL. CONCLUSIONS: The PK/PD profile of dosing regimens tested will assist in selecting the appropriate meropenem regimens for these patients. At a target of 40%T>MIC, the usual dosing regimens can provide good coverage for pathogens with MICs of ≤4 µg/mL. However, when a higher target (80% or 100%) is desired for difficult-to-treat infections, larger doses, prolonged infusions, shorter intervals, and/or combination therapy may be required.

Management of ventilator associated pneumonia with a new antibiotic adjuvant entity (ceftriaxone+sulbactam+disodium edetate) - A novel approach to spare carbapenems.

BACKGROUND: Ventilator associated pneumonia (VAP) is one of the most serious nosocomial infections in Intensive Care Unit (ICU). The aim of this study was to evaluate a new approach to spare the carbapenems for the management of patients diagnosed with VAP due to Acinetobacter baumannii (A. baumannii). METHOD: This retrospective study was conducted on VAP patients presenting for treatment at tertiary care centre between May 2014 and March 2016. The case sheets of patients who have been treated for VAP with meropenem, antibiotic adjuvant entity (AAE) and colistin were analysed. RESULTS: Out of 113 patients analysed, 24 (21.3%) patients were having VAP due to MDR A. baumannii. Microbial sensitivity has shown that 87.5% of patients were sensitive to AAE and colistin whereas all of them were resistant to meropenem, imipenem and gentamycin. The mean treatment durations were 12.4±2.1, 13.2±2.4 and 14.3±2.1days for AAE, meropenem+colistin and AAE+colistin treatment groups. In AAE susceptible patients, the mean treatment duration and cost could be reduced by 23-24% and 43-53% if AAE is used empirically. In AAE-resistant patients, the mean treatment duration and cost could be reduced by 21% and 26% if AAE+colistin regime is used empirically instead of meropenem followed by AAE+colistin. CONCLUSIONS: Clinical assessment with microbial eradication and pharmaco-economic evaluation clearly shows benefits in using AAE empirically in the management of A. baumannii infected VAP cases.

Population pharmacokinetics of meropenem in elderly patients: dosing simulations based on renal function.

OBJECTIVES: The aim of this study was to evaluate different dosage regimens of meropenem in elderly patients in relation with renal function using a population pharmacokinetic (popPK) model. METHODS: The data of 178 elderly patients treated with meropenem was collected from different sources. A popPK model was developed by using NONMEM® and the influence of different covariates on meropenem CL and V1 was observed. Monte Carlo dosing simulations were performed at steady state to observe the % T > MIC for targets of 40, 60 and 80% of dosage intervals at different levels of creatinine clearance (CLCR). RESULTS: The data was described by a two-compartment model and the values of parameter estimates for CL, V1, Q and V2 were 5.27 L/h, 17.2 L, 9.92 L/h and 10.6 L, respectively. The CLCR, body weight and centre had a significant influence on meropenem CL while no direct influence of age was observed. Extended infusions had pharmacokinetic and pharmacodynamic (PK/PD) breakpoint one dilution greater than corresponding short infusion regimens for each target of % T > MIC. CONCLUSION: Meropenem CL was significantly lower in the elderly compared to CL reported in younger patients due to the reduced renal function. An extended infusion of 1000 mg q8h can be considered for empirical treatment of infections in elderly patients when CLCR is ≤ 50 mL/min. A continuous infusion of 3000 mg daily dose is preferred if CLCR > 50 mL/min. However, a higher daily dose of meropenem would be required for resistant strains (MIC >8 mg/L) of bacteria if CLCR is >100 mL/min.

Population Pharmacokinetics and Pharmacodynamics of Meropenem in Nonobese, Obese, and Morbidly Obese Patients.

The study objective was to evaluate meropenem population pharmacokinetics and pharmacodynamics in nonobese, obese, and morbidly obese patients. Forty adult patients-11 nonobese (body mass index [BMI] < 30 kg/m2 ), 9 obese (30 kg/m2 ≤ BMI < 40 kg/m2 ), and 20 morbidly obese (BMI ≥ 40 kg/m2 )-received meropenem 500 mg every 6 hours (q6h), q8h, or q12h or 1 g q6h or q8h, infused over 0.5 hour. Population pharmacokinetic modeling was performed using NONMEM, and 5000-patient Monte-Carlo simulations were performed to calculate probability of target attainment (PTA) for 5 dosing regimens, infused over 0.5 and 3 hours, using fT>MIC of 40%, 54%, and 100% of the dosing interval. A 2-compartment linear-elimination model best described the serum concentration-time data, and creatinine clearance was significantly associated with systemic clearance. Pharmacokinetic parameters were not significantly different among patient groups. In patients with creatinine clearances ≥50 mL/min, all simulated dosing regimens achieved >90% PTA at 40% fT>MIC in all patient groups at MICs ≤2 mg/L. Only 500 mg q8h, infused over 0.5 hour, did not achieve >90% PTA at 54% fT>MIC in nonobese and morbidly obese patients. At 100% fT>MIC, 1 g q6h and 2 g q8h, infused over 3 hours, reliably achieved >90% PTA in all patient groups. Meropenem pharmacokinetics are comparable among nonobese, obese, and morbidly obese patients. Standard dosing regimens provide adequate pharmacodynamic exposures for susceptible pathogens at 40% and 54% fT>MIC, but prolonged infusions of larger doses are needed for adequate exposures at 100% fT>MIC. Dosage adjustments based solely on body weight are unnecessary.

Optimising meropenem dosing in critically ill Australian Indigenous patients with severe sepsis.

Currently there are no pharmacokinetic (PK) data to guide antibiotic dosing in critically ill Australian Indigenous patients with severe sepsis. This study aimed to determine whether the population pharmacokinetics of meropenem were different between critically ill Australian Indigenous and critically ill Caucasian patients. Serial plasma and urine samples as well as clinical and demographic data were collected over two dosing intervals from critically ill Australian Indigenous patients. Plasma meropenem concentrations were assayed by validated chromatography. Concentration-time data were analysed with data from a previous PK study in critically ill Caucasian patients using Pmetrics. The population PK model was subsequently used for Monte Carlo dosing simulations to describe optimal doses for these patients. Six Indigenous and five Caucasian subjects were included. A two-compartment model described the data adequately, with meropenem clearance and volume of distribution of the central compartment described by creatinine clearance (CLCr) and patient weight, respectively. Patient ethnicity was not supported as a covariate in the final model. Significant differences were observed for meropenem clearance between the Indigenous and Caucasian groups [median 11.0 (range 3.0-14.1) L/h vs. 17.4 (4.3-30.3) L/h, respectively; P <0.01]. Standard dosing regimens (1 g intravenous every 8 h as a 30-min infusion) consistently achieved target exposures at the minimum inhibitory concentration breakpoint in the absence of augmented renal clearance. No significant interethnic differences in meropenem pharmacokinetics between the Indigenous and Caucasian groups were detected and CLCr was found to be the strongest determinant of appropriate dosing regimens.

Impact of piperacillin-tazobactam shortage on meropenem use: implications for antimicrobial stewardship programs.

Drug shortages pose a clear detriment to antimicrobial stewardship (AS) efforts. Our objective was to evaluate the effect of a piperacillin-tazobactam shortage on meropenem use, related costs, and associated changes in AS activity. A quasi-experimental quality improvement review compared adult patients receiving meropenem ≥72h three months pre-shortage and three months during the shortage. 320 patients were included (pre-shortage: 103; shortage: 217). Baseline characteristics were similar, but the length of stay was slightly longer in pre-shortage [19 (11-32) days] versus shortage [16 (11-32) days] (p=0.094). In pre-shortage and shortage, median days of therapy and estimated meropenem cost were 7 (5-11) and 7 (5-10) and $309.93 ($173.60-$507.03) and $255.30 ($204.24-$424.31), respectively (p=0.411 and p=0.050). Frequency of ID consultation was similar (16.8% in pre- and 25.3% in shortage, p=0.091). AS interventions increased during the shortage period (99 in pre-shortage and 205 in shortage). De-escalation occurred in 19.4% versus 32.7% of the patients in pre-shortage and shortage (p=0.014). The piperacillin-tazobactam shortage was associated with a 111% increase in meropenem prescriptions despite active AS, but was not associated with changes in mortality, length of therapy, or meropenem costs. AS should be aware that shortages may require proactive countermeasures to avoid inappropriate antimicrobial use during shortage periods.

A Nonparametric Pharmacokinetic Approach to Determine the Optimal Dosing Regimen for 30-Minute and 3-Hour Meropenem Infusions in Critically Ill Patients.

BACKGROUND: Pharmacokinetics of meropenem differ widely in the critically ill population. It is imperative to maintain meropenem concentrations above the inhibitory concentrations for most of the interdose interval. A population pharmacokinetic/pharmacodynamic model was developed to determine the probability of target attainment for 3-hour and 30-minute infusion regimens in this population. METHODS: This study was performed in an intensive care setting among adult patients who were initiated on meropenem at a dose of 1000 mg. Multiple blood specimens were collected at predetermined time points during the interdose period, and meropenem concentrations were measured using high performance liquid chromatography. Using Pmetrics, a pharmacokinetic/pharmacodynamic model was developed and validated. Monte Carlo simulation was performed, and probability of target attainment (100% T > minimum inhibitory concentration (MIC), with a probability >0.9) for doubling MICs was determined for different regimens of meropenem. RESULTS: A 2-compartment multiplicative gamma error model best described the population parameters from 34 patients. The pharmacokinetic parameters used in the final model were Ke (elimination rate constant from the central compartment), Vc (volume of distribution of central compartment), KCP and KPC (intercompartmental rate constants), and IC2 (the fitted amount of meropenem in the peripheral compartment). Inclusion of creatinine clearance (CLcreat) and body weight as covariates improved the model prediction (Ke = Ke0 × (Equation is included in full-text article.), Vc = Vc0 × Weight). The Ke and Vc [geometric mean (range)] of the individuals were 0.54 (0.01-2.61)/h and 9.36 (4.35-21.62) L, respectively. The probability of attaining the target, T > MIC of 100%, was higher for 3-hour infusion regimens compared with 30-minute infusion regimens for all ranges of CLcreat. CONCLUSIONS: This study emphasizes that extended regimens of meropenem are preferable for treating infections caused by bacteria with higher MICs. The nonparametric analysis using body weight and CLcreat as covariate adequately predicted the pharmacokinetics of meropenem in critically ill patients with a wide range of renal function.

Meropenem dosing requirements against Enterobacteriaceae in critically ill patients: influence of renal function, geographical area and presence of extended-spectrum ß-lactamases.

The aim of this study was the evaluation of the influence of the susceptibility patterns of Escherichia coli and Klebsiella pneumoniae isolates, specifically the presence of extended-spectrum ß-lactamases and the geographical area (Europe and USA), on the meropenem dosing requirements in critically ill patients with different degrees of renal function by estimation of the probability of pharmacokinetic/pharmacodynamic (PK/PD) target attainment. Additionally, estimation of the PK/PD breakpoints according to the European Committee on Antimicrobial Susceptibility Testing (EUCAST) approach was also an objective. Six dosing regimens were evaluated: 0.5 g, 1 g and 2 g every 8 h given as 0.5-h or 3-h infusions. Pharmacokinetic data were obtained from the literature, and susceptibility data to meropenem for E. coli and K. pneumoniae were collected from the Tigecycline Evaluation and Surveillance Trial (T.E.S.T.) surveillance study. For the same dose level, the 3-h infusion provided a probability of target attainment (PTA) ≥90 % for minimum inhibitory concentration (MIC) values up to two-fold dilution higher than those obtained with the 0.5-h infusion. For E. coli, the cumulative fraction of response (CFR) was 100 % in most cases, and neither the dose nor the infusion length nor the geographical area significantly affected the probability to reach the target. With regards to K. pneumoniae, the CFR increased when increasing the dose and decreasing the creatinine clearance (CLCR). The CFR for Spanish and USA strains was higher than that calculated for European strains. Meropenem PK/PD breakpoints are dependent on the dose, infusion length and CLCR, ranging from 2 to 32 mg/L. Based on our results, meropenem administered as a extended infusion is the best option to treat infections due to E. coli and K. pneumoniae.

Population pharmacokinetics of meropenem administered as a prolonged infusion in children with cystic fibrosis.

OBJECTIVES: Meropenem is frequently used to treat pulmonary exacerbations in children with cystic fibrosis (CF) in the USA. Prolonged-infusion meropenem improves the time that free drug concentrations remain above the MIC (fT> MIC) in adults, but data in CF children are sparse. We describe the population pharmacokinetics, tolerability and treatment burden of prolonged-infusion meropenem in CF children. METHODS: Thirty children aged 6-17 years with a pulmonary exacerbation received 40 mg/kg meropenem every 8 h; each dose was administered as a 3 h infusion. Pharmacokinetics were determined using population methods in Pmetrics. Monte Carlo simulation was employed to compare 0.5 with 3 h infusions to estimate the probability of pharmacodynamic target attainment (PTA) at 40% fT> MIC. NCT#01429259. RESULTS: A two-compartment model fitted the data best with clearance and volume predicted by body weight. Clearance and volume of the central compartment were 0.41 ±â€Š0.23 L/h/kg and 0.30 ±â€Š0.17 L/kg, respectively. Half-life was 1.11 ±â€Š0.38 h. At MICs of 1, 2 and 4 mg/L, PTAs for the 0.5 h infusion were 87.6%, 70.1% and 35.4%, respectively. The prolonged infusion increased PTAs to >99% for these MICs and achieved 82.8% at 8 mg/L. Of the 30 children, 18 (60%) completed treatment with prolonged infusion; 5 did so at home without any reported burden. Nine patients were changed to a 0.5 h infusion when discharged home. CONCLUSIONS: In these CF children, meropenem clearance was greater compared with published values from non-CF children. Prolonged infusion provided an exposure benefit against pathogens with MICs ≥1 mg/L, was well tolerated and was feasible to administer in the hospital and home settings, the latter depending on perception and family schedule.

Development and Assessment of a Nomogram to Propose the Initial Dosage Regimen of a Meropenem Infusion Based on Serum Creatinine and Age Using a Monte Carlo Simulation.

A conventional nomogram, based on serum creatinine (sCr) and age, was developed in order to determine the correct initial dosage regimen for meropenem (MEPM) infusions in elderly patients with severe community-acquired pneumonia (CAP), using a target minimum inhibitory concentration (MIC) of 2 mg/L. A correlation between age and actual bodyweight (BW) in a development cohort of 44 males and 45 females was performed by linear regression using the least-squares method (male: y=-0.4676x+80.281, R(2)=0.4888; female: y=-0.4373x+77.502, R(2)=0.3194). There were no significant differences between actual BW and the BW (e-BW) estimated using this equation in this cohort (male: e-BW 41.6±3.1 kg, BW 41.7±3.5 kg, p=0.93; female: e-BW 39.5±2.1 kg, BW 39.5±3.7 kg, p=0.20). By integrating these equations using the Monte Carlo simulation method, a dosage regime was calculated which would have an 80% probability of maintaining plasma drug levels above the MIC for more than 40% of the time (>40%TAM), using only the age and sCr of individual patients. This relationship was summarized as a nomogram. The nomogram was validated using an independent validation cohort (n=28) of patients. An optimized dosage regimen could be predicted in 84 patients (94.4%) in the development cohort and 25 patients (89.3%) in the validation cohort. This nomogram may be a useful tool for clinicians and pharmacists in determining an initial MEPM regimen in elderly patients with severe CAP, based only on age and sCr.

Evaluation of a pharmacokineticpharmacodynamic approach using software to optimize the carbapenem antibiotic regimen.

OBJECTIVE: Meropenem (MEPM) and doripenem (DRPM), whose antipseudomonal activity is more potent than that of other carbapenem antimicrobials, were used in the study. Monte Carlo simulation of drug concentrations was performed to develop an administration plan for MEPM and DRPM that takes into account the pharmacokinetics (PK)-pharmacodynamics (PD) of MEPM and DRPM and the renal function of each patient. Drug administration plans were proactively applied to patients with pneumonia to determine the usefulness of the method by assessing treatment efficacy and safety. METHODS: Patients with healthcareassociated pneumonia and an indication for MEPM or DRPM chemotherapy underwent drug administration in accordance with the MEPM and DRPM treatment plan developed by the PK-PD software applications. The primary efficacy endpoints were the clinical and bacteriological efficacy of the drugs agains pneumonia. The safety of the antimicrobials was assessed based on abnormal laboratory findings and the seizure disorders in accordance with the criteria for safety evaluation of antimicrobial agents. RESULTS: This study examined 12 and 11 patients in the MEPM and DRPM group, respectively; however, 3 DRPM patients were excluded due to the administration of anti-methicillin-resistant Staphylococcus aureus drugs after the initiation of DRPM treatment. MEPM and DRPM drug administration was determined to be safe and effective in all patients. CONCLUSIONS: The present results suggest that the Monte Carlo simulation-based PK-PD software is an effective tool for planning individualized antimicrobial chemotherapy with carbapenem in accordance with the PK-PD theory of antimicrobials. It is also possible to propose safe and effective drug administration plans for patients with healthcare-associated pneumonia.

Dosing regimen of meropenem for adults with severe burns: a population pharmacokinetic study with Monte Carlo simulations.

OBJECTIVES: To develop a population model to describe the pharmacokinetics (PK) of intravenous meropenem in adult patients with severe burns and investigate potential relationships between dosage regimens and antimicrobial efficacy. PATIENTS AND METHODS: A dose of 1 g every 8 h was administered to adult patients with total body surface area burns of ≥15%. Doses for subsequent courses were determined using results from the initial course and the patient's clinical condition. Five plasma meropenem concentrations were typically measured over the dosage interval on one to four occasions. An open, two-compartment PK model was fitted to the meropenem concentrations using NONMEM and the effect of covariates on meropenem PK was investigated. Monte Carlo simulations investigated dosage regimens to achieve a target T>MIC for ≥40%, ≥60% or ≥80% of the dose interval. RESULTS: Data comprised 113 meropenem concentration measurements from 20 dosage intervals in 12 patients. The parameters were CL (L/h) = 0.196 L/h/kg × [1 - 0.023 × (age - 46)] × [1 - 0.049 × (albumin - 15)], V1 = 0.273 L/kg × [1 - 0.049 × (albumin - 15)], Q = 0.199 L/h/kg and V2 = 0.309 L/kg × [1 - 0.049 × (albumin - 15)]. For a target of ≥80% T>MIC, the breakpoint was 8 mg/L for doses of 1 g every 4 h and 2 g every 8 h given over 3 h, but only 4 mg/L if given over 5 min. CONCLUSIONS: Although 1 g 8 hourly should be effective against Escherichia coli and CoNS, higher doses, ideally with a longer infusion time, would be more appropriate for empirical therapy, mixed infections and bacteria with MIC values ≥4 mg/L.

Steady-state pharmacokinetics and pharmacodynamics of meropenem in morbidly obese patients hospitalized in an intensive care unit.

The study objective was to evaluate meropenem pharmacokinetics and pharmacodynamics in morbid obesity. Nine patients hospitalized in an intensive care unit with a body mass index ≥40 kg/m(2) received meropenem 500 mg or 1 g q6h, infused over 0.5 hours. Pharmacokinetic parameters were estimated, and Monte Carlo simulations were performed for 5 dosing regimens (500 mg q8h, 1 g q8h, 2 g q8h, 500 mg q6h, 1 g q6h) infused over 0.5 and 3 hours. Probability of target attainment (PTA) was calculated using fT > MIC of 40% and 54%. Total body weight and body mass index were 152.3 ± 31.0 kg and 54.7 ± 8.6 kg/m(2) , respectively. Volume of distribution of the central compartment was 13.3 ± 6.7 L, volume of distribution at steady-state was 37.4 ± 14.7 L, and systemic clearance was 10.2 ± 5.0 L/h. At an MIC of 2 µg/mL, PTA was ≥90% for 4/5 and 2/5 regimens infused over 0.5 hours and for 5/5 and 4/5 regimens infused over 3 hours at 40% and 54% fT > MIC, respectively. Standard doses achieve adequate exposures for susceptible bacteria at a pharmacodynamic target of 40% fT > MIC. Higher doses or prolonged infusion regimens are needed at the higher pharmacodynamic target.

The combined effects of extracorporeal membrane oxygenation and renal replacement therapy on meropenem pharmacokinetics: a matched cohort study.

INTRODUCTION: The scope of extracorporeal membrane oxygenation (ECMO) is expanding; however, optimal drug prescription during ECMO remains a developing science. Currently, there are no clear guidelines for antibiotic dosing during ECMO. This open-label, descriptive, matched-cohort pharmacokinetics (PK) study aimed to compare the PK of meropenem in ECMO patients to critically ill patients with sepsis not receiving ECMO (controls). METHODS: Eleven adult patients on ECMO (venovenous (VV) ECMO, n = 6; venoarterial (VA) ECMO, n = 5) receiving intravenous (IV) meropenem were included. Meropenem plasma concentrations were determined using validated chromatography. Population PK analysis was performed using non-linear mixed effects modelling. This data was compared with previously published meropenem PK data from 10 critically ill adult patients not on ECMO (preserved renal function (n = 5) or receiving renal replacement therapy (RRT) (n = 5). Using these data, we then performed Monte Carlo simulations (n = 1,000) to describe the effect of creatinine clearance on meropenem plasma concentrations. RESULTS: In total, five (two VV, three VA) out of eleven ECMO patients received RRT. The other six patients (four VV, two VA) had no significant impairment in renal function. A two-compartment model adequately described the data. ECMO patients had numerically higher volume of distribution (0.45 ± 0.17 versus 0.41 ± 0.13 L/kg, P = 0.21) and lower clearance compared to controls (7.9 ± 5.9 versus 11.7 ± 6.5 L/h, P = 0.18). Variability in meropenem clearance was correlated with creatinine clearance or the presence of RRT. The observed median trough concentrations in the controls were 4.2 (0.0 to 5.7) mg/L. In ECMO patients, while trough meropenem concentrations >2 mg/L were achieved in all patients, a more aggressive target of >8 mg/L for less susceptible microorganisms was observed in only eight out of eleven patients, with five of them being on RRT. CONCLUSIONS: ECMO patients exhibit high PK variability. Decreased meropenem CL on ECMO appears to compensate for ECMO and critical illness-related increases in volume of distribution. Routine target concentrations >2 mg/L are maintained with standard dosing (1 g IV 8-hourly). However, an increase in dose may be necessary when targeting higher concentrations or in patients with elevated creatinine clearance.

Pharmacodynamics of meropenem in critically ill patients with ventilator-associated pneumonia.

BACKGROUND: Pharmacokinetic changes have been found in critically ill patients, including ventilator-associated pneumonia (VAP) when compared with healthy volunteers leading to fluctuation of plasma concentrations. OBJECTIVE: To compare the probability of target attainment (PTA) and cumulative fraction of response (CFR) for meropenem between administration by a bolus injection and a 3-hour infusion. MATERIAL AND METHOD: The study was a randomized three-way crossover in nine patients with VAP. Each patient received meropenem in three regimens consecutively: (i) a bolus injection of 1 g every eight hours (q8h) for 24 hours; (ii) a 3-hour infusion of 1 g q8h for 24 hours; and (iii) a 3-hour infusion of 2 g q8h for 24 hours. The pharmacodynamic analysis of meropenem was performed to determine the PTA by using the Monte Carlo simulation and the study used susceptibility patterns obtained from EUCAST and MYSTIC for assessment of CFR. RESULTS: For an MIC of 4 microg/ml, the PTAs achieving 40% T > MIC following a bolus injection of 1 g q8h, a 3-hour infusion of 1 g q8h, and a 3-hour infusion of 2 g q8h were 87.71%, 98.80%, and 99.90%, respectively. Only the 3-hour infusion regimens were predicted to achieve a CFR > or = 90% against E. coli, Klebsiella spp., P. aeruginosa, and Acinetobacter spp. CONCLUSION: A 3-hour infusion of 2 g of meropenem regimen was predicted to have the highest PTA rates. Only the prolonged infusion regimens achieved a high CFR against E. coli, Klebsiella spp., P. aeruginosa, and Acinetobacter spp.

When pharmacodynamics trump costs: an antimicrobial stewardship program's approach to selecting optimal antimicrobial agents.

BACKGROUND: Treatment of Pseudomonas aeruginosa infections is increasingly challenging because of escalating resistance. Antimicrobial stewardship programs provide guidance for clinicians regarding use of the most appropriate antimicrobial at the right dose, duration, and route in addition to being cost-effective. Optimizing antimicrobial therapy by using pharmacokinetic/pharmacodynamic principles such as extending time above the MIC is 1 stewardship strategy to reduce antimicrobial resistance. OBJECTIVE: The goal of this study was to evaluate our current dosing strategy for cefepime and the formulary carbapenem (imipenem) compared with meropenem and doripenem to determine the best dosing strategy for achieving maximal pharmacodynamic activity against an institution-specific population of P aeruginosa isolates. METHODS: Consecutive, nonduplicate, blood (n = 39) or bronchial alveolar lavage (n = 25) isolates of P aeruginosa from adult, hospitalized (2009-2010) critically ill patients underwent MIC testing by using broth microdilution. A pharmacokinetic model was developed and used with Monte Carlo simulation to evaluate the ability of imipenem, meropenem, doripenem, and cefepime to achieve optimal bactericidal activity as varying doses infused over standard infusions (SIs; 0.5-1 hour) or prolonged infusions (PIs; 3-4 hours). A regimen was defined as optimal if the cumulative fraction response (CFR) was ≥90%. RESULTS: None of the imipenem regimens modeled as SI or PI achieved a CFR ≥90%. Meropenem at 1 to 2 g q8h PI achieved a CFR ≥90%. Doripenem 0.5, 1, or 2 g q8h PI achieved a CFR ≥90%. The only cefepime regimen that achieved a CFR ≥90% was 2 g q8h PI. Overall susceptibility rates to P aeruginosa were highest with cefepime (91%), followed by meropenem (83%), doripenem (78%), and imipenem (72%). Our antimicrobial stewardship programs recommended switching from imipenem to doripenem 0.5g q8h PI, which was 36% more costly in drug acquisition costs. Cefepime dosing was increased from 2 g q12h SI to 2 g q8h PI, a 52% increase in drug acquisition cost. CONCLUSIONS: Antimicrobial stewardship programs should consider pharmacodynamic modeling to select the optimal dosing strategies to guide therapy in an era of escalating antimicrobial resistance. Using the percent susceptibility alone can be misleading and ultimately the most expensive if the patient fails to respond.