Comparative Pharmacodynamics of Intermittent and Prolonged Infusions of Piperacillin/Tazobactam Using Monte Carlo Simulations and Steady-State Pharmacokinetic Data from Hospitalized Patients

Optimizing Clinical Outcomes Through Rational Dosing Strategies: Roles of Pharmacokinetic/Pharmacodynamic Modeling Tools

Significant progress in previous decades has led to several methodologies developed to facilitate the design of optimal antimicrobial dosing. In this review, we highlight common pharmacokinetic/pharmacodynamic (PKPD) modeling techniques and their roles in guiding rational dosing regimen design. In the early drug development phases, dose fractionation studies identify the PKPD index most closely associated with bacterial killing. Once discerned, this index is linked to clinical efficacy end points, and classification and regression tree analysis can be used to define the PKPD target goal. Monte Carlo simulations integrate PKPD and microbiological data to identify dosing strategies with a high probability of achieving the established PKPD target. Results then determine dosing regimens to investigate and/or validate the findings of randomized controlled trials. Further improvements in PKPD modeling could lead to an era of precision dosing and personalized therapeutics.

Quantification of Antibiotics in Patient Samples: State of the Art in Standardization and Proficiency Testing

BACKGROUND

For many antibiotics, the convenient one-fits-all dosing regimen had to be abandoned. Owing to highly variable pharmacokinetics, therapeutic drug monitoring has become an indispensable prerequisite. It is based on a suitable measuring method, sample materials, and standardization. Appropriate quality control including external quality assessment (EQA) is essential. For many antibiotics, EQAs have been established for many decades, whereas others have only lately been introduced. This article gives an insight into the state of the art regarding the therapeutic drug monitoring of antibiotics regarding standardization, EQAs, and reference measurement procedures (RMPs).

METHODS

An overview of the currently available international EQA schemes for antibiotics and a literature overview of available RMPs are given. EQAs including gentamicin and vancomycin have been offered by German providers for more than 25 years. The period 2000-2020 was selected for a detailed analysis. The experiences with a new EQA including linezolid, meropenem, and piperacillin are described.

RESULTS

EQAs for gentamicin and vancomycin are provided in many countries. Those for linezolid, meropenem, and piperacillin do not seem to be very common. Most of the antibiotics monitored for decades are measured by commercially available assays. EQAs for linezolid, meropenem, and piperacillin introduced in 2018 were rapidly accepted in Germany. Methods reported in this study were HPLC based either with UV or mass spectrometric detection. The number of participants succeeding was comparable between UV and mass spectrometry. Candidate RMPs for gentamicin, vancomycin, and linezolid based on isotope dilution mass spectrometry were published.

CONCLUSIONS

EQAs are offered regularly for many antibiotics worldwide. The results of EQAs in Germany generally compare well, but there is potential for improvement. Both immunoassays and HPLC-based methods work properly in EQAs evaluated in Germany. From a quality control perspective, fast and inexpensive methods may be selected without endangering the patient's health based on clinical needs.

Implementation of an Extended-Infusion Piperacillin-Tazobactam Dosing Protocol: Unexpected Findings when Monitoring Safety and Compliance with Smart Pump Technology

Compliance with recommended infusion rates was evaluated before, during, and after the implementation of extended-infusion (EI) piperacillin-tazobactam at an academic medical center. Software-controlled infusion-pump alert data were studied for piperacillin-tazobactam administrations before and after implementation of a four-hour EI protocol. Compliance was analyzed 16 weeks before (pre-EI), two weeks after (peri-EI), and an additional 16 weeks after (post-EI) protocol implementation. We defined potential harm as a programmed infusion rate exceeding the recommended rate, possible harm as a programmed infusion aborted by the user, and compliance as reversion to recommended rates. Potential and possible harm were standardized to 1000 patient days. Overall, 3110 alerts were identified during the period. Potential harm per 1000 patient days for pre-, peri-, and post-EI were 0, 6.12, and 1.05 (p < 0.001). Possible harm per 1000 patient days for the pre-, peri-, and post-EI were 0.33, 21.9, and 5.02 (p < 0.001). Compliance after an initial potential harm alert occurred more often post-EI (0.4 per 1000 patient days vs. 0 per 1000 patient days for pre- and peri-EI; p < 0.001), while alerts remaining in non-compliance were more prevalent if they initially occurred during the peri- and post-EI vs. pre-EI (6.1 and 0.6 per 1000 patient days vs. 0 per 1000 patient days; p < 0.001) period. Piperacillin-tazobactam infusions were administered faster than recommended during implementation (i.e., peri-EI) despite standardized orders.

The Pharmacodynamics of Prolonged Infusion β-Lactams for the Treatment of Pseudomonas aeruginosa Infections: A Systematic Review

PURPOSE

Pseudomonas aeruginosa is a commonly isolated nosocomial pathogen for which treatment options are often limited for multidrug-resistant isolates. In addition to newer available antimicrobial agents active against P. aeruginosa, strategies such as extended (eg, prolonged or continuous) infusion have been suggested to optimize the pharmacokinetic and pharmacodynamic profiles of β-lactams. Literature regarding clinical outcomes for extended infusion β-lactams has been controversial; however, this use seems most beneficial in patients with severe illness. Prolonged infusion of β-lactams (eg, 3- to 4-hour infusion) can enhance the pharmacodynamic target attainment via increasing the amount of time throughout the dosing interval to which the free drug concentration remains above the MIC (minimum inhibitory concentration) of the organism (fT > MIC). This systematic review summarizes current literature related to the probability of target attainment (PTA) of various antipseudomonal β-lactam regimens administered as prolonged infusions in an effort to provide guidance in selecting optimal dosing regimens and infusion times for the treatment of P. aeruginosa infections.

METHODS

A literature search for all pertinent studies was performed by using the PubMed database (with no year limit) through March 31, 2019.

FINDINGS

Thirty-nine studies were included. Although many standard antipseudomonal β-lactam intermittent infusion regimens can provide adequate PTA against most susceptible isolates, prolonged infusion may enhance percent fT > MIC for organisms with higher MICs (eg, nonsusceptible) or patients with altered pharmacokinetic profiles (eg, obese, critically ill, those with febrile neutropenia).

IMPLICATIONS

Prolonged infusion β-lactam regimens can enhance PTA against nonsusceptible P. aeruginosa isolates and may provide a potential therapeutic option for multidrug-resistant infections. Before implementing prolonged infusion antipseudomonal β-lactams, institutions should consider the half-life of the antibiotic, local incidence of P. aeruginosa infections, antibiotic MIC distributions or MICs isolated from individual patients, individual patient characteristics that may alter pharmacokinetic variables, and PTA (eg, critically ill), as well as implementation challenges.

Application of Antibiotic Pharmacodynamics and Dosing Principles in Patients With Sepsis

Sepsis is associated with marked mortality, which may be reduced by prompt initiation of adequate, appropriate doses of antibiotic. Critically ill patients often have physiological changes that reduce blood and tissue concentrations of antibiotic and high rates of multidrug-resistant pathogens, which may affect patients' outcomes. All critical care professionals, including critical care nurses, should understand antibiotic pharmacokinetics and pharmacodynamics to ensure sound antibiotic dosing and administration strategies for optimal microbial killing and patients' outcomes. Effective pathogen eradication occurs when the dose of antibiotic reaches or maintains optimal concentrations relative to the minimum inhibitory concentration for the pathogen. Time-dependent antibiotics, such as β-lactams, can be given as extended or continuous infusions. Concentration-dependent antibiotics such as aminoglycosides are optimized by using high, once-daily dosing strategies with serum concentration monitoring. Vancomycin and fluoroquinolones are dependent on both time and concentration above the minimum inhibitory concentration.

Dosing antibiotics in neonates: review of the pharmacokinetic data

Antibiotics are often used in neonates despite the absence of relevant dosing information in drug labels. For neonatal dosing, clinicians must extrapolate data from studies for adults and older children, who have strikingly different physiologies. As a result, dosing extrapolation can lead to increased toxicity or efficacy failures in neonates. Driven by these differences and recent legislation mandating the study of drugs in children and neonates, an increasing number of pharmacokinetic studies of antibiotics are being performed in neonates. These studies have led to new dosing recommendations with particular consideration for neonate body size and maturation. Herein, we highlight the available pharmacokinetic data for commonly used systemic antibiotics in neonates.

Optimizing β-lactams treatment in critically-ill patients using pharmacokinetics/pharmacodynamics targets: are first conventional doses effective?

INTRODUCTION

The pharmacokinetic/pharmacodynamic index determining β-lactam activity is the percentage of the dosing interval (%T) during which their free serum concentration remains above a critical threshold over the minimum inhibitory concentration (MIC). Regrettably, neither the value of %T nor that of the threshold are clearly defined for critically-ill patients. Areas covered: We review and assess the targets proposed for β-lactams in critical illness by screening the literature since 1997. Depending on the study intention (clinical cure vs. suppression of resistance), targets proposed range from 20%T > 1xMIC to 100%T > 5xMIC. Assessment and comparative analysis of their respective clinical efficacy suggest that a value of 100%T > 4xMIC may be needed. Simulation studies, however, show that this target will not be reached at first dose for the majority of critically-ill patients if using the most commonly recommended doses. Expert commentary: Considering that critically-ill patients are highly vulnerable and likely to experience antibiotic underexposure, and because effective initial treatment is a key determinant of clinical outcome, we support the use of a target of 100%T > 4xMIC, which could not only maximize efficacy but also minimize emergence of resistance. Clinical and microbiological studies are needed to test for the feasibility and effectiveness of reaching such a demanding target.

Extended Infusion of Piperacillin/Tazobactam in Children

OBJECTIVES

Extended-infusion piperacillin/tazobactam (TZP) has been associated with positive clinical outcomes in adults, but similar data in children are lacking. The objective of this study was to describe efficacy outcomes with pediatric patients receiving extended-infusion TZP.

METHODS

This was a retrospective case series of children aged 1 month to 17 years who had documented Gram-negative infection and received extended-infusion TZP between April 2011 and March 2012. The primary outcome was 21-day clinical cure defined as negative follow-up cultures, where available, and infection resolution.

RESULTS

Fifty children with a median (interquartile range [IQR]) age of 5 (2-9) years were included in the study. Patients received a median (IQR) TZP dose of 111.4 (100-112.5) mg/kg administered every 8 hours over 4 hours. Clinical and microbiologic cure were observed in 74% and 100% of patients, respectively. Patients not meeting criterial for 21-day clinical cure were younger (1 vs 7 years, p = 0.087) and had a longer length of hospital stay (23 vs 11 days, p = 0.037).

CONCLUSIONS

The majority of children in this cohort achieved 21-day clinical cure with extended-interval TZP. Those without clinical cure tended to be younger and critically ill. Additional comparative studies evaluating traditional and extended-infusion TZP in children are needed.

Continuous and Prolonged Intravenous β-Lactam Dosing: Implications for the Clinical Laboratory

Beta-lactam antibiotics serve as a cornerstone in the management of bacterial infections because of their wide spectrum of activity and low toxicity. Since resistance rates among bacteria are continuously on the rise and the pipeline for new antibiotics does not meet this trend, an optimization of current beta-lactam treatment is needed. This review provides an overview of optimization through use of prolonged- and continuous-infusion dosing strategies compared with more traditional intermittent infusions. Included is an overview of the scientific basis for using these nontraditional prolonged- and continuous-infusion-based regimens, with a focus on major areas in which the clinical laboratory can support the clinical use of these regimens.

Target attainment analysis and optimal sampling designs for population pharmacokinetic study on piperacillin/tazobactam in neonates and young infants

OBJECTIVES

Population pharmacokinetic (popPK) analyses for piperacillin/tazobactam in neonates and infants of less than 2 months of age have been performed by our group previously. The results indicate that a dose of 44.44/5.56 mg/kg piperacillin/tazobactam every 8 or 12 h may not be enough for controlling infection in this population. In order to determine the appropriate dosing regimen and to provide a rationale for the development of dosing guidelines suitable for this population, further popPK studies of piperacillin/tazobactam would need to be conducted. The aim of the present study was to determine the appropriate dosing regimen and optimal sampling schedules in neonates and infants of less than 2 months of age.

METHODS

Pharmacodynamic profiling of piperacillin using Monte Carlo simulation was performed to explore the target attainment probability of different dosing regimens for infections caused by different isolated pathogens. D-optimal designs for piperacillin and tazobactam were conducted separately, and the times that overlapped were chosen as the final sampling scheme for future popPK studies in neonates and young infants of less than 2 months of age.

RESULTS

Our findings revealed that compared to the current empirical piperacillin/tazobactam dose regimen (50 mg/kg every 12 h by 5-min infusion in our hospital), the clinical outcome could be improved by increasing doses, increasing administration frequency, and prolonging intravenous infusion in neonates and infants of less than 2 months of age. The following optimal sampling windows were chosen as the final sampling scheme: 0.1-0.11, 0.26-0.29, 0.97-2.62, and 7.95-11.9 h administered every 12 h with 5-min infusion; 0.1-0.12, 0.39-0.56, 2.86-4.95, and 8.91-11.8 h administered every 12 h with 3-h infusion; 0.1-0.11, 0.22-0.29, 0.91-1.96, and 5.56-7.93 h administered every 8 h with 5-min infusion; 0.1-0.11, 0.38-0.48, 2.54-3.82, and 6.86-7.93 h administered every 8 h with 3-h infusion; 0.1-0.11, 0.25-0.28, 0.84-1.69, and 4.55-5.94 h administered every 6 h with 5-min infusion; and 0.1-0.11, 0.37-0.54, 3.13-3.72, and 5.57-5.99 h administered every 6 h with 3-h infusion.

CONCLUSIONS

The dosing regimen and sampling schedules proposed in this study should be evaluated in future popPK studies of piperacillin/tazobactam in neonates and infants. To the best of our knowledge, this is the first study that combined optimal sampling design with Monte Carlo simulation for designing popPK studies of piperacillin/tazobactam.

Pharmacokinetics of an extended 4-hour infusion of piperacillin-tazobactam in critically ill patients undergoing continuous renal replacement therapy

STUDY OBJECTIVE

To evaluate the pharmacokinetic and pharmacodynamic profiles of piperacillin-tazobactam administered as a 4-hour infusion in critically ill patients undergoing continuous renal replacement therapy (CRRT).

DESIGN

Prospective, observational, pharmacokinetic study.

SETTING

Intensive care unit of a tertiary care hospital in Montréal, Canada.

PATIENTS

Twenty critically ill adults who were undergoing continuous venovenous hemodiafiltration and receiving a 4-hour infusion of piperacillin 4 g-tazobactam 0.5 g every 8 hours for a documented or suspected infection.

INTERVENTION

Blood samples were collected every hour over an 8-hour dosing interval. Prefilter and postfilter blood samples, and effluent and urine samples were also collected.

MEASUREMENTS AND MAIN RESULTS

The primary outcome was the proportion of patients who achieved an unbound piperacillin plasma concentration above a target minimum inhibitory concentration (MIC) of 64 mg/L (MIC that inhibits 90% of isolates for Pseudomonas aeruginosa) for at least 50% of the dosing interval; 18 (90%) of the 20 patients achieved this outcome. In all patients, the free piperacillin concentrations were above the Pseudomonas aeruginosa breakpoint of 16 mg/L for the entire time interval. Regarding piperacillin pharmacokinetic parameters, the median (interquartile range) minimum unbound plasma concentration was 65.15 mg/L (51.30-89.30), maximum unbound plasma concentration was 141.3 mg/L (116.75-173.90), sieving coefficient was 0.809 (0.738-0.938), total clearance was 65.82 ml/minute (53.79-102.87), and renal clearance was 0.16 ml/minute (0.05-3.04). The median CRRT dose was 32.0 ml/kg/h (25.0-39.8).

CONCLUSIONS

Administration of a 4-hour infusion of piperacillin-tazobactam was associated with a favorable pharmacodynamic profile in patients undergoing CRRT. Concentrations associated with maximal activity were attained in our patients.

Population Pharmacokinetics and Pharmacodynamics of Extended-Infusion Piperacillin and Tazobactam in Critically Ill Children

The study objective was to evaluate the population pharmacokinetics and pharmacodynamics of extended-infusion piperacillin-tazobactam in children hospitalized in an intensive care unit. Seventy-two serum samples were collected at steady state from 12 patients who received piperacillin-tazobactam at 100/12.5 mg/kg of body weight every 8 h infused over 4 h. Population pharmacokinetic analyses were performed using NONMEM, and Monte Carlo simulations were performed to estimate the piperacillin pharmacokinetic profiles for dosing regimens of 80 to 100 mg/kg of the piperacillin component given every 6 to 8 h and infused over 0.5, 3, or 4 h. The probability of target attainment (PTA) for a cumulative percentage of the dosing interval that the drug concentration exceeds the MIC under steady-state pharmacokinetic conditions (TMIC) of ≥50% was calculated at MICs ranging from 0.25 to 64 mg/liter. The mean ± standard deviation (SD) age, weight, and estimated glomerular filtration rate were 5 ± 3 years, 17 ± 6.2 kg, and 118 ± 41 ml/min/1.73 m(2), respectively. A one-compartment model with zero-order input and first-order elimination best fit the pharmacokinetic data for both drugs. Weight was significantly associated with piperacillin clearance, and weight and sex were significantly associated with tazobactam clearance. Pharmacokinetic parameters (mean ± SD) for piperacillin and tazobactam were as follows: clearance, 0.22 ± 0.07 and 0.19 ± 0.07 liter/h/kg, respectively; volume of distribution, 0.43 ± 0.16 and 0.37 ± 0.14 liter/kg, respectively. All extended-infusion regimens achieved PTAs of >90% at MICs of ≤16 mg/liter. Only the 3-h infusion regimens given every 6 h achieved PTAs of >90% at an MIC of 32 mg/liter. For susceptible bacterial pathogens, piperacillin-tazobactam doses of ≥80/10 mg/kg given every 8 h and infused over 4 h achieve adequate pharmacodynamic exposures in critically ill children.

Microbiologic clearance following transition from standard infusion piperacillin-tazobactam to extended-infusion for persistent Gram-negative bacteremia and possible endocarditis: A case report and review of the literature

INTRODUCTION

We sought to describe a case of pharmacodynamically-optimized dosing of piperacillin-tazobactam in a patient that cleared their infections after treatment with high-dose, extended-infusion piperacillin-tazobactam and summarize the literature on the benefits of extended-infusion of beta-lactams.

CASE REPORT

At an outside hospital, a 78 year-old male presented with fevers and shortness of breath. He was empirically initiated on standard doses of vancomycin and piperacillin-tazobactam for suspected pneumonia and sepsis. Blood and sputum cultures identified Elizabethkingia meningosepticum sensitive only to piperacillin-tazobactam by E-test susceptibility testing. After 10 days of empiric therapy with piperacillin-tazobactam dosed at 3.375 g IV every 8 h over 30 min, the patient transferred to our institution and was initiated on piperacillin-tazobactam at 3.375 g IV every 8 h administered as a 4 h infusion. The patient failed to improve; piperacillin-tazobactam was changed to 4.5 g IV over 4 h every 8 h and later changed to the hospital protocol dose of 3.375 g IV over 4 h every 6 h. The patient achieved negative blood cultures within 24 h of optimized dosing.

DISCUSSION

We present the first case to our knowledge that describes failure to respond and subsequent response within a single patient where beta-lactam dosing was altered to optimize pharmacokinetics and pharmacodynamics (PK-PD). Our patient received non-standard dose-escalation for piperacillin-tazobactam. Drug exposure was estimated post-hoc utilizing robust mathematical simulations to describe alterations in disposition over time. This case demonstrates that extended-infusion administration of beta-lactams may provide improved microbiological activity.

New antibiotic dosing in infants

To prevent the devastating consequences of infection, most infants admitted to the neonatal intensive care unit are exposed to antibiotics. However, dosing regimens are often extrapolated from data in adults and older children, increasing the risk for drug toxicity and lack of clinical efficacy because they fail to account for developmental changes in infant physiology. However, newer technologies are emerging with minimal-risk study designs, including ultra-low-volume assays, pharmacokinetic modeling and simulation, and opportunistic drug protocols. With minimal-risk study designs, pharmacokinetic data and dosing regimens for infants are now available for ampicillin, clindamycin, meropenem, metronidazole, and piperacillin/tazobactam.

Developmental pharmacokinetics of piperacillin and tazobactam using plasma and dried blood spots from infants

Piperacillin-tazobactam is often given to infants with severe infection in spite of limited pharmacokinetics (PK) data. We evaluated piperacillin-tazobactam PK in premature and term infants of ages <61 days with suspected systemic infection. Infants received intravenous piperacillin-tazobactam (80 to 100 mg/kg of body weight every 8 h [q 8 h]) based on gestational and postnatal age. Sparse plasma samples were obtained after first and multiple doses. Drug concentrations were measured by tandem mass spectrometry. PK data were analyzed using population nonlinear mixed-effect modeling. Target attainment rates for the time unbound piperacillin concentrations remained above the MIC for 50% and 75% of the dosing interval at steady state were evaluated. Bias in population PK parameter estimates was assessed for dried blood spot (DBS) samples, and a comparability analysis was performed for DBS and plasma drug concentrations using linear regression. We obtained 128 plasma samples from 32 infants, median gestational age of 30 weeks (range, 23 to 40 weeks) and postnatal age of 8 days (range, 1 to 60). Piperacillin and tazobactam PK models included body weight (WT) and postmenstrual age (PMA) as covariates for clearance and WT for volume of distribution and were used to optimize dosing in infants. DBS drug concentrations were 50 to 60% lower than those in plasma, but when combined with plasma concentrations and a matrix effect, the data generated PK model parameters similar to those for plasma alone. With PMA-based dosing (100 mg/kg q 8 h, 80 mg/kg q 6 h, and 80 mg/kg q 4 h for PMA of ≤30, 30 to 35, and 35 to 49 weeks, respectively), 90% of simulated infants achieved the surrogate therapeutic target of time above the MIC (≤32 mg/liter) for 75% of the dosing interval.

Outcomes of extended-infusion piperacillin-tazobactam: a retrospective analysis of critically ill patients

Studies evaluating the outcomes of an extended-infusion (EI) piperacillin-tazobactam dosing strategy in specific cohorts of critically ill patients are lacking. A retrospective, pre-implementation and post-implementation study of 148 critically ill patients was conducted to compare EI and traditional infusion piperacillin-tazobactam. In this retrospective study, the EI piperacillin-tazobactam dosing strategy was associated with improved 30-day mortality. EI piperacillin-tazobactam may be an effective alternative to TI of piperacillin-tazobactam among critically ill patients treated for suspected gram-negative infections.

Medical resource utilization among patients with ventilator-associated pneumonia: pooled analysis of randomized studies of doripenem versus comparators

Introduction

Ventilator-associated pneumonia (VAP) is associated with increased medical resource utilization, but few randomized studies have been conducted to evaluate the effect of initial antibiotic therapy. To assess medical resource utilization in patients with VAP, we conducted a pooled analysis of two prospective, randomized, open-label, multicenter, phase III studies, which also showed that doripenem was clinically noninferior to comparators.

Methods

We assessed durations of mechanical ventilation, intensive care unit (ICU) stay, and hospitalization in patients with VAP who received at least 1 dose of doripenem or a comparator in the phase III studies. Comparators were piperacillin/tazobactam (study 1) and imipenem (study 2). We analyzed between-group differences in medical resource utilization endpoints by comparison of Kaplan-Meier curves with generalized Wilcoxon test and in microbiologic eradication rates by two-sided Fisher's exact test.

Results

625 patients with VAP were evaluated and received at least 1 dose of doripenem (n = 312) or a comparator (n = 313). Median durations of mechanical ventilation (7 versus 10 days; P = 0.008) and hospitalization (22 versus 26 days; P = 0.010) were shorter for doripenem than comparators; corresponding ICU stays were 12 and 13 days (P = 0.065). All-cause, overall mortality rates were similar (51/312 [16%] versus 47/313 [15%]; P = 0.648). MIC₉₀ values against Pseudomonas aeruginosa for doripenem versus imipenem were 4 versus 16 μg/mL in study 2. P. aeruginosa was eradicated from 16/24 (67%) doripenem recipients and 10/24 (42%) comparator recipients (P = 0.147). In patients with P. aeruginosa at baseline, median durations of mechanical ventilation (7 versus 13 days; P = 0.031) and ICU stay (13 versus 21 days; P = 0.027) were shorter for doripenem; corresponding hospital stays were 24 and 35 days (P = 0.129).

Conclusions

Doripenem was associated with lower medical resource utilization than comparators. Differences in antipseudomonal activity may have contributed to these findings.

Trial registration

ClinicalTrials.gov number NCT00211003 (study 1) and NCT00211016 (study 2).

Comparative Pharmacodynamics of Intermittent and Prolonged Infusions of Piperacillin/Tazobactam Using Monte Carlo Simulation and Steady-State Pharmacokinetic Data from Hospitalized Patients

With increasing antibiotic resistance in gram-negative pathogens, dosing strategies that optimize pharmacodynamic parameters of currently available antibiotics play an important role in treatment. The likelihood of success with piperacillin/tazobactam, a widely used broad-spectrum antibiotic, can be manipulated by increasing the amount of time that unbound drug concentrations remain above the pathogen's minimum inhibitory concentration (MIC). However, this success depends greatly on knowing the MIC value as well as accurately estimating the individual's pharmacokinetic parameters. Clinicians should carefully factor these variables into their decision-making process when considering prolonged infusion strategies with piperacillin/tazobactam.