Continuous infusion of ceftazidime in febrile neutropenic patients with acute myeloid leukemia

Does Cytokine-Release Syndrome Induced by CAR T-Cell Treatment Have an Impact on the Pharmacokinetics of Meropenem and Piperacillin/Tazobactam in Patients with Hematological Malignancies? Findings from an Observational Case-Control Study

Chimeric antigen receptor (CAR) T-cell therapy is a promising approach for some relapse/refractory hematological B-cell malignancies; however, in most patients, cytokine release syndrome (CRS) may occur. CRS is associated with acute kidney injury (AKI) that may affect the pharmacokinetics of some beta-lactams. The aim of this study was to assess whether the pharmacokinetics of meropenem and piperacillin may be affected by CAR T-cell treatment. The study included CAR T-cell treated patients (cases) and oncohematological patients (controls), who were administered 24-h continuous infusion (CI) meropenem or piperacillin/tazobactam, optimized by therapeutic drug monitoring, over a 2-year period. Patient data were retrospectively retrieved and matched on a 1:2 ratio. Beta-lactam clearance (CL) was calculated as CL = daily dose/infusion rate. A total of 38 cases (of whom 14 and 24 were treated with meropenem and piperacillin/tazobactam, respectively) was matched with 76 controls. CRS occurred in 85.7% (12/14) and 95.8% (23/24) of patients treated with meropenem and piperacillin/tazobactam, respectively. CRS-induced AKI was observed in only 1 patient. CL did not differ between cases and controls for both meropenem (11.1 vs. 11.7 L/h, p = 0.835) and piperacillin (14.0 vs. 10.4 L/h, p = 0.074). Our findings suggest that 24-h CI meropenem and piperacillin dosages should not be reduced a priori in CAR T-cell patients experiencing CRS.

Population pharmacokinetics and dosing considerations for the use of daptomycin in adult patients with haematological malignancies

Objectives

To assess the population pharmacokinetics (popPK) of daptomycin at the conventional dose of 6 mg/kg/day in a cohort of oncohaematological patients.

Methods

Patients underwent serial blood sampling on day 3 of therapy (before dosing and at 0, 0.5, 1, 2, 3, 5, 7, 9 and 12 h after dosing) to assess the pharmacokinetic profile of daptomycin. PopPK and Monte Carlo simulation were performed to define the probability of target attainment (PTA) with 6, 8, 10 and 12 mg/kg/day of the pharmacokinetic/pharmacodynamic target of AUC 24 /MIC >1081.

Results

Thirty patients were recruited. A two-compartment open model with first-order intravenous input and first-order elimination was developed. Estimated creatinine clearance (CL CR ), serum albumin concentration (Alb) and presence of AML were covariates included in the final model. Monte Carlo simulation showed that the conventional 6 mg/kg/day dose resulted in optimal PTAs (≥80%) in the presence of pathogens with an MIC up to 0.5 mg/L only in patients with CL CR 50-100 mL/min/1.73 m 2 , Alb 26-45 g/L and a haematological diagnosis other than AML. Conversely, higher dosages, up to 12 mg/kg/day, were needed to achieve this goal in the presence of pathogens with an MIC of 0.25-0.5 mg/L in all of the other tested scenarios. In patients with CL CR 101-150 mL/min/1.73 m 2 and Alb 15-25 g/L, suboptimal PTAs (<60%) were predicted even with 12 mg/kg/day dosing .

Conclusions

Our study provides a strong rationale for considering daptomycin dosages of ≥ 8 mg/kg/day in several clinical scenarios for oncohaematological patients. In some of these scenarios therapeutic drug monitoring could be a useful adjunct for optimized care.

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.

Continuous versus intermittent piperacillin/tazobactam infusion in infection due to or suspected pseudomonas aeruginosa

BACKGROUND

There is lack of information on the efficacy and safety of piperacillin–tazobactam administered by continuous infusion.

OBJECTIVE

The aim of this study was to investigate whether continuous infusion of piperacillin–tazobactam is superior in terms of efficacy to a 30 % higher dose administered by intermittent infusion to treat suspected or confirmed infection due to Pseudomonas aeruginosa. Setting Multicenter clinical trial with 11 third level Spanish hospitals.

METHOD

Randomized, double-blind parallel-group clinical trial, controlled by conventional administration of the drug. Patients randomly assigned in a 1:1 ratio to receive piperacillin–tazobactam as continuous infusion (CI) or intermittent (II).

MAIN OUTCOME MEASURE

Primary efficacy endpoint was percentage of patients having a satisfactory clinical response at completion of treatment, defined as clinical cure or clinical improvement. Adverse events were reported. Results 78 patients were included, 40 in the CI group and 38 in the II group. Mean (standard deviation) duration of treatment was 7 (±4.44) days. 58 patients (74.4 %) experienced cure or improvement at the end of the treatment. There were no statistical differences in cure rates between the two treatment arms and no adverse events were reported.

CONCLUSION

Continuous infusion of piperacillin–tazobactam is an alternative administration drug method at least similar in efficacy and safety to conventional intermittent infusion. Multivariate analysis is needed to determine whether continuous administration might be more beneficial than intermittent in certain patient subgroups.

Pharmacokinetics of Cefepime in Patients with Cancer and Febrile Neutropenia in the Setting of Hematologic Malignancies or Hematopoeitic Cell Transplantation

STUDY OBJECTIVE

To evaluate the steady-state pharmacokinetic parameters of standard cefepime dosing regimens in a hematologic malignancy and hematopoietic cell transplant patient population with febrile neutropenia.

DESIGN

Open-label, single-center, prospective pharmacokinetic study.

SETTING

National Cancer Institute-designated cancer center.

PATIENTS

Nine adults with hematologic malignancies or hematopoietic cell transplants who had febrile neutropenia and were admitted to a hematology-oncology service between January and July 2014.

INTERVENTION

Patients received empirical cefepime 2 g every 8 hours, administered as a 30-minute intravenous infusion, for febrile neutropenia.

MEASUREMENTS AND MAIN RESULTS

Steady-state cefepime serum concentrations were measured after at least 2 days of continuous therapy. Venous blood samples were intensively sampled between 0 and 8 hours after the start of the 30-minute infusion at steady state. Seven of the nine patients had a hematologic malignancy diagnosis of acute leukemia, lymphoma, or myeloma, and two patients had a germ cell tumor diagnosis. Noncompartmental analysis revealed mean ± SD parameters as follows at steady state: area under the plasma concentration-time curve from 0-8 hours 222.9 ± 72.9 mg hour/L, maximum concentration 120.9 ± 21.8 mg/L, clearance 9.7 ± 3.7 L/hour, apparent volume of distribution 19.2 ± 4.65 L, and elimination half-life 1.4 ± 0.3 hours. A one-compartment pharmacokinetic model identified a mean ± SD volume of distribution of 20.9 ± 1.3 L and an elimination rate constant of 0.39 ± 0.03 hour(-1) . The mean estimated percentage of time that drug concentration remains above the pathogen minimum inhibitory concentration (fT>MIC) in serum was 55%, 77%, and 99% at MICs of 16, 8, and 4 mg/L, respectively.

CONCLUSION

Patients with hematologic malignancies or hematopoietic cell transplants who had febrile neutropenia demonstrated homogeneous calculated cefepime volumes and clearances. The population parameters presented in this study may aid in the calculation of patient-specific fT>MIC for similar patients.

Population pharmacokinetics of the piperacillin component of piperacillin/tazobactam in pediatric oncology patients with fever and neutropenia

BACKGROUND

To describe the population pharmacokinetics of the piperacillin component of piperacillin/tazobactam.

PROCEDURE

This pharmacokinetic study included 21 pediatric (age 3-10 years) patients receiving piperacillin/tazobactam to treat fever with neutropenia. Each patient contributed 1-3 blood samples for piperacillin concentration determination. Population pharmacokinetic analyses were conducted using Pmetrics software. A 5,000 patient Monte Carlo simulation was performed to determine the probability of target attainment (PTA) for multiple dosing regimens, using 50% of free drug time above the minimum inhibitory concentration (MIC) as the primary pharmacodynamic threshold.

RESULTS

Mean ± SD body weight was 28.5 ± 9.7 kg. Piperacillin concentration data best fit a two-compartment model with linear clearance, using total body weight as a covariate for clearance (CLθ ) and volume of the central compartment (Vcθ ). Population estimates for CLθ , Vcθ , and intercompartment transfer constants were 0.204 ± 0.076 L/h/kg, 0.199 ± 0.107 L/kg, 0.897 ± 1.050 h(-1) , and 1.427 ± 1.609 h(-1) , respectively. R(2) , bias, and precision for the Bayesian fit were 0.998, -0.032, and 2.2 µg/ml, respectively. At the MIC breakpoint of 16 µg/ml for Pseudomonas aeruginosa, PTAs for 50 mg/kg q4h as a 0.5 hr infusion was 93.9%; for 100 mg/kg q8h as 0.5 and 4 hr infusion: 64.6% and 100%; for 100 mg/kg q6h as 0.5 and 3 hr infusion: 86.5% and 100%; and for 400 mg/kg continuous infusion: 100%, respectively.

CONCLUSIONS

In children with fever and neutropenia, piperacillin/tazobactam dosing regimens that are administered every 4 hr or that employ prolonged or continuous infusions should be considered to optimize pharmacodynamic exposure.

Effect of meropenem administration in extended infusion on the clinical outcome of febrile neutropenia: a retrospective observational study

OBJECTIVES

Information on the efficacy of extended meropenem administration in neutropenic patients is scarce. Our objective was to determine whether the administration of meropenem in a 4 h extended infusion (EI) leads to a better clinical outcome in patients with febrile neutropenia than the conventional short infusion (SI).

METHODS

This was a retrospective observational study. The subjects were neutropenic patients who presented with fever after receiving haematopoietic stem-cell transplantation or induction chemotherapy for acute myeloid leukaemia. The primary endpoint was the success of treatment after 5 days of meropenem therapy, defined as follows: the disappearance of fever leading to a maintained (≥ 24 h) feverless state; the resolution or improvement of the clinical signs and symptoms of infection; the absence of persistent or breakthrough bacteraemia; and no additional antibiotics prescribed because of an unsatisfactory clinical evolution.

RESULTS

Eighty-eight patients received meropenem (1 g/8 h) in SI and 76 received the same dose in EI. Treatment success on day 5 was superior in the EI group [52/76 (68.4%) versus 36/88 (40.9%); P<0.001]. Meropenem administered in EI was independently associated with success (OR 3.13, 95% CI 1.61-6.10). Fewer additional antibiotics were prescribed in the EI group during the first 5 days of treatment [20/76 (26.3%) versus 44/88 (50.0%); P=0.002]. Using Kaplan-Meier survival analysis a more prompt defervescence and a faster decrease in C-reactive protein concentration were observed in the EI group (P=0.021 and P=0.037, respectively). There were no significant differences in the length of hospital stay and in the mortality rate.

CONCLUSIONS

Meropenem administration in EI results in a better clinical outcome for febrile neutropenia episodes, with fewer additional antibiotics needed.

Antimicrobial treatment of febrile neutropenia: pharmacokinetic-pharmacodynamic considerations

Patients with cancer or hematologic diseases are particularly at risk of infection leading to high morbidity, mortality and costs. Extensive data show that optimization of the administration of antimicrobials according to their pharmacokinetic and pharmacodynamic parameters improves clinical outcome. Evidence is growing that when pharmacokinetic and pharmacodynamic parameters are used to target not only clinical cure but also eradication, the selection resistance is also contained. This is of particular importance in patients with neutropenia in whom increasing rates of drug-resistant Gram-negative bacteria have been reported, particularly Pseudomonas aeruginosa. Based on experimental and clinical studies, pharmacokinetic and pharmacodynamic parameters are discussed in this review for each antibiotic used in febrile neutropenia in order to help physicians improve dosing and optimization of antimicrobial agents.

Pharmacokinetics of meropenem in critically ill patients with severe infections

BACKGROUND

Meropenem is an effective β-lactam antibiotic that is frequently used to treat serious infections in both intensive care unit (ICU) and febrile neutropenic hematology/oncology (Hem/Onc) patients. Studies suggest that to be effective, meropenem concentrations must be maintained above the inhibitory concentrations for the majority of a dosing interval. However, the pharmacokinetics (PK) of meropenem seem to differ in critically ill patients compared with healthy or less ill subjects used to select labeled dosing regimens.

OBJECTIVES

This study was designed to investigate meropenem PK in critically ill patients and to see how often standard dosing regimens produced adequate plasma concentrations. A secondary objective was to investigate how achieved concentrations were related to outcomes (morbidity and mortality) in these patients.

METHODS

Meropenem plasma concentrations over time were measured using a high pressure liquid chromatography assay in febrile Hem/Onc and ICU patients who were treated with standard meropenem dosing schedules. Outcomes such as fever control and survival were assessed in these patients and compared with individual meropenem PK data and with recommended target concentrations.

RESULTS

A total of 25 subjects including 10 febrile Hem/Onc and 15 ICU patients with a variety of serious illnesses and baseline renal function were studied. Mean peak concentrations were less variable than were pre-dose concentrations. Post peak and trough concentrations were often below recommended minimum inhibitory concentrations. Both clearance and volumes of distribution were greater than reported in less ill subjects, only in part explained by increased renal clearance. Therefore, serum concentrations often did not exceed recommended concentration targets even for moderately sensitive organisms. Inadequate concentrations were especially common in the mostly ill, febrile neutropenic Hem/Onc subjects and seemed to explain at least some therapeutic failures. Conversely, drug accumulation occurred in ICU subjects with decreased renal function.

CONCLUSIONS

Standard meropenem dosing regimens were inadequate in many critically ill febrile, neutropenic Hem/Onc, and septic ICU patients. These data suggest a role for meropenem concentration monitoring in such patients.

Infusional β-lactam antibiotics in febrile neutropenia: has the time come?

PURPOSE OF REVIEW

Febrile neutropenia presents a clinical challenge in which timely and appropriate antibiotic exposure is crucial. In the context of altered pharmacokinetics and rising bacterial resistance, standard antibiotic doses are unlikely to be sufficient. This review explores the potential utility of altered dosing approaches of β-lactam antibiotics to optimize treatment in febrile neutropenia.

RECENT FINDINGS

There is a dynamic relationship between the antibiotic, the infecting pathogen, and the host. Great advancements have been made in the understanding of the pharmacokinetic changes in critical illness and the pharmacodynamic relationships of antibiotics in these settings.

SUMMARY

Antibiotic treatment in febrile neutropenia is becoming increasingly difficult. Patients are of higher acuity, receive more intensive chemotherapy regimens leading to prolonged neutropenia, and are often exposed to multiple antibiotic courses. These patients display significant variability in antibiotic clearances and increases in volume of distribution compared with standard ward-based patients. Rising antibiotic resistance and a lack of new antibiotics in production have prompted alternative dosing strategies based on pharmacokinetic/pharmacodynamic data, such as extended or continuous infusions of β-lactam antibiotics, to maximize the likelihood of treatment success. A definitive study that describes a mortality benefit of such dosing regimens remains elusive and the theoretical advantages require testing in well designed clinical trials.

Nonlinear pharmacokinetics of piperacillin in healthy volunteers--implications for optimal dosage regimens

AIMS

(i) To describe the first-order and mixed-order elimination pathways of piperacillin, (ii) to determine the between occasion variability (BOV) of pharmacokinetic parameters and (iii) to propose optimized dosage regimens.

METHODS

We performed a five-period replicate dose study in four healthy volunteers. Each subject received 4g piperacillin as a single 5min intravenous infusion in each study period. Drug analysis was performed by HPLC. We used NONMEM and S-ADAPT for population pharmacokinetic analysis and Monte Carlo simulation to predict the probability of target attainment (PTA) with a target time of non-protein bound concentration above MIC >50% of the dosing interval.

RESULTS

A model with first-order nonrenal elimination and parallel first-order and mixed-order renal elimination had the best predictive performance. For a 70kg subject we estimated 4.40lh(-1) for nonrenal clearance, 5.70lh(-1) for first-order renal clearance, 170mgh(-1) for V(max) , and 49.7mgl(-1) for K(m) for the mixed-order renal elimination. The BOV was 39% for V(max) , 117% for K(m) , and 8.5% for total clearance. A 30min infusion of 4g every 6h achieved robust (≥90%) PTAs for MICs ≤12mgl(-1) . As an alternative mode of administration, a 5h infusion of 6g every 8h achieved robust PTAs for MICs ≤48mgl(-1) .

CONCLUSIONS

Part of the renal elimination of piperacillin is saturable at clinically used doses. The BOV of total clearance and volume of distribution were low. Prolonged infusions achieved better PTAs compared with shorter infusions at similar daily doses. This benefit was most pronounced for MICs between 12 and 48mgl(-1) .

Continuous versus intermittent infusions of ceftazidime for treating exacerbation of cystic fibrosis

The present multicenter, randomized crossover study compared the safety and efficacy of continuous infusion with those of short infusions of ceftazidime in patients with cystic fibrosis. Patients with chronic Pseudomonas aeruginosa colonization received two successive courses of intravenous tobramycin and ceftazidime (200 mg/kg of body weight/day) for pulmonary exacerbation administered as thrice-daily short infusions or as a continuous infusion. The primary endpoint was the variation in the forced expiratory volume in 1 s (FEV1) during the course of antibiotic treatment. Sixty-nine of the 70 patients enrolled in the study received at least one course of antibiotic treatment. The improvement in FEV1 at the end of therapy was not statistically different between the two treatment procedures (+7.6% after continuous infusion and +5.5% after short infusions) but was better after continuous ceftazidime treatment in patients harboring resistant isolates (P < 0.05). The interval between the course of antibiotic treatments was longer after the continuous infusion than after the short infusion of ceftazidime (P = 0.04). The mean serum ceftazidime concentration during the continuous infusion was 56.2 +/- 23.2 microg/ml; the mean peak and trough concentrations during the short infusions were 216.3 +/- 71.5 and 12.1 +/- 8.7 microg/ml, respectively. The susceptibility profiles of the P. aeruginosa isolates remained unchanged and were similar for both regimens. Quality-of-life scores were similar whatever the treatment procedure, but 82% of the patients preferred the continuous-infusion regimen. Adverse events were not significantly different between the two regimens. In conclusion, the continuous infusion of ceftazidime did not increase its toxicity and appeared to be as efficient as short infusions in patients with cystic fibrosis as a whole, but it gave better results in patients harboring resistant isolates of P. aeruginosa.

Continuous infusion of beta-lactams

PURPOSE OF REVIEW

Continuous infusion of beta-lactam antibiotics is becoming increasingly popular. The background and current clinical evidence are discussed. Tools to apply continuous infusion are analyzed.

RECENT FINDINGS

One randomized controlled trial in an ICU setting and two nonrandomized controlled trials have shown continuous infusion to be more beneficial than intermittent infusion. One randomized controlled trial in chronic obstructive pulmonary disorder patients, however, showed no difference between the two treatments. The stability of most beta-lactams for use during continuous infusion has been documented.

SUMMARY

Killing of bacteria by beta-lactam antibiotics is maximal at around four times the minimum inhibitory concentration in vitro. To ensure an optimal effect when treating severe infections, free unbound concentrations at or above four times the minimum inhibitory concentration should be maintained. Although continuous infusion has been demonstrated to be superior in animal studies, randomized clinical trials have failed to confirm this in humans, primarily because of suboptimal design. A better designed randomized clinical trial, set up as a pilot study, recently demonstrated a favorable outcome with continuous infusion. A major issue during continuous infusion is the stability of the antibiotic, which may limit its application. The calculation of the infusion rate necessary to obtain the desired free drug concentration is relatively straightforward.

Algunas reflexiones acerca de la administración de antibióticos betalactámicos en infusión continua

Numerous studies on continuous intravenous infusion of betalactam antibiotics have indicated that this could be a useful strategy for treating nosocomial infections as well as exacerbations of pulmonary infections in patients with cystic fibrosis and episodes of febrile neutropenia. From the pharmacodynamic viewpoint, betalactam antibiotics have a time-dependent behavior. Thus, the pharmacokinetic/pharmacodynamic index that best correlates with therapeutic efficacy appears to be the time during which free antibiotic concentrations remain above the minimum inhibitory concentration (MIC) of the infecting microorganism. Continuous infusion of betalactams successfully optimizes this pharmacokinetic/ pharmacodynamic index. Furthermore, some studies have shown that this therapeutic strategy may be favorable economically.

Randomized, open-label, comparative study of piperacillin-tazobactam administered by continuous infusion versus intermittent infusion for treatment of hospitalized patients with complicated intra-abdominal infection

The purpose of this randomized, multicenter, open-label study was to compare the continuous infusion of piperacillin-tazobactam with the standard intermittent infusion in 262 hospitalized patients with complicated intra-abdominal infections. Within 1 day of surgical intervention, eligible patients were randomized (1:1) to piperacillin-tazobactam 12 g/1.5 g administered continuously over 24 h or 3 g/0.375 g administered over 30 min intermittently every 6 h for 4 to 14 days. The demographics of the patients in the groups were similar, with a median APACHE II score of 7 and a median length of hospitalization of 7 days. Among 167 clinically evaluable patients, 86.4% and 88.4% of the patients treated with the continuous infusion and the intermittent infusion, respectively, were clinically cured or improved at the test-of-cure visit (P = 0.817). Bacteriological success was observed in 83.9% and 87.9% of patients (P = 0.597) in the two groups, respectively, and no differences in bacteriological response by pathogen were noted. Defervesence and white blood cell count normalization occurred in the majority of patients within 3 days and were similar between patients receiving the continuous infusion and those receiving the intermittent infusion. Drug-related adverse events were generally mild and were reported in similar numbers of patients in each arm of the trial. The results of this study support continuous infusion as a safe and reasonable alternate mode of administration of piperacillin-tazobactam for the treatment of complicated intra-abdominal infection.

Continuous versus intermittent intravenous administration of antibacterials with time-dependent action: a systematic review of pharmacokinetic and pharmacodynamic parameters

We performed a systematic review of randomised clinical trials to evaluate the comparative pharmacokinetic and pharmacodynamic properties of the continuous versus intermittent mode of intravenous administration of various antibacterials. Data were identified from PubMed (January 1950 to January 2005), Current Contents, the Cochrane central register of controlled trials, and references from relevant articles and reviews. Seventeen randomised clinical trials comparing continuous with intermittent intravenous administration of the same antibacterial regimen and examining the pharmacokinetic and pharmacodynamic properties were included in this systematic review. We reviewed data regarding the clinical setting, number of participants, antibacterial agents and dosages used, as well as maximum serum concentration (Cmax), trough serum concentration (Cmin), steady-state or plateau serum concentration (Css), area under the concentration-time curve (AUC), time above the minimum inhibitory concentration (MIC) [T>MIC], AUC: MIC, elimination rate constant, elimination half-life, volume of distribution and systematic clearance. The mean Cmax of the intermittently administered antibacterials was higher compared with Css achieved by the continuous infusion of the same antibacterial in all eligible studies (Cmax was on average 5.5 times higher than Css, range 1.9-11.2). Css was on average 5.8 times higher than the Cmin of the intermittently administered antibacterials (range 1.2-15.6). In three of six studies the length of time that the drug concentration was above the MIC of the responsible pathogens was longer in patients receiving the antibacterials continuously. In conclusion, the reviewed data suggest that the continuous intravenous infusion of antibacterials with time-dependent bacterial killing seems to be superior than the intermittent intravenous administration, from a pharmacodynamic point of view, at least when treating bacteria with high MIC values for the studied antibacterials.

Trough serum concentrations of β-lactam antibiotics in cancer patients: inappropriateness of conventional schedules to pharmacokinetic/pharmacodynamic properties of β-lactams

Serum concentrations of beta-lactams that continuously exceed the minimum inhibitory concentration may improve therapeutic outcomes for immunosuppressed patients. The trough serum levels of ceftazidime (CAZ), cefepime (FEP) or imipenem (IMP) were prospectively determined on days 1 and 3 of treatment in cancer patients. Seventy-eight episodes of suspected infection were analysed. Trough serum levels were higher than 4 mg/L in 62%, 24% and 0% of cases in the CAZ, FEP and IMP groups, respectively, and were higher than 20 mg/L in 24% of cases in the CAZ group compared with 0% both in the FEP and IMP groups. For suspected infectious episodes in cancer patients, the traditional intermittent regimen of beta-lactams does not appear to be appropriate for the pharmacokinetic/pharmacodynamic properties of these antibiotics.

Ceftazidime in acute myeloid leukemia patients with febrile neutropenia: helpfulness of continuous intravenous infusion in maximizing pharmacodynamic exposure

The pharmacokinetic-pharmacodynamic profile of a fixed 6-g daily continuous intravenous infusion of ceftazidime was assessed in 20 febrile neutropenic patients with acute myeloid leukemia. Mean steady-state ceftazidime concentrations averaging 40 mg/liter from day 2 on ensured maximized pharmacodynamic exposure (values close to four to five times the MIC breakpoint against Pseudomonas aeruginosa). However, large intra- and interindividual pharmacokinetic variability was documented throughout the study period.

Continuous versus intermittent intravenous administration of antibiotics: a meta-analysis of randomised controlled trials

Intermittent intravenous administration of antibiotics is the first-line approach in the management of severe infections worldwide. However, the potential benefits of alternate modes of administration of antibiotics, including continuous intravenous infusion, deserve further evaluation. We did a meta-analysis of randomised controlled trials comparing continuous intravenous infusion with intermittent intravenous administration of the same antibiotic regimen. Nine randomised controlled trials studying beta-lactams, aminoglycosides, and vancomycin were included. Clinical failure was lower, although without statistical significance, in patients receiving continuous infusion of antibiotics (pooled OR 0.73, 95% CI 0.53-1.01); the difference was statistically significant in a subset of randomised controlled trials that used the same total daily antibiotic dose for both intervention arms (0.70, 0.50-0.98, fixed and random effects models). Regarding mortality and nephrotoxicity, no differences were found (mortality 0.89, 0.48-1.64; nephrotoxicity 0.91, 0.56-1.47). In conclusion, the data suggest that the administration of the same total antibiotic dose by continuous intravenous infusion may be more efficient, with regard to clinical effectiveness, compared with the intermittent mode. In an era of gradually increasing resistance among most pathogens, the potential advantages of continuous intravenous administration of antibiotics on several clinical outcomes should be further investigated.

Evaluation by monte carlo simulation of the pharmacokinetics of two doses of meropenem administered intermittently or as a continuous infusion in healthy volunteers

Meropenem is a broad-spectrum carbapenem antibacterial agent. In order to optimize levels in plasma relative to the MICs, the ideal dose level and dosage regimen need to be determined. The pharmacokinetics of meropenem were studied in two groups, each comprising eight healthy volunteers who received the following doses: 500 mg as an intravenous infusion over 30 min three times a day (t.i.d.) versus a 250-mg loading dose followed by a 1,500 mg continuous infusion over 24 h for group A and 1,000 mg as an intravenous infusion over 30 min t.i.d. versus a 500-mg loading dose followed by a 3,000-mg continuous infusion over 24 h for group B. Meropenem concentrations in plasma and urine were determined by liquid chromatography-mass spectrometry/mass spectrometry and high-performance liquid chromatography with UV detection, respectively. Pharmacokinetic calculations were done by use of a two-compartment open model, and the data were extrapolated by Monte Carlo simulations for 10,000 simulated subjects for pharmacodynamic evaluation. There were no significant differences in total clearance and renal clearance between group A and group B or between the intermittent treatment and the continuous infusion. The analyses of the probability of target attainment by MIC for the high- and low-dose continuous infusions were robust up to MICs of 4 mg/liter and 2 mg/liter, respectively. The corresponding values for intermittent infusions were only 0.5 mg/liter and 0.25 mg/liter. When these observations were correlated with MICs obtained from the MYSTIC database, intermittent infusion results in adequate activity against two of the most common nosocomially acquired pathogens, Klebsiella pneumoniae and Enterobacter cloacae. However, against Pseudomonas aeruginosa, the evaluation shows a clear advantage of high-dose therapy administered as a continuous infusion. We believe that in the empirical therapy situation, the continuous-infusion mode of administration is most worth the extra efforts. We conclude that clinical trials for evaluation of the continuous infusions of meropenem in critically ill patients are warranted.

Is there a rationale for the continuous infusion of cefepime? A multidisciplinary approach

This review is the fruit of multidisciplinary discussions concerning the continuous administration of beta-lactams, with a special focus on cefepime. Pooling of the analyses and viewpoints of all members of the group, based on a review of the literature on this subject, has made it possible to test the hypothesis concerning the applicability of this method of administering cefepime. Cefepime is a cephalosporin for injection which exhibits a broader spectrum of activity than that of older, third-generation cephalosporins for injection (cefotaxime, ceftriaxone, ceftazidime). The specific activity of cefepime is based on its more rapid penetration (probably due to its zwitterionic structure, this molecule being both positively and negatively charged) through the outer membrane of Gram-negative bacteria, its greater affinity for penicillin-binding proteins, its weak affinity for beta-lactamases, and its stability versus certain beta-lactamases, particularly derepressed cephalosporinases. The stability of cefepime in various solutions intended for parenteral administration has been studied, and the results obtained demonstrated the good compatibility of cefepime with these different solutions. These results thus permit the administration of cefepime in a continuous infusion over a 24-h period, using two consecutive syringes.

Continuous infusion of ceftazidime in the empiric treatment of febrile neutropenic children with cancer

PURPOSE

Infection remains one of the most important complications in cancer therapy. The choice of antibiotics and the method of administration can affect results. Beta-lactam antibiotics can be administered by several short injections per day or by continuous infusion. The latter modality may provide superior pharmacokinetics.

PATIENTS AND METHODS

The authors studied the pharmacokinetics of ceftazidime in children treated for malignancy and in febrile aplasia after chemotherapy. They received a continuous infusion of ceftazidime (200 mg/kg/day) after a loading dose (65 mg/kg/day) administered with amikacin (25 mg/kg/day) and vancomycin (50 mg/kg/day). RESULTS Twenty-three pharmacokinetic studies were performed. Mean ceftazidime serum levels were 31.1 +/- 11.9, 31.2 +/- 10, 32.4 +/- 11.6, 33 +/- 11.6, and 30.4 +/- 12.1 mg/L at 25, 27, 30, 36, and 43 hours, respectively. Treatment was tolerated well. There were no toxic or infectious deaths.

CONCLUSIONS

Ceftazidime's time-dependent pharmacokinetics shows the advantage of continuous infusion. This study confirmed the feasibility and safety of this administration schedule in the empiric treatment of febrile neutropenic children with cancer.

Pharmacokinetics and pharmacodynamics of piperacillin/tazobactam when administered by continuous infusion and intermittent dosing

BACKGROUND

Although intermittent bolus dosing is currently the standard of practice for many antimicrobial agents, beta-lactams exhibit time-dependent bacterial killing. Maximizing the time above the minimum inhibitory concentration (MIC) for a pathogen is the best pharmacodynamic predictor of efficacy. Use of a continuous infusion has been advocated for maximizing the time above the MIC compared with intermittent bolus dosing.

OBJECTIVE

This study compared the pharmacokinetics and pharmacodynamics of piperacillin/tazobactam when administered as an intermittent bolus versus a continuous infusion against clinical isolates of Pseudomonas aeruginosa and Klebsiella pneumoniae.

METHODS

Healthy volunteers were randomly assigned to receive piperacillin 3 g/ tazobactam 0.375 g q6h for 24 hours, piperacillin 6 g/tazobactam 0.75 g continuous infusion over 24 hours, and piperacillin 12 g/tazobactam 1.5 g continuous infusion over 24 hours. Five clinical isolates each of P aeruginosa and K pneumoniae were used for pharmacodynamic analyses.

RESULTS

Eleven healthy subjects (7 men, 4 women; mean +/- SD age, 28 +/- 4.7 years) were enrolled. Mean steady-state serum concentrations of piperacillin were 16.0 +/- 5.0 and 37.2 +/- 6.8 microg/mL with piperacillin 6 and 12 g, respectively. Piperacillin/tazobactam 13.5 g continuous infusion (piperacillin 12 g/tazobactam 1.5 g) was significantly more likely to produce a serum inhibitory titer > or = 1:2 against P aeruginosa at 24 hours than either the 6.75 g continuous infusion (piperacillin 6 g/tazobactam 0.75 g) or 3.375 g q6h (piperacillin 3 g/ tazobactam 0.375 g). There were no statistical differences against K pneumoniae between regimens. The median area under the inhibitory activity-time curve (AUIC) for the 13.5 g continuous infusion was higher than that for 3.375 g q6h and the 6.75 g continuous infusion against both P aeruginosa and Kpneumoniae (P < or = 0.007, 13.5 g continuous infusion and 3.375 g q6h vs 6.75 g continuous infusion against K pneumoniae). The percentage of subjects with an AUIC > or = 125 was higher with both 3.375 g q6h and the 13.5 g continuous infusion than with the 6.75 g continuous infusion against P aeruginosa and K pneumoniae (both, P < 0.001 vs 6.75 g continuous infusion against K pneumoniae).

CONCLUSIONS

Piperacillin 12 g/tazobactam 1.5 g continuous infusion consistently resulted in serum concentrations above the breakpoint for Enterobacteriaceae and many of the susceptible strains of P aeruginosa in this study in 11 healthy subjects. Randomized controlled clinical trials are warranted to determine the appropriate dose of piperacillin/tazobactam.

Management of antimicrobial use in the intensive care unit

Indications for the use of antimicrobials in critically ill patients are similar to those for other hospitalised patients. However, the selection of agents depends on the particular characteristics of patients in the intensive care unit (ICU), the form of presentation of infection, the type of infection and the bacteriological features of the causative pathogens. The use of antimicrobials in patients admitted to medical-surgical ICUs varies between 33 and 53%. The selection of empirical antimicrobials to be included in treatment protocols of the most common infections depends on the strong interrelationship between patient characteristics, predominant pathogens in each focus. and antimicrobials used for treatment. Epidemiological studies carried out in the past have identified the microorganisms most frequently responsible for community-acquired and nosocomial infections in patients admitted to ICUs. Susceptibility to antimicrobial agents may be different between each geographical area, between each hospital and even within the same hospital service. In addition, susceptibility patterns may change temporarily in relation to the use of particular antimicrobials or in association with other unknown factors so that assessment of endemic antimicrobial resistance patterns is very useful in order to tailor the antimicrobial regimens of therapeutic protocols. Antimicrobial use should not be a routine procedure. The clinical course of the patient (an indicator of effectiveness) should be closely monitored as well as the possible appearance of adverse effects and/or multiresistant pathogens. Controls are based on the assessment of plasma drug concentrations and microbiological surveillance to detect the presence of multiresistant strains or new antibacterial-resistant pathogens. Prevention of the development of multiresistant pathogens is the main goal of the ICU antimicrobial policy. Although a series of general strategies to reduce the presence of multiresistant pathogens have been proposed, the implementation of these recommendations in ICUs requires the cooperation of a member of the intensive care team.

Cost-effectiveness of ceftazidime by continuous infusion versus intermittent infusion for nosocomial pneumonia

STUDY OBJECTIVE

To determine if continuous-infusion ceftazidime is more cost-effective and efficacious than intermittent infusion in patients with nosocomial pneumonia.

DESIGN

Prospective, open-label, randomized trial.

SETTING

Large, community teaching hospital.

PATIENTS

Intensive care unit (ICU) patients with nosocomial pneumonia.

INTERVENTIONS

Ceftazidime 3 g/day was administered as a continuous infusion or as 2 g 3 times/day by intermittent infusion to treat nosocomial pneumonia in the ICU. Patients also received tobramycin 7 mg/kg once/day.

MEASUREMENTS AND MAIN RESULTS

Thirty-five patients were evaluable; 17 received continuous infusion and 18 intermittent infusion. Clinical efficacy (94% and 83% successful outcomes with continuous and intermittent infusion, respectively), adverse events, and length of stay did not vary significantly between groups. Costs associated with continuous infusion, $627 +/- 388, were significantly lower (p < or = 0.001) than with intermittent infusion, $1007 +/- 430.

CONCLUSIONS

Continuous infusion of ceftazidime is a cost-effective alternative to intermittent infusion for nosocomial pneumonia in the ICU.

Temporary interruption of ceftazidime continuous infusion without reduction of activity: a computer-assisted simulation

Continuous infusion (CI) of ceftazidime has been demonstrated to add clinical advantages in the treatment of infection of neutropenic cancer patients, especially in the presence of gram-negative bacteremia. However, this particular administration route is not always feasible in this particular clinical setting because of the patient's need of additional care or drug administration. The aim of this study was to evaluate, through a computer-assisted simulation, the modifications of drug concentration in presence of a single or repeated 2-hour interruptions of CI ceftazidime in critically ill patients. Our analysis shows that a loading dose of 20 mg/kg, followed by a CI of 100/mg/kg/die, should be able to maintain efficacious plasma concentrations in all subjects, even when it is interrupted for a 2-hour period every 8 hours. Plasma concentrations after interruption should not fall below 8 microg/mL and for about 65-80% of time should reach levels equal to 5 times the MIC of the infecting pathogen. A 2-hour interruption of CI ceftazidime up to 3 times a day is likely to represent a safe and efficacious administration regimen that may enhance the management of the treatment of infectious complications in critically ill patients such as neutropenic cancer patients.

Continuous versus intermittent administration of ceftazidime in intensive care unit patients with nosocomial pneumonia

A prospective, randomized pilot study was undertaken to compare the efficacy of continuous versus intermittent ceftazidime in ICU patients with nosocomial pneumonia. Ceftazidime was administered either as a 3 g/day continuous infusion (CI) or an intermittent infusion (II) of 2 g every 8 h. In addition, all patients received concomitant once-daily tobramycin. The demographics of the evaluable patients (n = 35) were similar between the groups: age (years), CI 46 +/- 16, II 56 +/- 20; Apache score, CI 14 +/- 4, II 16 +/- 6; time (days) from admission to diagnosis, CI 9 +/- 6, II 9 +/- 6. Clinical efficacy, defined as cure/improvement was similar between groups [n (%), CI 16/17 (94), II 15/18 (83)], while microbiological response was also comparable [n (%), CI 10/13 (76), II 12/15 (80)]. Minimal inhibitory concentrations (MICs) for all isolates were measured throughout the treatment course; there was no development of resistance during therapy for either regimen. While limited clinical data exist, our results suggest that the use of ceftazidime by CI administration maintains clinical efficacy, optimizes the pharmacodynamic profile and uses less antibiotic compared with the standard 2 g every 8 h intermittent dosing regimen.

Continuous beta-lactam antibiotic therapy in a double-lung transplanted patient with a multidrug-resistant Pseudomonas aeruginosa infection

BACKGROUND

It is well known that the bactericidal effect of beta-lactam antibiotics is closely related to the time which the serum concentration of the antibiotic remains above the minimal inhibitory concentration of the target pathogen. Thus, the optimal administration of beta-lactam antibiotics would be the continuous infusion of the drug.

METHODS

We present a case report with a critically ill double-lung transplanted patient with pneumonia due to a multidrug-resistant Pseudomonas aeruginosa who received continuously 8 g meropenem/24 hr. Based on a previous pharmacokinetic study showing that continuous infusion of meropenem is at least equivalent to intermittent administration this case report is reported to demonstrate the clinical efficacy of continuous infusion.

RESULTS

C-reactive protein and pneumonia decreased rapidly when clinical conditions were improved significantly. Continuous administration of meropenem did not interfere with cyclosporine, no side effects were seen, and the patient's renal function was not impaired during the whole period of treatment.

CONCLUSION

The continuous administration of beta-lactam antibiotics is a powerful application in critically ill patients to intensify antimicrobial therapy.

Pharmacokinetics of ceftazidime in dogs following subcutaneous administration and continuous infusion and the association with in vitro susceptibility of Pseudomonas aeruginosa

OBJECTIVE

To determine the pharmacokinetics of ceftazidime following subcutaneous administration and continuous IV infusion to healthy dogs and to determine the minimum inhibitory concentration (MIC) of ceftazidime for clinical isolates of Pseudomonas aeruginosa.

ANIMALS

10 healthy adult dogs.

PROCEDURE

MIC of ceftazidime for 101 clinical isolates of P aeruginosa was determined in vitro. Serum concentrations of ceftazidime were determined following subcutaneous administration of ceftazidime (30 mg/kg of body weight) to 5 dogs and continuous IV infusion of ceftazidime (loading dose, 4.4 mg/kg; infusion rate, 4.1 mg/kg/h) for 36 hours to 5 dogs.

RESULTS

The MIC of ceftazidime for P aeruginosa was < or = 8 microg/ml; all isolates were considered susceptible. Following SC administration of ceftazidime, mean beta disappearance half-life was 0.8 hours, and mean serum ceftazidime concentration exceeded the MIC for P aeruginosa for only 4.3 hours. Two dogs had gastrointestinal tract effects. Mean serum ceftazidime concentration exceeded 16 microg/ml during continuous IV infusion. None of the dogs developed adverse effects.

CONCLUSIONS AND CLINICAL RELEVANCE

Administration of ceftazidime subcutaneously (30 mg/kg, q 4 h) or as a constant IV infusion (loading dose, 4.4 mg/kg; rate, 4.1 mg/kg/h) would maintain serum ceftazidime concentrations above the MIC determined for 101 clinical isolates of P aeruginosa. Use of these dosages may be appropriate for treatment of dogs with infections caused by P aeruginosa.

Intermittent and continuous ceftazidime infusion for critically ill trauma patients

BACKGROUND

The adequacy of intermittent and continuous infusion ceftazidime for the treatment of nosocomial pneumonia in critically ill trauma patients was assessed by analyzing ceftazidime pharmacokinetics in relation to the minimum inhibitory concentration (MIC) and treatment outcome.

METHODS

Serial blood samples were obtained during ceftazidime therapy in 31 trauma patients. Ceftazidime pharmacokinetics were compared with that of previously studied healthy volunteers. Ceftazidime pharmacokinetics were analyzed according to the time above the MIC and treatment outcome.

RESULTS

Critically ill trauma patients had a significantly increased volume of distribution and clearance (0.32 +/- 0.14 L/kg and 2.35 +/- 0.89 mL. min(-1). kg(-1), respectively) compared with healthy volunteers (0.21 +/- 0.03 and 1.58 +/- 0.23 mL. min(-1). kg(-1)). The time above the MIC was >/=92% of the dosing interval for all patients and treatment outcomes were similar between the two treatment groups.

CONCLUSIONS

Ceftazidime pharmacokinetics are significantly altered in critically ill trauma patients. Both intermittent and continuous ceftazidime regimens were equally effective for the treatment of nosocomial pneumonia caused by less virulent bacteria.

Continuous infusion versus intermittent administration of meropenem in critically ill patients

This prospective crossover study compared the pharmacokinetics of meropenem by continuous infusion and by intermittent administration in critically ill patients. Fifteen patients were randomized to receive meropenem either as a 2 g iv loading dose, followed by a 3 g continuous infusion (CI) over 24 h, or by intermittent administration (IA) of 2 g iv every 8 h (q8h). Each regimen was followed for a period of 2 days, succeeded by crossover to the alternative regimen for the same period. Pharmacokinetic parameters (mean +/- SD) of CI included the following: concentration at steady state (Css) was 11.9+/-5.0 mg/L; area under the curve (AUC) was 117.5+/-12.9 mg/L x h. The maximum and minimum serum concentrations of meropenem (Cmax, Cmin) and total meropenem clearance (CItot) for IA were 110.1+/-6.9 mg/L, 8.5+/-1.0 mg/L and 9.4+/-1.2 L/h, respectively. The AUC during the IA regimen was larger than the AUC during CI (P < 0.001). In both treatment groups, meropenem serum concentrations remained above the MICs for the most common bacterial pathogens. We conclude that CI of meropenem is equivalent to the IA regimen and is therefore suitable for treating critically ill patients. Further studies are necessary to compare the clinical effects of CI and IA in this patient group.

Pharmacokinetics of meropenem in febrile neutropenic patients. Swedish study group

To determine the impact of neutropenia on the pharmacokinetics of meropenem, 14 patients with fever and neutropenia were given 1 g of meropenem i.v. every 8 h as an infusion over 30 min. The volume of distribution (16.2 l/1.73 m2) and the nonrenal clearance [75 ml/(min x 1.73 m2)] in this group were significantly increased compared to healthy subjects studied previously with identical techniques. The kinetic study was repeated when the patients had a normal temperature and a raised neutrophil count; most kinetic variables did not differ from the findings on the first day of treatment. The pharmacokinetic profile of meropenem in febrile neutropenic patients differs from earlier findings in healthy subjects. Considering these data and known minimum inhibitory concentration values for common pathogens, meropenem administered every 6 to 8 h seems an appropriate regimen in patients with febrile neutropenia. The shorter time interval may be used for treatment of Pseudomonas infection.

In vitro pharmacodynamics of ceftazidime against Pseudomonas aeruginosa isolates from cystic fibrosis patients

The concentration/MIC (C/MIC) ratio maximizing the bactericidal activity of ceftazidime against 10 Pseudomonas aeruginosa isolates from cystic fibrosis patients was identified. Bactericidal activity was assessed by determining the percent difference in the area under the killing curve at each C/MIC ratio for all of the isolates from that of their growth control. The percent effect at each C/MIC ratio was fitted to a sigmoidal Emax model with maximum bactericidal activity defined as the C/MIC ratio that produced an effect that was 90% of the Emax. Our results suggest that at least some isolates may require higher C/MIC ratios than previously reported for maximal activity.

Antimicrobial effects of continuous versus intermittent administration of carbapenem antibiotics in an in vitro dynamic model

In an in vitro dynamic model we compared the antimicrobial effects of two carbapenems, imipenem (MIC, 1 microg/ml) and meropenem (MIC, 0.25 microg/ml) on Pseudomonas aeruginosa. The antibiotics were administered either as short-time infusions once or three times a day or as continuous infusions with steady-state levels ranging from 0.5 to 20 microg/ml. From the resulting kill curves the period of time until the onset of bacterial death (dt), the rate constant of bacterial death (ka), the maximal reduction of CFU (mr), and the period of time until bacterial regrowth occurred (tr) were determined. Additionally, the occurrence of bacterial resistance during the simulations (rq) and the postantibiotic effect (PAE) were recorded. For both investigated carbapenems no significant difference in dt, ka, mr, and PAE values between the short-time infusions and continuous infusions with steady-state levels above 2 microg/ml could be detected. The tr was longest with continuous infusions of over approximately 24 h, corresponding to steady-state levels of 3 microg/ml for imipenem and 2.5 microg/ml for meropenem. An increase in MIC was observed only during continuous infusions with steady-state levels below 2 microg/ml. Independent of the chosen method of application and despite the lower MIC of meropenem, imipenem was slightly more effective than meropenem.