Determination of tazobactam and piperacillin in human plasma, serum, bile and urine by gradient elution reversed-phase high-performance liquid chromatography

Pharmacokinetics of intravenous piperacillin/tazobactam among patients with peritoneal dialysis-associated peritonitis

Currently, pharmacokinetic information on intravenous (IV) piperacillin/tazobactam in patients with peritoneal dialysis-associated peritonitis (PD peritonitis) is limited. This study employed a prospective single-dose pharmacokinetic design to assess the pharmacokinetics of IV piperacillin/tazobactam in these patients. Four patients with PD peritonitis who received an IV loading dose of 4000 mg/500 mg piperacillin/tazobactam were enrolled in this study. The concentrations of piperacillin and tazobactam in plasma, peritoneal dialysis fluid (PDF) and urine were determined by high-performance liquid chromatography. Non-compartmental methods were used for pharmacokinetic analysis. During a 6-h dwell time for chronic ambulatory peritoneal dialysis (CAPD), 9.23 ± 4.01% of the piperacillin was recovered in the PDF. This result is greater than that observed in patients without peritonitis in prior research. Piperacillin's PD clearance (CLPD), steady-state volume of distribution (Vss) and terminal half-life (t 1/2) were 5.79 ± 2.55 mL/min, 24.35 ± 11.26 L and 5.74 ± 1.53 h, respectively. These values are also higher than those of patients without peritonitis in a prior study. Eight hours following the loading dosage, the plasma and PDF piperacillin concentrations of all patients (98.25 ± 26.03 and 52.70 ± 22.99 mg/L, respectively) surpassed the Pseudomonas aeruginosa and Enterobacterales Clinical and Laboratory Standards Institute susceptible breakpoints. In summary, the CLPD, Vss and t 1/2 for piperacillin were found to be greater in patients with PD peritonitis than in CAPD patients without peritonitis when compared with the results of a previous study. The IV loading dose of 4000 mg/500 mg piperacillin/tazobactam is sufficient to treat peritonitis caused by susceptible P. aeruginosa and Enterobacterales. The multiple-dose pharmacokinetics of IV piperacillin and tazobactam in this specific patient group should be further investigated.

Therapeutic drug monitoring of piperacillin and tazobactam by RP-HPLC of residual blood specimens

BACKGROUND

Sepsis is a common diagnosis in critical care with inpatient mortality rates up to 50%. Sepsis care is organized around source control, antibiotics, and supportive care. Drug disposition is deranged by changes in volume of distribution and regional blood flow, as well as multiple organ failure. Thus, assuring that each patient with sepsis attains pharmacokinetic targets is challenging. There is currently no commercially available FDA-approved assay to measure piperacillin-tazobactam, very commonly used as a beta-lactam/beta-lactamase inhibitor combination antibiotic in the intensive care unit (ICU).

METHODS

Samples were prepared by ultrafiltration of plasma collected in lithium heparin Vacutainers. Separation was achieved by gradient elution on a C-18 column followed by UV detection at 214 nm. The method is validated in residual blood samples allowing investigators to exploit a waste product to develop insight into beta-lactam pharmacokinetics in the ICU.

RESULTS

Accuracy and precision were within the 25% CLIA error standard for other antibiotic assays. Free piperacillin concentrations were also in good agreement with total piperacillin concentrations measured in the same plasma by an assay in clinical use outside the United States.

CONCLUSION

We describe a method for measuring piperacillin and tazobactam that meets clinical validation standards. Quick turnaround time and excellent accuracy on a low-cost platform make this method more than adequate for use as a routine therapeutic drug monitoring tool.

A UHPLC-MS/MS method for the simultaneous determination of piperacillin and tazobactam in plasma (total and unbound), urine and renal replacement therapy effluent

Piperacillin-tazobactam is a beta-lactam/beta-lactamase combination antibiotic used in patients with moderate to severe infection. Dosing of piperacillin-tazobactam requires an understanding of this patient group to maximise the effectiveness of this antibiotic and limit a further emergence of resistant pathogens. This is the first method that measures piperacillin and tazobactam simultaneously, across this range of clinically-relevant biological matrices. The calibration line was linear across the concentration range of 0.5-500μg/mL for piperacillin and 0.625-62.5μg/mL for tazobactam. All validation testing for matrix effects, precision and accuracy, specificity and stability were within 15%. A calibration equivalence study was performed to investigate the suitability of applying calibration curves prepared in an alternative matrix, with a mean bias of -10.8% identified for the application of a calibration line prepared for tazobactam in plasma only. Bias for all other calibration lines prepared in alternate matrices was within the 5% acceptance criteria. The method was successfully applied to a pharmacokinetic study of a critically ill patient receiving renal replacement therapy, with the results included.

In vivo antibiotic removal during coupled plasma filtration adsorption: a retrospective study

Coupled plasma filtration adsorption (CPFA) is a blood purification therapy aimed at modulating the host inflammatory response involved in sepsis pathogenesis. One potential drawback of this technique is the unexpected elimination of antibiotics. The aim of this study was to assess the elimination of several antibiotics with CPFA. We performed a retrospective analysis of the serum and ultrafiltrate concentrations of different antibiotics routinely measured during CPFA sessions in five patients experiencing septic shock. The adsorbent extraction ratio (AER) for piperacillin and vancomycin 2 h into the CPFA session were high: 95.4 ± 6.9% and 99.6 ± 0.9%, respectively. These AER decreased significantly by 8 h (at 8 h: 6.3 ± 51.8% and -30.2 ± 25.6%, respectively), suggesting saturation of the resin cartridge. Conversely, the tazobactam AER was low (7.2 ± 15% after 2 h of CPFA). No significant changes in the mean serum concentrations of piperacillin, tazobactam, and vancomycin were observed. Thus, as opposed to tazobactam, we report high adsorption of piperacillin and vancomycin on the CPFA resin but with no reduction in serum concentrations.

Therapeutic drug monitoring of piperacillin-tazobactam using spent dialysate effluent in patients receiving continuous venovenous hemodialysis

Sepsis and multisystem organ failure are common diagnoses affecting nearly three-quarters of a million Americans annually. Infection is the leading cause of death in acute kidney injury, and the majority of critically ill patients who receive continuous dialysis also receive antibiotics. Dialysis equipment and prescriptions have gradually changed over time, raising concern that current drug dosing recommendations in the literature may result in underdosing of antibiotics. Our research group directed its attention toward antibiotic dosing strategies in patients with acute renal failure (ARF), and we sought data confirming that patients receiving continuous dialysis and antibiotics actually were achieving therapeutic plasma drug levels during treatment. In the course of those investigations, we explored "fast-track" strategies to estimate plasma drug concentrations. As most antimicrobial antibiotics are small molecules and should pass freely through modern high-flux hemodialyzer filters, we hypothesized that continuous renal replacement therapy (CRRT) effluent could be used as the medium for drug concentration measurement by reverse-phase high-pressure liquid chromatography (HPLC). Here we present the first data demonstrating this approach for piperacillin-tazobactam. Paired blood and dialysate trough-peak-trough samples were drawn from 19 patients receiving piperacillin-tazobactam and continuous venovenous hemodialysis (CVVHD). Total, free, and dialysate drug concentrations were measured by HPLC. Dialysate drug levels predicted plasma free drug levels well (r(2) = 0.91 and 0.92 for piperacillin and tazobactam, respectively) in all patients. These data suggest a strategy for therapeutic drug monitoring that minimizes blood loss from phlebotomy and simplifies analytic procedures.

First-dose and steady-state population pharmacokinetics and pharmacodynamics of piperacillin by continuous or intermittent dosing in critically ill patients with sepsis

The objectives of this study were (i) to compare the plasma concentration-time profiles for first-dose and steady-state piperacillin administered by intermittent or continuous dosing to critically ill patients with sepsis and (ii) to use population pharmacokinetics to perform Monte Carlo dosing simulations in order to assess the probability of target attainment (PTA) by minimum inhibitory concentration (MIC) for different piperacillin dosing regimens against bacterial pathogens commonly encountered in critical care units. Plasma samples were collected on Days 1 and 2 of therapy in 16 critically ill patients, with 8 patients receiving intermittent bolus dosing and 8 patients receiving continuous infusion of piperacillin (administered with tazobactam). A population pharmacokinetic model was developed using NONMEM, which found that a two-compartment population pharmacokinetic model best described the data. Total body weight was found to be correlated with drug clearance and was included in the final model. In addition, 2000 critically ill patients were simulated for pharmacodynamic evaluation of PTA by MIC [free (unbound) concentration maintained above the MIC for 50% of the dosing interval (50% f(T>MIC))] and it was found that continuous infusion maintained superior free piperacillin concentrations compared with bolus administration across the dosing interval. Dosing simulations showed that administration of 16g/day by continuous infusion vs. bolus dosing (4g every 6h) provided superior achievement of the pharmacodynamic endpoint (PTA by MIC) at 93% and 53%, respectively. These data suggest that administration of piperacillin by continuous infusion, with a loading dose, both for first dose and for subsequent dosing achieves superior pharmacodynamic targets compared with conventional bolus dosing.

High performance liquid chromatographic determination of plasma free and total tazobactam and piperacillin

A high-pressure liquid chromatography (HPLC) method with ultraviolet detection was developed for the measurement of plasma free and total tazobactam and piperacillin. This method is simple and fast, requiring only 11 min for the HPLC run and a sample preparation of about 11 min for total drugs and 10 min for free drugs. The procedure for the assay involves the treatment of plasma with acetonitrile for total drugs determination, and the use of a centrifugal filter device to deproteinize plasma for free drugs determination. The HPLC column, a Hypersil-ODS, was equilibrated with an eluent mixture composed of acetonitrile-potassium phosphate (pH 2.6). CVs for repeatability of tazobactam and piperacillin measurements ranged from 4.30 to 6.60; CVs for reproducibility ranged from 5.60 to 9.40. Mean analytical recoveries ranged from 100.4 to 103%. A linear relationship was obtained between peak area and drugs concentration in the range studied (0-62.5mg/L for tazobactam and 0-500mg/L for piperacillin). The equation for regression line were y=19x-1.4 for tazobactam and y=1.7x-0.9 for piperacillin; correlation coefficients were >0.999. The lower limit of quantitation (LLQ) for standard samples was about 0.12 mg/L for tazobactam and 0.49 mg/L for piperacillin, respectively. The lower limit of detection (LLD) was 0.06 mg/L for tazobactam and 0.24 mg/L for piperacillin. This HPLC assay for tazobactam and piperacillin is sensitive and accurate, and provides a reliable determination of both free and total tazobactam and piperacillin in human plasma, thus allowing the determination of these analytes in patients receiving tazocillin therapy.

An improved high-performance liquid chromatographic method with a solid-phase extraction for the determination of piperacillin and tazobactam: application to pharmacokinetic study of different dosage in Chinese healthy volunteers

An improved HPLC method was developed for the determination of piperacillin and tazobactam in human plasma and pharmacokinetic study in Chinese healthy volunteers. Piperacillin and tazobactam in human plasma were extracted by solid-phase extraction and separated on a C(18) column and detected at 220 nm. The mobile phase for piepracillin consisted of 0.01 mol/L sodium dihydrogen phosphate (pH = 4.65) and acetonitrile (71:29, v/v), and that for tazobactam was 0.05 mol/L sodium dihydrogen phosphate (pH = 4.45) and methanol (90:10, v/v). The method was linear in the range 0.25-320.00 microg/mL for piperacillin (r(2) = 0.995) and 0.25-64.00 microg/mL for tazobactam (r(2) = 0.994). The lower limit of quantification of both compounds was 0.25 microg/mL. The intra- and inter-day precisions of piperacillin and tazobactam at three concentrations were all less than 9.2% and accuracies were within the range 97.0-108.0%. The method was used to investigate the pharmacokinetics of piperacillin and tazobactam in 12 volunteers who were intravenously given a dosage of 1.25, 2.50 and 3.75 g in three periods. The results showed that piperacillin sodium-tazobactom sodium (4:1) for injection in Chinese people fits linear dynamics, and the administred dosage can be adjusted with therapeutic effect.

Influence of renal function on trough serum concentrations of piperacillin in intensive care unit patients

OBJECTIVE

To explore the effects of renal function estimated by measured creatinine clearance (Cl(CR)) on trough serum concentration (C(min)) of piperacillin given to critically ill patients.

DESIGN

Prospective observational study.

SETTING

An intensive care unit and research ward in a university hospital.

PATIENTS

Seventy critically ill patients, including 22 with severe trauma.

INTERVENTIONS

All subjects received an intravenous infusion of piperacillin 4 g three times (n = 61) or four times (n = 9) per day. Piperacillin C(min) values were determined 24 h after treatment started and compared to the French breakpoint defining antibiotic susceptibility against Enterobacteriaceae (8 mg/l) or Pseudomonas sp. (16 mg/l).

RESULTS

Median (range) piperacillin C(min) was 11.9 (< 1-156.3) mg/l, with a great variability among patients. Although the median value was close to the breakpoints, sub-therapeutic plasma levels were frequently observed. Piperacillin C(min) was lower than the breakpoint for Enterobacteriaceae in 37% of patients, and lower than the breakpoint for P. aeruginosa in 67% of them. A strong relationship was observed between piperacillin C(min) and Cl(CR): the higher the Cl(CR,) the lower the piperacillin C(min )in serum. For patients with a Cl(CR) < 50 ml/min, enough piperacillin C(min) was achieved in most patients with 12 g piperacillin per day. For patients with higher Cl(CR) values, a piperacillin daily dose of 16 g or more may be warranted.

CONCLUSIONS

In critically ill patients, therapeutic monitoring must be part of the routine, and knowledge of Cl(CR) value may be useful for the choice of adequate initial piperacillin dosing.

Chromatographic analysis of penicillins in pharmaceutical formulations and biological fluids

Natural penicillin (benzylpenicillin) is the oldest antibiotic observed by Alexander Fleming in 1928. To broaden its spectrum of activity, natural penicillin was modified, giving rise to a group of antibiotics under the name 'penicillins'. Although an increasing number of bacteria appear to be resistant to them, penicillins are used to treat a variety of bacterial infections including Gram-positive, Gram-negative aerobic and anaerobic bacteria. Consequently, they are widely used in human and veterinary medicine to prevent and treat diseases. This review covers the analytical methodologies, mainly chromatographic, employed to the penicillins determination in pharmaceutical formulations, biological fluids and in production-scale fermentations reported in the literature. Results of published assays are comparatively presented focusing on sample preparation regarding isolation and purification, chromatographic conditions and method validation. Information on chemical structure, spectrum of activity and action mechanism of common penicillins has also been given.

Penetration of piperacillin and tazobactam into inflamed soft tissue of patients with diabetic foot infection

We investigated the pharmacokinetics of piperacillin and tazobactam in the extracellular space fluid of inflamed soft tissues of six patients with diabetic foot infection using in vivo microdialysis and found similar penetration for piperacillin but not for tazobactam into inflamed and noninflamed soft tissue.

Simultaneous analysis of piperacillin and tazobactam in rabbits: application to pharmacokinetic study

A simple and rapid assay is developed for the simultaneous analysis of piperacillin and tazobactam in rabbit serum and tissue cage fluid (TCF). To eliminate endogenous interferences, a wavelength switch technique was applied, in which the programmable UV detector changed the monitoring wavelength from 218 to 254 nm at 10 min. After liquid-liquid extraction, sample analyses were performed on a C(18) column by gradient elution; the mobile phase consisted of acetonitrile and phosphate buffer (0.014 m, pH 2.4). Owing to the limited amount of rabbit TCF available, a cross-validation of a proxy matrix was evaluated. The relative standard deviation of the between- and within-batch precision of both compounds was less than 5.1%; the relative error of the between- and within-batch accuracy was less than 7.3%. The recoveries of both compounds in serum and TCF were larger than 80%. This assay was successfully applied to simultaneously analyze piperacillin and tazobactam in rabbit serum and TCF samples.

Quantitation and stability of piperacillin and tazobactam in plasma and ultrafiltrate from patients undergoing continuous venovenous hemofiltration by HPLC

Simple and reproducible HPLC methods for the determination of piperacillin and tazobactam have been developed and a complete stability study carried out. The method for piperacillin plasma samples consisted of protein precipitation with methanol using penicillin G as internal standard. No sample preparation was needed for ultrafiltrate samples. Tazobactam sample preparation involved protein precipitation with acetonitrile and the removal of lipids with dichloromethane. Piperacillin separation was performed on a microBondapack C(18) column (300 x 3.9, 10 microm) and tazobactam on a Novapack C(18) column (150 x 3.9, 4 microm) with UV detection set at 229 and 225 nm, respectively. The mobile phase consisted of phosphate buffer-acetonitrile, delivered at 1.5 mL[sol ]min. Calibration curves determination coefficients were >or=0.999 and response factors CV% < 5%. Intra- and inter-assay precision and accuracy of the quality control and limit of quantification were satisfactory. Plasma and ultrafiltrate samples were stable at -20 and -80 degrees C for 2 months and after three freeze-thaw cycles. In the chromatographic rack, tazobactam ultrafiltrate samples were stable for 24 h and plasma samples for 12 h, piperacillin ultrafiltrate samples for 8 h, but plasma samples for only 4 h. Storage of piperacillin samples at 4 degrees C until analysis is recommended. Piperacillin was stable in the presence of tazobactam.

Penetration of piperacillin and tazobactam into pneumonic human lung tissue measured by in vivo microdialysis

OBJECTIVES

The pharmacokinetic profile of antibiotics at the site of anti-infective action is one of the most important determinants of drug response, since it correlates with antimicrobial effect. Up to now, only limited information on the lung tissue pharmacokinetics of antibiotic agents has been available. The aim of this study was to measure, using a new microdialysis-based approach, antibiotic penetration into the extracellular space fluid of pneumonic human lung parenchyma.

PATIENTS AND METHODS

The lung penetration of a combination of piperacillin and tazobactam, substances with low protein binding, was determined in five patients suffering from pneumonia and metapneumonic pleural empyema. The condition was treated by decortication after lateral thoracotomy. Intra-, or post-operatively, respectively, two microdialysis probes were inserted into pneumonic lung tissue, and into healthy skeletal muscle to obtain reference values. Serum and microdialysis samples were collected at 20-min intervals for at last 8 h following i.v. administration of a single dose of 4 g piperacillin and 500 mg tazobactam.

RESULTS

The mean free interstitial concentration profiles of piperacillin in infected lung tissue and serum showed a maximal tissue concentration (Cmax) of 176.0 +/- 105.0 mg l-1 and 326.0 +/- 60.6 mg l-1, respectively. The mean AUC (area under the curve) for infected lung tissue was 288.0 +/- 167.0 mg.h l-1 and for serum 470.0 +/- 142.0 mg.h l-1. There was a statistically significant difference between AUC (lung) and AUC (serum) (P = 0.018) as well as between AUC (lung) and AUC (muscle) (P = 0.043). The intrapulmonary concentrations of piperacillin and tazobactam exceeded the minimum inhibitory concentrations (MIC) for most relevant bacteria for 4-6 h. The procedure was well tolerated by all patients and no adverse events or microdialysis-associated side-effects were observed.

CONCLUSION

This microdialysis technique enabled continuous tissue pharmacokinetic measurement of free, unbound anti-infective agents in the lung tissue of patients with pneumonia. The present data corroborate the use of piperacillin and tazobactam in the treatment of lung infections caused by extracellular bacteria and demonstrate the distribution of piperacillin and tazobactam in the interstitial space of pneumonic lung tissue.

Development and optimization of a reversed-phase high-performance liquid chromatographic method for the determination of piperacillin and tazobactam in tazocin injectable powder

A reversed phase high-performance liquid chromatographic method with detection at 220 nm was developed and validated for the determination of piperacillin, I, and tazobactam, II, in Tazocin injectable powder. Acetaminophen was used as internal standard. A Hypersil BDS RP-C(18) column (250 x 4.6 mm), 5 microm particle size, was equilibrated with a mobile phase composed of aqueous solution of sodium dihydrogenphosphate-dihydrate (20 mM)-acetonitrile-methanol (70:15:15, v/v/v) and pH 5.0. Its flow rate was 1.0 ml/min. Calibration curves were linear for I and II in the concentration ranges of 3.0 x 10(-7)-2.0 x 10(-4) M and 7.0 x 10(-7)-2.0 x 10(-4) M, respectively. Limits of detection and quantitation were 1 x 10(-7), 3 x 10(-7) M for I and 2 x 10(-7), 7 x 10(-7) M for II, respectively. Relative standard deviation, for I and II was less than 0.40 and 0.75%, respectively. Extensive recovery studies were also performed.

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.

Pharmacokinetics of piperacillin-tazobactam in anuric intensive care patients during continuous venovenous hemodialysis

The pharmacokinetics of piperacillin-tazobactam were investigated in eight anuric intensive care patients treated by continuous venovenous hemodialysis (CVVHD). The elimination half-life of piperacillin was 4.3 +/- 1.2 h, and that of tazobactam was 5.6 +/- 1.3 h. The contribution of CVVHD to the overall elimination was relevant (>25%) for both drugs.

[Comparison of 2 administration protocols (continuous or discontinuous) of a time-dependent antibiotic, Tazocin]

A predictive parameter of beta-lactam therapeutic efficacy is the time (T > MIC) while antibiotic serum concentrations are above the MIC of suspected bacteriological agents. This led us to carry out a randomised open study to compare the usually used intermittent administration of Tazocin (three injections of 4 g/0.5 g a day) and continuous perfusion of 12 g/1.5 g a day by calculating these T > MIC. Patients from digestive reanimation department were randomised within two arms: continuous or intermittent administration. Sixteen takings of blood were executed over a forty-hour period. After liquid/liquid extraction, piperacillin and tazobactam serum concentrations were determined by HPLC with a reversed phase column (C18) and a UV spectrophotometry detection. Then, from the time-concentration curves we have evaluated the T > MIC for an enterobacteria (MIC = 8 micrograms/mL) and for Pseudomonas (MIC = 16 micrograms/mL). Concerning intermittent administration T > MIC were 74% (c > MICenterobacteria) and 62% (c > MICPseudomonas). These percentages in the continuous arm were 100% (c > MICenterobacteria) and 99% (c > MICPseudomonas). Tazobactam concentrations were low and even undetectable between each injection in the intermittent administration arm. This was not found within the continuous administration arm. In conclusion, for the intermittent administration, we observed some long periods occurring before each injection while antibiotic concentrations were under the MIC of most bacteria. During these same periods tazobactam concentrations were under the efficacy threshold. These periods were not observed within the continuous administration arm.

Study on fluorescent property of degrading products of piperacillin and its analytical application

The fluorimetric property of the degrading products of piperacillin has been studied in detail. The studies on degrading pH, degrading time, detection alkalinity and other corresponding analytical parameters of acid degradation have been made. Then fluorometry of piperacillin was established by producing its stable fluorescent products. The detection limit for acid degradation analytical method is 2.34 ng/ml, the linear range is 7.80-4.0 x 10(2) ppb. The analytical sensitivity, precision and stability of degrading products of acid degradation are satisfactory, which has been used for the determination of the trace piperacillin in human serum and urine with satisfactory results.

Pharmacokinetics of Intraperitoneal Piperacillin/Tazobactam in Patients on Peritoneal Dialysis with and without Pseudomonas Peritonitis

Objective

The objective of this study was to assess the pharmacokinetics of intraperitoneal (IP) administration of the antibiotic combination piperacillin/tazobactam (PIP/TAZ) to patients on chronic ambulatory peritoneal dialysis (CAPD) with and without pseudomonas peritonitis.

Design

Open-labeled study.

Setting

The study was carried out in the CAPD unit of Assaf Harofeh Medical Center, Zerifin, Israel.

Patients and Methods

Six patients participated in the study, 4 had pseudomonas peritonitis, all were given an IP loading dose of 4 g/0.5 g PIP/TAZ. Twenty-four hours after the initial dose, a maintenance dose of 0.5 g/0.0625 g PIP/TAZ was administered with each dialysate exchange for a period of 1 week. The patients without peritonitis received only the loading dose. High performance liquid chromatography was used to determine the concentrations of PIP/TAZ in plasma obtained at 0, 30, 60, 90, 120, 360, 480, 600, 720, and 1440 minutes after administration. Samples of the dialysate fluid for determination of PIP/TAZ concentration were collected at 6, 10, 14, 24, and 72, 120, and 168 hours.

Results

After the loading dose, the highest plasma PIP concentration (Cmax) was 51.6 ± 21.25 μg/mL and appeared at 1.5 ± 0.45 hours (tmax). During the maintenance period plasma PIP concentration was 5.2 ± 4.75 μg/mL. Tazobactam was detected in the plasma of 1 patient only. The concentration of TAZ in the dialysate fluid during the maintenance period was 2.3 ± 0.5 μg/mL.

Conclusions

Piperacillin administered IP at 4 g reached plasma concentrations comparable to intravenous administration and considered therapeutic (above the MIC90for Pseudomonas aeruginosa) in CAPD patients with or without peritonitis. The maintenance dose, however, should be augmented. Tazobactam could not be detected in the plasma of most patients and the therapeutic implications of IP administration of TAZ cannot be directly correlated to intravenous administration.

Piperacillin and tazobactam exhibit linear pharmacokinetics after multiple standard clinical doses

A population pharmacokinetic (PK) analysis was conducted to determine if piperacillin and tazobactam exhibited linear or nonlinear PKs and if incremental changes in the daily dosage of piperacillin affected tazobactam PKs. Four dosage groups were evaluated after multiple dosing regimens. Concentrations of drug in plasma and amounts in urine were best fitted by using a linear two-compartment PK model. No significant difference between dosing groups was seen for any piperacillin or tazobactam PK parameters. Both drugs exhibited linear PKs when given at usual clinical doses. Tazobactam PKs did not appear to be affected by the different dosing regimens of piperacillin.

Chromatography as an analytical tool for selected antibiotic classes: a reappraisal addressed to pharmacokinetic applications

The first antibiotic discovered, penicillin, appeared on the market just after the Second World War. Intensive research in subsequent years led to the discovery and development of cephalosporins, aminoglycosides, tetracyclines and rifamycin. The chemotherapeutic quinolones and the more recently discovered fluoroquinolones have added promising new therapeutic weapons to fight the microbial challenge. The major role pharmacokinetics has played in developing these compounds should be highlighted. Plasma concentration-time profiles and the therapeutic activity evoked by these compounds allow the therapeutic window, doses and dose turnovers to be appropriately defined as well as possible dose adjustment to be made in renal failure. The pharmacokinetics of antimicrobial agents were initially explored by using microbiological methods, but these lack specificity. The HPLC technique with UV, fluorometric, electrochemical and, in some cases, mass spectrometry detection has satisfactory solved the problem of antimicrobial agent assay for pharmacokinetic, bioavailability and bioequivalence purposes alike. Indeed, in these studies, plasma concentrations of the given analyte must be followed up for a period > or = 3 times the half-life, which calls for specific sensitive assays. In the review, the authors have described the analytical methods employed in the pharmacokinetics of antibiotics, including some chemotherapeutic agents which are used in medical practice as alternatives to antibiotics. The pharmacokinetic characteristics of each class of drugs are also briefly described, and some historical and chemical notes on the various classes are given.

Determination of piperacillin and mezlocillin in human serum and urine by high-performance liquid chromatography after derivatisation with 1,2,4-triazole

High-performance liquid chromatographic methods have been developed for the determination of piperacillin and mezlocillin in human serum and urine samples. The methods involve ultrafiltration of samples followed by reaction with 1.5 M 1, 2, 4-triazole and 0.5 x 10(-3) M mercury (II) chloride in solution (pH 8.50) at 50 degrees C for 15 min. The resulting products were separated on a C18 column following stabilisation in an eluent containing sodium thiosulphate. They were detected at 323 nm for both penicillins. The methods have been applied to assays applied to assays of these penicillins in human serum and urine samples. The procedures, which permit the determination of penicillin concentration down to 0.1 microgram m1-1 in serum and 1 microgram m1-1 in urine samples, are specific to intact penicillins without interference from corresponding penicilloates [see J. Haginaka et al., Anal. Sci. 1 (1985) 73]. At concentrations of 1-500 micrograms ml-1 for each compound, the within- and between-day precisions were 1.8-4.8 and 3.7-6.9, respectively. The accuracy was ca. 100% for all samples assayed.

Pharmacokinetics and pharmacodynamics of two multiple-dose piperacillin-tazobactam regimens

The pharmacokinetics and pharmacodynamics of two multiple-dose regimens of piperacillin-tazobactam (3.375 g every 6 h and 4.5 g every 8 h) were evaluated at steady state for 12 healthy adult volunteers. Inhibitory and bactericidal activities for the two regimens were determined with five American Type Culture Collection (ATCC) organisms (Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Bacteroides fragilis). The percentage of time that plasma concentrations remained above the MIC (T > MIC) for each organism and dosage regimen was calculated. Areas under the inhibitory (AUIC0-24) and bactericidal activity (AUBC0-24) curves were calculated with the trapezoidal rule by using the reciprocal of the inhibitory and bactericidal titers determined for each dosage regimen. In order to assess the validity of predicted measures of bactericidal (AUC0-24/MBC) and inhibitory (AUC0-24/MIC) activity to determine bacteriological response to beta-lactam antimicrobial agents, AUC0-24/MBC and AUC0-24/MIC values were compared with measured AUBC0-24 and AUIC0-24 values. Total body clearance values were equivalent for piperacillin (183.96 +/- 22.66 versus 181.72 +/- 19.54 ml/min/1.73 m2, P > 0.05) and tazobactam (184.71 +/- 19.89 versus 184.87 +/- 18.35 ml/min/1.73 m2, P > 0.05) following the administration of the 3.375-g-every-6-h and 4.5-g-every-8-h dosages, respectively. Comparison of area under the plasma concentration-time curve (AUC0-24) for piperacillin (967.74 +/- 135.56 microg x h/ml versus 978.88 +/- 140.96 microg x h/ml) and tazobactam (120.14 +/- 15.78 microg x h/ml versus 120.01 +/- 16.22 microg x h/ml) revealed no significant differences (P > 0.05) between the 3.375-g-every-6-h and 4.5-g-every-8-h regimens, respectively. Both regimens provided T > MIC values of > 60% for all organisms tested. Measured values of bactericidal (AUBC) and inhibitory (AUIC) activity were significantly different (P < 0.05) from predicted values (AUC0-24/MBC and AUC0-24/MIC) for all organisms studied with the exception of the bactericidal activity for P. aeruginosa and S. aureus. Additionally, ATCC organisms possessing the same MICs and MBCs exhibited great differences in measured AUBC0-24 and AUIC0-24 values. Reasons for this difference may be inherent differences in organism specific susceptibility.

High-performance liquid chromatographic determination of tazobactam and piperacillin in human plasma and urine

A high-performance liquid chromatographic (HPLC) method with ultraviolet (UV) absorbance was developed for the analysis of piperacillin-tazobactam (tazocillin), in plasma and urine. The detection was performed at 218 nm for tazobactam and 222 nm for piperacillin. The procedure for assay of these two compounds in plasma and of piperacillin in urine involves the addition of an internal standard (ceftazidime for tazobactam and benzylpenicillin for piperacillin) followed by a treatment of the samples with acetonitrile and chloroform. To quantify tazobactam in urine, diluted samples were analysed using a column-switching technique without internal standard. The HPLC column, LiChrosorb RP-select B, was equilibrated with an eluent mixture composed of acetonitrile-ammonium acetate (pH 5). The proposed technique is reproducible, selective, and reliable. The method has been validated, and stability tests under various conditions have been performed. Linear detector responses were observed for the calibration curve standards in the ranges 5-60 micrograms/ml for tazobactam, and 1-100 micrograms/ml for piperacillin and spans what is currently though to be the clinically relevant range for tazocillin concentrations in body fluids. The limit of quantification was 3 micrograms/ml for tazobactam and 0.5 microgram/ml for piperacillin in plasma and urine. Extraction recoveries from plasma proved to be more than 85%. Precision, expressed as C.V., was in the range 0.4-18%.

High-performance liquid chromatographic determination of tazobactam by precolumn derivatization

A new reversed-phase high-performance liquid chromatography (RP-HPLC) method for the detection and quantification of tazobactam in serum and haemofiltration fluid is described. The assay for these biological fluids involves an extraction with diethyl ether followed by derivatization using 1,2,4-triazole. The mobile phase consisted of phosphate buffer-methanol and the detection wavelength was 325 nm. The limit of detection was 0.05 microgram/ml in the two fluids and the calibration curves were linear over the range 0.1-50 micrograms/ml. For a tazobactam concentration equal to 1, 5 or 20 micrograms ml-1, the coefficients of variation were less than 5%. The assay was successfully applied to the analysis of samples from drug monitoring in a patient with renal insufficiency undergoing continuous venovenous haemofiltration (CVVH).

Rapid determination of sulbactam and tazobactam in human serum by high-performance liquid chromatography

A simple and rapid HPLC method for the determination of tazobactam and sulbactam, two beta-lactamase inhibitors, in serum for the therapeutic follow-up of patients is described. The effect of the pH of the aqueous mobile phase and column temperature on column efficiency and retention were examined and equations for their dependences were derived. The use of a chromatographic response function showed that methanol-buffer (5:95, v/v) (pH 6.3) as the mobile phase and a 45 degrees C column temperature were optimum values for chromatographic separation. The analytical method was linear from 10 to 200 micrograms/ml. This assay limit range is sufficient for the analysis of human serum. The limit of detection was 10 micrograms/ml for sulbactam and 5 micrograms/ml for tazobactam. The coefficient of variation was less than 5%. The speed at which this assay can be performed makes it especially useful for estimating the levels of these drugs in human serum.

Pharmacokinetics of tazobactam M1 metabolite after administration of piperacillin/tazobactam in subjects with renal impairment

Tazobactam is a new derivative of penicillinic acid sulfone, which functions as an irreversible inhibitor of many beta-lactamases. The disposition of tazobactam M1 metabolite after intravenous (i.v.) infusion of 3 g of piperacillin/0.375 g of tazobactam was evaluated in 26 subjects with various degrees of renal impairment. Participants in the study were 18 subjects with creatinine clearances (ClCR) ranging from 7.4-41.8 mL/min, 4 subjects maintained on continuous ambulatory peritoneal dialysis (CAPD), and 4 subjects undergoing chronic hemodialysis (HD). The pharmacokinetic parameters of piperacillin and tazobactam were evaluated and were similar to previous reports. Tazobactam M1 metabolite maximum plasma concentration increased as renal function declined. The terminal elimination half-life and area under the plasma concentration-time curve of the tazobactam M1 metabolite increased as renal function declined. The mean rate of recovery of the tazobactam M1 metabolite in hemodialysate during a 3- to 4.2-hour HD session 1 hour after the i.v. infusion of piperacillin/tazobactam was 25.3%. However, when HD was performed at 36-48 hours after the i.v. infusion, 57.6% of the tazobactam dose was recovered as M1 metabolite, suggesting further conversion of tazobactam to M1 metabolite. Peritoneal dialysis removed 15.8% (n = 2) of the tazobactam dose as the M1 metabolite. Using a dose of 3 g of piperacillin/0.375 g of tazobactam, the predicted maximum steady-state plasma concentrations of the tazobactam M1 metabolite are 14.6 micrograms/mL, 34.8 micrograms/mL, and 48.8 micrograms/mL for subjects with ClCR 20-40 mL/min (every 6 hour dosing), ClCR < 20 mL/min (every 8 hour dosing), and on CAPD (every 12 hour dosing), respectively.

Pharmacodynamics of piperacillin alone and in combination with tazobactam against piperacillin-resistant and -susceptible organisms in an in vitro model of infection

The pharmacodynamics of dosage regimens of piperacillin alone or in combination with tazobactam against piperacillin-resistant or -susceptible bacteria were studied in an in vitro model of infection. Experiments were conducted by using a fixed daily exposure of 12 g of piperacillin, given as 3 g alone or in combination with tazobactam at 0.375 g every 6 h, or the same total dose of the combination given as 4 g of piperacillin plus 0.5 g of tazobactam every 8 h. The addition of tazobactam to piperacillin, irrespective of the dosing interval, did not alter the killing of piperacillin-susceptible organisms (Escherichia coli J53 and Pseudomonas aeruginosa ATCC 27853). In contrast, experiments with an isogenic TEM-3-containing transconjugant of E. coli J53 (E. coli J53.2-TEM-3) that was resistant to piperacillin (MIC, 128 micrograms/ml) showed that the addition of tazobactam resulted in bacterial killing similar to that observed with the wild-type strain. Although tazobactam concentrations fell to less than 4 mg/liter (the concentration associated with a reduction in the piperacillin MIC from 128 to 2 mg/liter) 2 to 3 h after a dose, a similar degree of bacterial killing was observed when the same total 24-h dose of piperacillin-tazobactam was fractionated into dosing intervals of every 6 or 8 h. Investigations with Staphylococcus aureus 7176 (piperacillin MIC, 128 micrograms/ml) showed that the addition of tazobactam, again irrespective of dosing interval, also resulted in net bacterial killing which was not seen with piperacillin alone. These data support the use of extended dosing intervals (every 8 h) of piperacillin-tazobactam in the treatment of infections caused by piperacillin-resistant bacteria.

Piperacillin/tazobactam. A review of its antibacterial activity, pharmacokinetic properties and therapeutic potential

Combining tazobactam, a beta-lactamase inhibitor, with the ureidopenicillin, piperacillin, successfully restores the activity of piperacillin against beta-lactamase-producing bacteria. Tazobactam has inhibitory activity, and therefore protects piperacillin against Richmond and Sykes types II, III, IV and V beta-lactamases, staphylococcal penicillinase and extended-spectrum beta-lactamases. However, tazobactam has only species-specific activity against class I chromosomally-mediated enzymes. Resistant organisms include some Citrobacter spp., Enterobacter spp., Serratia spp., Xanthomonas maltophilia and Enterococcus faecium. Consistent with its in vitro activity, preliminary clinical data indicate that the fixed combination of piperacillin/tazobactam (dose ratio 8:1) is effective in the treatment of moderate to severe polymicrobial infections, including intra-abdominal, skin and soft-tissue and lower respiratory tract infections. In limited comparative trials, piperacillin/tazobactam demonstrated equivalent or better efficacy than standard comparator regimens in these infections. Piperacillin/tazobactam in combination with an aminoglycoside was effective in the empirical treatment of fever in patients with neutropenia and compared favourably with ceftazidime in combination with an aminoglycoside, although second-line therapy with a glycopeptide antibiotic may be indicated in unresponsive episodes. Data from phase III trials indicate that piperacillin/tazobactam has a tolerability profile typical of a penicillin agent. Piperacillin/tazobactam provides a broad spectrum of antibacterial activity in a convenient single formulation suitable for use in the treatment of polymicrobial infections. Possible limitations concern its restricted activity against class I beta-lactamases, enzymes that are becoming increasingly important in the nosocomial environment. Combined therapy with an aminoglycoside may be necessary in more serious infections.