Comparative pharmacokinetics of piperacillin in normals and in patients with renal failure

Using a Validated Population Pharmacokinetic Model for Dosing Recommendations of Continuous Infusion Piperacillin for Critically Ill Adult Patients

BACKGROUND AND OBJECTIVE: Piperacillin is a broad-spectrum β-lactam antibiotic commonly prescribed in intensive care units. Many piperacillin population pharmacokinetic models have been published, but few underwent an external evaluation. External evaluation is an important process to determine a model's capability of being generalized to other hospitals. We aimed to assess the predictive performance of these models with an external validation dataset.

METHODS

Six models were evaluated with a dataset consisting of 30 critically ill patients (35 samples) receiving piperacillin by continuous infusion. Models were subject to prediction-based (bias and imprecision) and simulation-based evaluations. When a model had an acceptable evaluation, it was used for dosing simulations to evaluate the probability of target attainment.

RESULTS

Bias and imprecision ranged from - 35.7 to 295% and from 22.7 to 295%, respectively. The models of Klastrup et al. and of Udy et al. were acceptable according to our criteria and were used for dosing simulations. Simulations showed that a loading dose of 4 g followed by a maintenance dose of 16 g/24 h of piperacillin infused continuously was necessary to remain above a pharmacokinetic-pharmacodynamic target set as a minimal inhibitory concentration of 16 mg/L in 90% of patients, for a median patient with a creatinine clearance of 76 mL/min.

CONCLUSIONS

Despite the considerable variation in the predictive performance of the models with the external validation dataset, this study was able to validate two of these models and led to the elaboration of a dosing nomogram for piperacillin by continuous infusion that can be used by clinicians in intensive care units.

Piperacillin-Tazobactam in Intensive Care Units: A Review of Population Pharmacokinetic Analyses

Piperacillin-tazobactam is a potent β-lactam/β-lactamase inhibitor antibiotic commonly prescribed in the intensive care unit setting. Admitted patients often show large variability in treatment response due to multiple pathophysiological changes present in this population that alter the drug's pharmacokinetics. This review summarizes the population pharmacokinetic models developed for piperacillin-tazobactam and provides comprehensive data on current dosing strategies while identifying significant covariates in critically ill patients. A literature search on the PubMed database was conducted, from its inception to July 2020. Relevant articles were retained if they met the defined inclusion/exclusion criteria. A total of ten studies, published between 2009 and 2020, were eligible. One- and two-compartment models were used in two and eight studies, respectively. The lowest estimated piperacillin clearance value was 3.12 L/h, and the highest value was 19.9 L/h. The estimations for volume of distribution varied between 11.2 and 41.2 L. Tazobactam clearance values ranged between 5.1 and 6.78 L/h, and tazobactam volume of distribution values ranged between 17.5 and 76.1 L. The most frequent covariates were creatinine clearance and body weight, each present in four studies. Almost all studies used an exponential approach for the interindividual variability. The highest variability was observed in piperacillin central volume of distribution, at a value of 75.0%. Simulations showed that continuous or extended infusion methods performed better than intermittent administration to achieve appropriate pharmacodynamic targets. This review synthesizes important pharmacokinetic elements for piperacillin-tazobactam in an intensive care unit setting. This will help clinicians better understand changes in the drug's pharmacokinetic parameters in this specific population.

Population pharmacokinetics and pharmacodynamics of piperacillin in critically ill patients during the early phase of sepsis

This study aimed to characterize the population pharmacokinetics (PKs) of piperacillin and investigate probability of target attainment (PTA) and cumulative fraction of response (CFR) of various dosage regimens in critically ill patients during the early phase of sepsis. Forty-eight patients treated with piperacillin/tazobactam were recruited. Five blood samples were drawn before and during 0-0.5, 0.5-2, 2-4 and 4-6 or 8 h after administration. Population PKs was analyzed using NONMEM^®. The PTA of 90%fT_>MIC target and CFR were determined by Monte Carlo simulation. The two compartment model best described the data. Piperacillin clearance (CL) was 5.37 L/h, central volume of distribution (V₁) was 9.35 L, and peripheral volume of distribution was 7.77 L. Creatinine clearance (CL_Cr) and mean arterial pressure had a significant effect on CL while adjusted body weight had a significant impact on V₁. Subtherapeutic concentrations can occur during the early phase of sepsis in critically ill patients with normal renal function. The usual dosage regimen, 4 g of piperacillin infused over 0.5 h every 6 h, could not achieve the target for susceptible organisms with MIC 16 mg/L in patients with CL_Cr ≥ 60 mL/min. Our proposed regimen for the patients with CL_Cr 60-120 mL/min was an extended 2 h infusion of 4 g of piperacillin every 6 h. Most regimens provided CFR ≥ 90% for the E. coli infection while there was no dosage regimen achieved a CFR of 90% for the P. aeruginosa infection.

[Pharmacokinetics and pharmacodynamics of antibiotics in intensive care]

Optimized dosage regimens of antibiotics have remained obscure since their introduction. During the last two decades pharmacokinetic(PK)-pharmacodynamic(PD) relationships, originally established in animal experiments, have been increasingly used in patients. The action of betalactams is believed to be governed by the time the plasma concentration is above the minimum inhibitory concentration (MIC). Aminoglycosides act as planned when the peak concentration is a multiple of the MIC and vancomycin seems to work best when the area under the plasma vs. time curve (AUC) to MIC has a certain ratio. Clinicians should be aware that these relationships can only be an indication in which direction dosing should go. Larger studies with sufficiently high numbers of patients and particularly severely sick patients are needed to prove the concepts. In times where all antibiotics can be measured with new technologies, the introduction of therapeutic drug monitoring (TDM) is suggested for ICUs (Intensive Care Unit). The idea of a central lab for TDM of antibiotics such as PEAK (Paul Ehrlich Antibiotika Konzentrationsmessung) is supported.

Differences in antimicrobial drug exposure in patients with various degrees of renal function based on recommendations from dosing references

STUDY OBJECTIVE

To calculate and compare 24-hour area under the unbound drug concentration-time curves (AUC(0-24)) of antimicrobials with dosing recommendations from six commonly used dosing references.

INTERVENTION

Unbound plasma concentration-time profiles of 13 antimicrobial agents (4 penicillins, 3 cephalosporins, 2 carbapenems, aztreonam, 3 fluoroquinolones) were simulated at steady state using a one-compartment open model for a 70-kg adult based on pharmacokinetic parameters obtained from peer-reviewed literature. Simulations were performed at five levels of creatinine clearance (Cl(cr)).

MEASUREMENTS AND MAIN RESULTS

Differences in AUC(0-24) for each antimicrobial agent were noted among the six references at each level of Cl(cr) as well as within references across the range of Cl(cr). In addition, up to 16-fold and 3-fold ranges in AUC(0-24) values were observed for beta-lactams and fluoroquinolones, respectively, in one reference based on dosing recommendations at a single level of Cl(cr) (due to more than one dose and/or dosing interval).

CONCLUSION

Clinicians should be aware of differences among common references when selecting dosages of antimicrobial agents, especially for patients with moderate-to-severe renal impairment.

Comparison of five beta-lactam antibiotics against common nosocomial pathogens using the time above MIC at different creatinine clearances

STUDY OBJECTIVE

To compare the time above the minimum inhibitory concentration (T>MIC) for five parenteral beta-lactam antibiotics against common nosocomial bacterial pathogens at different creatinine clearances (Clcr).

INTERVENTIONS

Serum concentration-time profiles were simulated for cefepime, ceftazidime, piperacillin, piperacillin-tazobactam, and imipenem at Clcr ranging from 120-30 ml/minute. The MIC data for 90% of organisms (MIC90) were collected for Escherichia coli, Klebsiella pneumoniae, Serratia marcescens, Citrobacter freundii, Enterobacter aerogenes, Enterobacter cloacae, Pseudomonas aeruginosa, and oxacillin-susceptible Staphylococcus aureus, and a weighted geometric mean MIC90 was calculated. The T>MIC was calculated as percentage of the dosing interval in which free concentrations exceeded the weighted geometric mean MIC90. A T>MIC of 70% or greater was considered desirable for all organisms except S. aureus (> or = 50%).

MEASUREMENTS AND MAIN RESULTS

Cefepime 2 g every 12 hours (Clcr > or = 70 ml/min) and every 24 hours (Clcr < or = 60 ml/min) achieved desirable T>MIC for all Enterobacteriaceae and S. aureus at every Clcr. Imipenem 0.5 g achieved desirable T>MIC for E. coli, K. pneumoniae, C. freundii, and S. aureus at every Clcr. However, imipenem T>MIC was less than 70% for the following regimens and organisms: S. marcescens 0.5 g every 6 hours (Clcr > or = 90 ml/min), E. aerogenes 0.5 g every 6 hours (Clcr > or = 80 ml/min), E. cloacae 0.5 g every 6 hours (Clcr > or = 100 ml/min), S. marcescens 0.5 g every 8 hours (Clcr 60-70 ml/min), E. cloacae 0.5 g every 8 hours (Clcr 60-70 ml/min), and E. aerogenes 0.5 g every 8 hours (Clcr 50-70 ml/min). Ceftazidime 2 g every 8 hours (Clcr 60-100 ml/min) and every 12 hours (Clcr 40-50 ml/min) achieved desirable T>MIC for E. coli, K. pneumoniae, S. marcescens, and S. aureus only. At every dose and Clcr, piperacillintazobactam achieved desirable T>MIC for S. aureus but not for any Enterobacteriaceae at Clcr > 50 ml/minute. Piperacillin did not achieve desirable T>MIC for any organism, and none of the beta-lactams attained a T>MIC of 70% or above for P. aeruginosa at any Clcr.

CONCLUSION

At every Clcr, cefepime achieved a desirable T>MIC for more nosocomial pathogens than any other beta-lactam evaluated. Based on pharmacodynamic data, cefepime is an appropriate empiric choice for treatment of nosocomial infections. However, when P. aeruginosa is a potential pathogen, empiric combination therapy should be considered.

Dosing adjustment of 10 antimicrobials for patients with renal impairment

OBJECTIVE

To describe a program of creatinine clearance-based dosage adjustment of 10 renally eliminated antimicrobial agents and to discuss the utility of such a program in a hospital as a method of quality assurance (by ensuring that patients with renal impairment receive generally accepted dosage adjustments), based on pharmacodynamic principles.

METHODS

Consecutive patients prescribed any of 10 targeted renally eliminated antibiotics were included. Recommendations for dosage adjustment were made to the prescriber based on a calculated creatinine clearance. Additional adjustments in drug therapy were performed, including dosage recommendations of nontargeted drugs, simplification of antibiotic regimens, and conversion of intravenous to oral therapy. A cost analysis was performed.

RESULTS

During a 6-month study period, 160 dosage changes (7.6% of total number screened) were recommended in 137 patients receiving the targeted antimicrobial agents. Prescribers accepted 147 recommendations (91.9%). A dosage change recommendation was necessary more than 12% of the time for acyclovir, ceftazidime, and imipenem/cilastatin. A cost avoidance of $11,702.08 was realized. Ancillary drug recommendations that were offered and accepted during the program realized a cost avoidance of $6613.75.

CONCLUSIONS

This dosage adjustment program using pharmacodynamic principles was successful in optimization of dosing, potential minimization of morbidity caused by excessive dosing, and demonstration of direct and potentially indirect cost avoidance. A dosing program for patients with renal impairment would be of benefit to other clinicians and institutions seeking to optimize patient care.

Comparison of the bactericidal activities of ofloxacin and ciprofloxacin alone and in combination with ceftazidime and piperacillin against clinical strains of Pseudomonas aeruginosa

On the basis of MIC data, ciprofloxacin exhibits superior activity against Pseudomonas aeruginosa than the other currently available fluoroquinolones do. Despite the antipseudomonal advantage noted for ciprofloxacin monotherapy, it is unknown whether this advantage is maintained when the fluoroquinolones are used in combination with antipseudomonal beta-lactams such as ceftazidime and piperacillin. Twelve healthy volunteers were enrolled in this open-label, randomized, steady-state, six-way cross-over, comparative trial. All subjects received the following regimens: (i) 400 mg of ofloxacin given intravenously (i.v.) every 12 h (q12h), (ii) 400 mg of ciprofloxacin given i.v. q12h, (iii) 400 mg of ofloxacin given i.v. q12h plus 1 g of ceftazidime given i.v. every 8 h (q8h), (iv) 400 mg of ciprofloxacin given i.v. q12h plus 1 g of ceftazidime given i.v. q8h, (v) 400 mg of ofloxacin given i.v. q12h plus 4 g of piperacillin given i.v. q8h, and (vi) 400 mg of ciprofloxacin given i.v. q12h plus 4 g of piperacillin given i.v. q8h. Serum bactericidal titers with subsequent calculation of the area under the bactericidal curve were determined against three clinical isolates of P. aeruginosa. As monotherapy, ciprofloxacin demonstrated superior antipseudomonal activity than ofloxacin did; however, combination of these agents with ceftazidime yielded remarkably similar and statistically comparable activity profiles. In contrast, ciprofloxacin-piperacillin retained a bactericidal advantage over ofloxacin-piperacillin. Although ciprofloxacin exhibits superior antipseudomonal activity when used as monotherapy, combination of ofloxacin or ciprofloxacin with ceftazidime yielded equivalent activity profiles against susceptible strains of P. aeruginosa.

Pharmacodynamic effects of antibiotics. Studies on bacterial morphology, initial killing, postantibiotic effect and effective regrowth time

Pharmacodynamics of antibiotics deals with time course of drug activity and mechanisms of action of drugs on bacteria. In this thesis pharmacodynamic parameters have been studied after brief exposure of gram-positive bacteria to daptomycin, imipenem or vancomycin and after short exposure of gram-negative bacteria to amikacin, ampicillin, aztreonam, cefepime, cefotaxime, ceftazidime, ceftriaxone, cefuroxime, imipenem, mecillinam, or piperacillin. The studies have been focused on morphological alterations, initial killing, postantibiotic effect (PAE) and effective regrowth time (ERT) and a method, based on bioluminescence assay of intracellular ATP has been used. The basic principle behind this technique is that ATP in living cells is present in a relatively constant amount, and hence affords a measure of the number of microbial cells. The PAE describes the delayed regrowth of bacteria after brief exposure to antibiotics. The number of cells measured after this antibiotic exposure describes the initial killing and is also the start value for calculating the PAE. PAEs of 2-3 h were obtained by bioluminescence for gram-positive bacteria exposed to imipenem or vancomycin. This is in agreement with results obtained by viable count and is probably due to similar weak initial decrease in cell density when assayed by both methods. Long (greater than 3 h) concentration dependent PAEs and moderate (less than or equal to 1 log10) initial decrease in intracellular ATP were in general seen for gram-positive bacteria exposed to daptomycin and for gram-negative bacteria exposed to imipenem or amikacin when assayed by bioluminescence. These very long PAEs and rather weak initial killing have to be compared with the shorter PAEs and stronger initial killing reported by us and others using viable count. Furthermore, this study showed that there was a relatively good concordance between microscopy and bioluminescence, which are direct methods, in determining the initial killing and PAE of imipenem on Escherichia coli. The ERT, defined as the time for bacterial density to increase 1 log10 from the pre-exposure inoculum, was independent of the method used for measuring regrowth of E. coli after brief exposure to imipenem. The combination of mecillinam with ampicillin, aztreonam, ceftazidime or piperacillin and the combination of amikacin with ceftazidime, ceftriaxone or piperacillin induced longer PAEs on gram-negative bacteria than the sum of PAEs of the individual antibiotics. A strong initial killing in combination with a long PAE cause a long ERT and may allow the antibiotic concentration to stay below MIC during long periods of time without any regrowth. This may, in clinical practice, have implications for long dosing intervals.

Pharmacokinetics and tissue penetration of tazobactam administered alone and with piperacillin

The pharmacokinetics of tazobactam (500 mg) administered intravenously alone were compared with the pharmacokinetics of tazobactam coadministered with piperacillin (4 g), and the penetration into an inflammatory exudate in six healthy males was studied. Piperacillin influenced the pharmacokinetics of tazobactam. The mean levels of tazobactam in plasma at 4 h were 0.6 microgram/ml when it was given alone and 1.2 micrograms/ml when it was given with piperacillin (P = 0.0003). The mean total clearances of tazobactam were 203.5 and 134.2 ml/min (P = 0.035) when it was given alone and with piperacillin, respectively There were no significant differences in the elimination half lives, areas under the concentration-time curve from 0 h to infinity, or volumes of distribution. Inflammatory exudate penetration was rapid, and the mean maximum levels of tazobactam attained were 6.4 and 11.3 micrograms/ml when it was given alone or with piperacillin, respectively (P less than 0.06). The mean percent penetration of tazobactam and the area under the concentration-time curve from 0 h to infinity in inflammatory exudate were greater when tazobactam was given with piperacillin. The mean 24-h urinary recoveries of tazobactam were 63.7% +/- 7.9% when it was given alone and 56.8% +/- 2.7% when it was given with piperacillin. The explanation for the differences in the pharmacokinetics of tazobactam when it was administered alone compared with those when it was given with piperacillin was unclear.

In vivo inactivation of tobramycin by piperacillin

In vivo inactivation of aminoglycosides by antipseudomonal penicillins in patients with renal failure can be a significant problem when these drugs are used together in certain gram-negative infections. Our article illustrates the possible magnitude of this interaction and the resultant effect on aminoglycoside pharmacokinetic parameters. Penicillin concentrations remain relatively unaffected by this interaction. This article stresses the need for close monitoring of aminoglycoside concentrations when combined with antipseudomonal penicillins in this patient population.

Thermal injury effects on drug disposition: a prospective study with piperacillin

The disposition of piperacillin was prospectively evaluated in nine severely burned patients who had normal renal and hepatic function. Wide interpatient variations were demonstrated in the drug's distribution volume, half-life, and clearance, with mean (+/- SD) values of 55.0 (+/- 44.2) liters, 3.6 (+/- 5.2) hours, and 14.9 (+/- 6.3) liters/hour, respectively. Piperacillin clearance was best explained by patient factors other than age, renal function, and the percentage of body surface area burns. Piperacillin disposition was related to the patients' serum albumin, total bilirubin, blood urea nitrogen, and the amount of urea nitrogen excreted daily in urine. Altered piperacillin disposition thus appeared to occur secondary to changes in the patients' physiologic and metabolic state caused by injury-related stress and fluid therapy. The patient's physiologic and metabolic response to injury, along with age and renal function, should be considered when instituting treatment with piperacillin or other agents cleared from the body in a similar manner.

Piperacillin. A review of its antibacterial activity, pharmacokinetic properties and therapeutic use

Piperacillin is one of the new generation of semisynthetic penicillins which can be administered intravenously or intramuscularly. It has a broad spectrum of activity against Gram-positive and Gram-negative aerobic and anaerobic bacteria. Although piperacillin has shown greater activity against beta-lactamase-producing organisms than the other penicillins, it is hydrolysed by the plasmid-mediated beta-lactamases (TEM-1). Activity against Pseudomonas aeruginosa is better than that of ticarcillin, carbenicillin and mezlocillin. Although only limited controlled studies have been reported, in those which have been conducted and in a larger number of open studies piperacillin was effective in the treatment of complicated urinary tract infections and lower respiratory tract infections, particularly pneumonia, caused by Gram-negative bacilli. Favourable clinical results have been obtained in patients with infections caused by mixed aerobic/anaerobic organisms (such as intra-abdominal infections) but the relatively average in vitro activity of piperacillin against Bacteroides fragilis may not indicate its usage in situations where this organism is the suspected or proven pathogen. Piperacillin in combination with an aminoglycoside or a 'third generation' cephalosporin gave encouraging results in the treatment of infections in immunocompromised patients, whilst its penetration into the diseased central nervous system and lack of toxicity indicate a potential value in the treatment of neonatal Gram-negative bacillary meningitis, particularly where the causative organism is Pseudomonas aeruginosa. Whether piperacillin alone is appropriate therapy for conditions usually treated with aminoglycosides (other than pseudomonal infections) needs additional clarification, but if established as equally effective in such conditions it has the advantages of its apparent lack of serious adverse effects and freedom from the need to undertake plasma concentration monitoring. These advantages would not, however, apply when considering one of the new (third generation) cephalosporins as alternative therapy in non-pseudomonal infections. Generally, however, it is still considered necessary to treat serious and complicated infections with combination therapy, either a cephalosporin, or in cases of resistance to P. aeruginosa an aminoglycoside.