The effect of tazobactam on the pharmacokinetics and the antibacterial activity of piperacillin in dogs

Suitability of Piperacillin-Tazobactam for Treating Dogs Infected with Extended-Spectrum β-Lactamase-Producing Enterobacterales: Pharmacokinetic and Pharmacodynamic Analysis

Background/Objectives: Piperacillin-tazobactam (TZP) is a potential alternative to carbapenems for the treatment of dogs infected with extended-spectrum β-lactamase-producing Enterobacterales (ESBL-E), but its efficacy remains unestablished. In this study, pharmacokinetic-pharmacodynamic (PK/PD) analysis was performed to estimate the clinical efficacy of TZP against ESBL-E infections in dogs. Methods: We determined the minimum inhibitory concentrations (MICs) of TZP in canine ESBL-E isolates, including Escherichia coli (n = 62), Klebsiella pneumoniae (n = 89), and Enterobacter cloacae (n = 31), using agar dilution. Monte Carlo Simulation (MCS) was performed to estimate the probability of target attainment (PTA) based on the PK/PD characteristics of TZP. Results: The MICs that can inhibit the growth of 90% of the isolates for the three bacterial species were determined as 16/4 µg/mL. MCS analysis revealed that the piperacillin PK/PD cutoff values (highest MICs with a PTA ≥90%) were ≤0.031, ≤0.5, and ≤2 μg/mL at a bolus dose of 50 mg/kg TZP (44.4 mg/kg piperacillin) every 12, 8, and 6 h (q12h, q8h, and q6h), respectively. The cumulative fractions of response were ≤90% based on the MIC distribution of ESBL-producing E. coli, K. pneumoniae, and E. cloacae isolates from dogs: 1.60, 0.48, and 0.15% at q12h; 32.56, 14.57, and 9.65% at q8h; and 74.51, 45.85, and 43.92% at q6h, respectively. Conclusions: We believe that TZP is not recommended for the treatment of canine ESBL-E infections, except for cases with a lower MIC than the PK/PD cutoff values determined in this study.

Pharmacokinetics of piperacillin-tazobactam in plasma, peritoneal fluid and peritoneum of surgery patients, and dosing considerations based on site-specific pharmacodynamic target attainment

Piperacillin-tazobactam (PIP-TAZ) is commonly used to treat intraabdominal infections; however, its penetration into abdominal sites is unclear. A pharmacokinetic analysis of plasma, peritoneal fluid, and peritoneum drug concentrations was conducted to simulate dosing regimens needed to attain the pharmacodynamic target in abdominal sites. PIP-TAZ (4 g-0.5 g) was intravenously administered to 10 patients before abdominal surgery for inflammatory bowel disease. Blood, peritoneal fluid, and peritoneum samples were obtained at the end of infusion (0.5 h) and up to 4 h thereafter. PIP and TAZ concentrations were measured, both noncompartmental and compartmental pharmacokinetic parameters were estimated, and a simulation was conducted to evaluate site-specific pharmacodynamic target attainment. The mean peritoneal fluid:plasma ratios in the area under the drug concentration-time curve (AUC) were 0.75 for PIP and 0.79 for TAZ, and the mean peritoneal fluid:plasma ratios in the AUC were 0.49 for PIP and 0.53 for TAZ. The mean PIP:TAZ ratio was 8.1 at both peritoneal sites. The regimens that achieved a bactericidal effect with PIP (time above minimum inhibitory concentration [MIC] >50%) at both peritoneal sites were PIP-TAZ 4.5 g twice daily for an MIC of 8 mg/L, as well as 4.5 g three times daily, and 3.375 g four times daily for an MIC of 16 mg/L. These findings clarify the peritoneal pharmacokinetics of PIP-TAZ, and help consider the dosing regimens for intraabdominal infections based on site-specific pharmacodynamic target attainment.

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) .

Piperacillin-tazobactam penetration into human pancreatic juice

Piperacillin-tazobactam was administered as a single dose (4.5 g intravenous) to five patients with stabilized external pancreatic fistula. The penetration into pancreatic juice was prompt, and inhibitory concentrations were achieved and maintained for different periods (0.5 to 6 h) according to bacterial susceptibility and patients' characteristics. Piperacillin and tazobactam showed superimposable pharmacokinetics in both serum and pancreatic juice.

Species-specific uncertainty factors for compounds eliminated principally by renal excretion in humans

An uncertainty factor of 100 is used to derive health-based guidance values for human intakes of chemicals based on data from studies in animals. The 100-fold factor comprises 10-fold factors for species differences and for interindividual differences in response. Each 10-fold factor can be subdivided into toxicokinetic and toxicodynamic aspects with a 4.0-fold factor to allow for kinetic differences between test species and humans. The current work determined the extent of interspecies differences in the internal dose (toxicokinetics) of compounds which are eliminated primarily by renal excretion in humans. An analysis of the published data showed that renal excretion was also the main route of elimination in the test species for most of the identified probe substrates. Interspecies differences were apparent for both the mechanism of renal excretion (glomerular filtration, tubular secretion and/or reabsorption) and the extent of plasma protein binding, both of which may affect renal clearance and therefore the magnitude of species differences in the internal dose. For compounds which are eliminated unchanged by both humans and the test species, the average differences in the internal doses between humans and animals were 1.6 for dogs, 3.3 for rabbits, 5.2 for rats and 13 for mice. This suggests that for renal excretion, the differences between humans and the rat and especially the mouse may exceed the 4.0-fold default factor for toxicokinetics.

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.