Prostatic Pharmacokinetic/Pharmacodynamic Evaluation of Ampicillin-Sulbactam for Bacterial Prostatitis and Preoperative Prophylaxis

Model-Informed Clinical Practice - Determining an Appropriate Ampicillin-Sulbactam Redosing Regimen in Surgical Patients by Utilizing Population Pharmacokinetics and Target Attainment Analysis

In the current study, population pharmacokinetic (PK) of ampicillin-sulbactam was performed based on the clinical pharmacokinetics data collected from a prospective study conducted in 40 surgical patients undergoing prolonged surgery where antibiotic redosing was implemented. A population PK model was successfully developed to characterize the disposition of ampicillin and sulbactam. The final models were two-compartment models for both drugs, with creatinine clearance and heart failure affecting clearance and body surface area having an impact on the central volume of distribution of both ampicillin and sulbactam. Comprehensive Monte Carlo simulations were performed to evaluate the probability of target attainment (PTA) of 24 different redosing scenarios. Simulation results indicated that the ampicillin-sulbactam 2-h redosing scheme recommended by ASHP guidelines is likely too conservative given that 3-g dose (2-g ampicillin/1-g sulbactam) with 4-h redosing interval can reach the breakpoint of 2 mg/L for ampicillin in all populations even with the aggressive pharmacokinetic/pharmacodynamic (PK/PD) target of 100% fT > MIC. With the target 50% fT > MIC, all redosing schemes evaluated, including the 8-h redosing scenario, are predicted to be able to reach the breakpoint of 64 mg/L in all patients. According to our findings, redosing of ampicillin-sulbactam should be every 4 h instead of the currently recommended 2-h redosing schedule. Our PTA results should inform future updates to existing general antibiotic redosing guidelines; and, when used in combination with the availability of institution- and/or unit-specific ampicillin susceptibility patterns, our PTA results may be used to customize SSI prophylaxis redosing recommendations for ampicillin-sulbactam at individual hospitals.

Pulmonary Pharmacokinetic and Pharmacodynamic Evaluation of Ampicillin/Sulbactam Regimens for Pneumonia Caused by Various Bacteria, including Acinetobacter baumannii

This study aimed to assess the dosing regimens of ampicillin/sulbactam for pneumonia based on pulmonary pharmacokinetic (PK)/pharmacodynamic (PD) target attainment. Using the literature data, we developed pulmonary PK models and estimated the probabilities of attaining PK/PD targets in lung tissue. Against bacteria other than A. baumannii (the general treatment), the PK/PD target was set as both 50% time above the minimum inhibitory concentration (T > MIC) for ampicillin and 50% T > 0.5 MIC for sulbactam. For the A. baumannii treatment, the PK/PD target was set as 60% T > MIC for sulbactam. The pulmonary PK/PD breakpoint was defined as the highest minimum inhibitory concentration (MIC) at which the target attainment probability in the lung tissue was ≥90%. The lung tissue/serum area under the drug concentration-time curve from 0 to 3 h (AUC_0-3h) ratios for ampicillin and sulbactam were 0.881 and 0.368, respectively. The ampicillin/sulbactam AUC_0-3h ratio in the lung tissue was 3.89. For the general treatment, the pulmonary PK/PD breakpoint for ampicillin/sulbactam at 3 g four times daily in typical patients with creatinine clearance (CL_cr) of 60 mL/min was 2 μg/mL, which covered the MIC_90s (the MICs that inhibited the growth of 90% of the strains) of most gram-positive and gram-negative bacteria. For the A. baumannii treatment, the pulmonary PK/PD breakpoint for ampicillin/sulbactam at 9 g 4-h infusion three times daily (27 g/day) in patients with a CL_cr of 60 mL/min was 4 μg/mL, which covered the MIC₉₀ of A. baumannii. A PK/PD evaluation for pneumonia should be performed in the lung tissue (the target site) rather than in the blood because sulbactam concentrations are lower in lung tissue. These findings should facilitate the selection of ampicillin/sulbactam regimens for pneumonia caused by various bacteria, including A. baumannii.

In silico and in vitro evaluation of efflux pumps inhibition of α,β-amyrin

The use of the bacterial efflux pump mechanism to reduce the concentrations of antibiotics in the intracellular to the extracellular region is one of the main mechanisms by which bacteria acquire resistance to antibiotics. The present study aims to evaluate the antibacterial activity of the α,β-amyrin mixture isolated from Protium heptaphyllum against the multidrug-resistant strains of Escherichia coli 06 and Staphylococcus aureus 10, and to verify the inhibition of the efflux resistance mechanisms against the strains of S. aureus 1199B and K2068, carrying the NorA and MepA efflux pumps, respectively. The α,β-amyrin did not show clinically relevant direct bacterial activity. However, the α,β-amyrin when associated with the gentamicin antibiotic presented synergistic effect against the multidrug-resistant bacterial strain of S. aureus 10. In strains with efflux pumps, α,β-amyrin was able to inhibit the action of the efflux protein NorA against Ethidium Bromide. However, this inhibitory effect was not observed in the MepA efflux pump. In addition, when evaluating the effect of standard efflux pump inhibitors, clorptomazine and CCCP, α,β-amyrin showed a decrease in MIC, demonstrating the presence of the efflux mechanism through synergism. Docking studies indicate that α, β-amyrin have a higher affinity energy to MepA, and NorA than ciprofloxacin and norfloxacin. Also, α, β-amyrin bind to the same region of the binding site as these antibiotics. It was concluded that the α, β-amyrin has the potential to increase antibacterial activity with the association of antibiotics, together with the ability to be a strong candidate for an efflux pump inhibitor.Communicated by Ramaswamy H. Sarma.

Pharmacodynamic Evaluation of Ampicillin-sulbactam in Pediatric Patients Using Plasma and Urine Data

BACKGROUND

We aimed to develop population pharmacokinetic (PK) models of ampicillin and sulbactam using pooled data analysis and to optimize dosing regimens of ampicillin-sulbactam (combination ratio of 2:1) in pediatric patients.

METHODS

Population PK models of ampicillin and sulbactam were separately developed by simultaneously fitting plasma and urine data from pediatric patients in 14 published studies. Based on these models, we estimated the probability of attaining a pharmacodynamic (PD) target [50% of time that free drug concentrations above the minimum inhibitory concentration, 50% fT > minimum inhibitory concentration (MIC)] against MIC90 [MIC that blocked the growth of 90% of the strains] of common bacteria in community-acquired pneumonia.

RESULTS

The analysis included 54 pediatric patients (0.083-16.42 years of age, 4.0-77.0 kg of body weight). A total of 284 plasma concentrations and 90 urinary excretions from 0 to 6 hours after administration were used for population PK modeling. The data were adequately described by 2-compartment models for ampicillin and sulbactam. Age was not a statistically significant covariate in the PK of either drug. The PK/PD breakpoint MICs for 45 mg/kg 3 times daily and 75 mg/kg 4 times daily (q.i.d.) were 0.25 and 1 μg/mL, respectively. For empiric therapy of community-acquired pneumonia, because MIC90 values for the main target pathogens is high (MIC90 = 2 μg/mL for Streptococcus pneumoniae and MIC90 = 4 μg/mL for Haemophilus influenzae), 75 mg/kg q.i.d. (Food and Drug Administration-approved maximum dosage in United States) might be better than 45 mg/kg 3 times daily (within approved dosage in Japan) to cover many pathogens.

CONCLUSIONS

From the results of this PK/PD approach, 75 mg/kg q.i.d. (Food and Drug Administration-approved maximum dosage) should be recommended in the empiric therapy of community-acquired pneumonia.