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A deep understanding of an antimicrobial’s critical pharmacokinetic and pharmacodynamic properties is crucial towards optimizing its use in patients and bolstering the drug development program. With the growing threat of antimicrobial resistance and decline in antimicrobial development, the advancement of complex and rigorous pharmacokinetic and pharmacodynamic studies over a short time span has renewed confidence in the value of pharmacokinetic and pharmacodynamic studies and allowed it to become fundamental component of a robust drug development program with high chances of successful approval. In addition, recent guidance by various regulatory bodies have reinforced that a strong and dedicated focus on pharmacokinetics and pharmacodynamics throughout research and development lead to the use of an optimized dosing regimen in Phase 3 trials, improving the probability of drug approval. The objective of this review is to demonstrate the importance of pharmacokinetic and pharmacodynamic studies in the drug development decision-making process by highlighting the developments in pharmacokinetic and pharmacodynamic methods and discuss the role of pharmacokinetic and pharmacodynamic studies in antimicrobial successes and failures.

Background To evaluate the transmembrane clearance (CLTM) of apixaban during modeled in vitro continuous renal replacement therapy (CRRT), assess protein binding and circuit adsorption, and provide initial dosing recommendations. Methods Apixaban was added to the CRRT circuit and serial pre-filter bovine blood samples were collected along with post-filter blood and effluent samples. All experiments were performed in duplicate using continuous veno-venous hemofiltration (CVVH) and hemodialysis (CVVHD) modes, with varying filter types, flow rates, and point of CVVH replacement fluid dilution. Concentrations of apixaban and urea were quantified via liquid chromatography-tandem mass spectrometry. Plasma pharmacokinetic parameters for apixaban were estimated via noncompartmental analysis. CLTM was calculated via the estimated area under the curve (AUC) and by the product of the sieving/saturation coefficient (SC/SA) and flow rate. Two and three-way analysis of variance (ANOVA) models were built to assess the effects of mode, filter type, flow rate, and point of dilution on CLTM by each method. Optimal doses were suggested by matching the AUC observed in vitro to the systemic exposure demonstrated in Phase 2/3 studies of apixaban. Linear regression was utilized to provide dosing estimations for flow rates from 0.5–5 L/h. Results Mean adsorption to the HF1400 and M150 filters differed significantly at 38 and 13%, respectively, while mean (± standard deviation, SD) percent protein binding was 70.81 ± 0.01%. Effect of CVVH point of dilution did not differ across filter types, although CLTM was consistently significantly higher during CRRT with the HF1400 filter compared to the M150. The three-way ANOVA demonstrated improved fit when CLTM values calculated by AUC were used (adjusted R2 0.87 vs. 0.52), and therefore, these values were used to generate optimal dosing recommendations. Linear regression revealed significant effects of filter type and flow rate on CLTM by AUC, suggesting doses of 2.5–7.5 mg twice daily (BID) may be needed for flow rates ranging from 0.5–5 L/h, respectively. Conclusion For CRRT flow rates most commonly employed in clinical practice, the standard labeled 5 mg BID dose of apixaban is predicted to achieve target systemic exposure thresholds. The safety and efficacy of these proposed dosing regimens warrants further investigation in clinical studies.

Background Due to the mechanisms of action of conventional catecholamine vasopressors, there is increased risk of renal allograft injury and adverse events in transplant recipients with fluid‐refractory distributive shock during the perioperative period. As such, mechanistically alternative vasopressors like angiotensin II (ATII) may avoid these complications, but there is an absence of data supporting use in this population. Methods This was a single‐center, single‐arm, open‐label, phase 4 study conducted as a 1‐year pilot of 20 adult renal transplant recipients receiving ATII as their first continuous infusion vasopressor in the perioperative period. The study aim was to systematically assess the safety and hemodynamic effects of ATII. Safety was assessed based on the incidence of adverse events. Hemodynamic effect was assessed by the achievement of per protocol hemodynamic goals (i.e., SBP ≥120 mmHg) and the need for adjunct vasopressors. Results Most cases involved deceased donors (70%), with a corresponding mean (SD) cold ischemia time of 14.7 (8.6) h. Over a surgery duration of 5.3 (1.2) h, subjects received 3.2 (2.0) L of total volume resuscitation prior to ATII initiation. No adverse events were directly related to ATII administration. Throughout this period, ATII was utilized for a median of 1.0 (IQR, 1.5) h intraoperatively (N = 7), 26.5 (IQR, 84.8) h postoperatively (N = 4), and 63.8 (IQR, 57.8) h in subjects who required ATII both intra‐ and postoperatively (N = 9). Only one of the 20 patients needed adjunct continuous infusion vasopressors in addition to ATII. Conclusions Based on the observations of this pilot study, ATII is a safe and effective vasopressor option for renal transplant recipients requiring perioperative hypotension reversal.