Evaluation of Hemodialysis Effect on Pharmacokinetics of Meropenem/Vaborbactam in End-Stage Renal Disease Patients Using Modeling and Simulation.

The objectives of this study were to evaluate the effect of hemodialysis (HD) on the pharmacokinetics (PK) of meropenem/vaborbactam, an approved beta-lactam/beta-lactamase inhibitor combination, and provide the rationale for the recommended timing of meropenem/vaborbactam administration relative to HD in end-stage renal disease (ESRD) patients. Population PK models were developed separately for meropenem and vaborbactam in subjects with normal renal function and different degrees of renal impairment, including those receiving HD. Simulations were performed to evaluate the exposure of meropenem and vaborbactam in ESRD patients who received a fixed dose of 0.5 g/0.5 g meropenem/vaborbactam every 12 hours as a 3-hour intravenous infusion under various drug administration schedules relative to HD. The probability of target attainment (PTA) analyses were conducted with pharmacokinetic/pharmacodynamic (PK/PD) targets of meropenem and vaborbactam. Simulations showed that HD reduces the accumulation of vaborbactam, but the exposure of vaborbactam is still above the PK/PD target regardless of whether meropenem/vaborbactam is administered predialysis or postdialysis. For meropenem, drug infusion completed right prior to initiation of HD may substantially reduce exposure leading to poor PTA results. In contrast, drug infusion completed at least 2 hours prior to initiation of HD is not predicted to result in efficacy loss based on PTA analysis. The results of simulation indicate that meropenem/vaborbactam infusion completed at least 2 hours prior to initiation of HD or administered immediately after the end of HD can avoid potential efficacy loss in ESRD patients.

Single-Dose Pharmacokinetics and Safety of Meropenem-Vaborbactam in Subjects with Chronic Renal Impairment.

Vaborbactam is a member of a new class of ß-lactamase inhibitors with inhibitory activity against serine carbapenemases (e.g., Klebsiella pneumoniae carbapenemase) that has been developed in combination with meropenem. The pharmacokinetics of the combination was evaluated in 41 subjects with chronic renal impairment in a phase 1, open-label, single-dose study. Subjects were assigned to one of five groups based on renal function: normal (creatinine clearance of ≥90 ml/min), mild (estimated glomerular filtration rate [eGFR] of 60 to 89 ml/min/1.73 m2), moderate (eGFR of 30 to <60), or severe (eGFR of <30) impairment plus end-stage renal disease (ESRD) patients on hemodialysis. Subjects received a single intravenous dose of 1 g of meropenem plus 1 g of vaborbactam by 3-h infusion. The ESRD group received two doses (on and off dialysis) separated by a washout. Pharmacokinetic parameters were estimated by standard noncompartmental methods. For both meropenem and vaborbactam, the area under the concentration-time curve was larger and the elimination half-life was longer with decreasing renal function. Meropenem and vaborbactam total plasma clearance (CLt) rates were similar and decreased with decreasing renal function. Slopes of the linear relationship between eGFR and CLt were similar, indicating a similar proportional reduction in CLt with decreasing renal function. Hemodialysis significantly increased drug clearance of meropenem (mean of 2.21-fold increase in CLt, P < 0.001) and vaborbactam (mean of 5.11-fold increase, P = 0.0235) relative to drug administration off dialysis, consistent with dose recovery rates of 38.3% and 52.9% for meropenem and vaborbactam, respectively, in dialysate. Plasma clearance of meropenem and vaborbactam is reduced with renal impairment, requiring dose adjustment. Hemodialysis removes both drugs. (This study has been registered at ClinicalTrials.gov under identifier NCT02020434.).

Simultaneous extraction and determination of monoamine neurotransmitters in human urine for clinical routine testing based on a dual functional solid phase extraction assisted by phenylboronic acid coupled with liquid chromatography-tandem mass spectrometry.

The major monoamine neurotransmitters, serotonin (5-HT) and catecholamines (i.e., norepinephrine (NE), epinephrine (E), and dopamine (DA)), are critical to the nervous system function, and imbalances of the neurotransmitters have been connected to a variety of diseases, making their measurement useful in a clinical setting. A simple, rapid, robust, sensitive, and specific LC-MS/MS method has been developed and validated for the simultaneous quantitation of urinary serotonin and catecholamines with low cost, which is ideal for routine clinical applications. A simple extraction from complex urine was accomplished using tailored solid phase extraction incorporating phenylboronic acid complexation on a 96-well HLB microplate for the sample extraction and resulted in significantly improved throughput, selectivity, and extraction recovery. Compared to 1-10 mL of urine typically used, this method required only 10 µL. A rapid chromatographic elution with a total cycle time of 6 min per sample compared to reported run times of 19-75 min was achieved on a PFP column. The sensitivity of l and 2 ng mL-1 for the detection of low abundant E and NE combined with the high coverage of 1024 ng mL-1 for DA enabled the multi-analyte detection of these biogenic amines in a single run. Good linearity (2.0-512, 1.0-512, 4.0-1024, and 4.0-1024 ng mL-1 for NE, E, DA, and 5-HT, respectively), accuracy (87.6-104.0%), precision (≤8.0%), extraction recovery (69.6-103.7%), and matrix effect (87.1-113.1% for catecholamines and 63.6-71.4% for 5-HT) were obtained. No autosampler carryover was observed. The analytes were stable for 5 days at 20 °C, 14 days at 4 °C, and 30 days at -20 °C and five freeze-thaw cycles. The easy sample preparation, rapid LC, and multi-analyte MS detection allow two 96-well plates of samples to be extracted within 2 h and analyzed on an LC-MS/MS system within 24 h. The applicability and reliability of the assay were demonstrated by assessment of the reference interval for authentic urine specimens from 90 healthy individuals. Graphical abstract A simple, rapid, robust, sensitive and specific LC-MS/MS method combined with a dual functional solid phase extraction has been developed and validated for the simultaneous extraction and quantitation of monoamine neurotransmitters in human urine with low cost.

Determination of free catecholamines in urine by tandem affinity/ion-pair chromatography and flow injection analysis.

BACKGROUND: A system was developed for the simultaneous measurement in urine of free catecholamines (i.e., dopamine, norepinephrine, epinephrine) and creatinine (i.e., an indicator of urine output and volume). This method was based on the use of tandem affinity/ion-pair HPLC and flow injection analysis. METHODS: The free catecholamines were extracted directly from urine by using an on-line phenylboronic acid affinity column. The extracted solutes were then separated and measured by ion-pair chromatography followed by amperometric detection. Creatinine was measured by an on-line flow injection analysis system based on the Jaffe reaction, which analyzed creatinine as it eluted non-retained from the phenylboronic acid column. RESULTS: Various factors were considered in the design and optimization of the phenylboronic acid column, the tandem affinity/ion-pair HPLC columns and the flow injection analysis system. The total analysis time for the final combined system was approximately 16 min per injection at 1 ml/min. This method was found to have good agreement with the expected results for control urine samples. The limits of detection for 20 microl samples (S/N=3.0) were 1.8, 1.0 and 4.3 microg/l for norepinephrine, epinephrine and dopamine, respectively, while the limit of detection of creatinine was 5.0 mg/l. The linear response of this method extended over a 450 to 930-fold range in concentration for the catecholamines and covered the range of clinical interest. The within-day precision of this method was +/-2.0-2.7%. CONCLUSIONS: The ability of this method to simultaneously monitor both creatinine and other analytes makes this HPLC/FIA system an attractive method for use in monitoring urinary compounds. With this approach it was possible to provide fast results for small volumes of random urine samples that were collected as part of a psychological study. The same method could also be utilized with 12 or 24 h urine specimens.