Search

INTRODUCTION: Methicillin-resistant Staphylococcus aureus (MRSA) infections are a serious threat to public health. Vancomycin (VAN) remains the primary treatment for these infections, and achieving the recommended area under the curve (AUC) target has been linked to improved clinical outcomes. The current VAN therapeutic monitoring guidelines recommend a loading dose (LD) of 20-35 mg/kg to rapidly attain targeted VAN exposures within 24 h of therapy. However, there is a paucity of data describing the impact of VAN LD on day 1 area under the curve (AUC0-24). This study aims to employ pharmacokinetic (PK) equations to calculate and describe the AUC0-24 following a VAN LD of 20 mg/kg. METHODS: This was a retrospective study of adult patients who were loaded with VAN 20 mg/kg, received ≥ 48 h of treatment, and had two consecutive serum VAN levels collected within 24 h. Linear, non-trapezoidal PK equations and two post-infusion VAN levels were used to calculate AUC0-24. Therapeutic AUC0-24 was defined as 400-600 mg/l*h. RESULTS: Among 123 included patients, the median age was 46 years (IQR 36, 62), 54% (67/123) of the patients had a body mass index (BMI) ≥ 30 kg/m2 and 27% (33/123) were admitted to the intensive care unit (ICU). Following a LD of 20 mg/kg, 50% (61/123) of the patients met the therapeutic AUC0-24, while 22% (27/123) of the patients were subtherapeutic, and 28% (35/123) were supratherapeutic. Compared with patients who achieved therapeutic AUC0-24, patients with subtherapeutic AUC0-24 were more likely to be younger (44 vs. 37 years old) and have a BMI ≥ 30 kg/m2 (67 vs. 52%). In contrast, patients with supratherapeutic AUC0-24 were more likely to be older (64 vs. 44 years old) and to have chronic kidney disease diagnosis (23 vs. 7%) when compared to patients who achieved a therapeutic AUC0-24. CONCLUSIONS: Only 50% of patients achieve the target AUC0-24 following a VAN 20 mg/kg LD, with

Volume of distribution at steady state (Vss) is an important pharmacokinetic endpoint. In this study we apply machine learning and conformal prediction for human Vss prediction, and make a head-to-head comparison with rat-to-man scaling, allometric scaling and the Rodgers-Lukova method on combined in silico and in vitro data, using a test set of 105 compounds with experimentally observed Vss. The mean prediction error and % with <2-fold prediction error for our method were 2.4-fold and 64%, respectively. 69% of test compounds had an observed Vss within the prediction interval at a 70% confidence level. In comparison, 2.2-, 2.9- and 3.1-fold mean errors and 69, 64 and 61% of predictions with <2-fold error was reached with rat-to-man and allometric scaling and Rodgers-Lukova method, respectively. We conclude that our method has theoretically proven validity that was empirically confirmed, and showing predictive accuracy on par with animal models and superior to an alternative widely used in silico-based method. The option for the user to select the level of confidence in predictions offers better guidance on how to optimise Vss in drug discovery applications.

Complex drug-drug interactions are defined as those in which both metabolic enzymes and xenobiotic transporters are implicated as clinically significant determinants of drug disposition. Both metabolic enzymes and xenobiotic transporters have the potential to contribute to clearance pathways (i.e. metabolic, renal or biliary elimination) and bioavailability-related processes (i.e. drug absorption, intestinal metabolism, or first pass hepatic elimination). Transporters have the unique ability to influence the distribution of drug throughout the body, in addition to influencing intestinal drug absorption or drug clearance via renal or biliary routes. Thus, characterization of the contributions of metabolic enzymes and xenobiotic transporters is crucial in anticipating any potential alterations in drug exposure due to a drug-drug interaction, pharmacogenomic or disease state variance of activity or expression of relevant metabolic enzymes or transporters.Predictions of drug-drug interactions are routinely conducted based on results of in vitro metabolic enzyme or xenobiotic transporter inhibition studies. However, translating such results to clinical significance continues to challenge the field, particularly for transporter-mediated interactions since the susceptibility of a drug to transporters in vitro does not always translate to clinically significant in vivo involvement and due to a lack of specific and clinically validated index substrates, inhibitors and inducers for major xenobiotic transporters. The objective of this research was to provide a framework for recognizing transporter involvement in clinical drug-drug interactions, grounded in basic pharmacokinetic theory.Since xenobiotic transporters can allow (or disallow) substrates access to various tissues throughout the body, it was recognized that significant xenobiotic transporter interactions are accompanied by changes in volume of distribution, in addition to potential changes in clearance, which can res

Background: Therapies with novel mechanisms of action against hepatitis B virus (HBV) infection are being explored with the goal of achieving a functional cure (sustained off-treatment response) without requiring lifelong therapy. We aimed to evaluate the pharmacokinetics, safety, and antiviral activity of ABI-H0731, an investigational inhibitor of the HBV core protein. Method(s): This phase 1, randomised, placebo-controlled study was done in two parts. In part 1, healthy adults without hepatitis B aged 18-65 years at one clinical research centre in New Zealand (eight participants per dose cohort) were randomly assigned (3:1) to receive single oral doses of ABI-H0731 (100, 300, 600, or 1000 mg) or matching placebo, or once-daily or twice-daily doses of ABI-H0731 800 mg or matching placebo for 7 days. In part 2, adults aged 18-65 years at clinical research centres in New Zealand, Australia, the UK, Hong Kong, Taiwan, and South Korea with chronic HBV (12 participants per dose cohort) were randomly assigned (5:1) to receive ABI-H0731 (100, 200, 300, or 400 mg) or matching placebo once daily for 28 days. In part 2, participants were required to have HBeAg-positive or HBeAg-negative chronic HBV infection, with serum HBV DNA concentrations of at least 2 x 104 IU/mL (HBeAg-positive) or 2 x 103 IU/mL (HBeAg-negative) and serum alanine aminotransferase concentrations less than seven times the upper limit of normal. Both parts used simple randomisation, with study participants, site personnel, and study monitors masked to treatment assignments. The primary study objective was dose-related safety and tolerability of ABI-H0731 in healthy volunteers and in participants with chronic HBV infection, assessed in all treated participants. Key secondary assessments included pharmacokinetic analyses and virological responses. This study is registered with ClinicalTrials.gov, identifier NCT02908191 and is completed. Finding(s): 48 [61%] of 79 healthy volunteers were enrolled in the sing

Background: Therapies with novel mechanisms of action against hepatitis B virus (HBV) infection are being explored with the goal of achieving a functional cure (sustained off-treatment response) without requiring lifelong therapy. We aimed to evaluate the pharmacokinetics, safety, and antiviral activity of ABI-H0731, an investigational inhibitor of the HBV core protein. Method(s): This phase 1, randomised, placebo-controlled study was done in two parts. In part 1, healthy adults without hepatitis B aged 18-65 years at one clinical research centre in New Zealand (eight participants per dose cohort) were randomly assigned (3:1) to receive single oral doses of ABI-H0731 (100, 300, 600, or 1000 mg) or matching placebo, or once-daily or twice-daily doses of ABI-H0731 800 mg or matching placebo for 7 days. In part 2, adults aged 18-65 years at clinical research centres in New Zealand, Australia, the UK, Hong Kong, Taiwan, and South Korea with chronic HBV (12 participants per dose cohort) were randomly assigned (5:1) to receive ABI-H0731 (100, 200, 300, or 400 mg) or matching placebo once daily for 28 days. In part 2, participants were required to have HBeAg-positive or HBeAg-negative chronic HBV infection, with serum HBV DNA concentrations of at least 2 x 104 IU/mL (HBeAg-positive) or 2 x 103 IU/mL (HBeAg-negative) and serum alanine aminotransferase concentrations less than seven times the upper limit of normal. Both parts used simple randomisation, with study participants, site personnel, and study monitors masked to treatment assignments. The primary study objective was dose-related safety and tolerability of ABI-H0731 in healthy volunteers and in participants with chronic HBV infection, assessed in all treated participants. Key secondary assessments included pharmacokinetic analyses and virological responses. This study is registered with ClinicalTrials.gov, identifier NCT02908191 and is completed. Finding(s): 48 [61%] of 79 healthy volunteers were enrolled in the sing

Complex drug-drug interactions are defined as those in which both metabolic enzymes and xenobiotic transporters are implicated as clinically significant determinants of drug disposition. Both metabolic enzymes and xenobiotic transporters have the potential to contribute to clearance pathways (i.e. metabolic, renal or biliary elimination) and bioavailability-related processes (i.e. drug absorption, intestinal metabolism, or first pass hepatic elimination). Transporters have the unique ability to influence the distribution of drug throughout the body, in addition to influencing intestinal drug absorption or drug clearance via renal or biliary routes. Thus, characterization of the contributions of metabolic enzymes and xenobiotic transporters is crucial in anticipating any potential alterations in drug exposure due to a drug-drug interaction, pharmacogenomic or disease state variance of activity or expression of relevant metabolic enzymes or transporters.Predictions of drug-drug interactions are routinely conducted based on results of in vitro metabolic enzyme or xenobiotic transporter inhibition studies. However, translating such results to clinical significance continues to challenge the field, particularly for transporter-mediated interactions since the susceptibility of a drug to transporters in vitro does not always translate to clinically significant in vivo involvement and due to a lack of specific and clinically validated index substrates, inhibitors and inducers for major xenobiotic transporters. The objective of this research was to provide a framework for recognizing transporter involvement in clinical drug-drug interactions, grounded in basic pharmacokinetic theory.Since xenobiotic transporters can allow (or disallow) substrates access to various tissues throughout the body, it was recognized that significant xenobiotic transporter interactions are accompanied by changes in volume of distribution, in addition to potential changes in clearance, which can res

The optimisation of antibiotic dosing therapy with therapeutic drug monitoring is widely recommended. The aim of therapeutic drug monitoring is to help the clinician to achieve target pharmacokinetic/pharmacodynamic parameters, maximising efficacy and minimising toxicity. Computerised programs, utilising the Bayesian estimation procedures, are able to achieve target concentrations in a greater percentage of patients earlier in the course of therapy compared to linear regression analysis and population methods. This article summarises various methods for dose optimisation of antibiotics with a focus on Bayesian programs.Copyright © 2019, Springer Nature Switzerland AG.

The optimisation of antibiotic dosing therapy with therapeutic drug monitoring is widely recommended. The aim of therapeutic drug monitoring is to help the clinician to achieve target pharmacokinetic/pharmacodynamic parameters, maximising efficacy and minimising toxicity. Computerised programs, utilising the Bayesian estimation procedures, are able to achieve target concentrations in a greater percentage of patients earlier in the course of therapy compared to linear regression analysis and population methods. This article summarises various methods for dose optimisation of antibiotics with a focus on Bayesian programs.Copyright © 2019, Springer Nature Switzerland AG.

Volume of distribution (Vdss ) is a measure of how effectively a drug molecule is distributed throughout the body. Along with the clearance, it determines the half-life and therefore the drug dosing interval. A number of different pre-clinical approaches are available to predict the Vdss in human including quantitative structure activity relationship (QSAR) models. Vdss QSAR models have been reported for human and rat, but not important pre-clinical species including dog, mouse and monkey. In this study, we have generated Vdss QSAR model on the human and commonly used pre-clinical species, each of which differs in terms of size, chemical diversity and data quality. We discuss the model performance by species, assess the effect the domain of applicability and the relative merits of building chemical series-specific models. In addition, we compare the intrinsic variability of the experimental logVdss data (∼1.2 fold error) to in-vivo interspecies differences (∼2 fold error) and in silico based models (∼3 fold error). This prompted us to explore whether one species could be used to predict another, particularly where little data for that species is available. i. e. does the expansion in domain of applicability prove beneficial over and above any deterioration due to the use of response values from an alternative species.

The emergence and continued evolution of the transporter field has caused re-evaluation and refinement of the original principles surrounding drug disposition. In this paper, we emphasize the impact that transporters can have on volume of distribution and how this can affect the other major pharmacokinetic parameters. When metabolic drug-drug interactions or pharmacogenomic variance changes the metabolism of a drug, the volume of distribution appears to be unchanged while clearance, bioavailability, and half-life are changed. When transporters are involved in the drug-drug interactions or pharmacogenomic variance, the volume of distribution can be markedly affected causing counterintuitive changes in half-life. Cases are examined where a volume of distribution change is significant enough that although clearance decreases, half-life decreases. Thus, drug dosing decisions must be made based on CL/F changes, not half-life changes, as such volume of distribution alterations will also influence the half-life results.

There are no available pharmacokinetic data to guide piperacillin dosing in critically ill Australian Indigenous patients despite numerous reported physiological differences. This study aimed to describe the population pharmacokinetics of piperacillin in critically ill Australian Indigenous patients with severe sepsis. A population pharmacokinetic study of Indigenous patients with severe sepsis was conducted in a remote hospital intensive care unit. Plasma samples were collected over two dosing intervals and assayed by validated chromatography. Population pharmacokinetic modeling was conducted using Pmetrics. Nine patients were recruited, and a two-compartment model adequately described the data. The piperacillin clearance (CL), volume of distribution of the central compartment (Vc), and distribution rate constants from the central to the peripheral compartment and from the peripheral to the central compartment were 5.6 +/- 3.2 liters/h, 14.5 +/- 6.6 liters, 1.5 +/- 0.4 h-1, and 1.8 +/- 0.9 h-1, respectively, where CL and Vc were found to be described by creatinine clearance (CLCR) and total body weight, respectively. In this patient population, piperacillin demonstrated high interindividual pharmacokinetic variability. CLCR was found to be the most important determinant of piperacillin pharmacokinetics.Copyright © Crown copyright 2016.

There are no available pharmacokinetic data to guide piperacillin dosing in critically ill Australian Indigenous patients despite numerous reported physiological differences. This study aimed to describe the population pharmacokinetics of piperacillin in critically ill Australian Indigenous patients with severe sepsis. A population pharmacokinetic study of Indigenous patients with severe sepsis was conducted in a remote hospital intensive care unit. Plasma samples were collected over two dosing intervals and assayed by validated chromatography. Population pharmacokinetic modeling was conducted using Pmetrics. Nine patients were recruited, and a two-compartment model adequately described the data. The piperacillin clearance (CL), volume of distribution of the central compartment (Vc), and distribution rate constants from the central to the peripheral compartment and from the peripheral to the central compartment were 5.6 +/- 3.2 liters/h, 14.5 +/- 6.6 liters, 1.5 +/- 0.4 h-1, and 1.8 +/- 0.9 h-1, respectively, where CL and Vc were found to be described by creatinine clearance (CLCR) and total body weight, respectively. In this patient population, piperacillin demonstrated high interindividual pharmacokinetic variability. CLCR was found to be the most important determinant of piperacillin pharmacokinetics.Copyright © Crown copyright 2016.

Aim The aim was to investigate the population pharmacokinetics of levamisole in children with steroid-sensitive nephrotic syndrome. Methods Non-linear mixed effects modelling was performed on samples collected during a randomized controlled trial. Samples were collected from children who were receiving 2.5mg kg-1 levamisole (or placebo) orally once every other day. One hundred and thirty-six plasma samples were collected from 38 children from India and Europe and included in the analysis. A one compartment model described the data well. Results The apparent clearance rate (CL/F) and distribution volume (V/F) were 44l h-1 70kg-1 and 236l 70kg-1, respectively; estimated interindividual variability was 32-42%. In addition to allometric scaling of CL/F and V/F to body weight, we identified a significant proportional effect of age on CL/F (-10.1% per year). The pharmacokinetics parameters were not affected by gender, tablet strength or study centre. The median (interquartile range) maximum plasma concentration of levamisole was 438.3 (316.5-621.8) ng ml-1, and the median area under the concentration-time curve was 2847 (2267-3761) ng ml-1 h. Median tmax and t1/2; values were 1.65 (1.32-2.0) h and 2.60 (2.06-3.65) h, respectively. Conclusions Here, we present the first pharmacokinetic data regarding levamisole in children with steroid-sensitive nephrotic syndrome. The pharmacokinetic profile of levamisole in children was similar to findings reported in adults, although the elimination rate was slightly higher in children.

Agonism of GPR119 is viewed as a potential therapeutic approach for the treatment of type II diabetes and other elements of metabolic syndrome. During progression of a previously disclosed candidate 1 through mice toxicity studies, we observed tonic-clonic convulsions in several mice at high doses. An in vitro hippocampal brain slice assay was used to assess the seizure liability of subsequent compounds, leading to the identification of an aryl sulfone as a replacement for the 3-cyano pyridyl group. Subsequent optimization to improve the overall profile, specifically with regard to hERG activity, led to alkyl sulfone 16. This compound did not cause tonic-clonic convulsions in mice, had a good pharmacokinetic profile, and displayed in vivo efficacy in murine models. Importantly, it was shown to be effective in wild-type (WT) but not GPR119 knockout (KO) animals, consistent with the pharmacology observed being due to agonism of GPR119., QC 20200921

A number of experimental observations in the late 1960s, early 1970s could not be explained by the pharmacokinetic theory available at that time. For example rats receiving phenobarbital as an enzyme inducing agent exhibited increased elimination of phenylbutazone in vitro in liver microsomes and in vivo in whole animals compared to that observed in non-induced animals. However, for desipramine, although phenobarbital increased elimination in microsomes, no change in plasma disappearance was noted in vivo for this drug between rats induced with phenobarbital and control rats. Similar in vitro-in vivo discordancies were seen with changes in protein binding. The introduction of clearance concepts in the early 1970s by Professor Rowland and others provided the scientific rationale for these apparently contradictory findings and the recognition that clearance, not half-life, was the measure of the body's ability to eliminate drugs and most importantly that changes in pathology and physiology could be correlated with measures of clearance. Up to that time half-life was well recognized in terms of basic chemical principles as an appropriate measure of the rate of elimination and reflective of changes in the rate of elimination. The difference between chemistry and pharmacokinetics, however, is that in chemistry the volume in which the reaction occurs does not change. In contrast, in pharmacokinetics, disease states and differences in physiology can change the space available in which the drug may distribute in the body. Thus, it was necessary to develop a pharmacokinetic measure of volume that was independent of elimination, i.e., V(ss). Now, the relationship between V(ss) and clearance led to a unique measure of time of drug in the body, the mean residence time. Although this parameter is calculated in all PK programs, very few pharmaceutical scientists know how it can be useful. Very recently, we have shown that the concepts of accumulation, prediction of which is the c

A number of experimental observations in the late 1960s, early 1970s could not be explained by the pharmacokinetic theory available at that time. For example rats receiving phenobarbital as an enzyme inducing agent exhibited increased elimination of phenylbutazone in vitro in liver microsomes and in vivo in whole animals compared to that observed in non-induced animals. However, for desipramine, although phenobarbital increased elimination in microsomes, no change in plasma disappearance was noted in vivo for this drug between rats induced with phenobarbital and control rats. Similar in vitro–in vivo discordancies were seen with changes in protein binding. The introduction of clearance concepts in the early 1970s by Professor Rowland and others provided the scientific rationale for these apparently contradictory findings and the recognition that clearance, not half-life, was the measure of the body’s ability to eliminate drugs and most importantly that changes in pathology and physiology could be correlated with measures of clearance. Up to that time half-life was well recognized in terms of basic chemical principles as an appropriate measure of the rate of elimination and reflective of changes in the rate of elimination. The difference between chemistry and pharmacokinetics, however, is that in chemistry the volume in which the reaction occurs does not change. In contrast, in pharmacokinetics, disease states and differences in physiology can change the space available in which the drug may distribute in the body. Thus, it was necessary to develop a pharmacokinetic measure of volume that was independent of elimination, i.e., Vss. Now, the relationship between Vss and clearance led to a unique measure of time of drug in the body, the mean residence time. Although this parameter is calculated in all PK programs, very few pharmaceutical scientists know how it can be useful. Very recently, we have shown that the concepts of accumulation, prediction of which is the clini

A number of experimental observations in the late 1960s, early 1970s could not be explained by the pharmacokinetic theory available at that time. For example rats receiving phenobarbital as an enzyme inducing agent exhibited increased elimination of phenylbutazone in vitro in liver microsomes and in vivo in whole animals compared to that observed in non-induced animals. However, for desipramine, although phenobarbital increased elimination in microsomes, no change in plasma disappearance was noted in vivo for this drug between rats induced with phenobarbital and control rats. Similar in vitro–in vivo discordancies were seen with changes in protein binding. The introduction of clearance concepts in the early 1970s by Professor Rowland and others provided the scientific rationale for these apparently contradictory findings and the recognition that clearance, not half-life, was the measure of the body’s ability to eliminate drugs and most importantly that changes in pathology and physiology could be correlated with measures of clearance. Up to that time half-life was well recognized in terms of basic chemical principles as an appropriate measure of the rate of elimination and reflective of changes in the rate of elimination. The difference between chemistry and pharmacokinetics, however, is that in chemistry the volume in which the reaction occurs does not change. In contrast, in pharmacokinetics, disease states and differences in physiology can change the space available in which the drug may distribute in the body. Thus, it was necessary to develop a pharmacokinetic measure of volume that was independent of elimination, i.e., Vss. Now, the relationship between Vss and clearance led to a unique measure of time of drug in the body, the mean residence time. Although this parameter is calculated in all PK programs, very few pharmaceutical scientists know how it can be useful. Very recently, we have shown that the concepts of accumulation, prediction of which is the clini

A number of experimental observations in the late 1960s, early 1970s could not be explained by the pharmacokinetic theory available at that time. For example rats receiving phenobarbital as an enzyme inducing agent exhibited increased elimination of phenylbutazone in vitro in liver microsomes and in vivo in whole animals compared to that observed in non-induced animals. However, for desipramine, although phenobarbital increased elimination in microsomes, no change in plasma disappearance was noted in vivo for this drug between rats induced with phenobarbital and control rats. Similar in vitro-in vivo discordancies were seen with changes in protein binding. The introduction of clearance concepts in the early 1970s by Professor Rowland and others provided the scientific rationale for these apparently contradictory findings and the recognition that clearance, not half-life, was the measure of the body's ability to eliminate drugs and most importantly that changes in pathology and physiology could be correlated with measures of clearance. Up to that time half-life was well recognized in terms of basic chemical principles as an appropriate measure of the rate of elimination and reflective of changes in the rate of elimination. The difference between chemistry and pharmacokinetics, however, is that in chemistry the volume in which the reaction occurs does not change. In contrast, in pharmacokinetics, disease states and differences in physiology can change the space available in which the drug may distribute in the body. Thus, it was necessary to develop a pharmacokinetic measure of volume that was independent of elimination, i.e., V(ss). Now, the relationship between V(ss) and clearance led to a unique measure of time of drug in the body, the mean residence time. Although this parameter is calculated in all PK programs, very few pharmaceutical scientists know how it can be useful. Very recently, we have shown that the concepts of accumulation, prediction of which is the c