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Objectives: Taking advantage of its food‐dependent bioavailability, the present study investigated the effect of a reduced dose taken with real‐life meals on the pharmacokinetics (PK) of nilotinib in chronic myeloid leukaemia (CML) patients. Methods: Nilotinib was taken fasted (300 mg BID, days 1‐4) or with real‐life meals (200 mg BID, days 5‐11). Rich sampling (days 1, 3, 8, 11) allowed for non‐compartmental PK analysis. Nilotinib exposure (AUC0–12 h ‐Cmin ‐Cmax) and its intra‐ and interpatient variability were compared between the two regimens. Adverse events were recorded by means of a patient diary and ECG monitoring. Results: Fifteen patients aged 40‐74 years participated. Nilotinib PK following 200 mg BID taken with a meal strongly resembled that of 300 mg BID taken fasted (Cmin percentile (P)10‐P90: 665‐1404 ng/mL and 557‐1743 ng/mL, respectively). Meals delayed nilotinib absorption. Intra‐ and interpatient variability were not increased by intake with meals. Nilotinib with food was well tolerated. Conclusion: With support of therapeutic drug monitoring, the use of a reduced 200 mg nilotinib dose with real‐life meals seems feasible and safe. Future (confirmatory) studies should further explore the usefulness of nilotinib dosing together with food, including the relationship with treatment efficacy as well as long‐term effects on quality of life. Clinical Trial Registration: NTR5000 (Netherlands Trial Register, www.trialregister.nl). [ABSTRACT FROM AUTHOR]

Background: Early high-dose IV vitamin C is being investigated as adjuvant therapy in patients who are critically ill, but the optimal dose and infusion method are unclear. The primary aim of this study was to describe the dose-plasma concentration relationship and safety of four different dosing regimens.Methods: This was a four-group randomized pharmacokinetic trial. Patients who were critically ill with multiple organ dysfunction were randomized to receive 2 or 10 g/d vitamin C as a twice daily bolus infusion or continuous infusion for 48 h. End points were plasma vitamin C concentrations during 96 h, 12-h urine excretion of vitamin C, and oxalate excretion and base excess. A population pharmacokinetic model was developed using NONMEM.Results: Twenty patients were included. A two-compartment pharmacokinetic model with creatinine clearance and weight as independent covariates described all four regimens best. With 2 g/d bolus, plasma vitamin C concentrations at 1 h were 29 to 50 mg/L and trough concentrations were 5.6 to 16 mg/L. With 2 g/d continuous, steady-state concentrations were 7 to 37 mg/L at 48 h. With 10 g/d bolus, 1-h concentrations were 186 to 244 mg/L and trough concentrations were 14 to 55 mg/L. With 10 g/d continuous, steady-state concentrations were 40 to 295 mg/L at 48 h. Oxalate excretion and base excess were increased in the 10 g/d dose. Forty-eight hours after discontinuation, plasma concentrations declined to hypovitaminosis levels in 15% of patients.Conclusions: The 2 g/d dose was associated with normal plasma concentrations, and the 10 g/d dose was associated with supranormal plasma concentrations, increased oxalate excretion, and metabolic alkalosis. Sustained therapy is needed to prevent hypovitaminosis.Trial Registry: ClinicalTrials.gov; No.: NCT02455180; URL: www.clinicaltrials.gov. [ABSTRACT FROM AUTHOR]

Aims: Inflammation and organ failure have been reported to have an impact on cytochrome P450 (CYP) 3A‐mediated clearance of midazolam in critically ill children. Our aim was to evaluate a previously developed population pharmacokinetic model both in critically ill children and other populations, in order to allow the model to be used to guide dosing in clinical practice. Methods: The model was evaluated externally in 136 individuals, including (pre)term neonates, infants, children and adults (body weight 0.77–90 kg, C‐reactive protein level 0.1–341 mg l–1 and 0–4 failing organs) using graphical and numerical diagnostics. Results: The pharmacokinetic model predicted midazolam clearance and plasma concentrations without bias in postoperative or critically ill paediatric patients and term neonates [median prediction error (MPE) <30%]. Using the model for extrapolation resulted in well‐predicted clearance values in critically ill and healthy adults (MPE <30%), while clearance in preterm neonates was over predicted (MPE >180%). Conclusion: The recently published pharmacokinetic model for midazolam, quantifying the influence of maturation, inflammation and organ failure in children, yields unbiased clearance predictions and can therefore be used for dosing instructions in term neonates, children and adults with varying levels of critical illness, including healthy adults, but not for extrapolation to preterm neonates. [ABSTRACT FROM AUTHOR]

Introduction: Capecitabine is a widely prescribed oral anticancer agent. We studied medication adherence and explored its use in daily practice from a patients' perspective. Patients and Methods: Patients (n = 92) starting capecitabine were followed up to five 3-week cycles. Adherence was assessed using a pill count, pharmacy data and dosing information from the patients' medical file. Self-reported adherence was measured using the Medication Adherence Report Scale (MARS). At baseline and during week 2 of cycles 1, 3, and 5, patients filled out questionnaires about quality of life, symptoms, attitude toward medicines and disease and use in daily practice. Simultaneously, blood samples were taken to determine the area under the curve (AUC) of 5'-deoxy-5-fluorouridine (5'-DFUR), 5-fluorouracil (5-FU), and a-fluoro-b-alanine (FBAL) by a population pharmacokinetic model. Associations between AUCs and patient-reported symptoms were tested for cycles 3 and 5. Results: Most patients (84/92; 91%) had an adherence rate of ≥95 and ≤105%. The percentage of patients reporting any non-adherence behavior measured with MARS increased from 16% at cycle 1 to 29% at cycle 5. Symptoms were reported frequently and the dosing regimen was adjusted by the physician at least once in 62% of patients. In multivariate analysis the probability of an adjustment increased with the number of co-medication (OR 1.19, 95% CI: 1.03-1.39) and a stronger emotional response to the disease (OR 1.32, 95% CI: 1.10-1.59). The AUC of 5'-DFUR was associated with weight loss (OR 1.10, 95% CI: 1.01-1.19), AUC of FBAL with hand-foot syndrome (OR 0.90, 95% CI: 0.83-0.99), rhinorrhea (OR 1.21, 95% CI: 1.03-1.42 weight loss (OR 1.09, 95% CI: 1.00-1.20) and depression (OR 0.90, 95% CI: 0.82-0.99). Side effects were reported by one third of patients as the reason to discontinue treatment. Conclusion: Adherence to capecitabine was generally high. Nevertheless, adherence measured with MARS decreased over time Adherence management to support implementation of correct capecitabine use is specifically relevant in longer term treatment. In addition, it appears that adverse event management is important to support persistence. With the extending armamentarium of oral targeted anticancer agents and prolonged treatment duration, we expect the issue of medication adherence of increasing importance in oncology. [ABSTRACT FROM AUTHOR]

Background: The antitumor drug nilotinib has a large inter- and intra individual variability in pharmacokinetics. Adherence to treatment may substantially influence plasma levels and has been recognized as the most important determinant of treatment failure in chronic myeloid leukemia (CML). A better understanding of the various factors contributing to the efficacy of treatment is essential for the development of interventions to optimize the treatment of chronic phase CML (CP-CML) with a protein kinase inhibitor like nilotinib. Methods/Design: In this multicenter prospective observational cohort study 70 adult patients with CP-CML starting treatment with nilotinib will be followed up for at least 12 months. Response to treatment is evaluated after 3, 6 and 12 months. Adherence is primarily assessed by counting the daily intake of nilotinib capsules by means of a medication event monitoring system (MEMS). Before the start of nilotinib treatment and after 3, 6 and 12 months, patients are asked to fill in a comprehensive questionnaire including topics on quality of life, side effects, attitude towards disease and medication, the patients' appreciation of information received about the medication, and discontinuation, and trough plasma levels of nilotinib are measured. Discussion: The present study aims to get more insight into the efficacy of treatment with nilotinib and the various aspects that govern optimal response, of which adherence is a primary endpoint. We hypothesize that patients who experience inadequate response levels to nilotinib are less adherent. In addition, their plasma levels of nilotinib may be lower. We expect that our findings will be useful for health care professionals to support patients with the use of nilotinib in order to derive optimal benefit from their medication. [ABSTRACT FROM AUTHOR]

WHAT IS ALREADY KNOWN ABOUT THIS SUBJECT • The population pharmacokinetics and limited sampling strategies for ciclosporin monitoring have been extensively studied in renal and liver transplant recipients. Little is known about the pharmacokinetics of ciclosporin in patients undergoing haematopoietic allogeneic stem cell transplantation (HSCT). • It is anticipated that there is a difference in pharmacokinetics in patients after kidney or liver transplantation compared with patients undergoing stem cell transplantation, because of mucositis and interacting drugs (e.g. fluconazole). • Data on the pharmacokinetics of ciclosporin and the relationship between its systemic exposure, as reflected by the area under the curve (AUC), and the biological effect as graft vs. host-disease (GVHD) prophylaxis and graft vs. tumour (GVT) response are scarce in patients after HSCT. WHAT THIS STUDY ADDS • A pharmacokinetic model was developed for orally and intravenously administered ciclosporin, enabling an adequate estimate of the systemic exposure of ciclosporin in patients after HSCT. A limited sampling strategy was tested that may serve as a tool to study the optimum systemic exposure (AUC) of ciclosporin in HSCT to prevent GVHD but establish adequate GVT response and to guide therapeutic drug monitoring. AIM To develop a population pharmacokinetic model of ciclosporin (CsA) in haematopoietic allogeneic stem cell transplantation to facilitate a limited sampling strategy to determine systemic exposure (area under the curve [AUC]), in order to optimize CsA therapy in this patient population. METHODS The pharmacokinetics of CsA were investigated prospectively in 20 patients following allogeneic haematopoietic stem cell transplantation (HSCT). CsA was given twice daily, as a 3 h i.v. infusion starting at day 1 of the conditioning scheme, and orally later on, when oral intake was well tolerated. Fluconazole was given as antimycotic prophylaxis. Pharmacokinetic parameter estimation was performed using nonlinear mixed effect modelling as implemented in the NONMEM program. A first order absorption model with lag time was compared with Erlang frequency distribution and Weibull distribution models. The influence of demographic variables on the individual empirical Bayesian estimates of clearance and distribution volume was tested. Subsequently two limited sampling strategies (LSS) were evaluated: posterior Bayesian fitting and limited sampling equations. RESULTS Twenty patients were included and 435 samples were collected after i.v. and oral administration of CsA. A two compartment model with first order absorption best described the data. Clearance (CL) was 21.9 l h−1 (relative standard deviation [RSD]± 5.2%) with an inter-individual variability of 21%. The central volume of distribution ( Vc) was 18.3 l (RSD ± 8.7%) with an inter-individual variability of 29%. Bioavailability ( F) was 0.71 (RSD ± 9.9%) with and inter-individual variability of 25% and lag time ( tlag) was 0.44 h (RSD 5.5%). Weight, body surface area, haematocrit, albumin, ALAT and ASAT had no significant influence on pharmacokinetic parameters. The best multiple point combination for posterior Bayesian fitting, in terms of estimating systemic CsA exposure, appeared to be C0 + C2 + C3. Two selected LSS two time point equations and all selected three and four time point equations predicted de all AUC(0,12 h) within 15% bias and prediction. CONCLUSIONS The i.v. and oralcurves were best described with a two compartment model with first-order absorption with lag time. With the Bayesian estimators from this model, the area under the concentration−time curve in HSCT patients taking fluconazole can be estimated with only three blood samples (0, 2, 3 h) with a bias of 1% and precision of 4%. [ABSTRACT FROM AUTHOR]

Objective: The objective of the present investigation was to develop a population pharmacodynamic model for midazolam- and lorazepam-induced sedation upon long-term continuous infusion in critically ill patients. Methods: The study was conducted in 59 patients receiving lorazepam and 54 patients receiving midazolam by continuous infusion for at least 24 h. Repeated blood samples were obtained for determination of the concentrations of lorazepam and midazolam. The level of sedation was assessed using a 5-point sedation scale. Results: The pharmacokinetics of lorazepam and midazolam was described with previously proposed pharmacokinetic models. For the pharmacodynamics, the probability that the sedation was equal to or more than a specific score was described using a sigmoid Emax model. The EC50 values of lorazepam for the sedation scores equal or larger than 2–5 were 6.1, 57, 184 and 529 ng/ml, respectively. The corresponding values for midazolam were 216, 483, 1100 and 2200 ng/ml. Inter-individual variability in the EC50 values was relatively high with a CV of 68% for lorazepam and 86% for midazolam (p=0.035). No covariates explaining part of the observed inter-individual variability were identified. Conclusion: The population pharmacodynamic model shows a similarly wide intra- and inter-individual variability in the pharmacodynamics of both lorazepam and midazolam. Thus, the previously observed differences in ‘ease of titration’ between lorazepam and midazolam are unrelated to pharmacodynamic factors. [ABSTRACT FROM AUTHOR]

Objective The objectives of the study were to develop a population pharmacokinetic model for 11C-flumazenil at tracer concentrations, to assess the effects of patient-related covariates and to derive an optimal sampling protocol for clinical use. Methods A population pharmacokinetic model was developed using nonlinear mixed effects modelling (NONMEM) with data obtained from 51 patients with either depression or epilepsy. Each patient received ∼370 MBq (1–4 µg) of 11C-flumazenil. The effects of selected covariates (gender, weight, type of disease and age) were investigated. The model was validated using a bootstrap method. Finally, an optimal sampling design was established. Results The population pharmacokinetics of tracer quantities of 11C-flumazenil were best described by a two compartment model. Type of disease and weight were identified as significant covariates ( P < 0.002). Mean population pharmacokinetic parameters (percent coefficient of variation) were: CL 1530 mL min−1 (6.6%), V1 24.8 × 103 mL (3.8%), V2 27.3 × 103 mL (5.4%), and Q 2510 mL min−1 (6.5%). CL was 20% lower in patients with epilepsy, and the influence of weight on V1 was 0.55% kg−1. For the prediction of the AUC, a combination of two time points at t = 30 and 60 min post injection was considered optimal (bias −0.7% (95% CI −2.2 to 0.8%), precision 5.7% (95% CI 4.5–6.9%)). The optimal sampling strategy was cross-validated (observed AUC = 296 MBql−1 min−1 (95% CI 102–490), predicted AUC = 288 MBql−1 min−1 (95% CI 70–506)). Conclusions The population pharmacokinetics of tracer quantities of 11C-flumazenil are well described by a two-compartment model. Inclusion of weight and type of disease as covariates significantly improved the model. Furthermore, an optimal sampling procedure may increase the feasibility and applicability of 11C-flumazenil PET. [ABSTRACT FROM AUTHOR]

It is well established that there is a wide intra- and interindividual variability in dose requirements for lorazepam and midazolam in intensive care patients. The objective of this study was to compare the population pharmacokinetics of lorazepam and midazolam after long-term continuous infusion in mechanically ventilated critically ill patients. Forty-nine critically ill patients randomly received either lorazepam ( n = 28) or midazolam ( n = 21) by continuous infusion for at least 24 h. Multiple blood samples were obtained for determination of the drug and metabolite concentrations by HPLC. Population pharmacokinetic models were developed using the Non-Linear Mixed Effect Modelling (NONMEM) program. The influence of selected covariates was investigated. The prospective performance of the models was evaluated on the basis of results in separate groups of patients for lorazepam ( n = 31) and midazolam ( n = 33). The pharmacokinetics of lorazepam were best described by a two-compartment model. Alcohol abuse, positive end expiratory pressure (PEEP) and age were identified as significant covariates. Total body clearance for patients without alcohol abuse was 4.13 − (PEEP − 5) × 0.42 l h−1, and 0.74 l h−1 for patients with alcohol abuse. The volume of distribution was 0.74 l, the steady state volume of distribution was 56 − (age − 58) × 2.1 l and the intercompartmental clearance was 10 l h−1. The proportional residual error was 15% and the median absolute prediction error was 13.6% with a bias of 1.5%. The pharmacokinetics of midazolam were best described by a two-compartment model with alcohol abuse, APACHE score and age as significant covariates. Total body clearance for patients without alcohol abuse was 11.3 − (age − 57) × 0.14 l h−1, and 7.27 – (age −57) × 0.14 l h−1 for patients with alcohol abuse. The volume of distribution was 7.15 l, the steady state volume of distribution was 431 l, and the intercompartmental clearance was 40.8 − (APACHE score − 26) × 2.75 l h−1. The proportional residual error was 31% with an additive residual error of 32 ng ml−1. The median absolute prediction error was 12.9% with a bias of 1.2%. The prospective performance in the lorazepam evaluation group was better with the covariate adjusted model, but in the midazolam evaluation group it was not better than with the simple model. In all models a tendency to overestimate the lower plasma concentrations was observed. The pharmacokinetics of both lorazepam and midazolam were well described by a two-compartment model. Inclusion of alcohol abuse and age as covariates improved both models. PEEP was identified as an additional covariate for lorazepam, and the APACHE score for midazolam. For both drugs there is a large interindividual variability in their pharmacokinetics when used for long-term sedation in critically ill patients. However, the intra-individual variability is much lower for lorazepam. [ABSTRACT FROM AUTHOR]

Aims The objectives of the present investigation were: (a) to determine the correlation between lignocaine and midazolam pharmacokinetics following intravenous administration in healthy volunteers, (b) to determine the effects of treatment with an inhibitor of CYP3A4 (erythromycin) on this correlation and (c) to assess the precision of the MEGX-test as a sole predictor of lignocaine and midazolam pharmacokinetics. Methods The study was conducted in four male and four female healthy volunteers, aged between 21 and 26 years, who received 1 mg kg-1 lignocaine HCl i.v. on days 1, 3, 5, 9 and 10 of the investigation. On days 5 and 10 they also received midazolam, 0.075 mg kg-1 i.v. and from days 6–10 they took erythromycin 500 mg orally, four times daily. Following administration of lignocaine and midazolam, frequent venous blood samples were obtained for determination of the concentrations of lignocaine, MEGX and midazolam. Results In the absence of erythromycin a statistically significant linear correlation was observed between the clearance of lignocaine and midazolam (CLmidazolam = 0.41×CLlignocaine +1.2; r 2 = 0.857; P < 0.001). Erythromycin cotreatment resulted in a loss of the correlation between the two clearances (r 2 = 0.39; P = 0.1). Erythromycin caused a statistically significant reduction in midazolam clearance from the original value of 3.8 to 2.5 (95% CI for the difference -2.27, -0.35) ml kg-1 min-1 . Interestingly there was no significant change in the clearance of lignocaine (6.4 vs 5.8 (95% CI for the difference -2.74, -1.51) ml kg-1 min-1 ). Furthermore no correlation at all was observed between the MEGX-test and lignocaine or midazolam clearances. Considering the data on day 1, 3 and 5 the intra-individual coefficient of variation in the MEGX-test was 45.3% at 15 min and 23.5% at 30 min, respectively. Conclusions It is... [ABSTRACT FROM AUTHOR]

• This is the first study to report exposure-response analyses of oral imatinib in COVID-19 patients. • Higher total imatinib concentrations were found in COVID-19 patients compared to cancer patients, which can be attributed to differences in plasma protein concentrations. • Inverse associations between imatinib exposure and clinical response parameters were found in COVID-19 patients, which may be explained by disease course. In the randomized double-blind placebo-controlled CounterCOVID study, oral imatinib treatment conferred a positive clinical outcome and a signal for reduced mortality in COVID-19 patients. High concentrations of alpha-1 acid glycoprotein (AAG) were observed in these patients and were associated with increased total imatinib concentrations. This post-hoc study aimed to compare the difference in exposure following oral imatinib administration in COVID-19 patients to cancer patients and assess assocations between pharmacokinetic (PK) parameters and pharmacodynamic (PD) outcomes of imatinib in COVID-19 patients. We hypothesize that a relatively higher drug exposure of imatinib in severe COVID-19 patients leads to improved pharmacodynamic outcome parameters. 648 total concentration plasma samples obtained from 168 COVID-19 patients were compared to 475 samples of 105 cancer patients, using an AAG-binding model. Total trough concentration at steady state (Ct trough) and total average area under the concentration-time curve (AUCt ave) were associated with ratio between partial oxygen pressure and fraction of inspired oxygen (P/F), WHO ordinal scale (WHO-score) and liberation of oxygen supplementation (O 2 lib). Linear regression, linear mixed effects models and time-to-event analysis were adjusted for possible confounders. AUCt ave and Ct trough were respectively 2.21-fold (95%CI 2.07–2.37) and 1.53-fold (95%CI 1.44–1.63) lower for cancer compared to COVID-19 patients. Ct trough , not AUCt ave , associated significantly with P/F (β=-19,64; p-value=0.014) and O 2 lib (HR 0.78; p-value= 0.032), after adjusting for sex, age, neutrophil-lymphocyte ratio, dexamethasone concomitant treatment, AAG and baseline P/F-and WHO-score. Ct trough , but not AUCt ave associated significantly with WHO-score. These results suggest an inverse relationship between PK-parameters, Ct trough and AUCt ave , and PD outcomes. COVID-19 patients exhibit higher total imatinib exposure compared to cancer patients, attributed to differences in plasma protein concentrations. Higher imatinib exposure in COVID-19 patients did not associate with improved clinical outcomes. Ct trough and AUCt ave inversely associated with some PD-outcomes, which may be biased by disease course, variability in metabolic rate and protein binding. Therefore, additional PKPD analyses into unbound imatinib and its main metabolite may better explain exposure-response. [Display omitted] [ABSTRACT FROM AUTHOR]

Abstract: A simple, sensitive and specific liquid chromatography tandem mass spectrometry method with minimal sample pretreatment was developed for the simultaneous analysis of sildenafil and its metabolite desmethylsildenafil in human serum. Sample pretreatment consisted of adding a methanolic solution of the internal standard vardenafil to the samples. After vortexing and centrifugation the samples were directly injected onto the C18 column using gradient elution. The aqueous and organic mobile phases were ammonium acetate 2mM supplemented with 0.1% formic acid in water and methanol, respectively. The detection by a triple quadrupole mass spectrometer in positive ESI ionization mode was completed within 5min. The lower limits of quantification for sildenafil and desmethylsildenafil are 1.0ng/ml. The intra- and inter-day precisions measured as relative standard deviation were within 10% for both compounds over the linear range. Intra- and inter-day accuracy of sildenafil and desmethylsildenafil ranged from 92 to 103%. This method has been used in a clinical pharmacokinetic study of sildenafil in intensive care patients. [Copyright &y& Elsevier]