| 51. |
- Nielsen, Elisabet I., et al.
(författare)
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Developmental Pharmacokinetics of Gentamicin in Preterm and Term Neonates : Population Modelling of a Prospective Study
- 2009
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Ingår i: Clinical Pharmacokinetics. - : Springer Science and Business Media LLC. - 0312-5963 .- 1179-1926. ; 48:4, s. 253-263
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Tidskriftsartikel (refereegranskat)abstract
- Background and objective:Preterm and term newborn infants show wide interindividual variability (IIV) in pharmacokinetic parameters of gentamicin. More extensive knowledge and use of predictive covariates could lead to faster attainment of therapeutic concentrations and a reduced need for concentration monitoring. This study was performed to characterize the population pharmacokinetics of gentamicin in preterm and term neonates and to identify and quantify relationships between patient characteristics and IIV. A secondary aim was to evaluate cystatin C as a marker for gentamicin clearance in this patient population.Methods:Data were collected in a prospective study performed in the Neonatal Intensive Care Unit at the University Children's Hospital, Uppsala, Sweden. Population pharmacokinetic modelling was performed using nonlinear mixed-effects modelling (NONMEM) software. Bodyweight was included as the primary covariate according to an allometric power model. Other evaluated covariates were age (postmenstrual age, gestational age [GA], postnatal age [PNA]), markers for renal function (serum creatinine, serum cystatin Q and concomitant medication with cefuroxime, vancomycin or indometacin. Covariate-parameter relationships were explored using a stepwise covariate model building procedure. The predictive performance of the developed model was evaluated using an independent external dataset for a similar patient population.Results:Sixty-one newborn infants (GA range 23.3-42.1 weeks, PNA range 0-45 days) were enrolled in the study. In total, 894 serum gentamicin samples were included in the analysis. The concentration-time profile was described using a three-compartment model. Gentamicin clearance increased with the GA and PNA (included in a nonlinear fashion). The GA was also identified as having a significant influence on the central volume of distribution, with a preterm neonate having a larger central volume of distribution per kilogram of bodyweight than a term neonate. Cystatin C and creatinine were not correlated with gentamicin clearance in this study population. The external dataset was well predicted by the developed model.Conclusion:Bodyweight and age (GA and PNA) were found to be major factors contributing to IIV in gentamicin clearance in neonates. Based on these data, cystatin C and serum creatinine were not correlated with gentamicin clearance and therefore not likely to be predictive markers of renal function in this patient population. Based on predictions from the developed model, preterm neonates do not reach targeted peak and trough gentamicin concentrations after a standard dosage regimen of 4mg/kg given once daily, suggesting a need for higher loading doses and prolonged dosing intervals in this patient population.
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| 52. |
- Norberg, Å, et al.
(författare)
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Role of variability in explaining ethanol pharmacokinetics : Research and forensic applications
- 2003
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Ingår i: Clinical Pharmacokinetics. - : Springer Science and Business Media LLC. - 0312-5963 .- 1179-1926. ; 42:1
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Tidskriftsartikel (refereegranskat)abstract
- Variability in the rate and extent of absorption, distribution and elimination of ethanol has important ramifications in clinical and legal medicine. The speed of absorption of ethanol from the gut depends on time of day, drinking pattern, dosage form, concentration of ethanol in the beverage, and particularly the fed or fasting state of the individual. During the absorption phase, a concentration gradient exists between the stomach, portal vein and the peripheral venous circulation. First-pass metabolism and bioavailability are difficult to assess because of dose-, time- and flow-dependent kinetics. Ethanol is transported by the bloodstream to all parts of the body. The rate of equilibration is governed by the ratio of blood flow to tissue mass. Arterial and venous concentrations differ as a function of time after drinking. Ethanol has low solubility in lipids and does not bind to plasma proteins, so volume of distribution is closely related to the amount of water in the body, contributing to sex- and age-related differences in disposition. The bulk of ethanol ingested (95-98%) is metabolised and the remainder is excreted in breath, urine and sweat. The rate-limiting step in oxidation is conversion of ethanol into acetaldehyde by cytosolic alcohol dehydrogenase (ADH), which has a low Michaelis-Menten constant (Km) of 0.05-0.1 g/L. Moreover, this enzyme displays polymorphism, which accounts for racial and ethnic variations in pharmacokinetics. When a moderate dose is ingested, zero-order elimination operates for a large part of the blood-concentration time course, since ADH quickly becomes saturated. Another ethanol-metabolising enzyme, cytochrome P450 2E1, has a higher Km (0.5-0.8 g/L) and is also inducible, so that the clearance of ethanol is increased in heavy drinkers. Study design influences variability in blood ethanol pharmacokinetics. Oral or intravenous administration, or fed or fasted state, might require different pharmacokinetic models. Recent work supports the need for multicompartment models to describe the disposition of ethanol instead of the traditional one-compartment model with zero-order elimination. Moreover, appropriate statistical analysis is needed to isolate between- and within-subject components of variation. Samples at low blood ethanol concentrations improve the estimation of parameters and reduce variability. Variability in ethanol pharmacokinetics stems from a combination of both genetic and environmental factors, and also from the nonlinear nature of ethanol disposition, experimental design, subject selection strategy and dose dependency. More work is needed to document variability in ethanol pharmacokinetics in real-world situations.
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| 53. |
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| 54. |
- Oosten, Astrid W, et al.
(författare)
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A Prospective Population Pharmacokinetic Study on Morphine Metabolism in Cancer Patients.
- 2017
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Ingår i: Clinical Pharmacokinetics. - : Springer Science and Business Media LLC. - 0312-5963 .- 1179-1926. ; 56:7, s. 733-746
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: Oral and subcutaneous morphine is widely used for the treatment of cancer-related pain; however, solid pharmacokinetic data on this practice are lacking. Furthermore, it is largely unknown which factors contribute to the variability in clearances of morphine and its metabolites and whether morphine clearance is related to treatment outcome.METHODS: Blood samples from 49 cancer patients treated with oral and/or subcutaneous morphine were prospectively collected and were used to develop a population pharmacokinetic model for morphine, morphine-3-glucuronide (M3G) and morphine-6-glucuronide (M6G). The influence of age, gender, renal function and several polymorphisms possibly related to the pharmacokinetics of the three compounds was investigated. In addition, the relation between treatment failure and morphine and metabolite clearances was explored.RESULTS: A one-compartment model including an extensive first-pass effect adequately described the data of morphine and its metabolites. Estimated mean area under the plasma concentration-time curve (AUC) ratios following oral versus subcutaneous administration were: M3G/morphine 29.7:1 vs. 11.1:1; M6G/morphine 5.26:1 vs. 1.95:1; and M3G/M6G 5.65:1 vs. 5.70:1. Renal function was significantly correlated with clearance of the metabolites, which increased 0.602 L/h per every 10 mL/min/1.73 m(2) increase of estimated glomerular filtration rate (eGFR), reaching a plateau for eGFR >90 mL/min/1.73 m(2). The clearance of morphine or its metabolites was not found to be correlated with treatment failure.CONCLUSION: The influence of age-, gender- and pharmacokinetic-related polymorphisms was not identified on the pharmacokinetics of morphine. Clearance of morphine or its metabolites was not found to explain treatment outcome; however, large variations in plasma concentrations of morphine, M3G and M6G support further studies on the relation between plasma concentrations and treatment outcome. Dutch Trial Register ID: NTR4369.
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| 55. |
- Pan, Shan, et al.
(författare)
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Assessment of the Relationship Between Methotrexate Polyglutamates in Red Blood Cells and Clinical Response in Patients Commencing Methotrexate for Rheumatoid Arthritis
- 2014
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Ingår i: Clinical Pharmacokinetics. - : Springer Science and Business Media LLC. - 0312-5963 .- 1179-1926. ; 53:12, s. 1161-1170
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Tidskriftsartikel (refereegranskat)abstract
- Therapeutic drug monitoring in patients with rheumatoid arthritis (RA) receiving methotrexate (MTX, MTXGlu(1)) has not been established. In this study, we aim to explore the relationship between red blood cell (RBC) concentrations of MTX and its polyglutamate metabolites (MTXGlu (n) ; n = 2, 3, 4, 5) and clinical response in RA patients commencing MTX. The binding activity of MTXGlu (n) to three putative enzymes involved in the MTX mechanism of action-dihydrofolate reductase, thymidylate synthase, and 5-aminoimidazole-4-carboxamide ribonucleotide transformylase-was simulated. RBC MTXGlu (n) concentrations that gave the highest inhibition activity across all three enzymes were linked with the disease activity score DAS28-3v (C-reactive protein [CRP]). A population pharmacokinetic-pharmacodynamic model was developed to describe the relationship between RBC MTX polyglutamate concentrations and clinical response in 12 RA patients commencing MTX. The highest inhibition activity was with RBC MTXGlu(3-5). These polyglutamates were further evaluated for their relationship with DAS28-3v (CRP). Three of the 12 patients had a high DAS28-3v (CRP) at baseline (mean = 6.1) and showed a delayed response to MTX treatment. The remaining nine patients with a lower DAS28-3v (CRP) baseline (mean = 3.6) showed an immediate response. The developed MTX pharmacokinetic-pharmacodynamic model provided an acceptable description of the observed DAS28-3v (CRP) across all patients. The developed model describes a longitudinal relationship between RBC MTXGlu(3-5) concentrations and DAS28-3v (CRP) in patients with RA commencing MTX. Further work is required to determine whether measurement of RBC MTX polyglutamates might be useful for dose individualisation in patients with RA.
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| 56. |
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| 57. |
- Savic, Radojka M., et al.
(författare)
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Population pharmacokinetics of cladribine in patients with multiple sclerosis
- 2017
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Ingår i: Clinical Pharmacokinetics. - : Springer Science and Business Media LLC. - 0312-5963 .- 1179-1926. ; 56:10, s. 1245-1253
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Tidskriftsartikel (refereegranskat)abstract
- The aims of this study were to characterize the concentration-time course of cladribine (CdA) and its main metabolite 2-chloroadenine (CAde), estimate interindividual variability in pharmacokinetics (PK), and identify covariates explaining variability in the PK of CdA. This population PK analysis was based on the combined dataset from four clinical studies in patients with multiple sclerosis (MS): three phase I studies, including one food and one drug-drug interaction study, and one phase III clinical study. Plasma and urine concentration data of CdA and CAde were modeled simultaneously. The analysis comprised a total of 2619 CdA and CAde plasma and urine concentration observations from 173 patients with MS who received an intravenous infusion or oral tablet doses of CdA as a single agent or in combination with interferon (IFN) beta-1a. CdA PK data were best described by a three-compartment model, while a one-compartment model best described the PK of CAde. CdA renal clearance (CLR) was correlated with creatinine clearance (CLCR), predicting a decrease in the total clearance of 19%, 30% and 40% for patients with mild (CLCR = 65 ml/min), moderate (CLCR = 40 ml/min) and severe (CLCR = 20 ml/min) renal impairment, respectively. Food decreased the extent of CdA absorption by 11.2% and caused an absorption delay. Coadministration with IFN beta-1a was found to increase non-CLR (CLNR) by 21%, resulting in an increase of 11% in total clearance. Both CdA and CAde displayed linear PK after intravenous and oral administration of CdA, with CdA renal function depending on CLCR.
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| 58. |
- Siegmund, Werner, et al.
(författare)
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Pharmacokinetics and pharmacodynamics of propiverine in children aged between 5 and 10 years with symptoms of overactive bladder
- 2010
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Ingår i: Clinical Pharmacokinetics. - : Springer Science and Business Media LLC. - 0312-5963 .- 1179-1926. ; 49:5, s. 335-342
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND AND OBJECTIVES: Pharmacokinetic studies in children are particularly required for drugs with intensive hepatic and regioselective intestinal elimination and pharmacological effects that may be critical for absorption at therapeutic doses, such as a delay in intestinal transit. One example is the antimuscarinic drug propiverine, the pharmacokinetics of which were evaluated in the present study in children with symptoms of overactive bladder. METHODS: The pharmacokinetics of immediate-release propiverine were studied in a dose-escalating, parallel-group study (propiverine 5, 10 and 15 mg twice daily for 14 days) in 25 subjects (11 females and 14 males aged 5-10 years; bodyweight 17-44 kg; body mass index 14-21 kg/m2) with symptoms of overactive bladder during waking hours. Serum concentration-time curves of propiverine and its major metabolite propiverine N-oxide (M-5) were evaluated up to 3 hours and 8 hours after the first and last administration, respectively, using liquid chromatography with tandem mass spectrometry. The voiding frequency, number of incontinence and urgency episodes, single voided volume and urine flow variables were measured before and after treatment. RESULTS: Significant dose-related increases in the serum exposure (the area under the concentration-time curve, the maximum concentration and the minimum concentration) with propiverine and M-5 in the dose groups < or =0.3 mg/kg and 0.3 to < or =0.45 mg/kg after both single-dose and repeated-dose administration were found. The elimination half-lives of propiverine and M-5 at steady state were no different (mean +/- SD 12.2 +/- 11.2 and 14.5 +/- 9.94 hours, respectively). Higher doses did not result in additional dose-proportional increases in the respective pharmacokinetic parameters, particularly not after repeated-dose treatment. The voiding frequency, voided volume and urge symptoms were beneficially changed from baseline; significant dose-dependent changes were not observed. Most of the adverse events that were probably or possibly drug related were reported for patients in the high-dose group (>0.45 mg/kg). CONCLUSIONS: The disposition of propiverine is dose related after repeated administration of the recommended doses below 0.45 mg/kg (0.3-0.45 mg/kg) twice daily in children aged 5-10 years with symptoms of overactive bladder and urinary incontinence. (Trial registration numbers: [clinicaltrials.gov] NCT00795925; [EudraCT] 2004-001243-30).
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| 59. |
- Sinha, Vikash K., et al.
(författare)
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Towards a Better Prediction of Peak Concentration, Volume of Distribution and Half-Life after Oral Drug Administration in Man, Using Allometry
- 2011
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Ingår i: Clinical Pharmacokinetics. - : Springer Science and Business Media LLC. - 0312-5963 .- 1179-1926. ; 50:5, s. 307-318
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Tidskriftsartikel (refereegranskat)abstract
- Background: it is imperative that new drugs demonstrate adequate pharmacokinetic properties, allowing an optimal safety margin and convenient dosing regimens in clinical practice, which then lead to better patient compliance. Such pharmacokinetic properties include suitable peak (maximum) plasma drug concentration (C-max), area under the plasma concentration-time curve (AUC) and a suitable half-life (t(1/4)). The C-max and t(1/2) following oral drug administration are functions of the oral clearance (CL/F) and apparent volume of distribution during the terminal phase by the oral route (V-z/F), each of which may be predicted and combined to estimate C-max and t(1/4). Allometric scaling is a widely used methodology in the pharmaceutical industry to predict human pharmacokinetic parameters such as clearance and volume of distribution. In our previous published work, we have evaluated the use of allometry for prediction of CL/F and AUC. In this paper we describe the evaluation of different allometric scaling approaches for the prediction of C-max, V-z/F and t(1/2) after oral drug administration in man. Methods: Twenty-nine compounds developed at Janssen Research and Development (a division of Janssen Pharmaceutica NV), covering a wide range of physicochemical and pharmacokinetic properties, were selected. The C,, following oral dosing of a compound was predicted using (i) simple allometry alone; (ii) simple allometry along with correction factors such as plasma protein binding (PPB), maximum life-span potential or brain weight (reverse rule of exponents, unbound C-max approach); and (iii) an indirect approach using allometrically predicted CL/F and V-z/F and absorption rate constant (k(a)). The k(a) was estimated from (i) in vivo pharmacokinetic experiments in preclinical species; and (ii) predicted effective permeability in man Weir), using a Caco-2 permeability assay. The V-z/F was predicted using allometric scaling with or without PPB correction. The t(1/2) was estimated from the allometrically predicted parameters CL/F and V-z/F. Predictions were deemed adequate when errors were within a 2-fold range. Results: C-max and t(1/2), could be predicted within a 2-fold error range for 59% and 66% of the tested compounds, respectively, using allometrically predicted CL/F and V-z/F. The best predictions for Cif, were obtained when K-a values were calculated from the Caco-2 permeability assay. The V-z/F was predicted within a 2-fold error range for 72% of compounds when PPB correction was applied as the correction factor for scaling. Conclusions: We conclude that (i) C-max and t(1/2), are best predicted by indirect scaling approaches (using allometrically predicted CL/F and V-z/F and accounting for ka derived from permeability assay); and (ii) the PPB is an important correction factor for the prediction of V-z/F by using allometric scaling. Furthermore, additional work is warranted to understand the mechanisms governing the processes underlying determination of C-max so that the empirical approaches can be fine-tuned further.
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| 60. |
- Solms, Alexander, et al.
(författare)
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Favorable Pharmacokinetic Characteristics of Extended-Half-Life Recombinant Factor VIII BAY 94-9027 Enable Robust Individual Profiling Using a Population Pharmacokinetic Approach
- 2020
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Ingår i: Clinical Pharmacokinetics. - : Springer Science and Business Media LLC. - 0312-5963 .- 1179-1926. ; 59:5, s. 605-616
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Tidskriftsartikel (refereegranskat)abstract
- Background: Prophylaxis with factor VIII (FVIII) should be individualized based on patient characteristics, including FVIII pharmacokinetics. Population pharmacokinetic (popPK) modeling simplifies pharmacokinetic studies by obviating the need for multiple samples. Objective: The objective of this study was to characterize the pharmacokinetics and inter-individual variability (IIV) of BAY 94-9027 in relation to patient characteristics in support of a popPK-tailored approach, including identifying the optimal number and timing of pharmacokinetic samples. Methods: Pharmacokinetic samples from 198 males (aged 2‒62 years) with severe hemophilia A, enrolled in BAY 94-9027 clinical trials, were analyzed. Baseline age, height, weight, body mass index, lean body weight (LBW), von Willebrand factor (VWF) level, and race were evaluated. A popPK model was developed and used to simulate pharmacokinetic endpoints difficult to observe from measured FVIII levels, including time to maintain FVIII levels above 1, 3, and 5 IU/dL after different BAY 94-9027 doses. Results: A one-compartment model adequately described BAY 94-9027 pharmacokinetics. Clearance and central volume of distribution were significantly associated with LBW; clearance was inversely correlated with VWF. Due to the monophasic pharmacokinetics and well-understood IIV sources, identification of patient pharmacokinetics was achievable with sparse blood sampling. Median predicted time to maintain FVIII levels > 1 IU/dL in patients aged ≥ 12 years ranged from 120.1 to 127.2 h after single BAY 94-9027 doses of 45‒60 IU/kg. Conclusions: This analysis evaluated the pharmacokinetics of BAY 94-9027 and its sources of IIV. Using the model, determination of individual patient pharmacokinetics was possible with few FVIII samples, and a sparse sampling design to support pharmacokinetic-guided dosing was identified.
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