| 1. |
- Bergstrand, Martin, et al.
(author)
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Mechanistic modeling of a magnetic marker monitoring study linking gastrointestinal tablet transit, in vivo drug release, and pharmacokinetics
- 2009
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In: Clinical Pharmacology and Therapeutics. - : Springer Science and Business Media LLC. - 0009-9236 .- 1532-6535. ; 86:1, s. 77-83
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Journal article (peer-reviewed)abstract
- Magnetic marker monitoring (MMM) is a new technique for visualizing transit and disintegration of solid oral dosage forms through the gastrointestinal (GI) tract. The aim of this work was to develop a modeling approach for gaining information from MMM studies using data from a food interaction study with felodipine extended-release (ER) formulation. The interrelationship between tablet location in the GI tract, in vivo drug release, and felodipine disposition was modeled. A Markov model was developed to describe the tablet's movement through the GI tract. Tablet location within the GI tract significantly affected drug release and absorption through the gut wall. Food intake decreased the probability of tablet transition from the stomach, decreased the rate with which released felodipine left the stomach, and increased the fraction absorbed across the gut wall. In conclusion, the combined information of tablet location in the GI tract, in vivo drug release, and plasma concentration can be utilized in a mechanistically informative way with integrated modeling of data from MMM studies.
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| 2. |
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| 3. |
- Cullberg, M., et al.
(author)
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Pharmacokinetics of ximelagatran and relationship to clinical response in acute deep vein thrombosis
- 2005
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In: Clin Pharmacol Ther. - : Springer Science and Business Media LLC. - 0009-9236 .- 1532-6535. ; 77:4, s. 279-90
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Journal article (peer-reviewed)abstract
- OBJECTIVE: Our objective was to characterize the pharmacokinetics of melagatran, the active form of the oral direct thrombin inhibitor ximelagatran, and the relationship between melagatran exposure and clinical outcome in patients with acute deep vein thrombosis. METHODS: A population pharmacokinetic analysis was performed on samples from patients with deep vein thrombosis participating in a randomized dose-finding study (THRombin Inhibitor in Venous thrombo-Embolism [THRIVE I]). Patients received fixed doses of oral ximelagatran (24, 36, 48, or 60 mg twice daily) for 12 to 16 days. Thrombus size was evaluated by venography before and after treatment. Exposure-response curves were characterized for the probability of regression, no change, and progression of the thrombus extension and of having a bleeding-related event, by use of logistic regression models. RESULTS: The pharmacokinetics of melagatran (1836 samples in 264 patients) was predictable, without significant time or dose dependencies. Clearance after oral administration (population mean, 27.3 L/h) was correlated with creatinine clearance (P < 10(-6)), and volume of distribution (population mean, 176 L) was correlated with body weight (P = 2 x 10(-5)). Gender, age, or smoking did not significantly influence melagatran pharmacokinetics after the influence of renal function and body weight was accounted for. Unexplained interpatient variability values in total plasma clearance and bioavailability were 19% and 21%, respectively. The median area under the plasma melagatran concentration versus time curve across all patients and dose levels was 3.22 h x micromol/L (5th-95th percentiles, 1.35-7.69). There was no significant relationship between area under the plasma concentration versus time curve and change in thrombus extension (P = .59) or bleeding-related events (P = .77), and the estimated exposure-response curves were relatively flat. CONCLUSIONS: The pharmacokinetics of melagatran in patients with acute deep vein thrombosis was predictable after oral ximelagatran administration. Shallow exposure-response curves for efficacy and bleeding indicate that there is no need for individualized dosing or therapeutic drug monitoring in the patient population studied.
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| 4. |
- Darpo, B, et al.
(author)
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Design of the "Thorough QT Study"
- 2008
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In: Clinical pharmacology and therapeutics. - : Springer Science and Business Media LLC. - 1532-6535 .- 0009-9236. ; 83:4, s. 528-529
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Journal article (other academic/artistic)
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| 5. |
- de Jong, F. A., et al.
(author)
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Irinotecan-induced diarrhea : functional significance of the polymorphic ABCC2 transporter protein
- 2007
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In: Clinical Pharmacology and Therapeutics. - : Springer Science and Business Media LLC. - 0009-9236 .- 1532-6535. ; 81:1, s. 42-49
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Journal article (peer-reviewed)abstract
- Interindividual pharmacokinetic variability of the anticancer agent irinotecan is high. Life-threatening diarrhea is observed in up to 25% of patients receiving irinotecan and has been related with irinotecan pharmacokinetics and UGT1A1 genotype status. Here, we explore the association of ABCC2 (MRP2) polymorphisms and haplotypes with irinotecan disposition and diarrhea. A cohort of 167 Caucasian cancer patients who were previously assessed for irinotecan pharmacokinetics (90-min infusion given every 21 days), toxicity, and UGT1A1*28 genotype were genotyped for polymorphisms in ABCC2 using Pyrosequencing. Fifteen ABCC2 haplotypes were identified in the studied patients. The haplotype ABCC2*2 was associated with lower irinotecan clearance (28.3 versus 31.6 l/h; P=0.020). In patients who did not carry a UGT1A1*28 allele, a significant reduction of severe diarrhea was noted in patients with the ABCC2*2 haplotype (10 versus 44%; odds ratio, 0.15; 95% confidence interval, 0.04–0.61; P=0.005). This effect was not observed in patients with at least one UGT1A1*28 allele (32 versus 20%; odds ratio, 1.87; 95% confidence interval, 0.49–7.05; P=0.354). This study suggests that the presence of the ABCC2*2 haplotype is associated with less irinotecan-related diarrhea, maybe as a consequence of reduced hepatobiliary secretion of irinotecan. As the association was seen in patients not genetically predisposed at risk for diarrhea due to UGT1A1*28, confirmatory studies of the relationships of ABCC2 genotypes and irinotecan disposition and toxicity are warranted.
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| 7. |
- Friberg, L. E., et al.
(author)
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An agonist-antagonist interaction model for prolactin release following risperidone and paliperidone treatment
- 2009
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In: Clinical Pharmacology and Therapeutics. - : Springer Science and Business Media LLC. - 0009-9236 .- 1532-6535. ; 85:4, s. 409-417
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Journal article (peer-reviewed)abstract
- A mechanistic pharmacokinetic/pharmacodynamic model is presented, characterizing the time course of prolactin in healthy as well as schizophrenic subjects following the administration of various doses and formulations of the antipsychotic drugs risperidone and paliperidone. Prolactin concentrations from nine studies (1,462 subjects) were analyzed in NONMEM. A competitive agonist-antagonist interaction model described the competition between these drugs and dopamine for the D(2) receptors that regulate prolactin release. Tolerance development was explained by a feedback loop with prolactin stimulating dopamine release, whereas models wherein tolerance is described in terms of depletion of a prolactin pool did not explain the data well. The diurnal prolactin rhythm was described by a two-period cosine function. Baseline prolactin was health-status dependent and higher in women than in men, although the drug-induced release was less than proportional to baseline. This quantitative mechanism-based model is the first to describe prolactin release in patients, and it confirms that paliperidone and risperidone have similar potencies for prolactin release.
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| 8. |
- Friberg, Lena, et al.
(author)
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Modeling and Simulation of the Time Course of Asenapine Exposure Response and Dropout Patterns in Acute Schizophrenia
- 2009
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In: Clinical Pharmacology and Therapeutics. - : Springer Science and Business Media LLC. - 0009-9236 .- 1532-6535. ; 86:1, s. 84-91
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Journal article (peer-reviewed)abstract
- Modeling and simulation were utilized to characterize the efficacy dose response of sublingual asenapine in patients with schizophrenia and to understand the outcomes of six placebo-controlled trials in which placebo responses and dropout rates varied. The time course of total Positive and Negative Syndrome Scale (PANSS) scores was characterized for placebo and asenapine treatments in a pharmacokinetic-pharmacodynamic model in which the asenapine effect was described by an E-max model, increasing linearly over the 6-week study period. A logistic regression model described the time course of dropouts, with previous PANSS value being the most important predictor. The last observation carried forward (LOCF) time courses were well described in simulations from the combined PANSS + dropout model. The observed trial outcomes were successfully predicted for all the placebo arms and the majority of the treatment arms. Although simulations indicated that the post hoc probability of success of the performed trials was low to moderate, these analyses demonstrated that 5 and 10 mg twice-daily (b.i.d.) doses of asenapine have similar efficacy.
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| 10. |
- Hamberg, Anna Karin, et al.
(author)
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A PK-PD model for predicting the impact of age, CYP2C9, and VKORC1 genotype on individualization of warfarin therapy
- 2007
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In: Clinical Pharmacology and Therapeutics. - : Springer Science and Business Media LLC. - 0009-9236 .- 1532-6535. ; 81:4, s. 529-538
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Journal article (peer-reviewed)abstract
- The aim of this study was to characterize the relationship between warfarin concentrations and international normalized ratio (INR) response and to identify predictors important for dose individualization. S- and R-warfarin concentrations, INR, and CYP2C9 and VKORC1 genotypes from 150 patients were used to develop a population pharmacokinetic/pharmacodynamic model in NONMEM. The anticoagulant response was best described by an inhibitory E(MAX) model, with S-warfarin concentration as the only exposure predictor for response. Delay between exposure and response was accounted for by a transit compartment model with two parallel transit compartment chains. CYP2C9 genotype and age were identified as predictors for S-warfarin clearance, and VKORC1 genotype as a predictor for warfarin sensitivity. Predicted INR curves indicate important steady-state differences between patients with different sets of covariates; differences that cannot be foreseen from early INR assessments alone. It is important to account for CYP2C9 and VKORC1 genotypes and age to improve a priori and a posteriori individualization of warfarin therapy.
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