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- Liesenfeld, K. H., et al.
(författare)
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Effects of the direct thrombin inhibitor dabigatran on ex vivo coagulation time in orthopaedic surgery patients: a population model analysis
- 2006
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Ingår i: Br J Clin Pharmacol. - 0306-5251. ; 62:5, s. 527-37
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Tidskriftsartikel (refereegranskat)abstract
- AIMS: To describe the pharmacokinetic-pharmacodynamic (PK-PD) characteristics of the direct thrombin inhibitor dabigatran in hip replacement patients by assessing coagulation parameters activated partial thromboplastin time (aPTT) and ecarin clotting time (ECT), interindividual variability and factors affecting PD responses. METHODS: BISTRO I patients received oral dabigatran etexilate postsurgery for 6-10 days. Dabigatran plasma concentrations and aPTT/ECT were measured on the day of surgery, on subsequent days and at steady state. PK-PD characteristics of the dabigatran-aPTT/ECT relationships were evaluated using NONMEM V. RESULTS: The dabigatran concentration-aPTT relationship was described combining a linear and an E(max) model. Mean baseline aPTT was 33.4 s and E(max) (maximum increase in aPTT contributed by the E(max) model) was 26.9 s. The dabigatran concentration needed to attain 50% of maximum effect (EC(50)) was 94.7 ng ml(-1) and the mean slope of the linear concentration-response relationship (SLOP) was 0.0509 s ng(-1) ml(-1). Baseline aPTT and E(max) were highest following surgery and declined with time. The dabigatran concentration-ECT relationship fitted a linear model. Mean baseline ECT was 28 s and decreased with time; 50% of the maximum effect was observed after 2.9 days. SLOP decreased from 0.38 to 0.27 s ng(-1) ml(-1) with a half-life of 1.1 day, indicating greater PD effects on the day of surgery. Interindividual and residual variability was low. Covariates could not explain variability of this model. CONCLUSIONS: aPTT and ECT prolongation were directly correlated with dabigatran concentrations. Blood coagulation prolongation was most pronounced following surgery. Data suggest that ECT provides a more precise description of the anticoagulant effect than aPTT.
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| 3. |
- Liesenfeld, K-H, et al.
(författare)
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Population pharmacokinetic analysis of the oral thrombin inhibitor dabigatran etexilate in patients with non-valvular atrial fibrillation from the RE-LY trial
- 2011
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Ingår i: Journal of Thrombosis and Haemostasis. - : Elsevier BV. - 1538-7933 .- 1538-7836. ; 9:11, s. 2168-2175
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Tidskriftsartikel (refereegranskat)abstract
- Background: Dabigatran etexilate (DE) is an orally absorbed prodrug of dabigatran, a thrombin inhibitor that exerts potent anticoagulant and antithrombotic activity. Objectives: To characterize the pharmacokinetics of dabigatran in patients with non-valvular atrial fibrillation (AF) from the Randomized Evaluation of Long-term Anticoagulant Therapy (RE-LY) trial and to quantify the effect of selected factors on pharmacokinetic (PK) model parameters. Patients and methods: A total of 27 706 dabigatran plasma concentrations from 9522 patients who received DE 110 or 150 mg twice daily were analyzed with non-linear mixed-effects modeling. Results: The pharmacokinetics of dabigatran were best described by a two-compartment disposition model with first-order absorption. The covariates creatinine clearance (CRCL), age, sex, heart failure and the ethnic subgroup 'South Asian' exhibited statistically significant effects on apparent clearance of dabigatran. Body weight and hemoglobin significantly influenced the apparent volume of distribution of the central compartment. Concomitant medication with proton-pump inhibitors, amiodarone and verapamil significantly affected the bioavailability. However, all of the statistically significant factors that were identified, except for renal function status, showed only small to moderate effects (< 26% change in exposure at steady state). On the basis of simulations from the final population PK model, a dose of 75 mg twice daily would result in similar exposure for severely renally impaired patients with CRCL of 15-30 mL min(-1) and patients with normal renal function receiving 150 mg twice daily. Conclusions: The analysis provides a thorough PK characterization of dabigatran in the AF patient population from RE-LY. None of the covariates investigated, with the exception of renal function, warrants dose adjustment.
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