Michael Zuehlsdorf

Institut für klinische Pharmakologie, Stuttgart, Baden-Württemberg, Germany

Are you Michael Zuehlsdorf?

Claim your profile

Publications (10)22.74 Total impact

  • W Mueck, M Becka, D Kubitza, B Voith, M Zuehlsdorf
    [Show abstract] [Hide abstract]
    ABSTRACT: Rivaroxaban (BAY 59-7939) is an oral, direct Factor Xa (FXa) inhibitor being developed for the prevention and treatment of thromboembolic disorders. This analysis aimed to define population models for the pharmacokinetics (PK) and pharmacodynamics (PD) ofrivaroxaban in healthy males. Non-linear, mixed-effect modeling was used to analyze rivaroxaban plasma concentration and PD data (FXa activity and clotting tests) from subjects in a phase I, multiple-ascending-dose study. Subjects received 5 mg rivaroxaban once, twice or three times daily, or 10, 20 or 30 mg rivaroxaban twice daily. The population PK of rivaroxaban were well described by an oral, two-compartment model with first-order absorption and elimination from the central compartment. Population mean estimates for apparent oral clearance and volume of distribution for the central compartment were 9.2 1/h and 55 1, respectively, with moderate inter-individual variability (17.4% and 30.7%, respectively). Total volume of distribution for rivaroxaban at steady state was approximately 70 1. Residual (unexplained) variability was 25%. FXa activity correlated with rivaroxaban plasma concentrations following an inhibitory Emax model; prothrombin time (PT) and rivaroxaban plasma concentrations correlated with a linear model, with a slope of 4.6 s/(100 microg/1). Inter-individual variability was low for the correlation with PT. The models derived were used to define sampling windows for population PK/PD modeling in Phase II studies. This analysis confirms that rivaroxaban has predictable, dose-proportional PK and PD. The linear correlation between rivaroxaban plasma concentrations and PT suggests that this test might be useful to assess rivaroxaban exposure in patients, if required.
    International journal of clinical pharmacology and therapeutics 07/2007; 45(6):335-44. DOI:10.5414/CPP45335 · 1.04 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Rivaroxaban (BAY 59-7939) is in advanced clinical development for the prevention and treatment of thromboembolic disorders. Frequent co-medications in the patient populations likely to receive rivaroxaban include NSAIDs. This randomized, two-way crossover study, with a naproxen run-in period, was performed to determine whether naproxen influences the tolerability, pharmacodynamics and pharmacokinetics of rivaroxaban. Eleven healthy, young males received naproxen 500 mg on two consecutive days, a single dose of rivaroxaban 15 mg, or both. Treatments were well tolerated: adverse events (eight in total), reported by three subjects, were mild and not drug related. Rivaroxaban inhibited Factor Xa activity by 35% and prolonged prothrombin time [by 1.4 times baseline (tb)], activated partial thromboplastin time (1.3 tb) and the HepTest (1.9 tb). Naproxen had no influence on these measures and the combination of rivaroxaban and naproxen did not affect platelet aggregation. Rivaroxaban and naproxen given together significantly increased bleeding time compared with rivaroxaban alone (P = 0.017). However, this difference was small compared with the effect of naproxen given alone, except in one subject. Least squares-means ratios for the AUC and C(max) of rivaroxaban after administration alone and with naproxen were 1.125 [90% confidence interval (CI) 0.995, 1.271] and 1.095 (90% CI 0.905, 1.325), respectively. There appeared to be no clinically relevant interaction between rivaroxaban and naproxen in healthy subjects, although some individuals may be more sensitive to the combination. Large-scale Phase III clinical studies will be required to confirm whether there is an increased risk of bleeding during treatment with rivaroxaban and concomitant NSAIDs.
    British Journal of Clinical Pharmacology 05/2007; 63(4):469-76. DOI:10.1111/j.1365-2125.2006.02776.x · 3.69 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Anticoagulants are often dose adjusted, or their use restricted, in patients with extremes of body weight. Rivaroxaban (BAY 59-7939) is a novel, oral, direct factor Xa inhibitor in clinical development. This was a randomized, single-blind, placebo-controlled, parallel-group study in healthy male and female subjects to assess the effect of extreme body weight (< or = 50 kg and >120 kg), and gender, on the safety, tolerability, pharmacokinetics, and pharmacodynamics of rivaroxaban 10 mg, compared with subjects of normal weight (70-80 kg). Rivaroxaban was well tolerated. Cmax of rivaroxaban was unaffected in subjects >120 kg but was increased by 24% in subjects weighing < or = 50 kg, resulting in a small (15%) increase in prolongation of prothrombin time, which was not considered clinically relevant. The area under the curve was unaffected by body weight or gender. No other clinically relevant differences were observed, suggesting that rivaroxaban is unlikely to require dose adjustment for body weight or gender.
    The Journal of Clinical Pharmacology 03/2007; 47(2):218-26. DOI:10.1177/0091270006296058 · 2.47 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Rivaroxaban (BAY 59-7939) is an oral, direct Factor Xa inhibitor in advanced clinical development for the prevention and treatment of thromboembolic disorders. This was a randomized, 2-way crossover study in healthy male subjects, with an aspirin run-in period, to examine whether aspirin influences the safety, tolerability, pharmacodynamics, and pharmacokinetics of rivaroxaban. All treatments were well tolerated; drug-related adverse events were mild and transient. Aspirin did not alter the effects of rivaroxaban on Factor Xa activity or clotting tests. Platelet aggregation and bleeding time were not affected by rivaroxaban, and rivaroxaban did not influence the effects of aspirin on these parameters to a clinically relevant extent. Aspirin did not affect the pharmacokinetics of rivaroxaban, including the fraction unbound. This study suggests that there is no clinically relevant interaction between rivaroxaban and aspirin and that the 2 drugs could be administered concomitantly at the doses used in this study.
    The Journal of Clinical Pharmacology 10/2006; 46(9):981-90. DOI:10.1177/0091270006292127 · 2.47 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: To investigate the influence of food and administration of an antacid (aluminum-magnesium hydroxide) or ranitidine on the absorption of BAY 59-7939 (rivaroxaban), 4 randomized studies were performed in healthy male subjects. In 2 food interaction studies, subjects received BAY 59-7939, either as two 5-mg tablets (fasted and fed), four 5-mg tablets (fasted), or one 20-mg tablet (fasted and fed). In 2 drug interaction studies, BAY 59-7939 (six 5-mg tablets) was given alone or with ranitidine (150 mg twice daily, preceded by a 3-day pretreatment phase) or antacid (10 mL). Plasma samples were obtained to assess pharmacokinetic and pharmacodynamic parameters of BAY 59-7939. In the presence of food, time to maximum concentration (t(max)) was delayed by 1.25 hours; maximum concentration (C(max)) and area under the curve (AUC) were increased, with reduced interindividual variability at higher doses of BAY 59-7939. Compared with baseline, BAY 59-7939 resulted in a relative increase in maximum prothrombin time (PT) prolongation of 44% (10 mg) and 53% (20 mg) in the fasted state, compared with 53% and 83% after food. Time to maximum PT prolongation was delayed by 0.5 to 1.5 hours after food, with no relevant influence of food type. No significant difference in C(max) and AUC was observed with coadministration of BAY 59-7939 and ranitidine or antacid.
    The Journal of Clinical Pharmacology 06/2006; 46(5):549-58. DOI:10.1177/0091270006286904 · 2.47 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: There is a clinical need for safe new oral anticoagulants. The safety, tolerability, pharmacodynamics, and pharmacokinetics of BAY 59-7939--a novel, oral, direct Factor Xa (FXa) inhibitor--were investigated in this single-center, placebo-controlled, single-blind, parallel-group, multiple-dose escalation study. Healthy male subjects (aged 20-45 years, body mass index 18.6-31.4 kg/m(2)) received oral BAY 59-7939 (n=8 per dose regimen) or placebo (n=4 per dose regimen) on days 0 and 3-7. Dosing regimens were 5 mg once, twice (bid), or three times daily, and 10 mg, 20 mg, or 30 mg bid. There were no clinically relevant changes in bleeding time or other safety variables across all doses and regimens. There was no dose-related increase in the frequency or severity of adverse events with BAY 59-7939. Maximum inhibition of FXa activity occurred after approximately 3 h, and inhibition was maintained for at least 12 h for all doses. Prothrombin time, activated partial thromboplastin time, and HepTest were prolonged to a similar extent to inhibition of FXa activity for all doses. Dose-proportional pharmacokinetics (AUC(tau, norm) and C(max, norm)) were observed at steady state (day 7). Maximum plasma concentrations were achieved after 3-4 h. The terminal half-life of BAY 59-7939 was 5.7-9.2 h at steady state. There was no relevant accumulation at any dose. BAY 59-7939 was safe and well tolerated across the wide dose range studied, with predictable, dose-proportional pharmacokinetics and pharmacodynamics and no relevant accumulation beyond steady state. These results support further investigation of BAY 59-7939 in phase II clinical trials.
    European Journal of Clinical Pharmacology 01/2006; 61(12):873-80. DOI:10.1007/s00228-005-0043-5 · 2.70 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: There is a clinical need for new oral anticoagulants to prevent and treat thromboembolic diseases. Given its integral role in the coagulation cascade, factor Xa is a particularly promising target for new anticoagulation therapies. The aim of this study was to investigate the safety, pharmacodynamics, and pharmacokinetics of BAY 59--7939, an oral, direct factor Xa inhibitor. This single-center, randomized, single-blinded, placebo-controlled, dose-escalation study included 108 healthy white male subjects aged 19 to 45 years. Subjects received single oral doses of either BAY 59--7939 (1.25--80 mg) or placebo; in addition, 1 group received 2 doses of BAY 59--7939 (5--mg tablet and oral solution) or placebo in a crossover design. Oral BAY 59--7939 in single doses up to 80 mg was safe and well tolerated and was not associated with an increased risk of bleeding compared with placebo. Pharmacodynamic effects (inhibition of factor Xa activity, prothrombin time, activated partial thromboplastin time, and Hep Test) and plasma concentration profiles were dose-dependent. Maximum inhibition of factor Xa activity was achieved 1 to 4 hours after administration of BAY 59--7939 and ranged from 20% to 61% for the 5- to 80-mg doses. BAY 59--7939 selectively inhibited factor Xa activity; thrombin (factor IIa) and antithrombin were unaffected. Inhibition of factor Xa activity and prolongation of prothrombin time correlated well with BAY 59--7939 plasma concentrations (r=0.949 and 0.935, respectively). BAY 59--7939 was well tolerated with predictable pharmacodynamics and pharmacokinetics across a wide range of doses in healthy male subjects. BAY 59--7939 was shown to be an effective and specific factor Xa inhibitor.
    Clinical Pharmacology &#38 Therapeutics 11/2005; 78(4):412-21. DOI:10.1016/j.clpt.2005.06.011 · 7.39 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The purpose of this study was to validate a computerised psychometric test system by demonstrating the change of the test variables of the Bochum Diagnostic System after administration of alcohol. Twenty-four healthy young male or female volunteers participated in a doubleblind, randomised, placebo-controlled study in a 3-way cross-over design. The volunteers took single doses of placebo, 0.4 and 0.7 g alcohol/kg body weight (females: 10% less) in a random sequence. Psychometric tests were performed before as well as 1 and 3 h after the administration of alcohol. The effects of alcohol on the psychometric performance were most pronounced 1 h after administration. At this time a significant dose-dependent impairment of performance in the concentration test, the simple and complex reaction tests, the vigilance test and the coordination test was observed. 3 h after administration, significant effects were only observed in the complex reaction test and the concentration test. Maximal alcohol serum concentrations of 0.47 +/- 0.05 % per thousand and of 0.90 +/- 0.15 % per thousand were reached after administration of 0.4 g/kg and 0.7 g/kg, respectively. The correlations between individual serum alcohol concentrations and differences of psychometric variables from baseline were significant. It is concluded that the tests of the Bochum Diagnostic System can quantitatively measure the effects of alcohol. The most sensitive tests are the complex reaction test and the concentration test.
    Arzneimittel-Forschung 02/2005; 55(5):289-95. DOI:10.1055/s-0031-1296859 · 0.51 Impact Factor
  • Source
  • Source

Publication Stats

1k Citations
22.74 Total Impact Points


  • 2006–2007
    • Institut für klinische Pharmakologie
      Stuttgart, Baden-Württemberg, Germany
    • Bayer HealthCare
      • Bayer HealthCare Pharmaceuticals
      Leverkusen, North Rhine-Westphalia, Germany