Aims The novel direct thrombin inhibitor (DTI), dabigatran etexilate (Boehringer Ingelheim Pharma GmbH & Co. KG), shows potential as an oral antithrombotic agent. Two double‐blind, randomized trials were undertaken to investigate the pharmacokinetics (PK), pharmacodynamics (PD) and tolerability of orally administered dabigatran etexilate in healthy male subjects. Methods Dabigatran etexilate or placebo was administered orally at single doses of 10–400 mg (n = 40) or at multiple doses of 50–400 mg three times daily for 6 days (n = 40). Plasma and urine samples were collected over time to determine the PK profile of dabigatran. PD activity was assessed by its effects on blood coagulation parameters: activated partial thromboplastin time (aPTT), prothrombin time (PT), reported as international normalized ratio (INR), thrombin time (TT), and ecarin clotting time (ECT). All adverse events were recorded. Results Dabigatran etexilate was rapidly absorbed with peak plasma concentrations of dabigatran reached within 2 h of administration. This was followed by a rapid distribution/elimination phase and a terminal phase, with associated estimated half‐lives of 8–10 h and 14–17 h with single and multiple dose administrations, respectively. Dabigatran exhibited linear PK characteristics with dose‐proportional increases observed in maximum plasma concentration and area under the curve. Steady‐state conditions were reached within 3 days with multiple dosing. The mean apparent volume of distribution during the terminal phase (Vz/F) of 1860 l (range 1430–2400 l) and the apparent total clearance after oral administration (CLtot/F) of 2031 ml min−1 (range 1480–2430), were dose independent. Time curves for aPTT, INR, TT and ECT paralleled plasma concentration–time curves with values increasing rapidly and in a dose‐dependent manner. At the highest dose of 400 mg administered three times daily, maximum prolongations over baseline of 3.1 (aPTT), 3.5 (INR), 29 (TT) and 9.5‐fold (ECT) were observed. Dabigatran underwent conjugation with glucuronic acid to form pharmacologically active conjugates that accounted for approximately 20% of total dabigatran in plasma. Overall, variability in PK parameters was low to moderate, with an average interindividual coefficient of variation (CV) of approximately 30% and variability in PD parameters was low, with CV < 10%. Of the four assays, TT and ECT exhibited the greatest sensitivity and precision within the anticipated therapeutic dose range. Bleeding events were few and were mild‐to‐moderate in intensity, occurring only in the higher, multiple dose groups. Conclusions These data suggest that dabigatran etexilate is a promising novel oral DTI with predictable PK and PD characteristics and good tolerability. Further investigation of dabigatran etexilate for the treatment and prophylaxis of patients with arterial and venous thromboembolic disorders, acute coronary syndromes and other medical conditions is warranted.

Dabigatran etexilate is an oral direct thrombin inhibitor in clinical development for the prevention and treatment of thromboembolic disorders. Following oral administration, dabigatran etexilate is rapidly absorbed and converted into its active form, dabigatran. The aim of this study was to investigate the effect of renal impairment on the pharmacokinetics and pharmacodynamics of dabigatran following administration of a single oral dose of dabigatran etexilate in subjects with renal impairment (150 mg) or end-stage renal disease (ESRD) on maintenance haemodialysis (50 mg). This open-label, parallel-group, single-centre study enrolled 23 subjects with mild, moderate or severe renal impairment (creatinine clearance >50 to < or =80, >30 to < or =50 and < or =30 mL/min, respectively), 6 patients with ESRD and 6 healthy subjects. Blood and urine samples were collected up to 96 hours after dosing for determination of dabigatran pharmacokinetic and pharmacodynamic parameters. Compared with the values in healthy subjects, the area under the plasma concentration-time curve from time zero to infinity (AUC(infinity)) values were 1.5-, 3.2- and 6.3-fold higher in subjects with mild, moderate and severe renal impairment. Changes in the maximum plasma concentration (C(max)) were modest, and the time to reach the C(max) was unchanged. In subjects with severe renal impairment, the mean terminal elimination half-life was doubled (28 hours vs 14 hours for control). The AUC for prolongation of pharmacodynamic parameters (the activated partial thromboplastin time and ecarin clotting time) increased in line with the pharmacokinetic changes. In patients with ESRD, the dose-normalized AUC(infinity) was approximately twice the value in the control group. Haemodialysis removed 62-68% of the dose. Dabigatran etexilate was well tolerated in all groups. Exposure to dabigatran is increased by renal impairment and correlates with the severity of renal dysfunction. A decrease in the dose and/or an increase in the administration interval in these patients may be appropriate. In patients with ESRD, dabigatran can be partly removed from the plasma by haemodialysis.

Dabigatran demonstrated reproducible and predictable pharmacokinetic and pharmacodynamic characteristics, together with a good safety profile, when administered to healthy elderly subjects. Minor gender differences were not considered clinically relevant. The effects of pantoprazole coadministration on the bioavailability of dabigatran were considered acceptable, and dose adjustment is not considered necessary.

Dabigatran etexilate is an oral low-molecular-weight direct thrombin inhibitor. Following oral administration, dabigatran etexilate is rapidly converted to its active form, dabigatran. The authors investigated the absorption, distribution, and elimination of a single 150-mg dose capsule formulation of dabigatran etexilate in healthy volunteers and patients undergoing total hip replacement. In an open-label, 3-way crossover study, dabigatran etexilate was administered to 18 male volunteers in the fasted state, after administration of food and with coadministration of the proton pump inhibitor, pantoprazole. In a subsequent multicenter, open-label study, 59 patients received a single dose of dabigatran etexilate, administered 1 to 3 hours following total hip replacement. In healthy volunteers, food had no effect on the extent of absorption of dabigatran etexilate, although there was reduced interindividual variability for dabigatran maximum plasma concentration and AUC(0-infinity). A decrease in the mean dabigatran AUC(0-infinity) (904 to 705 ng*h/mL) occurred with coadministration of pantoprazole. In patients undergoing total hip replacement, immediate onset of absorption was seen with the maximum plasma concentration of dabigatran occurring after 6 hours. The AUC(0-24) of dabigatran was 88% of the steady-state AUC using a preliminary tablet formulation and 106% of that seen in the healthy volunteer study. Compared with healthy volunteers, the postoperative profile was flattened with delayed peak concentrations. In summary, administration of the dabigatran etexilate capsule with food has no effect on the extent of dabigatran absorption, with a moderate decrease when coadministered with pantoprazole. Adequate plasma concentrations of dabigatran were seen with early postoperative administration of the dabigatran etexilate capsule. These pharmacokinetic characteristics confirm the suitability of this oral solid dosage form for use in future clinical trials.

The impact of moderate hepatic impairment on the pharmacokinetics (PK) and pharmacodynamics (PD) of dabigatran etexilate was evaluated in an open, parallel-group study. Healthy volunteers (n = 12) and patients with hepatic impairment (Child-Pugh classification B; n = 12) received a single oral dose of 150 mg dabigatran etexilate. The mean values for area under the concentration-time curve, terminal half-life, and renal clearance of dabigatran were comparable between patients with hepatic impairment and healthy volunteers. Conversion of the dabigatran intermediate BIBR1087 to active dabigatran was slower in patients with hepatic impairment, indicating that the liver is partly involved in bioconversion of dabigatran etexilate. However, total drug exposure was comparable between groups; therefore, this observation is of no clinical relevance with respect to the anticoagulant activity of dabigatran. The extent of dabigatran glucuronidation was unchanged by liver disease; glucuronidation capacity was maintained in moderate liver disease. The activated partial thromboplastin time, ecarin clotting time, and thrombin time relationships were essentially identical in both groups. This study shows that moderate hepatic impairment does not affect the PK/PD or safety profile of dabigatran. Therefore, patients with moderate hepatic impairment can be given dabigatran etexilate without the need for dose adjustment.