Dabigatran etexilate

Absorption

Oral dabigatran has a bioavailability of 3-7%, although the relative bioavailability of dabigatran pellets is 37% higher than that for capsules and the bioavailability increases to 75% when the capsule shell is removed; dabigatran capsules should not be tampered with in any way prior to administration. The Cmax is achieved by one hour following oral dosing, which is extended to two hours if accompanied by a high-fat meal. Dabigatran can be taken with or without food. Dabigatran pharmacokinetics are approximately linear over a range of 10-400 mg in healthy adults and adult patients and it has an accumulation factor of two in adult and pediatric patients.

Toxicity

No human studies involving pregnancy, labor and delivery, nursing, or pediatrics. Geriatric patients are at higher risk of adverse effects than younger patients but the risk to benefit ratio is generally still favourable for older patients. Patients with a creatinine clearance of 15-30mL/min should have their doses of dabigatran etexilate reduced, and no data is available for patients with a creatinine clearance below 15mL/min.
In animal studies, dabigatran increases the rates of dead offspring and causes uterine and vaginal bleeding close to birth. Dabigatran may or may not be excreted in breast milk so the risk and benefit of stopping the drug or stopping breast feeding must be considered.

Description

Dabigatran etexilate is an orally administered pro-drug of dabigatran, which is a direct inhibitor of thrombin and a potent anticoagulant. The serine protease thrombin is the final mediator in the coagulation cascade that leads to the production of fibrin, the main protein component of blood clots. Thrombin is also a potent activator of platelets. Consequently, thrombin inhibitors have found utility as anticoagulants in treating arterial and venous thrombosis. Warfarin, although orally available, has a narrow therapeutic index and requires frequent monitoring and dosage adjustment. Low-molecular-weight heparins provide better safety profile and less inter-patient variability; however, these agents are only available for parenteral administration. Direct thrombin inhibitors (DTIs) are a new class of anticoagulants that act by directly binding to thrombin at its catalytic or fibrinogen-binding sites, or both. Unlike the heparins, DTIs do not require the activation of secondary factors such as antithrombin to derive their activity, which makes their action more predictable. In addition, their ability to inhibit both free and clot-bound thrombin predisposes them for enhanced anticoagulation effect.

Description

Dabigatran etexilate is an anticoagulant drug developed and marketed by Boehringer Ingelheim. The parent compound, dabigatran, is a potent thrombin blocker, but it cannot be administered orally. Adding the hydrophobic carbohexoxy group (“etexilate”) to the imine nitrogen created an orally absorbable prodrug.

The Uses of Dabigatran etexilate

Dabigatran Etexilate is an oral anticoagulant and direct thrombin inhibitor.

Background

Dabigatran etexilate is an oral prodrug that is hydrolyzed to the competitive and reversible direct thrombin inhibitor dabigatran. Dabigatran etexilate may be used to decrease the risk of venous thromboembolic events in patients in whom anticoagulation therapy is indicated. In contrast to warfarin, because its anticoagulant effects are predictable, lab monitoring is not necessary. Dabigatran etexilate was approved by the FDA in 2010.

What are the applications of Application

Dabigatran etexilate is an anticoagulant from the class of direct thrombin inhibitors

Indications

Dabigatran etexilate is available in both oral pellet and capsule form. Dabigatran etexilate pellets are indicated for the treatment of venous thromboembolic events (VTE) in pediatric patients between three months and 12 years of age who have been treated with a parenteral anticoagulant for at least 5 days. They are also indicated in the same age group to reduce the risk of recurrence of VTE in patients who have been previously treated.
In capsule form, dabigatran etexilate is indicated in adults to reduce the risk of stroke and systemic embolism associated with non-valvular atrial fibrillation and for the treatment of deep venous thrombosis (DVT) and pulmonary embolism (PE) in patients who have been treated with a parenteral anticoagulant for 5-10 days. It is also indicated in adults to reduce the risk of recurrence of DVT and PE in patients who have been previously treated and for the prophylaxis of DVT and PE in patients who have undergone hip replacement surgery. Lastly, it is indicated in pediatric patients between eight and 18 years of age for the treatment of venous thromboembolic events (VTE) in patients who have been treated with a parenteral anticoagulant for at least 5 days and to reduce the risk of recurrence of VTE in patients who have been previously treated.
Dabigatran etexilate is also approved by the EMA to prevent VTE in adult patients. For pediatric patients, Dabigatran etexilate is used to treat TVE and prevent recurrent TVE for patients from birth to less than 18 years of age.

Pharmacokinetics

Dabigatran etexilate is a double prodrug that is hydrolyzed to the active dabigatran by intestinal and hepatic carboxylesterases. Dabigatran is a reversible competitive thrombin inhibitor that directly inhibits the conversion by thrombin of fibrinogen to fibrin, impairing the clotting process and acting as an anticoagulant. Dabigatran use prolongs coagulation markers such as the activated partial thromboplastin time (aPTT), ecarin clotting time (ECT), thrombin time (TT), and dilute thrombin time (dTT), but not the international normalized ratio (INR), which cannot be used in this context as it can in warfarin monitoring.
As with all anticoagulant therapies, dabigatran carries a risk of bleeding, which may increase with concomitant use of antiplatelet agents, fibrinolytic therapy, heparins, or chronic NSAID use, and should be monitored for. Premature discontinuation of dabigatran, in the absence of an alternative anticoagulant, also carries an increased risk of thromboembolic events. Due to the risk of an epidural or spinal hematoma, dabigatran should generally not be used in the context of neuraxial anesthesia or spinal puncture; if such use is unavoidable, careful monitoring should be employed. Dabigatran should not be used in patients with prosthetic heart valves due to an increased occurrence of major bleeding and thromboembolic events. Dabigatran is a substrate of the P-gp transporter and should generally not be administered together with P-gp inhibitors or inducers, especially in patients with impaired renal function. Lastly, dabigatran or any other direct-acting oral anticoagulant should not be administered in patients with triple-positive antiphospholipid syndrome (APS) due to an increased risk of recurrent thrombotic events. In case of the need for emergency reversal, idarucizumab is available for use in adult patients; the safety and efficacy of idarucizumab has not been established in pediatric patients yet, for whom reversal may be achieved through hemodialysis, prothrombin complex concentrates, or recombinant FVIIa. However, none of these have been sufficiently evaluated in clinical trials.

Metabolism

Dabigatran is administered as the orally available prodrug dabigatran etexilate that is subsequently metabolized to the active form. In vitro studies and observations regarding the oral bioavailability and levels of plasma prodrug suggest extensive first-pass metabolism by carboxylesterases, first by intestinal CES2 to form BIBR0951 (also known as M2) and then subsequently by hepatic CES1 to form dabigatran. Dabigatran etexilate can also first undergo CES1-mediated hydrolysis to BIBR1087 (M1) followed by CES2-mediated hydrolysis to dabigatran, though it is hypothesized that the former pathway accounts for most of the active form in plasma. Dabigatran can undergo 1-O-acyl glucuronidation by UGT1A9, UGT2B7, and UGT2B15 followed by acyl migration to form the corresponding 2-O-, 3-O-, and 4-O-acyl glucuronides; all of these acyl glucuronides exhibit activity similar to dabigatran but account for a small fraction of recovered metabolites.
In addition to these better characterized metabolic pathways, detailed LC/MS characterization suggests a wide variety of possible metabolites following oral or intravenous administration, most of which are present in only trace amounts in plasma, urine, or feces. These include a variety of oxidation, hydrolysis, and conjugation products, including through the addition of mannitol.