Molecule

Drug Groups

approved

Description

Dabigatran etexilate is an oral prodrug that is metabolized by a serum esterase to dabigatran. It is a synthetic, competitive and reversible direct thrombin inhibitor. Inhibition of thrombin disrupts the coagulation cascade and inhibits the formation of clots. Dabigatran etexilate may be used to decrease the risk of venous thromboembolic events in patients who have undergone total hip or knee replacement surgery, or to prevent stroke and systemic embolism in patients with atrial fibrillation, in whom anticoagulation therapy is indicated.

Indication

Dabigatran is indicated for the prevention of venous thromboembolic events in patients who have undergone elective hip or knee replacement surgery (based on RE-NOVATE, RE-MODEL, and RE-MOBILIZE trials). In 2010, it was approved in the US and Canada for prevention of stroke and systemic embolism in patients with atrial fibrillation (approval based on the RE-LY trial). Contraindications: severe renal impairment (CrCL < 30 ml/min); haemorrhagic manifestations, bleeding diathesis or spontaneous or pharmacologic impairment of haemostasis; lesions at risk of clinically significant bleeding (e.g. extensive cerebral infarction (haemorrhagic or ischemic) in the last 6 months, active peptic ulcer disease); concomitant treatment with P-glycoprotein inhibitors (e.g. oral ketoconazole, verapamil); and those with known hypersensitivity to dabigatran, dabigatran etexilate or any ingredient used in the formulation or component of the container.

Pharmacology

Dabigatran etexilate is an inactive pro-drug that gets converted to dabigatran, the active form, by esterase-catalyzed hydrolysis in the plasma and liver. Dabigatran, the main active principle in plasma, is a rapid-acting competitive and reversible direct inhibitor of thrombin. Thrombin, a serine protease, is responsible for the conversion of fibrinogen to fibrin during the coagulation cascade. Inhibition of thrombin consequently prevents thrombus development. Dabigatran inhibits free thrombin, fibrin-bound thrombin and thrombin-induced platelet aggregation.

Toxicity

The most common adverse reactions include dyspepsia or gastritis-like symptoms. The approximate lethal dose in rats and mice was observed at single oral doses of > 2000 mg/kg. Oral doses of 600 mg/kg did not induce any toxicologically meaningful changes in dogs and Rhesus monkeys. Dabigatran was well-tolerated in rats and Rhesus monkeys during repeat-dose toxicity studies. No evidence of mutagenic potential.

Affected Organisms

Biotransformation

Dabigatran is typically metabolised by esterases and microsomal carboxylesterases. CYP450 enzymes do not seem to be involved. Pharmacologically active acylglucoronides are formed via conjugation. Four positional isomers, 1-O, 2-O, 3-O, and 4-O, acylglucuronides exist, each accounting for less than 10% of total plasma dabagatran.

Absorption

Peak plasma concentrations were achieved in 6 hours in post surgical patients. In healthy patients, maximum concentrations were achieved in 0.5 to 2 hours. The absolute bioavailability of dabigatran in the body after administration of dabigatran etexilate was 6.5%. Food does not affect the bioavailability of dabigatran etexilate, but it delays the time to peak plasma concentrations by 2 hours. Oral bioavailability may increase by up to 75% when pellets are taken out of the hydroxypropylmethylcellulose (HPMC) capsule. Therefore, capsules should not be opened and pellets taken alone.

Half Life

12-14 hours in healthy volunteers. 14-17 hours in patients treated for prevention of venous thromboembolism following hip- or knee-replacement surgery.

Protein Binding

Relatively low binding (34-35%) to plasma proteins.

Elimination

Mainly excreted in urine (85%). Fecal excretion accounts for 6% of the orally administered dose. Dabigatran is primarily eliminated unchanged via the kidneys at a rate of 100 ml/min corresponding to the glomerular filtration rate.

Distribution

Moderate tissue distribution with V_d of 60-70L

References

External Links