Oral Direct Thrombin Inhibitor

The question asks for an anticoagulant that is both a direct thrombin (Factor IIa) inhibitor and administered by the oral route. The correct answer is Dabigatran.

Analysis of Options

• Apixaban: An oral anticoagulant, but it acts by inhibiting Factor Xa, not thrombin. Incorrect.
• Rivaroxaban: Also an oral Factor Xa inhibitor, not a thrombin inhibitor. Incorrect.
• Argatroban: This is indeed a direct thrombin inhibitor, but it is available only as an intravenous (IV) formulation, used mainly in heparin-induced thrombocytopenia (HIT). Since it is not administered orally, it does not satisfy the question's requirement. Incorrect for this question.
• Dabigatran (etexilate): This is the only agent among the options that is both a direct thrombin inhibitor and formulated for oral administration. It directly binds and inhibits thrombin (Factor IIa), preventing the conversion of fibrinogen to fibrin, and is used clinically for stroke prevention in non-valvular atrial fibrillation and for treatment/prophylaxis of venous thromboembolism. Correct.

Conclusion

Since the question specifically asks for an oral direct thrombin inhibitor, Argatroban is excluded despite sharing the same mechanism, because it is IV-only. Dabigatran is the correct answer as it uniquely combines the direct thrombin-inhibiting mechanism with oral bioavailability.