A patient with heparin-induced thrombocytopenia (HIT) requires anticoagulation for DVT. The drug of choice is argatroban. Its mechanism is:

• A Binding antithrombin III to catalyze inhibition of thrombin and factor Xa
• B Direct competitive inhibition of both free and clot-bound thrombin (factor IIa) without requiring antithrombin ✓
• C Inhibition of vitamin K epoxide reductase preventing carboxylation of clotting factors
• D Blockade of thrombin receptor PAR-1 on platelets preventing thrombin-induced aggregation

Explanation

Argatroban is a direct thrombin inhibitor (DTI) that reversibly and competitively binds to the active site of thrombin (factor IIa), inhibiting both free thrombin and clot-bound thrombin. It does not require antithrombin as a cofactor, which is advantageous since HIT patients may have low antithrombin levels. It is metabolized hepatically (important: dose reduction in liver disease, not in renal failure). Heparin causes HIT by forming antigenic complexes with platelet factor 4, so all heparins must be avoided.

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.