Fondaparinux, a synthetic pentasaccharide anticoagulant, exerts its effect by selectively binding to antithrombin and inhibiting:

• A Factor Xa only, without directly inhibiting thrombin (factor IIa) ✓
• B Both factor Xa and thrombin equally
• C Factor IXa and VIIIa complex (intrinsic tenase)
• D Factor VIIa/tissue factor complex

Explanation

Fondaparinux is a synthetic pentasaccharide that specifically binds antithrombin, causing a conformational change that dramatically accelerates AT's inhibition of factor Xa. Unlike heparin (which bridges AT to both Xa and thrombin), fondaparinux's pentasaccharide chain is too short (18 saccharide units required for bridging AT to thrombin), so it inhibits only Xa. This selectivity results in no effect on thrombin (IIa), no need for coagulation monitoring (aPTT), and zero risk of heparin-induced thrombocytopenia.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.