Fondaparinux, unlike unfractionated heparin and LMWH, does NOT cause heparin-induced thrombocytopenia (HIT) because:

• A It is a direct thrombin inhibitor that does not interact with the PF4-heparin axis
• B It binds exclusively to antithrombin III without binding platelet factor 4 (PF4) or forming immunogenic PF4-drug complexes ✓
• C Its large molecular size prevents interaction with platelet receptors
• D It activates protein C, preventing the platelet activation seen with HIT

Explanation

HIT is caused by IgG antibodies against complexes of PF4 bound to heparin. Fondaparinux is a synthetic pentasaccharide that binds antithrombin with high specificity and specifically inhibits Factor Xa; it does not bind PF4 or form immunogenic PF4-fondaparinux complexes, so it does not trigger HIT. It is used as an alternative anticoagulant in HIT patients. Argatroban and bivalirudin (direct thrombin inhibitors) are also used in HIT.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.