Compared with unfractionated heparin, low molecular weight heparin has a relatively greater inhibitory action on:

• A Thrombin than factor Xa
• B Factor Xa than thrombin ✓
• C Platelet aggregation
• D Vitamin K dependent factors

Explanation

To inhibit thrombin, the heparin chain must be long enough to bind both antithrombin and thrombin simultaneously (at least 18 saccharide units). LMWH chains are shorter, so most molecules can accelerate antithrombin inhibition of factor Xa but not thrombin, giving an anti-Xa to anti-IIa ratio of about 4:1 versus 1:1 for unfractionated heparin. This shorter chain length also explains lower binding to platelet factor 4 and hence a lower incidence of HIT, killing option C.

Reference: Katzung Basic and Clinical Pharmacology, 15th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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