Anticoagulants

Heparin

Increases the ability of antithrombin molecule to irreversibly inhibit thrombin, IXa, Xa, XIa.

LMWH - mainly inhibits FXa only, less monitoring needed. Sub-cut inj. Unfractionated - continuous infusion, monitor aPTT ratio, uncommon can cause HIT (heparin induced thrombocytopenia)

• Chronic use → osteoporosis
• Reverse effects with protamine sulphate

Warfarin

Vitamin K antagonist with lots of interactions with drugs and food. FII, VII, IX, X, protein C +S all vit K dependant.

• Monitor INR \(\approx\) PT ratio
• Start on LMWH at same time to prevent warfarin induced skin necrosis
• Antidote: prothrombin complex concentrate - raises inhibitor factors + vit K

Direct oral anticoagulants

Predictable dose response and minimal interactions unlike warfarin. Fast onset and offset. Cannot use with mechanical heart valves

• Factor X inhibitors - -xaban eg rivaroxaban (reversal with andexanet alfa) 
• Direct thrombin inhibitors - dabigatran (reversed with idarucizumab)