Anticoagulants & Antithrombotics — Pharmacology

Also known as Anticoagulants · Heparin pharmacology · Warfarin pharmacology · DOAC pharmacology · Antiplatelets · Protamine · Idarucizumab · Andexanet alfa · Unfractionated heparin · Low-molecular-weight heparin · Vitamin K antagonists · Direct oral anticoagulants · P2Y12 inhibitors · GPIIb/IIIa antagonists · Reversal agents

Anticoagulants and antithrombotics — by mechanism of action. The indirect (heparins via antithrombin III), the direct (DTI, FXa), the vitamin K antagonist (warfarin). The antiplatelets (COX, P2Y12, GPIIb/IIIa). The PK/PD and the reversal. UFH (potentiates antithrombin III → inactivates IIa + Xa; aPTT monitoring; protamine reversal; short t1/2 60-90 min; safe in renal failure). LMWH (enoxaparin 1 mg/kg BD; anti-Xa monitoring; renal clearance; partial protamine reversal ~60%). Warfarin (vitamin K epoxide reductase inhibitor; INR target 2-3; slow onset days; teratogenic; food/drug interactions; vitamin K + PCC/FFP reversal; protein C depletion → skin necrosis → overlap heparin). DOACs — dabigatran (direct thrombin inhibitor; idarucizumab reversal; 80% renal), rivaroxaban/apixaban (factor Xa inhibitors; andexanet alfa reversal). Antiplatelets — aspirin (irreversible COX-1), clopidogrel (P2Y12), GPIIb/IIIa (abciximab, tirofiban). Indications: VTE treatment/prophylaxis, AF (CHA2DS2-VASc), mechanical valve (warfarin only), ACS. Bleeding risk (HAS-BLED), major bleeding management (stop drug, activated charcoal if recent, reversal agents, blood products).

medium59 referencesUpdated 17 Aug 202636 min readSource-verified · Sept 2026

Checked against its sources on 2 Sept 2026

Practise this topic

8 MCQs

Meet the patient

A 78-year-old man on dabigatran 150 mg BD for atrial fibrillation is brought in confused, hypotensive, and vomiting frank blood. His eGFR has slipped from 55 to 24 over the week. The registrar reaches for vitamin K and four-factor PCC — the warfarin reflex.^[1]

That reflex is wrong, and it is the single exam question this whole topic turns on: the antidote must follow the mechanism. Dabigatran is a direct thrombin inhibitor whose excretion is predominantly renal, as unchanged drug — it accumulates fast when the kidneys fail — and it is reversed by idarucizumab 5 g IV, not by anything that replaces vitamin-K-dependent factors. Hold that patient. Every class below answers the same question in its own way.^[1]^[8]^[9]^[37]

References59Show

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