Patient on Anticoagulant and Antiplatelet Therapy

Anticoagulants and antiplatelets are vital for preventing thrombosis but carry a major risk of bleeding. ✅ Indications: atrial fibrillation, DVT/PE, mechanical heart valves, MI, PCI, stroke prevention. ⚠️ Key complication: haemorrhage (minor bruising → life-threatening GI or intracranial bleed).

🧬 Mechanism of Action (Physiology)

• Anticoagulants: Act on the coagulation cascade, inhibiting clotting factor activation (extrinsic/intrinsic pathways). Prevent fibrin clot formation (e.g., warfarin, heparin, DOACs).
• Antiplatelets: Block platelet aggregation (primary haemostasis). Prevent arterial clot formation on ruptured plaques (e.g., aspirin, clopidogrel, ticagrelor).

📌 Common Anticoagulants

• Warfarin: Vitamin K antagonist (factors II, VII, IX, X). 🔎 Requires INR monitoring (target 2–3). ⚠️ Issues: drug/food interactions, teratogenicity, bleeding.
• Unfractionated Heparin (UFH): Potentiates antithrombin III → inhibits thrombin + factor Xa. 🔎 Monitor with aPTT. ⚠️ Risks: bleeding, heparin-induced thrombocytopenia (HIT).
• DOACs (Apixaban, Rivaroxaban, Dabigatran): Direct Xa or thrombin inhibitors. ✅ No routine monitoring needed. ⚠️ Consider renal clearance, drug interactions.

📊 Comparison: Anticoagulants vs Antiplatelets

🚨 Managing Bleeding – Anticoagulants

• Warfarin: ➡️ Minor: stop & monitor. ➡️ Moderate: oral vitamin K. ➡️ Severe/life-threatening: IV vitamin K + PCC (prothrombin complex) or FFP.
• Heparin: ➡️ Minor: stop infusion. ➡️ Moderate/severe: protamine sulfate (dose based on timing/dose of UFH/LMWH). ➡️ HIT: stop heparin, switch to non-heparin anticoagulant (argatroban, fondaparinux).
• DOACs: ➡️ Minor: stop drug & monitor renal function. ➡️ Dabigatran: idarucizumab is specific antidote. ➡️ Xa inhibitors: andexanet alfa (if available) or PCC. ➡️ Severe: supportive care + reversal agents.

💊 Common Antiplatelets

• Aspirin: Irreversible COX-1 inhibitor → ↓ thromboxane A2. Used in CAD, MI, stroke prevention. ⚠️ GI irritation, bleeding, allergy.
• Clopidogrel: Irreversible P2Y12 receptor blocker. Used post-stent, ACS, stroke/TIA prevention. ⚠️ Bleeding, dyspepsia.
• Ticagrelor: Reversible P2Y12 inhibitor. Used in ACS/PCI. ⚠️ Bleeding, dyspnoea, bradycardia.

🚨 Managing Bleeding – Antiplatelets

• Aspirin: ➡️ Minor: stop & monitor. ➡️ Severe: consider platelet transfusion + supportive care.
• Clopidogrel: ➡️ Minor: stop drug. ➡️ Severe: stop + platelet transfusion (variable benefit).
• Ticagrelor: ➡️ Severe bleed: stop + platelet transfusion (less effective due to reversible binding). ➡️ Supportive care essential.

⚖️ Balancing Risks

• ⚠️ Always weigh bleeding risk against thrombosis risk (e.g., stroke in AF, stent thrombosis post-PCI).
• 🫀 Dual antiplatelet therapy (DAPT: aspirin + clopidogrel/ticagrelor) is vital post-PCI but increases bleeding risk.
• 💊 Warfarin is still first-line in mechanical heart valves and severe renal impairment.
• ✅ DOACs are preferred in AF/VTE for ease and safety.

💡 Clinical Pearls

• 👴 Elderly, renal/hepatic impairment = ↑ bleeding risk. Adjust doses.
• 🔄 Reversal agents should be readily available in all hospitals.
• 📊 Use bleeding risk scores (HAS-BLED) and thrombotic risk scores (CHA₂DS₂-VASc) to guide decisions.
• 🧑‍⚕️ In emergencies: resuscitate first, stop anticoagulant, reverse if needed, then re-evaluate thrombotic risk.