PH4.1-4 | PH4.1-4 | Drugs Affecting Blood and Coagulation — Summary & Reflection

KEY TAKEAWAYS

Blood pharmacology encompasses four competency families: haematinics/thrombocytopenia drugs, anticoagulants, fibrinolytics/antifibrinolytics, and antiplatelets. Iron deficiency anaemia is treated with ferrous sulphate orally (or IV iron when absorbed oral is insufficient); pernicious anaemia requires IM B12 (absent intrinsic factor prevents oral absorption — a critical distinction). ITP management: steroids first-line, IVIg for acute rescue, TPO agonists for chronic disease. Anticoagulants span UFH (monitored by aPTT, reversed by protamine), LMWH (enoxaparin, anti-Xa, partial protamine reversal), warfarin (INR 2–3 for AF/VTE; multiple drug interactions; reversed by vitamin K + PCC), and DOACs (apixaban/rivaroxaban/edoxaban = Xa inhibitors, andexanet alfa reversal; dabigatran = IIa inhibitor, idarucizumab reversal). HIT type II requires immediate cessation of all heparin (including LMWH) and switching to argatroban or fondaparinux. In pregnancy, LMWH is the only safe anticoagulant. Fibrinolytics: alteplase is fibrin-specific and re-usable; streptokinase is non-fibrin-specific and one-time only. Tranexamic acid prevents fibrinolysis (CRASH-2: saves lives in trauma within 3 hours). Antiplatelets: aspirin (irreversible COX-1); ticagrelor (PLATO-preferred in ACS; non-prodrug; reversible); prasugrel (contraindicated in prior stroke/TIA).

REFLECT

Return to the three emergency patients from the opening hook:

Patient A (AF, warfarin INR 2.4, acute stroke):
1. Can you give alteplase? What is the absolute contraindication here, and what alternative reperfusion option may exist?

Patient B (DVT, 28 weeks pregnant):
2. Which anticoagulant would you prescribe, and why specifically is warfarin contraindicated in pregnancy? At what gestational timing would you switch from LMWH to UFH?

Patient C (UFH 5 days, platelets 210 → 62, new DVT contralateral leg):
3. What diagnosis should you consider? What is the immediate management — and why is platelet transfusion contraindicated? What non-heparin anticoagulant would you start?

These three cases represent the clinical reality of blood pharmacology — correct management requires precise knowledge of indications, contraindications, monitoring, and reversal, applied under time pressure.