Anticoagulation and Antithrombotics

Always watch for a drop in platelets which could be due to Heparin-induced thrombocytopenia (HIT) and thrombosis.

About

• Most of us who deal with vascular disease of one sort or another spend our time trying to nudge a patient's clotting in their favour through the use of antithrombotic and anticoagulants drugs.
• You need to have a basic grasp of these agents. Misused can have serious and lethal side effects. Always take expert help if unsure. Safety first.
• Long-term anti-coagulation carries the risk of major haemorrhage (4% per annum) and death (about 0.5% per annum)

Antithrombotics

• Aspirin: Usually given as 300 mg loading dose followed by 75 mg daily afterwards. Some may use unorthodox doses such as 150 mg od. The main side effect is gastric irritation and those with dyspepsia will often also be prescribed a PPI. In stroke, a dose of 300 mg for 2 weeks may be used initially as this was a trial protocol. Some physicians adhere to this and others ignore it. Follow local conventions.
• Clopidogrel : Usually given as a single 300-600 mg loading dose especially in ACS. The maintenance dose is Clopidogrel 75 mg od.
• Dipyridamole: Given as a capsule of Dipyridamole MR 200 mg daily and was in the past given with Aspirin in secondary stroke prevention but since the drop in process of Clopidogrel which is now off licence Clopidogrel has replaced both these drugs and is given as a single antithrombotic agent.
• Aspirin and Dipyridamole: was used as a combination for secondary stroke and TIA prevention but NICE now favour Clopidogrel instead on a cost and compliance basis.
• Aspirin and Clopidogrel: May be used post ACS for a defined time period. Significant bleeding risk and so risks and benefits must be constantly assessed. Not used in stroke disease except in exceptional cases under specialist review.
• Dabigatran : see entry. A direct thrombin inhibitor and alternative to Warfarin. No need for regular blood tests. May be used for AF and VTE prevention post knee/hip replacement.
• Apixaban, Rivaroxaban, Edoxaban etc. Newer Factor Xa inhibitors used in AF and VTE

Unfractionated Heparin

• Used where there is a need to closely regulate and stop anticoagulation. It needs close monitoring. Unfortunately unless in a CCU or HDU staffing levels may not be sufficient to provide the degree of supervision needed.
• It may be reversed with protamine given IV. Dosing - Check local policy first as there are many treatment algorithms

Fractionated : Low molecular weight Heparin

• Clexane [enoxaparin]. Is used as follows
• VTE prophylaxis Clexane 40 mg s/c od
• VTE prophylaxis if renal impaired Clexane 20 mg s/c od
• ACS/MI Clexane 1 mg/kg bd
• DVT/PE Clexane 1.5 mg/kg od