Antiplatelets and anticoagulants

Question 1

Discuss anti-platelet and anticoagulants and give examples

Answer 1

a. Anticoagulants to prevent the clots getting bigger and breaking off

➢ Heparin:

2 types (know difference)
- Low molecular weight heparins is a pure polymer. they are mostly used e.g. dalteparin and enoxaparin
- Standard is a mixture of different polymers
- Mechanism: inhibitor of thrombin.
- Given as IV or subcutaneous injections
- Side effects: haemorrhage, thrombocytopenia and Osteoporosis (in prolonged use >6 months)

➢ Warfarin sodium (oral anticoagulant-tablet) – should be started same time as heparin – prevents further clotting
- Not recommended for pregnant women.
- Warfarin is a [vitamin K] antagonist and a competitive inhibitor.
- MOA: Prevents blood clot formation by inhibiting the production of vitamin K by vitamin K epoxide reductase. and depleting levels of the reduced form of vitamin K, a co-factor for the production of vitamin K-dependent clotting factors II (pro-thrombin), VII, IX and X

➢ Rivaroxaban (Factor Xa inhibitor)
➢ Apixaban (thrombin inhibitor)
➢ Compression stockings – to prevent formation of new clots or post-thrombotic syndrome
➢

b. Antiplatelet drugs to prevent blood clot( (mostly in arterial thrombosis) e.g

-    Aspirin blocks cox enzyme preventing the production of thromboxane A2. A2 is an agonist for platelets
➢ Use with caution if patient has asthma
➢ Use with caution in elderly with other medications or conditions
 
- Clopidogrel: Pro-drug of an active metabolite irreversibly binds to ADP receptor (P2Y12) on platelets, which prevents ADP–mediated activation of platelets and aggregation.
 
- Dipyridamole: Inhibiting phosphodiesterase (PDE), it prevents the hydrolysis of cAMP and cGMP and thus increase their levels to inhibit platelet activation.