Drugs affecting haemostasis and thrombosis Flashcards
What are the main constituents of the coagulation system?
- Vessel wall lined by endothelium
- Platelets derived from megakaryocytes in marrow
- Coagulation factors in inactive state
- Inhibitors of coagulation
- Fibrinolytic system and inhibitors
What is the mechanism of action of tranexamic acid?
Effective if given within 3-4 hours after trauma
CRASH-2 TRIAL involved 20,000 trauma patients
What are common adverse effects of heparin?
- Pain at site of injection
- Increased bleeding risk
- Osteoporosis with prolonged use
- Heparin-induced thrombocytopenia
What does warfarin inhibit?
Inhibits production of vitamin K in reduced form
What are the positive aspects of warfarin?
- Established for decades
- Cheap
- Easily measurable effect
- Can be reversed with vitamin K or factor concentrate
What are the negative aspects of warfarin?
- Lots of drug and food interactions
- Slow onset
- Unpredictable dose need
- Needs regular blood testing
- Risk of bleeding
- Narrow therapeutic window
List some drugs that increase the effect of warfarin.
- Amoxycillin
- Erythromycin
- Statins
- Acute alcohol intake
- Aspirin
- Clopidogrel
- NSAIDs
What are DOACs?
Direct Oral Anticoagulants, previously known as NOACs
What are the main types of DOACs?
- Xa inhibitors (e.g., apixaban, rivaroxaban, edoxaban)
- Direct thrombin inhibitors (e.g., dabigatran)
What is the CHA2DS2-VASc score used for?
Stroke risk scoring in atrial fibrillation
What are the components of the CHA2DS2-VASc score?
- Congestive heart failure
- Hypertension
- Age ≥75 years
- Diabetes Mellitus
- Prior Stroke or TIA
- Vascular disease
- Age 65–74 years
- Female sex
What is the ORBIT score used for?
Bleeding risk assessment
What is the primary use of aspirin in anticoagulation?
Secondary prevention of atherosclerotic arterial events
How does aspirin affect platelet function?
Irreversible inhibition of COX-1, leading to less thromboxane A2 production
What are the effects of clopidogrel and ticagrelor?
Inhibit ADP induced platelet aggregation
What are thrombolytic drugs used for?
Increase activation of plasminogen to plasmin
What are the risks associated with thrombolytic drugs?
Increased bleeding risk in hours after dose
What is the role of heparin in anticoagulation?
Naturally occurring anticoagulant that binds to and activates anti-thrombin
What is the difference between unfractionated heparin and low molecular weight heparin (LMWH)?
- Unfractionated: IV infusion, half-life <1 hour
- LMWH: Subcutaneous, half-life approx. 12 hours
What is the typical monitoring requirement for IV heparin?
Monitored by APPT plasma testing
What is the typical dose for fresh frozen plasma?
15 ml/Kg
What is the composition of cryoprecipitate?
Concentrated fibrinogen, Von Willebrand factor, and factor VIII
What is the dosing strategy for low molecular weight heparin?
Used as fixed dose for prophylaxis and weight adjusted dose for treatment
What are the alternative treatments to thrombolysis?
- Stenting
- Clot removal
