9: Anticoagulant drugs Flashcards
Why is the clinical effect of unfractionated heparin unpredictable?
Mix of variable length heparin chains (heterogenous)
Why must UH be administered intravenously?
Long chain wiht large negative charge - not lipid soluble so won’t be absorbed by GI tract
What are the uses of UH?
- Acute coronary syndrome
- Thromboembolism
- Temporary “warfarin” replacement e.g. pregnancy
What is the mechanism of UH?
Mainly binds and inactivates antithrombin III (IIa, Xa) but ALSO IXa, XIa, XIIa
What is the therapeutic range for UH?
50-80 secs
What are the adverse effects of UH?
- Bruising/bleeding
- Thrombocytopenia
- Osteoporosis
How do you manage bleeding in patients on UH?
- Stop heparin
- Give protamine if actively bleeding
- Monitor APTT
What is the mechanism of LMWH?
Bind to antithrombin III and inhibit Xa (NOT thrombin)
What are the disadvantages of LMWH?
- Cannot be monitored by APTT
- Not fully reversible by protamine
- Care in renal failure
Which form of anticoagulation should someone with prosthetic valves be on?
Warfarin
What are the uses of warfarin?
Treatment or prevention of venous or arterial thrombosis
How is warfarin metabolised?
In the liver via P450
What are the adverse effects of warfarin?
- Haemorrhage
- Teratogenic
Which drug, often used for AF is a warfarin inducer?
Amiodarone
How do you manage inc. INR?
- IV Vit K
- IV prothrombinex
- Not life threatening - withold and recheck
