Anticoagulant drugs Flashcards
What does heparin do?
Potentiates the naturally occurring anticoagulant action of anti-thrombin
What are the two forms of heparin?
Unfractionated
Low molecular weight (LMWH)
How is unfractionated heparin monitored?
Activated partial thromboplastin time (aPTT)
How is LMWH monitored?
Anti-Xa assay but typically little / no monitoring required
What are the 3 main complications of heparin?
Bleeding - main side effect!!
Heparin-induced thrombocytopenia
Osteoporosis with long term use
What is the mechanism of action of warfarin?
Inhibits vitamin K and thus results in the synthesis of non-functional coagulation factors (II, VII, IX and X)
When giving warfarin what are two things to be considered?
Narrow therapeutic window - need to monitor carefully
Maintenance - drug taken at same time every day
How is warfarin monitored?
INR - how quickly blood clots
(international normalised ratio)
What is the major adverse effect of warfarin?
Haemorrhage
What should always be checked before giving warfarin?
Drug interactions - check patients current medical status
Ensure patient is not pregnant
How is warfarin reversed if required?
Omit the warfarin
Administer oral vitamin K
Administer clotting factors
Assess
What does dabigatran do?
Why is it not used often?
Directly inhibits thrombin
It is renally excreted - not used in patients with renal failure risk
What does apixaban / rivaroxaban do?
Directly inhibits activated factor Xa
When are new anticoagulants (dabigatran, apixaban etc) used?
Treatment of DVT / PE
Used instead of LMWH as prophylaxis in elective hip and knee replacements
What is prolonged due to warfarin?
Prothrombin time (PT)
What is the biggest indication for the prescription of anticoagulant drugs?
What is another common indication?
Atrial fibrillation
Venous thrombosis
What stage of coagulation is targeted by anticoagulant drugs?
Formation of the fibrin clot
Which clotting factors are dependent on vitamin K?
Factors II, VII, IX and X
Name some naturally occurring anticoagulants?
Protein C
Protein S
Anti-thrombin
How can heparin be administered?
Intravenously or subcutaneously
How is heparin-induced thrombocytopenia monitored for?
Monitor FBC for signs, will typically present ~1 week from starting medication
What is the action of vitamin K on clotting factors II, VII, IX and X?
Carboxylation of glutamic acid residues
What is the recommended time to take warfarin?
6pm for hospital
Anytime compliance will be best for the individual
What is the INR / what is it used for?
A mathematical comparison allowing warfarin monitoring to be compared to databases using INR (international normalised ratio)
