Anti-Coagulants Flashcards
What is the elimination order of heparin?
zero
What is the benefit of orally active inhibitors?
predictable degree of anticoagulation
What is the adverse side effect of anticoagulant drugs?
significant risk of haemorrhage
How are low molecular weight heparins administered?
SC
Why are low molecular weight heparins preferred to heparins?
no clotting test, except in renal failure - eliminated via renal excretion
Give examples of low molecular weight heparins
enoxaparin, dalteparin
What is thrombosis?
clot formed in the absence of bleeding
What is the con of orally active inhibitors?
no specific agent to reduce haemorrhage in overdose
Which orally active inhibitor inhibits factor Xa?
rivaroxaban
Why does warfarin require monitoring?
low therapeutic index
What increases the risk of thrombosis in patients who are taking warfarin?
pregnancy - increased clotting factor synthesis, hypothyroidism - decreased degradation of clotting factors, vitamin K consumption, drugs that increase the hepatic metabolism of warfarin
What are the adverse effects of heparin and low molecular weight heparins?
haemorrhage, rare -osteoporosis, hypoaldersteronism, hypersensitivity reactions
How is heparin administered?
IV - immediate onset, SC - onset delayed by an hour
What orally active inhibitors inhibit thrombin?
dabigatran, etexilate
How is the optimum dosage of heparin determined?
in vitro clotting test
What is the mechanism of action of warfarin?
competes with vitamin K for binding to hepatic vitamin K reductase - renders factors II, VII, IX and X inactive
Give examples of anti-coagulants
warfarin, heparin, low molecular weight heparins, orally active inhibitors
What is the onset period for warfarin?
2-3 days - active factors cleared, heparin may be added for rapid effect
What increases the risk of haemorrhage in patients who are taking warfarin?
liver disease - decrease clotting factors, high metabolic rate - increased clearance of clotting, drugs that inhibit hepatic metabolism of warfarin, drugs that inhibit platelet function - e.g. aspirin, NSAIDs, decreased availability of vitamin K
How is warfarin administered?
oral
What colour is a venous thrombosis?
red
How are overdoses of warfarin treated?
vitamin K1 or IV concentrate of clotting factors
What is a venous thrombosis made of?
fibrin rich
Give examples of orally active inhibitors
dabigatran, etexilate, rivaroxaban
What are orally active inhibitors used in?
prevent thrombosis in patients undergoing hip and knee replacements
What are anti-coagulants used for?
deep vein thrombosis, prevention of post op thrombosis, patients with artificial heart valves, atrial fibrillation
What is the elimination order of low molecular weight heparins?
first
How is a haemorrhage caused by heparin or low molecular weight heparin treated?
discontinue drug - administer protamine sulfate IV
Give an example of a drug that decreases the metabolism of warfarin
Amiodarone
