Anticoagulants Flashcards
What clotting factors require vitamin K to be produced?
II, VII, IX, X
What does plasmin do?
- It is the enzyme that breaks down a fibrin enriched clot
- *plasmin medications are dangerous to give because they will break down clots everywhere, not just the one clot that may be causing a problem.
For what reasons are anti-coagulants most commonly given?
- in peri-op setting for CV procedures
- to prevent DVT (10-40% of surgical patients)
- to pts with chronic atrial fibrillation
How do the different types of anticuagulanst effect clots?
anticoagulants?
anti-platelet drugs?
Thrombolytic drugs?
- Anticoagulants- decrease the production of fibrin
- Anti-platelet drugs- reduce platelet aggregation/function
- Thrombolytic drugs- promote clot lysis/fibrinolysis
What are the anticoagulant drugs that decrease the production of fibrin?
- Warfarin (Coumadin)
- Heparin
- Low molecular weight heparin
- lovenox
- Xa inhibitors
- Direct thrombin inhibitors
- Argatroban
- Dabigatran
Warfarin
Use
origination
- Used for long term thrombosis prophylaxis
- DVT
- afib
- prosthetic heart valves
- recurrent TIA/MI
- Originally marketed as a rat poison, but in a much higher dose
If you are dealing with arterial clotting issues, you would use ___________ therapy.
If you are dealing with venous (hemostasis) issues, you would use _________ therapy.
anti-platelet
Anticoagulant
Warfarin (Coumadin) MOA?
Why do the effects differ so much from patient to patient?
- Inhibits vitamin K epoxide reductase complex I (VKORC1), preventing the synthesis of vitamin K
- decrease in vitamin K will decrease production of the clotting factors that require vit K (II, VII, IX, X)
- The effects of this drug differ so greatly between patients because everybody has a different amount of epoxide reductase and also a different amount of the enzyme that breaks down warfarin
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Warfarin:
absorption
peak effect
E1/2t
Pb
dosing
- Absorbed in 1-2 hours, but no effect until the clotting factors you already have are depleted
- Peak effect delayed 36-72 hours
- E1/2t = 24-36 hours
- 97% PB
- Very narrow therapeutic index, but doses can range from 0.5 mg to 30 mg/day
How is INR calculated?
What would INR be for a pt not on warfarin?
What would INR be for pt with DVT, Afib, or PE?
- (Pt’s PT/normal PT)ISI
- ISI= international sensitivity index that is given with each batch of thromboplastin
- Pt NOT on Warfarin = 0.8-1.2
- Pts with DVT, Afib, or PE = 2.0-3.0
What is pregnancy category for Warfarin?
What are adverse reactions to Warfarin
- Category X
- Do not take while breastfeeding
- Adverse reactions?
- bruising
- bloody nose
- bleeding when brushing teeth
- blood in urine and stool
- pelvic pain
- HA
- dizziness
- low BP
- Tachycardia
- **pts should wear a medical alert bracelet
How can dietary intake affect Warfarin?
How can medications interfere?
- Foods with vit K antagonize the effect of warfarin;
- have a consistent diet
- Medications can increase or decrease the anticoagulation effects of Warfarin
- alter protein binding
- alter function of CYP enzymes
- Acetaminophen increases risk of bleeding
- several anti-sz medication
- Alter the synthesis or function of clotting factors and/or platelets
- heparin, NSAIDS, ASA, clopidogrel
- Alter absorption of warfarin
How far before surgery should you have the pt discontinue their warfarin?
When should you assess how this affects them?
How can warfarin be reversed for emergent procedure
- d/c at least 5 days before elective procedure
- Assess INR 1-2 days prior to surgery
- if >1.5, consider 1-2 mg oral Vit K
- Reversal for urgent procedure: 2.5-5 mg oral or IV vitamin K or FFP
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What is the best way to reverse warfarin if INR is high?
- If INR is above range but less than 6.0, hold 1-2 doses of warfarin
- If INR is higher or pt is showing signs of bleeding, administer Vit K
- Low doses via oral route is best
- IV may be used in pts with absorption issues
Unfractionated Heparin
structure?
- Highly sulfated glycosaminoglycans
- Potency varies so it is always prescribed in units