Anticoagulants Flashcards
What is the MOA of unfractionated heparin?
UFH works by binding to a protein in the blood called antithrombin III. This boosts the activity of antithrombin III, which inactivates two important clotting factors: thrombin and factor Xa. Without these factors, the bloods’ ability to form clots is significantly reduced. It does not dissolve existing clots but stops their growth, allowing the body’s natural processes to break them down over time.
How is unfractionated heparin administered?
Either IV or SC.
IV route provides rapid onset of action, making it ideal for acute situations (PE, DVT, or MI).
SC route is used for situations requiring prolonged anticoagulation but not requiring an immediate effect, such as for prevention of thrombosis or clot formation.
What are the main uses of UFH?
DVT, PE, MI, hemodialysis patients, during and after cardiac/vascular surgeries, catheter patency maintenance.
Preferred anticoagulant in pregnancy due to its large molecular size and negative charge.
What are adverse effects of UFH?
Mild to severe bleeding (Antidote: Protamine sulfate)
Heparin induced Thrombocytopenia (HIT)
Osteoporosis with prolonged use
Hyperkalemia
What are contraindications of UFH?
Severe thrombocytopenia
Active bleeding
Recent surgery involving the brain, spinal cord, or eyes.
Liver/Renal disease
Uncontrolled HTN
What is drug-drug interactions with UFH to watch for?
Antiplatelets: Aspirin, Clopidogrel, NSAIDs
Anticoagulants: Warfarin, Dabigatran, Rivaroxaban
Thrombolytics: Alteplase
Dextran and Glycoprotein IIb/IIIa inhibitors: Further inhibit platelet aggregation, increasing hemorrhage risk
Nitroglycerin IV can reduce efficacy of the drug
Spironolactone, ACE, or ARBs can increase risk of hyperkalemia associated with heparin
How is UFH monitored?
aPTT: measures the time it takes for blood to clot, reflecting UFHs impact on clotting factors. (Primary)
Anti-Factor Xa: Directly measures UFH activity by quantifying its inhibition of Factor Xa. (Alternative or Adjunct Monitoring)
Why is UFH and warfarin used together?
UFH acts immediately, making it effective for initial anticoagulation. Warfarin takes 3-5 days to reach full effect, so to ensure continuous anticoagulation, UFH is started first and overlapped with warfarin until warfarin is therapeutic.
How is UFH and warfarin used together?
UFH is administered IV or SC and warfarin is started orally at the same time. Overlap therapy is continued until the INR is within therapeutic range (2-3). UFH is stopped once the INR has been therapeutic for 24 hours.
What are the advantages of prescribing low molecular weight heparin?
Convenient administration (administered SQ with fixed dosing, no IV access required, making it suitable for outpatient therapy. )
Reduced monitoring requirements
Lower risk of HIT
Longer half-life (3-5 hours) allowing for 1-2 daily dosing.
Can be easily used outpatient for DVT/PE prophylaxis reducing hospital stay and healthcare costs.
Preferred in pregnancy because it does not cross the placenta
What are the drugs under the LMWH drug class?
enoxaparin, dalteparin, and tizaparin
What is the MOA of Arixtra?
Selectively inhibits Factor Xa by binding to antithrombin III, enhancing its activity by 300-1000 times. Does not inhibit thrombin like Heparin does.
How is Arixtra different from heparin?
Does not require routine monitoring.
Administered SQ with 100% bioavailability.
Long half life (17-21 hours)
Does not cause HIT because it does not interact with platelet factor
What is a contraindication for taking Arixtra?
Contraindicated in severe renal impairment as it is eliminated through the kidneys.
What are the primary uses of prescribing Warfarin?
Prevention/Treatment of DVT, PE
Stroke Prevention (Patients with A-fib, prosthetic heart valves, thrombotic conditions like protein S or C deficiency, antiphospholipid antibody syndrome.
Used as adjunct therapy with parenteral anticoagulants during the transition to long-term anticoagulation.
