Anticoagulation Flashcards
What are anticoagulants?
Anticoagulants are medications that PREVENT blood clots from forming - they do NOT breakdown clots.
*Fibrinolytics breakdown existing clots.
*Antiplatelets interferes with platelet binding to each other.
When are anticoagulants used?
1) For the prevention and treatment of Venous Thromboembolism (VTE):
-DVT: Deep Vein Thrombosis
-PE: Pulmonary Embolism
2) Immediate treatment of STEMI and NSTEMI
3) Prevention of cardio-embolic stroke (This is where the clot forms in the heart)
4) Any other situation where there is an increased risk of clot formation (blood disorders)
What is the body’s natural anticoagulant?
Anti-thrombin
General Mechanisms of Action of Anticoagulants
1) Heparins (UFH & LMWH-Enoxaparin, Dalteparin): Indirectly inhibits factors Xa and IIa (thrombin) via. Antithrombin.
2) Factor Xa Inhibitors:
Direct inhibitions (RIvaroxaban, Apixaban, Edoxaban)
Indirect Inhibition (Fondaparinux)
3) Direct Thrombin Inhibitors (Argatroban, Bivalirudin, Dabigatran)
4) Vitamin K antagonist (Warfarin): Inhibits factors 2,7,9,10
Dosing of Unfractionated Heparin (UFH)
1) VTE Prophylaxis: 5000U SubQ q8-12h
2) VTE Treatment: 80 U/kg IV bolus; 18 U/kg/hr infusion
3) ACS/STEMI Treatment: 60 U/kg IV bolus; 12 U/kg/hr infusion
Reversal Agent: Protamine
*It is important to monitor platelets for thrombocytopenia
*Monitor via aPTT levels
What are the Low Molecular Weight Heparins (LMWH)?
1) Enoxaparin (Lovenox)
2) Dalteparin
Enoxaparin Dosing
1) VTE Prophylaxis: 30 mg subQ q12h or 40 mg daily
CrCl < 30: 30 mg subQ daily
2) VTE and Unstable Angina and NSTEMI Treatment: 1 mg/kg subQ q12h or 1.5 mg/kg subQ daily
CrCl < 30: 1 mg/kg subQ daily
3) STEMI Treatment (< 75 y.o.): 30 mg IV bolus plus a 1 mg/kg subQ dose followed by 1 mg/kg q12h
CrCl < 30: 30 mg IV bolus plus a 1 mg/kg dose, followed by 1 mg/kg subQ daily
4) STEMI Treatment (> 75 y.o.): 0.75 mg/kg subQ q12h (no bolus)
CrCl < 30: 1 mg/kg subQ daily
*Enoxaparin is renally excreted
Reversal Agent: Protamine
Contraindications of Heparin (UFH & LMWH)
1) Uncontrolled active bleed
2) History of HIT
3) Hypersensitivity to pork products
What is HIT?
Heparin-Induced Thrombocytopenia is an immune mediated IgG drug interaction. This leads the platelet activation and platelet aggregation, and increases the risk of clotting.
Diagnosis of HIT
4T Score:
1) Thrombocytopenia (> 50% drop in platelets)
2) Timing of platelet count fall
3) Thrombosis
4) Other causes of thrombocytopenia
*After, we can confirm that the patient has HIT by Labs: ELISA
Once the patient is diagnosed with HIT, we then stop all heparin products, and we reverse warfarin with vitamin K
-Start a non-heparin anticoagulant for patient
What are the Factor Xa inhibitors?
1) Apixaban (Eliquis)
2) Rivaroxaban (Xarelto)
3) Edoxaban
4) Fondaparinux (This is the only injectable, and it works INDIRECTLY by Antithrombin)
These DIRECTLY inhibit Factor Xa, except Fondaparinux.
Fondaparinux is contraindicated in CrCl < 30!
Apixaban (Eliquis) Dosing
1) Stroke prophylaxis in Non-valvular Atrial Fibrillation: 5 mg PO BID
*IF the patient has at least 2 of the following, dose 2.5 mg PO BID:
- Age >= 80 y.o.
-Weight <= 60 kg
-Serum Creatinine >= 1.5 mg/dL
2) VTE Treatment:
Initial: 10 mg PO BID x 7 days, followed by 5 mg PO BID
Rivaroxaban (Xarelto) dosing
Creatinine Clearance dependent!
1) Stroke Prophylaxis in Non-valve Atrial Fibrillation:
CrCl > 50: 20 mg PO daily
CrCl 15-50: 15 mg PO daily
CrCl < 15: AVOID
2) VTE Treatment:
Initial: 15 mg PO BID x 21 days, then 20 mg PO daily with food
CrCl < 30: AVOID
What is the antidote for Apixaban and Xarelto?
Andexanet alfa (Andexxa)
What medications causes an additive bleed risk when given with Factor Xa inhibitors?
1) Anticoagulants
2) Antiplatelets
3) NSAIDs
4) SSRIs
5) SNRIs
