VTE Flashcards
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Heparin
mix of sulfated glycosaminoglycans
MOA: alter binding site of antithrombin III so that it can more efficiently combine with the active site of the serine proteases it inhibits (factor Xa and IIa)
When reversibly binding IIa, its binds both antithrombin III and IIa
When reversibly binding Xa, it binds antithrombin III only
high density of negative charge on molecule is necessary for binding antithrombin III
Can also bind albumin, plasmin, fibrinogen, and lipases (may account for resistance)
admin: IV, SubQ
half life 1 -2 hrs
Elimination: inding to endothelial cells and macrophages that engulf and begin to breakdown heparin. Can have some renal elimination
Pregnancy category C
antidote: protamine
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Rivaroxaban
inhibitor of factor Xa and also binds to Xa in the prothrombinase complex
inhibits both extrinsic and intrinsic paths
Use: DVT, PE, prophylactic tx of DVT or PE in those undergoing hip surgery, stroke prevention in A-fib pt
High bioavailability
high PPB
half life 5-9 hrs
CYP3A4 metabolized
P-gp substrate
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Apixaban
Factor Xa inhibitor
Use: DVT prevention in hip/knee replacement surgery, prevention of stroke in A-fib pt
half life 9 - 14 hrs
CYP 3A4 metabolism to inactive metabolites (OOD, alpha oxidation, oxo-piperadine moeity)
P-gp substrate
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Dabigatran
direct reversible thrombin inhibitor
prodrug
admin oral
no effect on prothrobin time
Use: A - fib, prophylaxis for hip/knee replacement
Metabolized by esterases (NON CYP)
substrate for p-gp
half life 12 - 17 hr
excreted unchanged in urine
ADR: inc bleed risk
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Warfarin
anti coagulant
inhibits Vit K expoxide reductase (enzyme that recycles oxidized Vit K1 to its reduced form) - so it inhibits vit K recycling
Effects synthesis of factor VII, IX, X, and II
inhibits protein C, protein S
acidic hydroxyl group that can tautomerize to enol and keto
S isomer metabolized by 2C9
R isomer has 45 hr half life
S isomer has 30 hr half life
ADR: inc bleed risk, skin necrosis (due to its ability to inhibit protein C), purple toe, may inc risk of osteoporosis (vit K plays role in bone formation)
DDI: NSAID, ASA, clopidogrel, levothyroxine, Vit K foods, Antibiotics, acetaminophen, azole antifungals, amiodarone, ethanol, cig smoke, St. John Warts, rifampin