VTE Flashcards

1
Q
A

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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2
Q
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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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3
Q
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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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4
Q
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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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5
Q
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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

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