Antithrombotics Flashcards
what are the 3 categories of antithrombotic drugs?
- antiplatelets
- anticoagulants
- fibrinolytics
what do antiplatelets do?
prevent thrombus
what do anticoagulants do?
Prevent initial thrombus and prevent extension of current thrombus
what do fibrinolytics do?
Lyse active thrombus
all antithrombotics have a risk of ____
bleeding
antiplatelet drug names to be familiar with
- Aspirin
- clopidogrel (Plavix)
Aspirin MOA
- inhibits COX-1 and COX-2
- reduces production of thromboxane A2
- inhibits platelet aggregation
At low doses (81 mg), Aspirin primarily inhibits COX-1 for _____
cardiovascular protection
clopidogrel (Plavix) is an ADP receptor inhibitor, also known as ____ or ____
thienopyridines; P2Y12 inhibitors
clopidogrel (Plavix) MOA
- prevents ADP from binding to platelet by irreversibly blocking PY12 receptor
- prevents platelet aggregation for lifespan of platelet (7-10 days)
clopidogrel (Plavix) AEs
- generally well tolerated
- biggest concern is bleeding (monitor symptoms and lab values for Hgb/Hct)
T/F: clopidogrel (Plavix) is a prodrug
- true
- CYP2C19 to active metabolite
boxed warnings for clopidogrel (Plavix)
↓ efficacy in some genetic variants that make them CYP2C19 poor metabolizers (present in 50% of Asians, 30% African-Americans, 25% Caucasians)
heparin MOA
prevents conversion of fibrinogen to fibrin
heparin tx doses require monitoring of ____ levels
- aPTT
- these levels indicate how long it takes your blood to form a clot
what is the reversal agent for heparin?
- protamine sulfate
- binds heparin so it is inactivated
Heparin induced thrombocytopenia (HIT)
- Body creates antibodies which bind to heparin when it is in a complex platelet factor IX
- this activates platelets
- clotting and ↓ platelet levels
- Treat with direct thrombin inhibitors or Factor Xa inhibitors
Low-molecular weight heparin (LMWH) MOA
prevents conversion of fibrinogen to fibrin
why is LMWH preferred over regular heparin?
more simple dosing, no monitoring required, ↓ risk HIT
LMWH drug to be familiar with
“we love not being hit”
enoxaparin (Lovenox)
warfarin (Coumadin) MOA
- vitamin K antagonist (VKA)
- depletes vitamin K stores and inhibits synthesis of factors VII, IX, X and II, and protein C and S
warfarin reversal agent
vitamin K
warfarin usually takes ____ days for full effect
- 3-5
- takes even longer to stabilize dose
warfarin is an NTI drug and requires frequent monitoring of ____
INR (international normalized ratio)
low INR = risk of ____
clot
high INR = risk of ____
bleeding
PO Direct Thrombin Inhibitor MOA
- binds directly and reversibly to thrombin with high selectivity
- inhibits conversion of fibrinogen to fibrin
PO Direct Thrombin Inhibitor risks
- Less intracranial bleeding than warfarin but more GI bleeding
- Beers List: ↑ risk of GI bleeding in >75 years
other AE for PO Direct Thrombin Inhibitor
- dyspepsia (aka indigestion)
- 10%, take with food, improves with time
Factor XA Inhibitors MOA
- selectively and reversibly binds FXa
- stops further coagulation cascade
Factor XA Inhibitor drug names to know (end in “xaban”)
- apixaban (Eliquis)
- rivaroxaban (Xarelto)
rivaroxaban is on the Beers List because it has more risk of ____
GI bleed
which factor XA inhibitor has lowest bleed risk?
apixaban (Eliquis)
All factor XA inhibitors have less ____ than warfarin
- risk of intracranial bleed
- drug interactions
andexanet alfa (Andexxa) is a reversal agent for which drugs?
- LMWH
- Factor XA Inhibitors
T/F: rivaroxaban must be taken with food
true
fibrinolytics MOA
- mimic endogenous tissue plasminogen activator (TPA) which converts plasminogen to plasmin
- plasmin breaks fibrin links in the thrombus
when are fibrinolytics used?
immediately after stroke, MI, PE
