Coagluation Flashcards
What is the mechanism of action of heparin?
activating antithrombin III (ATIII)
accelerating the rate at which antithrombin inhibits thrombin (factor IIa) and factor Xa
1g protamine reverses 100U of heparin
Monitor aPTT
What is the mechanism of HIT type II?
immune-mediated
antibodies (IgG) against complex of platelet factor 4 (PF4) and heparin
5–14 days
What is the mechanism of action of LMWH (eg.enoxaparin, dalteparin) ?
activating AT III –> inhibiting factor Xa
little effect on thrombin inhibition
Protamine incompletely reverses
Is the risk of HIT higher or lower with LMWH compared to heparin?
fivefold lower with LMWH than with heparin due to its lower affinity for PF4
LMWH should NOT be used to anti-coagulate HIT patients because most HIT antibodies exhibit cross-reactivity with LMWH
What is the mechanism of action of fondaparinux?
factor Xa inhibition
cleared unchanged in the kidneys, it is contraindicated in patients with renal insufficiency
What is the mechanism of argatroban?
synthetic direct thrombin inhibitor
List the direct thrombin inhibitors and how do you monitor their effects?
argatroban
dagibitran
lepirudin
bivalrudin
Monitor = aPTT
What is the mechanism of action of warfarin?
interferes with the synthesis of the vitamin K–dependent clotting proteins, which include factors II, VII, IX, and X and protein C and S
How is warfarin’s anticoagulant effect monitored?
prothrombin time (PT) or INR
What is the mechanism of action of dabigatran?
oral direct thrombin inhibitor
Is there an antidote for the oral factor Xa inhibitors?
No
What is the mechanism of action and side effects of aspirin?
irreversible inhibition of cyclooxygenase 1 and 2 (COX-1 and COX-2)
antithrombotic effect = primarily inhibition of COX-1 on platelets
SE = dyspepsia, peptic ulcers with bleeding and perforation
What is the mechanism of action of dipyridamole?
inhibiting phosphodiesterase –> blocks breakdown of cyclic adenosine monophosphate (cAMP) –> Increased levels of cAMP reduce intracellular calcium and inhibit platelet activation
Name 3 platelet ADP receptor antagonists.
ticlopidine
clopidogrel
prasugrel
ticagrelor
Name 3 platelet Gp IIb/IIIa receptor inhibitors.
abciximab - long half-life
eptifibatide
tirofiban
List some drugs that decease warfarin’s effects
barbiturates carbamazepine cholestyramine nafcillin phenobarbital phenytoin rifampin
List some drugs that increase warfarin’s effects
Levofloxacin
omeprazole
amiodarone
What are the mechanisms of action for oral anti-platelet agents?
ASA - COX2 inhibitor
Dipyrimadole - PDE inhibitor
ADP inhibitors - block P2Y12 receptor on platelets
What drugs can be used w/ a history of HIT type-II?
fondaparinux
argatroban
bilavrudin
Explain the mechanism of action of un-fractioned Heparin.
binding to Antithrombin III (ATIII) and accelerating its activity by 100-1000 times
The ATIII-heparin complex primarily inhibits thrombin (Factor IIa) and factor Xa
What are the 3 types of protamine reactions?
Systemic hypotension from histamine release
Anaphylactic reaction (IgE Mediated)
Severe pulmonary hypertension and right ventricular failure - IgG mediated immune reaction - more common in patients with fish allergy, previous vasectomy, or prior exposure to protamine or NPH insulin.
Describe an advantage and a disadvantage of bivalirudin and argatroban to heparin.
Unlike heparin, bivalirudin and argatroban can be used in HIT patients, but they have no antidote to reverse their effects.
Compare the mechanism of action of Rivaroxaban (Xarelto) and Dabigatran (Pradaxa)?
Rivaroxaban (Xarelto) is a direct factor Xa inhibitor
Dabigatran (Pradaxa) is a direct thrombin inhibitor
