Antithrombotic Agents/Coagulation Flashcards
What triggers intrinsic clotting cascade? What factors are involved in Intrinsic cascade?
Endothelial damage. 12, 11, 9, 10
What triggers extrinsic clotting cascade? What factors are involved?
Vessel/extravascular tissue damage. 7, 10
What factors are common to both pathways?
Xa, 5a (converts prothrombin to thrombin)
What are inhibitors of clotting cascade?
Protein C/S (inhibit 8 and 5), Tissue factor pathway inhibitor (inhibits 7A-TF complex), Antithrombin III (inhibits protease, 10, 2)
How long do platelets circulate? What kind of thrombi are they found in?
7-10 days. Arterial only (not venous)
What’s MOA of aspirin? What effect does it have on CV dz?
Irreversible COX1 inhibitor at low dose, COX2 inhibitor at high dose (>1g/day). 25% mortality reduction from CV
What’s MOA of dipyridamole? When is it used?
inhibit PDA and adenosine deaminase->decrease plt aggregation/thrombosis. VTE ppx after valve replacement with coumadin 75-100 mg QID
What’s MOA of cilostazol? What are contraindications? How long do you take it for claudication?
PDE3 inhibitor -> decrease smooth muscle contractility, inhibit plt aggregation. Avoid grapefruit, CI in heart failure. 6-12 weeks to see effectiveness
How do P2Y12 inhibitors work? What’s score for PRU?
Inhibit P2Y12 -> inhibit ADP binding -> unable to stimulate platelet aggregation. PRU>235 indicates high likelihood of resistance
How is clopidogrel activated?
Metabolized/activated by hepatic CYP 2C19
What’s dose of Prasugrel?
Loading 60 mg, maintenance 10 mg daily (5 mg daily if <60kg)
What’s different about mechanism of Ticagrelor? What’s dose?
Binds P2Y12 but not at the ADP binding site. Loading 180 mg, 90 mg BID x 1y then 60 mg BID
What’s an IV P2Y12 inhibitor? What’s dose?
Cangrelor. Loading: 30 mcg/kg IV bolus, Maintenance: 4 mcg/kg/min.
What’s MOA of Tirofiban? What’s dose?
Reversible competitive inhibitor of GP IIb/IIIA receptor. Loading 25 mcg/kg IV, infusion 0.15 mcg/kg/min
What’s MOA of Eptifibatide? What’s dose?
Blocks fibrinogen/vWF binding to GP IIb/IIIA on platelet surface. 180 mg/kc IV bolus, maintenance 2 mcg/kg/min
What’s dose of heparin for VTE treatment?
80 units/kg bolus then 18 units/kg/hr
How does antithombin III deficiency present? How do you get heparin to work?
VTE (not arterial), inability to achieve therapeutic ACT despite heparin administration (give direct thrombin inhibitors). Administer 2u FFP immediately after heparin to provide antithrombin III for heparin to work
How does protamine work? How is it dosed?
Combines with heparin to form neurtalized salt. 1 mg protamine for 100 units of heparin
How does enoxaparin work?
Binds/potentiates antithrombin to inactivate factor Xa.
How does fondaprinux work?
bind antithormbin, does not inhibit thrombin
What are direct thrombin inhibitors? What are reversal agents?
Bivalirudin, argatroban, dabigatran. PCC, Idarucizumab for dabigatran
How does warfarin work?
Inhibit vitamin K epoxide reductase > inhibit synthesis of factor 2, 7, 9, 10, protein C/S
What are reversal agent for apixaban/rivaroxaban?
Recombinant factor xa (andexanet alfa)
What pathways are measured by PT and PTT?
PT: Extrinsic, PTT: intrinsic
What are components of FFP, CPP, PCC?
FFP: all factors except 8
CPP: 8, vWF, Fibrinogen
PCC: 2, 7, 9, 10
