Hematological agents I Flashcards
what allows fibrin to remain at the site of injury?
when bound to thrombin it cannot be inhibited by antithrombin / heparin
what are features of venous thrombi?
- platelet poor - “red thrombi”
- often occur at valves
- antiplatelet therapy not usually useful
what are features of arterial thrombi?
- platelet rich - “white thrombi”
2. occur atop plaque ruptures
what is the MOA of aspirin?
- irreversible inhibition of COX-1 in platelets
2. reduces TXA2 production - reduction in platelet activation and aggregation
what class of drug is dipyridamole? what is the MOA?
- antiplatelet
- inhibits phosphodiesterase
- more cAMP, less calcium (in platelets), less activation
what is the role of P2Y12?
- ADP receptor
2. binding leads to platelet activation
what class of drug are clopridogrel and prasugrel? what is the MOA?
- antiplatelet
- irreversible P2Y12 inhibitors - decrease GpIIb/IIIa
- must be activated by liver
what class of drug are ticagrelor and cangrelor? what is the MOA?
- antiplatelet
- irreversible P2Y12 inhibitors - decrease GpIIb/IIIa
- does NOT need to be metabolized by liver
prasugrel and ticagrelor are not recommended in patients with what history?
intracranial bleeding
what are the GpIIb/IIIa antagonists? what is the MOA?
- abciximab
- eptifibatide
- tirofiban
what is the MOA of abciximab?
- fragment of monoclonal against GpIIb/IIIa
2. prevents fibrinogen cross bridges between platelets
what class of drug is vorapaxar? what is the MOA?
- protease activated receptor (PAR) antagonist
2. blocks thrombin - does not allow to bind to GPCR
what are the indirect thrombin inhibitors (bind to antithrombin)?
- heparin
- enoxaparin
- fondaparinux
what are the direct thrombin inhibitors?
- lepirudin
- bivalirudin
- argatroban
- dabigatran
what are the direct Xa inhibitors?
- rivaroxaban
2. apixaban
how does heparin work?
binds antithrombin at endothelial surface, increases inhibition of factor Xa thrombin
how is unfractionated heparin different from regular heparin?
unfractionated heparin is shorter and cannot keep thrombin in close proximity - can only activate antithrombin and have effects on Xa inactivation
what are the two mechanisms of heparin clearance?
- rapid but saturable by endothelial cells
2. non-saturable via kidney and liver
what is the main test for heparin monitoring?
activated partial thromboplastin time (aPTT)
in instances of severe bleeding, what agent can be used to inactivate heparin?
protamine
