Antithrombolytics Flashcards
Anticoag Rxs
- Heparin/enoxaparin/fondaparinux
- Warfarin
- RivaroXaban, apiXaban
- DabigaTran/Argatroban/Desirudin/Bivalrudin
Antiplatelet Rx
- Aspirin, clopidogrel, prasugrel
* Abciximab / tirofiban / eptifibatide
Thombolytic
Alteplase
DOWN Clot formation Rxs
PROPHYLAXIS
Anticoagulants
Antiplatelets
UP Clot dissolution Rxs
Thrombolytic
Antithrombin catalysts
Heparin
Enoxaparin
Fondaparinux
Block clotting factor synthesis
Warfarin
Direct Xa inhibitors
RivaroXaban
ApiXaban
Direct thromibn (IIa) inhibitors
DabigaTran
Argatroban
Desirudin
Bivalrudin
Block platelet activation (G2b/3a activation)
Aspirin
Clopidogrel
Prasurel
Block glycoprotein 2b/3a function
Abciximab
tirofiban
Eptifibatide
Plasminogen activator
Alteplase
Red clot Tx
Anticoags
White clot Tx
Anticoags + antiplatelets
Just anticoag needed - Red clots
Hypercoaguable states
- stasis
- Afib
- immobility (DVT/PE)
- Foreign objects
- extracorporeal devices
- vascular access devices (heparin lock/central venous line)
White clots from
*Atherosclerosis ACS -->UA, MI CVD -->TIA, CVA PVD *Foreign objects (PCI, heart valve)
Treat ischemic CVA w/
Anticoag
Treat Hemorrhagic CVA w/
NO anticoag
Anticoags/antiplatelets
Physiology
Inhibit prevent clot growth
Anticoag/antiplatelet
Rx interaction
Many
Herbals
Anticoags/Antiplatelets
Contraindications
- Bleeding
- Impending surgery (ex. Spinal anesthesia/puncture–>hematoma–>paralysis)
- Hypersensitivity
Anticoags
Indirectly affect clotting factors UNFINISHED
Antithrombin catalys
-Heparin
What starts extrinsic pathway?
Tissue factor
What starts intrinsic pathway?
Intravascular trigger
What starts common pathway?
Factor 10
Which factor is prothrombin/thrombin?
II/IIa
Goal of anticoagulation?
Diminish activity of Factors 10a +/- 2a (common pathway)
What type of enzymes are clotting factors?
Zymogens (proenzymes)
Heparin
Bio characteristics
- polysaccharide
- glycosaminoglycan
- VERY suflated, VERY acidic
Unfractionated heparin
Chains?
Mixture of long chains
Some have pentasaccharide/some don’t
LMW Heparin
Mixture of short chains
Some have pentasaccharide/some don’t
Fondaparinux
Pure pentasaccharide
Antithrombin (AT)
Most potent anticoag in body
Looks like xymogem - 10A attaches, irreversible, suicide anti-coag
Heparins catalyze what?
Antithrombin (AT)
x1000
Heparin pentasaccharide mechanism for 10a + 2a?
10a - pentasaccharide increases at affinity for this
2a - long chain bridges this and AT, easier to bump into each other
Heparin antidote
Protamine = (+), binds with (-) heparin, inactive complax
NO w/ short heparin chains
Heparin-induced Thrombocytopenia (HIT)
- Hypersensitivity
- Autoimmune (PF4-heparin complex activate platelet)
- Get clot- gangrene
HIT
Tx
NO treat with Heparin/LMW, warfarin
*USE fondaparinux/argatoban (off-label)
LMW heparin/Fondaparinux
Future indications
Soon will include indications of unfractionated heparin
Heparin dosing
Read label carefully, don’t overdose
Heparin in pregnancy/neonate
USE W NO preservative (benzyl alcohol) fetal death
Heparin bleeding time monitored with
aPPT
Where does clotting occur?
On platelet surfaces
Not in solution
Warfarin blocks
Gla formation
Factor can’t attach to membrane
Vitamin K
Reduces Gla, then recycled by VKORC (nadh)
Warfarin blocks
VKORC regeneration of Vitamin K,
Not enough Gla for factors (10a) to stick to surface
INR 1
Normal clotting activity
Warfarin effects delayed - why?
Waiting for clotting factors to be used up (10a/2a take forever), and to build up useless clotting factors
Initiating warfarin
Heparin-bridge while waiting warfarin to get to steady state (slow onset)
Warfarin
S.E.
- Bleeding
- Clotting ?!? = stopping Protein C + S early (BRIDGE!)
- DEAD BABY
- NO HIT
Warfarin
Physiology
*S enantiomer - CYP2C9 metab
*t 1/2 = 20-60 h (human variation)
-CYP2C9 (elimination)
-VKORC (efficacy)
MONITOR INR
Warfarin
Rx interactions
Many
*need low Vitamin K (competitive inhibitor)
INR
HIGH = less clotting LOW = more clotting
10a /2a inhibitors
NOT WITH Afib + heart valve
If inhibit metabolism Rivaroxaban?
Up efficacy
Argatroban
MOA
Direct 2a (thrombin
inhibitor - blocks catalytic site)
*tx HIT
Hirudo medicinalis
Saliva - hirudin (anticoag) - surgery(reattaching fingers)
Hirudin derivatives
Desiruden (t1/2= 2-3 hrs)
Bivalirudin (t/12 = shorter)
*Direct thrombin (2a) inhibitors
COX 1 + ADP blocker
Synergistic effect
Aspirin
Irreversible COX inhibitor
- if stop - takes awhile to regenerate platelets (1week)
What if clopidogrel given to non metabolizer?
No effect, clopidogrel is pre-drug, need metabolism to activate
W/ heart valves?
Now, only warfarin
Thombolytics
Atleplase - plasminogen-like (fibrin), works best on fresh clots
Thienopyridine Anti-platelet agents (“grels”)
PRODRUG = Cyp metab to activate
Prasugrel
Thienopyridine Anti-platelet agents (“grels”)
More bleeding than clopidogrel
Clopidogrel
Thienopyridine Anti-platelet agents (“grels”)
Special metablolism consideration
CYP2C19 poor metabolizers = UP risk (MI/Ischemic Stroke/Death)
GP 2b/3a blocker Anti-platelet drugs
Block GP 2b/3a from binding fibrinogen, vWF+ others
Alteplase
GP 2b/3a blocker Anti-platelet drugs
Works best on fresh clots (less fibrin linking)
FOR ER CLOT BUSTING = T1/2 = 10 mins (shorter than Streptokinase)