Pharm of Anticoagulation Therapy (complete) Flashcards Preview

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Flashcards in Pharm of Anticoagulation Therapy (complete) Deck (22):

Describe the MOA of heparin

- proteoglycan w/sulfated polysaccharide --- varying lengths
- Binds to anti-thrombin III => leads to increased protease inactivation (especially thrombin and 10a)
- Also inactivates 9a, 12a
- Heparin increases rate of thrombin inactivation by 1000x
- prevents fibrin formation


Describe the pharmacokinetics of heparin

A: IV or SubQ, poor GI absorption

- Short t1/2 (poor bioavailability)
- Unpredictable dose response
- Requires hospital admission/monitoring
- Does NOT cross the placenta


Describe the MOA of low molecular weight heparin (LMWH)

- A smaller version of heparin
- Bind to anti-thrombin III but not thrombin
- Does not inhibit thrombin by anti-thrombin
- Does selectively bind to and inactivates 10a


Describe the pharmacokinetics of LMWH

A: SubQ

- Better bioavailability than heparin
- More predictable dose response
- Longer t1/2
- Less monitoring (out-patient)


What are the differences in management of patients on heparin and LMWH?

- You need to be admitted into the hospital if given heparin
- requires lots of monitoring due to unpredictability of dose response

Not the case with LMWH (can do outpatient)


What are the complications associated with heparin therapy?

1) Bleeding
2) Heparin-induced thrombocytopenia syndrome (HIT)
3) Allergic events


Describe bleeding as a complication associated with heparin therapy

- Must discontinue drug w/ hemorrhage
- Effects are reversed w/ protamine sulfate


Describe Heparin-induced thrombocytopenia syndrome (HIT) as a complication associated with heparin therapy

- There's a low platelet count b/c of production of Abs to platelet factor 4/heparin complexes => Abs bind to platelets => pro-thrombic state
- Less common w/ LMWH and fondaparinux


Describe allergic events as a complication associated with heparin therapy

- Due to contaminant: oversulfated chondroitin sulfate
- Activation of contact system (bradykinin, complement)


What are alternative anticoagulant therapies used for pts with HIT?

1) argatroban (novastan)
2) lepirudin (refludan)


Describe argatroban (novastan)

- an alternative therapy for pts w/ HIT
- a small molecule inhibitor


Describe lepirudin (refludan)

- an alternative therapy for pts w/ HIT
- recombinant form of hirudin (an anticoagulant from leeches)


Describe the MOA of oral anticoagulant warfarin

- Depletes vitamin K through inhibition of Vit K reductase
- W/depletion => no gamma-carboxylase => no modification of coag factors
- Ultimately depletion of coag factors


Describe the pharmacokinetics of warfarin

- Rapidly absorbed
- Good bioavailability
- Long t1/2
- Slow action onset

Effective dose = 3-5 days => b/c you can't get rid of all coag factors at once, still have some there


What are the uses of warfarin?

- Venous thromboembolism (w/heparin)
- Embolism in pts w/ prosthetic valves or atrial fibrillation
- Stroke, recurrent infarctions


What are the adverse rxns and potential complications associated with warfarin use?

- Hemorrhage (requires vitK admin or plasma transfusion)
- Cross placenta
- Drug interactions
- Delayed action onset
- Requires monitoring


Describe the MOA of fibrinolytic agents

- Lyse clots already formed
- Instead of preventing clot formation
- Increases activation of plasmin from plasminogen => then fibrin is broken down more quickly



What are the uses of fibrinolytic agents?

- Acute MI (emergency tx --- must be used w/in 3 hrs)
- Ischemic stroke
- DVT and PE


Describe the MOA of antiplatelet agents

- Inhibit platelet formation and aggregation

Three ways:
1) Inhibits thromboxane A2 production => irreversibly inactivates COX1
2) ADP receptor blockers (irreversibly) => prevents alpha granule secretion
3) GP2a/3a inhibitors => block binding of fibrinogen to GPs


What are the uses of antiplatelet agents?

- After acute MI
- Thrombotic stroke (w/ thrombolytics)

ADP blockers:

GP inhibitors:
- Tx of AMI
- Unstable angina
- before, during, after angioplasty


What are the uses of heparin?

- Venous thrombosis (w/warfarin)
- PE (w/warfarin)
- Management of unstable angina, MI (w/fibrinolytics)
- Coronary angioplasty, stent placement
- Surgery that require cardiopulm bypass
- Kidney dialysis


What are types of fibrinolytic agents?

- T-PA
- Urokinase
- Streptokinase