Therapeutic Anticoagulation — 16 Exam-Ready Flashcards

What is the aim of anticoagulant therapy?

Prevents thrombus formation and prevents extension of thrombus, also most effectively in fibrin-rich venous clots.

Where anticoagulants work best

Why are anticoagulants more effective in venous than arterial thrombosis?

Venous clots are fibrin-rich, Arterial clots are platelet-rich and Anticoagulants target the coagulation cascade, not platelets

UFH vs LMWH

How does low molecular weight heparin differ from UFH?

More selective for Factor Xa, Less platelet interaction, Better bioavailability, Longer half-life

What are common clinical uses of UFH and LMWH?

• DVT and PE

• Atrial fibrillation

• Unstable angina

• Peri-procedural anticoagulation

What is fondaparinux and how does it work?

• Synthetic pentasaccharide

• Binds antithrombin

• Selectively inhibits Factor Xa

Heparin adverse effect

What is the main adverse effect of heparin?

Bleeding, More common with UFH, Rapid reversal due to short half-life

How does warfarin exert its anticoagulant effect?

• Inhibits vitamin K-dependent factor synthesis, Affects II, VII, IX, X Also affects protein C and S

Why does warfarin take several days to become effective?

• Existing clotting factors persist

• Prothrombin has long half-life

• Anticoagulation effective after ~3 days

Monitoring warfarin

How is warfarin therapy monitored?

• Prothrombin Time (PT)

• Reported as INR

• Allows dose adjustment

Warfarin limitations

Front: Why does warfarin require close monitoring?

 

Narrow therapeutic window

Many drug interactions

Affected by diet and liver function

Strong pharmacogenomic effects

Warfarin contraindication

Why is warfarin contraindicated in pregnancy?

• Crosses placenta

• Teratogenic

• Causes fetal bleeding

Direct thrombin inhibitors

How do direct thrombin inhibitors work?

• Directly inhibits thrombin

• Act independently of antithrombin

• Example: dabigatran

Direct Factor Xa inhibitors

How do direct Factor Xa inhibitors differ from warfarin?

• Direct inhibition of Factor Xa

• Predictable effect

• Rapid onset

• No routine monitoring required

Fibrinolytic agents

When are fibrinolytic agents used?

Breakdown of fresh thrombi and STEMI in cases where PCI is unavailable. Most effective within 6 hours