Heparins - Enoxaparin

Question 1

enoxaparin is a low molecular weight heparin -what is it used for?

Answer 1

1) Venous thromboembolism (1st line for DVT and PE)
2) Acute coronary syndrome (ACS): LMWH and fondaparinux are part of 1st line therapy to improve re-vascularisation and prevent thrombus progression.

Question 2

What is the mechanism of action of Enoxaparin (LMW Heparin)

Answer 2

Heparins and fondaparinux prevent the formation of of blood clots by inhibiting thrombin and factorXa which are key components of the final common coagulation pathway.

** LMW heparins preferentially inhibit factor Xa

Question 3

What part of the coagulation pathway does heparin and fondaparinux inhibit?

Answer 3

LMW heparin (enoxaparin) preferentially inhibits Factor Xa.

Fondaparinux ONLY inhibits factor Xa.

Heparin inhibits thrombin and factor Xa
which are the part of final common coagulation pathway that leads to the formation of a fibrin clot.

Question 4

what is the difference between Unfractionated heparin, LMW heparin (enoxaparin) and fondaparinux?

Answer 4

LMW heparin inhibits both thrombin and factor Xa, but preferentially inhibits factor Xa. Has a predictable effect - does not need monitoring.

Fondaparinux is a synthetic compund similar to LMW heparin. But ONLY inhibits factor Xa . Has a similar effect to LMW heparin

Unfractionated heparin inhibits both thrombin and factor Xa. It has an unpredicatable affect unlike LMW H.

Question 5

What are the side effects of heparin?

Answer 5

• bleeding
• injection site reactions
• heparin induced thrombocytopeinia (less likely with LMW heparin and fondapa than UFH)

Question 6

What are the contraindications of heparin??

Answer 6

• clotting disorders
• severe uncontrolled hypertension
• recent surgery or trauma
• invasive procedures
• renal impairment (give lower dose as LMW heparin may accumulate)

Question 7

combining heparin with anitthrombotic drugs should be avoided due to increased risk of bleeding - what are the exceptions to this rule?

Answer 7

1) LMWH when initiating warfarin

2) with antiplatelet drugs e,g,aspirin and clopidogrel for acute coronary syndrome.

Question 8

What is the route of heparin?

Answer 8

• Sub cut injection

Question 9

What is the doese of enoxaparin for VTE prophylaxis?

Answer 9

40 mg daily SC

Question 10

how is heparin monitored?

Answer 10

UFH - activated partial thromboplastin ratio

LMWH or Fonda - don’t need regular monitoring ( but check FBC and renal profile)

monitor platelet count in case of thrombocytopenia - in which case stop drug

Question 11

LMWH doesnt need regular monitoring - if required what do you check?

Answer 11

Anti-Xa activity
FBC
Renal profile

Question 12

following diagnosis of VTE what anticoagulants would you prescribe?

Answer 12

• warfarin
  AND
• LMW heparin (stop once INR in range)