Anticoagulants

Question 1

Match the correct response

1. Warfarin
2. Clotting factor with the shortest half life
3. reverses warfarin
4. heaparin

A. normalize prothrombin time is used to measure intensity pf pharmacological effect
B. factor VII
C. phytonadione
D. aPTT is used to measure the intensity of pharmacologic effect

Question 2

which statement about warfarin is correct?

A. Foods containing large amounts of vitamin K can antagonize warfarin

B. Warfarin exerts its effect on coagulation through activation of antithrombin III

C. Patients should stop eating fruits and vegetables when treated with warfarin

D. Warfarin has an immediate effect on coagulation

Answer 2

A. Foods containing large amounts of vitamin K can antagonize warfarin

Question 3

what are the mechanism of action of these four drugs?

heparin
warfarin
dibigatran
rivaroxaban

Answer 3

heparin - activates anti-thrombin
warfarin - vitamin K antagonist
dibigatran - direct thrombin inhibitor
rivaroxaban - factor Xa inhibitor

Question 4

this question reviews your understanding of principles of pharmacology as applied to anticoagulant medication.

Your patient is responding well to warfarin and is stabilized for a month with a consistent INR of 2.2. Drug B is added but everything else stays the same. After starting on Drug B the INR falls and after two weeks stabilizes to 1.6. Drug B is stopped and Drug C is started. the INR increases but after 4 weeks stabilizes at 2.8.

One of the following explanations listed below correctly explains this observation. Which statement is correct?

This question is straight forward and fairly easy. Think through each possible explanation and the correct answer should be clear.

A. Drug B displaces warfarin from plasma binding proteins. Drug C is an antagonist to warfarin.

B. Drug B inhibits metabolism of warfarin. Drug C Enhances the activity of drug B.

C. Drug B stimulates metabolism of warfarin. Drug C displaces warfarin from plasma binding proteins. (Drug C Enhances warfarin)

D. Drug B increases renal clearance of warfarin. Drug C inhibits metabolism of Drug B

Answer 4

C. is correct: A drug that stimulates the metabolism of warfarin diminishes the warfarin effect. A drug that displaces warfarin from plasma binding proteins enhances the effect of warfarin.

Question 5

Today’s patient is a 69 year old woman presenting with pain in her left thigh muscle. Duplex ultrasonography indicates the presence of deep vein thrombosis in the affected muscle.

You decide to initiate treatment with enoxaparin. Compared to unfractionated heparin, enoxaparin:

A. Can be used without monitoring the aPTT.

B. Has a shorter duration of action.

C. Is less likely to have a teratogenic effect.

D. Is more likely to be administered intravenously.

E. Is more likely to cause thrombocytopenia.

Answer 5

A. Can be used without monitoring the aPTT.

Enoxaparin is a LMWH. LMWHs have a longer half life than plain or unfractionated heparin (UFH) and have a more consistent relationship between dose and effect. Enoxaparin is most often given SQ rather than IV. and is LESS likely to cause thrombocytopenia. UFH and LMWH do not cross the placenta and are not considered teratogens. UHF is usually used in patients who require monitoring of the aPTT, or prior to surgery or prior to delivery to take advantage of a shorter duration of action.

Question 6

Your patient today is a 57 year old woman with chronic hypertension, and type 2 diabetes recently discharged from the hospital for new onset atrial fibrillation and congestive heart failure. You have her hospital record, her echocardiogram and ECG. Her ECG is consistent with atrial fibrillation. According to her risk score she requires anticoagulation rather than anti-platelet therapy. You would like to use a direct thrombin inhibitor. Which of the following is a DTI?

A. Abiciximab
B. Dabigatran
C. Rivaroxaban
D. Warfarin

Answer 6

B. Dabigatran

Abciximab is an antiplatelet agent binding to GP IIb/IIIa.

Rivaroxaban is an oral factor X inhibitor (Xa in the name)