Antiplatelets, Anticoagulants, And Fibrinolytics
Through several mechanisms of action, these agents are used to achieve the fine balance between clotting and systemic bleeding. These drugs are very common, so you should become an expert on every detail regarding them. Test your wit with various forms of questions and see if you have what it takes to be a pharmacist!
Questions and Answers
- 1.
What is the average lifespan of a platelet?
- A.
1 day
- B.
2-5 days
- C.
5-10 days
- D.
90 days
Correct Answer
C. 5-10 daysExplanation
The answer is 5-10 days for the lifespan of platelets. This has implications for the use of irreversible anti platelet medications, which will have effects even when discontinued due to the time necessary for platelet regeneration. A normal platelet count is 150,000 to 400,000 per microLiter, which can be abbreviated as "150" to "400." Platelets are normally smooth, but have glycoproteins that can assist in the aggregation and formation of a clot.Rate this question:
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- 2.
Is Ticagrelor (Brilinta) reversible?
- A.
Yes
- B.
No
Correct Answer
A. YesExplanation
Ticagrelor is unique among the antiplatelets in that it is reversible. It is also a non-thienopyridine, and must be used with low-dose aspirin.Rate this question:
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- 3.
Which of the following is NOT an indication of aspirin?
- A.
Primary prophylaxis
- B.
Secondary prophylaxis
- C.
Treatment of acute coronary syndromes
- D.
Treatment of acute ischemic stroke
- E.
Treatment of peripheral arterial disease
- F.
All of the above are indications of aspirin
Correct Answer
F. All of the above are indications of aspirinExplanation
Please note that aspirin can be used for primary prophylaxis in appropriate individuals.Rate this question:
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- 4.
Clopidogrel (Plavix) has interactions primarily with which of the following CYP isozymes?
- A.
CYP 3A4 inhibitors
- B.
CYP 2D6 inhibitors
- C.
CYP 2E1 inhibitors
- D.
CYP 2C19 inhibitors
Correct Answer
D. CYP 2C19 inhibitorsExplanation
The inhibition of CYP 2C19 by drugs such as omeprazole, a PPI (proton pump inhibitor), will lead to less conversion of clopidogrel (a prodrug) to its active metabolite, and less antiplatelet activity. If a PPI is required, pantoprazole is the drug of choice due to less inhibition of CYP 2C19.Rate this question:
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- 5.
Ticagrelor (Brilinta) has interactions primarily with which CYP isozyme?
- A.
CYP 3A4 inhibitors
- B.
CYP 3A4 inducers
- C.
CYP 2C19 inhibitors
- D.
CYP 2D6 inhibitors
- E.
A and B
Correct Answer
E. A and BExplanation
Ticagrelor has interactions with both CYP 3A4 inhibitors and inducers; thus, it may have several clinically significant drug-drug interactions. As a result, the maximum doses of simvastatin and lovastatin are 40 mg to prevent the incidence of rhabdomyolysis.Rate this question:
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- 6.
Which of the following are indications of cilostazol (Pletal)? Check all that apply.
- A.
Secondary prophylaxis
- B.
Intermittent claudication (peripheral arterial disease)
- C.
Invasive management of PCI
- D.
Stroke prevention
Correct Answer
B. Intermittent claudication (peripheral arterial disease)Explanation
Cilostazol (Pletal) has a unique niche in being useful for the treatment of intermittent claudication symptoms due to peripheral arterial disease (PAD). This is its only FDA-labeled indication. Of note, avoid cilostazol in heart failure patients.Rate this question:
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- 7.
Which of the following are indications of aspirin/dipyridamole (Aggrenox)? Check all that apply
- A.
Secondary MI prophylaxis
- B.
Fibrinolysis
- C.
Recurrent stroke prophylaxis
- D.
Primary MI prophylaxis
Correct Answer
C. Recurrent stroke prophylaxisExplanation
This is a niche role for aspirin/dipyridamole (Aggrenox) and its only FDA-labeled indication.Rate this question:
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- 8.
What are glycoprotein IIb/IIIa inhibitors used for?
- A.
Invasive management during a PCI
- B.
Treatment of heart failure
- C.
Chronic prevention of blood clots
- D.
Coating of invasive lines
Correct Answer
A. Invasive management during a PCIExplanation
By inhibiting the final common pathway for platelet aggregation at greater than 80% of receptor occupancy, these extremely potent agents are used during a PCI to prevent clotting. Basically, the platelets cannot hold hands and form the clot, so the patient is spared further clotting.Rate this question:
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- 9.
Which of the following glycoprotein IIb/III inhibitors are reversible? Check all that may apply.
- A.
Abciximab (Reopro)
- B.
Eptifibatide (Integrilin)
- C.
Tirofiban (Aggrastat)
Correct Answer
A. Abciximab (Reopro)Explanation
The gold standard of glycoprotein IIb/IIIa inhibitors, abciximab (Reopro) is reversible by overwhelming the agent with platelets. The other agents (eptifibatide and tirofiban) are not reversible, have renal dosing, and are shorter-acting.Rate this question:
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- 10.
Which enzyme does warfarin act upon to exert its pharmacological effect?
Correct Answer
Vitamin K Oxide Reductase
VKORC1Explanation
Warfarin inhibits the enzyme "Vitamin K Oxide Reductase", which normally takes oxidized Vitamin K and reduces it in order for the reduced form to assist in the conversion of a prothrombin precursor to prothrombin. Less prothrombin means less thrombin, and less thrombin means less conversion of fibrinogen to fibrin. Warfarin inhibits the synthesis of the vitamin K dependent clotting factors (2, 7, 9, 10) and the ANTICOAGULANT proteins C and S. Since the anticoagulant proteins are inhibited first (shortest half lives), starting warfarin without a heparin or LMWH bridge can INCREASE the risk of clotting.Rate this question:
- 11.
Warfarin is bound to which plasma protein?
- A.
Albumin
- B.
Alpha-1 acid glycoprotein
- C.
Hemoglobin
Correct Answer
A. AlbuminExplanation
Acidic and neutral drugs bind to albumin, which is basic. Basic drugs bind to alpha-1 acid glycoprotein. Oxygen binds to hemoglobin. Warfarin binds to albumin at greater than 95%. These are facts. Thus, if a patient has another drug on board that displaces warfarin from albumin, there will be more free warfarin and more anticoagulation. Something to consider.Rate this question:
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- 12.
Which of the following can affect the INR for a patient on warfarin? Check all that apply.
- A.
Demographics
- B.
Vitamin K intake
- C.
Hepatic function
- D.
Drug interactions
Correct Answer(s)
A. Demographics
B. Vitamin K intake
C. Hepatic function
D. Drug interactionsExplanation
With vitamin K intake, always educate your patients to maintain a CONSISTENT intake of vitamin K. More vitamin K will lead to more clotting, but the patient can still eat their leafy green vegetables, since their increased intake was factored into their maintenance dosing.Rate this question:
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- 13.
For which indications should the goal INR be 2.0-3.0?
- A.
Prophylaxis of VTE
- B.
Treatment of VTE (DVT/PE)
- C.
Prophylaxis of stroke/systemic embolism
- D.
Mechanical aortic valve
- E.
Mechanical mitral valve
- F.
Bioprosthetic aortic valve
- G.
Bioprosthetic mitral valve
Correct Answer(s)
A. Prophylaxis of VTE
B. Treatment of VTE (DVT/PE)
C. Prophylaxis of stroke/systemic embolism
D. Mechanical aortic valve
F. Bioprosthetic aortic valve
G. Bioprosthetic mitral valveExplanation
Mechanical valves have greater risks of developing clots, and mitral valves have greater risks of clots due to the lower pressure compared to in the aorta. Therefore, the mechanical mitral valve requires a goal of 2.5-3.5. If a patient has both mechanical mitral and aortic valves, use the goal of 2.5-3.5.Rate this question:
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- 14.
The heparin or LMWH bridge with warfarin should be continued until the INR is greater than 2.0 for how many consecutive days?
Correct Answer(s)
2
twoExplanation
The heparin/LMWH bridge is necessary due to the depletion of proteins C and S, which are anticoagulant proteins, before the other Vitamin K dependent clotting factors (2, 7, 9, 10). Thus, warfarin without the bridge could lead to a clot with initial therapy.Rate this question:
- 15.
True or False: Unfractionated heparin can dissolve clots
- A.
True
- B.
False
Correct Answer
B. FalseExplanation
Heparin can only prevent further clotting; it cannot dissolve a clot. You will need a clot-buster, aka a fibrinolytic such as tPA (alteplase/Activase) to break up an active clot. This is due to heparin's mechanism of action, which has an indirect effect on thrombin via antithrombin; thrombin eventually converts fibrinogen to fibrin, which solidifies a clot. By stopping thrombin, you can stop more fibrin from solidifying the clot, but heparin cannot get into and bust up a clot.Rate this question:
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- 16.
Check all of the advantages of direct thrombin inhibitors.
- A.
Do not require cofactor (antithrombin)
- B.
Bind clot-bound thrombin
- C.
Predictable effects of anticoagulation
- D.
Decreased bleeding compared to heparin
Correct Answer(s)
A. Do not require cofactor (antithrombin)
B. Bind clot-bound thrombin
C. Predictable effects of anticoagulation
D. Decreased bleeding compared to heparinExplanation
A key point here is that direct thrombin inhibitors can get into clots and exert an effect on thrombin. In general, the direct thrombin inhibitors bivalirudin and argatroban are a good alternative to heparin or a glycoprotein IIb/IIIa inhibitor for PCI management.Rate this question:
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- 17.
True or false: fondaparinux (Arixtra) requires antithrombin to inhibit Factor Xa
- A.
True
- B.
False
Correct Answer
A. TrueExplanation
This is true; fondaparinux requires antithrombin in order to inhibit Factor Xa; this inhibition results in less conversion of prothrombin to thrombin and less conversion of fibrinogen to fibrin.Rate this question:
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- 18.
Which of the following plays a role in the dosing of fondaparinux? Check all that apply.
- A.
Weight
- B.
Indication
- C.
Renal function
- D.
Prior use of fondaparinux
Correct Answer(s)
A. Weight
B. Indication
C. Renal functionExplanation
Weight is used to determine the dose for treatment of VTE; for prophylaxis dosing, a weight less than 50kg results in the contraindication of fondaparinux. Indication (prophylaxis vs treatment) determines the dosing choices, which are then based on weight for treatment. Renal function is not used to determine dosing, but plays a role in that a CrCl of less than 30ml/min results in the contraindication of fondaparinux. As far as I know, prior use of fondaparinux does not affect its use.Rate this question:
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- 19.
Which of the following affect the dosing of apixaban (Eliquis)?
- A.
Age
- B.
Body weight
- C.
Serum creatinine
- D.
CYP 3A4 or P-gp inhibitors
Correct Answer(s)
A. Age
B. Body weight
C. Serum creatinine
D. CYP 3A4 or P-gp inhibitorsExplanation
While the usual dose of apixaban for non-valvular atrial fibrillation is 5 mg PO BID, if the patient has 2 of the following (age > 80, body weight 1.5mg/dL), then the dose should be 2.5 mg PO BID. If a patient is on a CYP 3A4 or P-gp inhibitor, then the dose should be 2.5 mg PO BID. If the patient is on the CYP 3A4/P-gp inhibitor and is eligible for the 2.5mg PO BID dosing due to their age, weight, or serum creatinine, then the patient cannot take apixaban.Rate this question:
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- 20.
True or false: fibrinolytics only work on fibrin to bust a clot.
- A.
True
- B.
False
Correct Answer
B. FalseExplanation
Fibrinolytics are also know as tissue plasminogen activators, and as such they activate plasminogen to plasmin, which then breaks up fibrin, but also breaks down fibrinogen, thus preventing more fibrin from forming. However, tPA is more specific for clot-bound fibrin than for fibrinogen. Breaking down too much circulating fibrinogen could lead to systemic fibrinolysis, which would not be good.Rate this question:
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- 21.
True or false: streptokinase is a direct tissue plasminogen activator?
- A.
True
- B.
False
Correct Answer
B. FalseExplanation
Streptokinase is less specific than tPA for clot-bound fibrin, and thus binds equally to circulating and the clot-bound plasminogen, resulting in more systemic bleeding. Therefore, tPA is preferred over streptokinase for dissolving coronary and cerebral vascular thrombi. Fun fact: streptokinase is derived from streptococci (the bacteria), so patients with a recent strep infection will need a higher dose!Rate this question:
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- 22.
To change the INR due to therapy with warfarin by 1.0, change the WEEKLY dose by how much?
- A.
5-10%
- B.
10-15%
- C.
15-20%
- D.
20-25%
Correct Answer
B. 10-15%Explanation
While there are many nomograms and tools for dosing warfarin, this is a rule of thumb for adjusting warfarin doses.Rate this question:
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Mar 22, 2023Quiz Edited by
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Jul 15, 2014Quiz Created by
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