Lippincott Chapter 23: Anticoagulants and Antiplatelet Agents Flashcards
22.1 Which of the P2Y12 ADP receptor antagonists reversibly
binds the receptor?
A. Clopidogrel.
B. Prasugrel.
C. Ticagrelor.
D. Ticlopidine
Correct answer = C. Of the four P2Y12 ADP receptor antag-
onists, ticagrelor is the only one that reversibly binds the
receptor. This is important when it comes to compliance.
If a patient is not compliant, then the antiplatelet activity of
ticagrelor stops when the drug is missed (since the platelets
inhibited are not irreversibly inhibited as they would be with
aspirin, clopidogrel, or prasugrel). On the other hand, the
waiting period prior to surgery may be shorter in patients
taking ticagrelor since it takes less time for the antiplatelet
effect to wear off.
22.2 A 70-year-old female is diagnosed with nonvalvular
atrial fibrillation. Her past medical history is significant
for chronic kidney disease, and her renal function is
moderately diminished. All of the following anticoagulants
would be expected to require a reduced dosage in this
patient except:
A. Apixaban.
B. Dabigatran.
C. Rivaroxaban.
D. Warfarin.
Correct answer = D. Warfarin does not require dosage
adjustment in renal dysfunction. The INR is monitored and
dosage adjustments are made on the basis of this infor-
mation. All of the other agents are renally cleared to some
extent and require dosage adjustments in renal dysfunction.
22.3 An 80-year-old male is taking warfarin indefinitely for
the prevention of deep venous thrombosis. He is a
compliant patient with a stable INR and has no issues
with bleeding or bruising. He is diagnosed with a urinary
tract infection and is prescribed sulfamethoxazole/
trimethoprim. What effect will this have on his warfarin
therapy?
A. Sulfamethoxazole/trimethoprim will decrease the
anticoagulant effect of warfarin.
B. Sulfamethoxazole/trimethoprim will increase the
anticoagulant effect of warfarin.
C. Sulfamethoxazole/trimethoprim will activate platelet
activity.
D. Sulfamethoxazole/trimethoprim will not change
anticoagulation status.
Correct answer = B. Sulfamethoxazole/trimethoprim has
a significant drug interaction with warfarin, such that it will
inhibit warfarin metabolism. Therefore, sulfamethoxazole/
trimethoprim will cause increased anticoagulation, and the
patient will need to have his warfarin dose decreased and
INR checked frequently while he is on this antibiotic.
22.4 In which disease state is cilostazol contraindicated?
A. Peripheral arterial disease.
B. Gout.
C. Heart failure with reduced ejection fraction.
D. Osteoporosis.
Correct answer = C. Cilostazol is contraindicated in heart
failure with reduced ejection fraction because it is a phos-
phodiesterase inhibitor and acts as a positive inotrope
(which can lead to sudden cardiac death).
22.5 Which must heparin bind to in order to exert its
anticoagulant effect?
A. GP IIb/IIIa receptor.
B. Thrombin.
C. Antithrombin III.
D. von Willebrand factor.
Correct answer = C. Heparin binds to antithrombin III, caus-
ing a conformational change. This heparin/antithrombin III
complex then inactivates thrombin and factor Xa
22.6 Which is considered “fibrin selective” because it rapidly
activates plasminogen that is bound to fibrin?
A. Alteplase.
B. Fondaparinux.
C. Streptokinase.
D. Urokinase.
Correct answer = A. Alteplase has a low affinity for free plas-
minogen in the plasma, but it rapidly activates plasminogen
that is bound to fibrin in a thrombus or a hemostatic plug.
It has the advantage of lysing only fibrin, without unwanted
degradation of other proteins (notably fibrinogen).
22.7 A 56-year-old man presents to the emergency room
with complaints of swelling, redness, and pain in his
right leg. The patient is diagnosed with acute DVT and
requires treatment with an anticoagulant. All of the
following are approved for treatment of this patient’s
DVT except:
A. Rivaroxaban.
B. Dabigatran.
C. Enoxaparin.
D. Heparin.
Correct answer = B. Dabigatran is only approved for the
prevention of stroke in nonvalvular atrial fibrillation; it is not
approved for the treatment of acute DVT. All of the other
options are approved for treatment of acute DVT.
22.8 Which is most appropriate for reversing the
anticoagulant effects of heparin?
A. Aminocaproic acid.
B. Protamine sulfate.
C. Vitamin K1
D. Tranexamic acid.
Correct answer = B. Excessive bleeding may be managed
by ceasing administration of heparin or by treating with prot-
amine sulfate. Infused slowly, protamine sulfate combines
ionically with heparin to form a stable, inactive complex.
Aminocaproic acid and tranexamic acid are approved for
the treatment of hemorrhage but do not specifically reverse
the effects of heparin to stop bleeding. Vitamin K1
is used to
help reverse the effects of warfarin-induced bleeding.
22.9 A 62-year-old male taking warfarin for stroke prevention
in atrial fibrillation presents to his primary care physician
with an elevated INR of 10.5 without bleeding. He is
instructed to hold his warfarin dose and given 2.5 mg of
oral vitamin K1
. When would the effects of vitamin K on
the INR most likely be noted in this patient?
A. 1 hour.
B. 6 hours.
C. 24 hours.
D. 72 hours.
Correct answer = C. Vitamin K1
takes about 24 hours to see
a reduction in the INR. This is due to the time required for
the body to synthesize new coagulation factors.
22.10 A 58-year-old man receives intravenous alteplase
treatment for acute stroke. Five minutes following
completion of alteplase infusion, he develops orolingual
angioedema. Which of the following drugs may have
increased the risk of developing orolingual angioedema
in this patient?
A. ACE inhibitor.
B. GP IIb/IIIa receptor antagonist.
C. Phosphodiesterase inhibitor.
D. Thiazide diuretic.
Correct answer = A. ACE inhibitors, aspirin, and prasug-
rel all have possible adverse effects including orolingual
angioedema. In the setting of alteplase administration, ACE
inhibitors have been associated with an increased risk of
developing orolingual angioedema with concomitant use.
