, Question 1
A patient receiving continuous IV heparin develops a sudden platelet drop
from 250,000 to 60,000/µL with new thrombosis. Which mechanism best
explains this paradoxical prothrombotic state?
A. Heparin-induced thrombocytopenia (HIT) type II mediated by IgG
antibodies against platelet factor 4-heparin complexes
B. Direct heparin activation of antithrombin III causing platelet
consumption
C. Immune-mediated destruction of megakaryocytes in the bone marrow
D. Heparin-induced fibrinolysis causing rebound thrombin generation
Correct Answer: A - Heparin-induced thrombocytopenia (HIT)
type II mediated by IgG antibodies against platelet factor
4-heparin complexes
RATIONALE
HIT type II is an immune-mediated disorder in which IgG antibodies
bind PF4-heparin complexes, activating platelets and triggering
thrombosis despite thrombocytopenia. Antithrombin III activation is
the therapeutic mechanism, not the cause of HIT. Bone marrow
megakaryocyte destruction and fibrinolysis are not features of HIT.
Question 2
Which pharmacokinetic parameter is most useful for predicting the time
required to reach steady-state plasma concentration during a continuous IV
infusion?
A. Volume of distribution (Vd)
B. Elimination half-life (t½)
C. Bioavailability (F)
D. Peak plasma concentration (Cmax)
Correct Answer: B - Elimination half-life (t½)
Page 2
, RATIONALE
Steady state is reached after approximately 4-5 half-lives regardless of
infusion rate or dose, making t½ the key determinant. Vd affects
loading dose, F applies to extravascular routes, and Cmax is a
resultant concentration, not a predictor of time to steady state.
Question 3
A patient on warfarin is prescribed trimethoprim-sulfamethoxazole for a UTI.
Which interaction best explains the anticipated INR rise?
A. TMP-SMX induces CYP2C9, accelerating warfarin metabolism
B. TMP-SMX displaces warfarin from albumin and inhibits CYP2C9
C. TMP-SMX increases vitamin K absorption, enhancing warfarin effect
D. TMP-SMX inhibits platelet aggregation, independently raising INR
Correct Answer: B - TMP-SMX displaces warfarin from albumin
and inhibits CYP2C9
RATIONALE
TMP-SMX inhibits CYP2C9 (the primary enzyme metabolizing
S-warfarin) and displaces warfarin from plasma proteins, both
increasing free active drug and INR. Induction of CYP2C9 would
lower INR, vitamin K absorption is not enhanced, and platelet
inhibition does not affect INR.
Question 4
Which finding most strongly indicates digoxin toxicity in a patient with
hypokalemia?
A. Serum digoxin level of 1.2 ng/mL
B. New-onset atrial fibrillation with rapid ventricular response
C. Visual halos and yellow-green discoloration with nausea
D. Blood pressure 150/90 mmHg
Correct Answer: C - Visual halos and yellow-green discoloration
Page 3
, with nausea
RATIONALE
Visual disturbances (halos, color changes) and GI symptoms are
classic signs of digoxin toxicity, exacerbated by hypokalemia which
increases digoxin binding to Na+/K+-ATPase. A level of 1.2 ng/mL is
therapeutic, atrial fibrillation is not typical, and hypertension is
nonspecific.
Question 5
A patient with myasthenia gravis is started on pyridostigmine. Which
concurrent medication would most likely precipitate a cholinergic crisis?
A. Prednisone
B. Neostigmine
C. Atropine
D. Albuterol
Correct Answer: B - Neostigmine
RATIONALE
Neostigmine, like pyridostigmine, is an acetylcholinesterase inhibitor;
combining them can cause excessive acetylcholine and cholinergic
crisis. Prednisone is an immunosuppressant used in MG but not
cholinergic. Atropine is anticholinergic and would oppose cholinergic
effects. Albuterol is a beta-2 agonist with no direct cholinergic action.
Question 6
Which statement best explains why levodopa is combined with carbidopa in
Parkinson disease therapy?
A. Carbidopa crosses the blood-brain barrier and enhances dopamine
synthesis
B. Carbidopa inhibits peripheral decarboxylase, increasing levodopa
delivery to the CNS
Page 4
A patient receiving continuous IV heparin develops a sudden platelet drop
from 250,000 to 60,000/µL with new thrombosis. Which mechanism best
explains this paradoxical prothrombotic state?
A. Heparin-induced thrombocytopenia (HIT) type II mediated by IgG
antibodies against platelet factor 4-heparin complexes
B. Direct heparin activation of antithrombin III causing platelet
consumption
C. Immune-mediated destruction of megakaryocytes in the bone marrow
D. Heparin-induced fibrinolysis causing rebound thrombin generation
Correct Answer: A - Heparin-induced thrombocytopenia (HIT)
type II mediated by IgG antibodies against platelet factor
4-heparin complexes
RATIONALE
HIT type II is an immune-mediated disorder in which IgG antibodies
bind PF4-heparin complexes, activating platelets and triggering
thrombosis despite thrombocytopenia. Antithrombin III activation is
the therapeutic mechanism, not the cause of HIT. Bone marrow
megakaryocyte destruction and fibrinolysis are not features of HIT.
Question 2
Which pharmacokinetic parameter is most useful for predicting the time
required to reach steady-state plasma concentration during a continuous IV
infusion?
A. Volume of distribution (Vd)
B. Elimination half-life (t½)
C. Bioavailability (F)
D. Peak plasma concentration (Cmax)
Correct Answer: B - Elimination half-life (t½)
Page 2
, RATIONALE
Steady state is reached after approximately 4-5 half-lives regardless of
infusion rate or dose, making t½ the key determinant. Vd affects
loading dose, F applies to extravascular routes, and Cmax is a
resultant concentration, not a predictor of time to steady state.
Question 3
A patient on warfarin is prescribed trimethoprim-sulfamethoxazole for a UTI.
Which interaction best explains the anticipated INR rise?
A. TMP-SMX induces CYP2C9, accelerating warfarin metabolism
B. TMP-SMX displaces warfarin from albumin and inhibits CYP2C9
C. TMP-SMX increases vitamin K absorption, enhancing warfarin effect
D. TMP-SMX inhibits platelet aggregation, independently raising INR
Correct Answer: B - TMP-SMX displaces warfarin from albumin
and inhibits CYP2C9
RATIONALE
TMP-SMX inhibits CYP2C9 (the primary enzyme metabolizing
S-warfarin) and displaces warfarin from plasma proteins, both
increasing free active drug and INR. Induction of CYP2C9 would
lower INR, vitamin K absorption is not enhanced, and platelet
inhibition does not affect INR.
Question 4
Which finding most strongly indicates digoxin toxicity in a patient with
hypokalemia?
A. Serum digoxin level of 1.2 ng/mL
B. New-onset atrial fibrillation with rapid ventricular response
C. Visual halos and yellow-green discoloration with nausea
D. Blood pressure 150/90 mmHg
Correct Answer: C - Visual halos and yellow-green discoloration
Page 3
, with nausea
RATIONALE
Visual disturbances (halos, color changes) and GI symptoms are
classic signs of digoxin toxicity, exacerbated by hypokalemia which
increases digoxin binding to Na+/K+-ATPase. A level of 1.2 ng/mL is
therapeutic, atrial fibrillation is not typical, and hypertension is
nonspecific.
Question 5
A patient with myasthenia gravis is started on pyridostigmine. Which
concurrent medication would most likely precipitate a cholinergic crisis?
A. Prednisone
B. Neostigmine
C. Atropine
D. Albuterol
Correct Answer: B - Neostigmine
RATIONALE
Neostigmine, like pyridostigmine, is an acetylcholinesterase inhibitor;
combining them can cause excessive acetylcholine and cholinergic
crisis. Prednisone is an immunosuppressant used in MG but not
cholinergic. Atropine is anticholinergic and would oppose cholinergic
effects. Albuterol is a beta-2 agonist with no direct cholinergic action.
Question 6
Which statement best explains why levodopa is combined with carbidopa in
Parkinson disease therapy?
A. Carbidopa crosses the blood-brain barrier and enhances dopamine
synthesis
B. Carbidopa inhibits peripheral decarboxylase, increasing levodopa
delivery to the CNS
Page 4
