, Question 1
A patient with vancomycin-resistant Enterococcus faecium bacteremia is
prescribed daptomycin. Which monitoring parameter is most critical to prevent
a serious adverse effect?
A. Serum creatinine kinase levels
B. Liver function tests
C. Complete blood count with differential
D. Serum potassium and magnesium
Correct Answer: A - Serum creatinine kinase levels
RATIONALE
Daptomycin can cause myopathy, so monitoring creatine kinase (CK)
is essential. Other options are not the primary concern; liver enzymes
and CBC are not routinely affected, and electrolytes are not directly
linked to daptomycin toxicity.
Question 2
Which statement best describes the mechanism by which beta-lactamase
inhibitors restore beta-lactam activity?
A. They irreversibly bind to beta-lactamase enzymes, preventing
hydrolysis of the companion beta-lactam.
B. They inhibit efflux pumps, increasing intracellular beta-lactam
concentrations.
C. They modify penicillin-binding proteins to increase beta-lactam
affinity.
D. They reduce porin expression in Gram-negative bacteria, enhancing
drug entry.
Correct Answer: A - They irreversibly bind to beta-lactamase
enzymes, preventing hydrolysis of the companion beta-lactam.
Page 2
, RATIONALE
Beta-lactamase inhibitors (e.g., clavulanate, tazobactam, avibactam)
act as suicide substrates that covalently bind beta-lactamases,
protecting the beta-lactam antibiotic. Efflux pump inhibition, PBP
modification, and porin changes are not their primary mechanisms.
Question 3
A patient with invasive aspergillosis is started on voriconazole. Which
pharmacokinetic property most strongly justifies therapeutic drug monitoring
for this agent?
A. Nonlinear, saturable metabolism via CYP2C19 leading to wide
interpatient variability
B. Renal elimination unchanged, requiring dose adjustment in CKD
C. High protein binding that displaces other drugs
D. Autoinduction of CYP3A4 resulting in decreased levels over time
Correct Answer: A - Nonlinear, saturable metabolism via
CYP2C19 leading to wide interpatient variability
RATIONALE
Voriconazole exhibits nonlinear pharmacokinetics due to saturable
CYP2C19 metabolism, causing unpredictable plasma concentrations
and necessitating TDM. Renal elimination, protein binding, and
autoinduction are not the main reasons for TDM.
Question 4
In a patient with penicillin allergy who requires prophylaxis for dental
procedures, which alternative is most appropriate according to current
guidelines?
A. Clindamycin 600 mg PO 1 hour before procedure
B. Azithromycin 500 mg PO 1 hour before procedure
C. Cephalexin 2 g PO 1 hour before procedure
Page 3
, D. Doxycycline 100 mg PO 1 hour before procedure
Correct Answer: B - Azithromycin 500 mg PO 1 hour before
procedure
RATIONALE
Current AHA guidelines recommend azithromycin or clarithromycin
for penicillin-allergic patients. Clindamycin is no longer preferred due
to C. difficile risk; cephalexin has cross-reactivity potential;
doxycycline is not recommended for prophylaxis.
Question 5
Which of the following best explains why rifampin is contraindicated with
certain protease inhibitors in HIV therapy?
A. Rifampin induces CYP3A4, significantly reducing protease inhibitor
levels.
B. Rifampin inhibits CYP3A4, increasing protease inhibitor toxicity.
C. Rifampin chelates protease inhibitors in the gut, reducing absorption.
D. Rifampin alters gastric pH, decreasing protease inhibitor solubility.
Correct Answer: A - Rifampin induces CYP3A4, significantly
reducing protease inhibitor levels.
RATIONALE
Rifampin is a potent CYP3A4 inducer, leading to subtherapeutic
protease inhibitor concentrations and risk of HIV resistance.
Inhibition, chelation, and pH effects are not the primary mechanisms.
Question 6
A patient on isoniazid for latent tuberculosis develops peripheral neuropathy.
Which intervention is most appropriate?
A. Discontinue isoniazid immediately
B. Add pyridoxine (vitamin B6) 25-50 mg/day
Page 4
A patient with vancomycin-resistant Enterococcus faecium bacteremia is
prescribed daptomycin. Which monitoring parameter is most critical to prevent
a serious adverse effect?
A. Serum creatinine kinase levels
B. Liver function tests
C. Complete blood count with differential
D. Serum potassium and magnesium
Correct Answer: A - Serum creatinine kinase levels
RATIONALE
Daptomycin can cause myopathy, so monitoring creatine kinase (CK)
is essential. Other options are not the primary concern; liver enzymes
and CBC are not routinely affected, and electrolytes are not directly
linked to daptomycin toxicity.
Question 2
Which statement best describes the mechanism by which beta-lactamase
inhibitors restore beta-lactam activity?
A. They irreversibly bind to beta-lactamase enzymes, preventing
hydrolysis of the companion beta-lactam.
B. They inhibit efflux pumps, increasing intracellular beta-lactam
concentrations.
C. They modify penicillin-binding proteins to increase beta-lactam
affinity.
D. They reduce porin expression in Gram-negative bacteria, enhancing
drug entry.
Correct Answer: A - They irreversibly bind to beta-lactamase
enzymes, preventing hydrolysis of the companion beta-lactam.
Page 2
, RATIONALE
Beta-lactamase inhibitors (e.g., clavulanate, tazobactam, avibactam)
act as suicide substrates that covalently bind beta-lactamases,
protecting the beta-lactam antibiotic. Efflux pump inhibition, PBP
modification, and porin changes are not their primary mechanisms.
Question 3
A patient with invasive aspergillosis is started on voriconazole. Which
pharmacokinetic property most strongly justifies therapeutic drug monitoring
for this agent?
A. Nonlinear, saturable metabolism via CYP2C19 leading to wide
interpatient variability
B. Renal elimination unchanged, requiring dose adjustment in CKD
C. High protein binding that displaces other drugs
D. Autoinduction of CYP3A4 resulting in decreased levels over time
Correct Answer: A - Nonlinear, saturable metabolism via
CYP2C19 leading to wide interpatient variability
RATIONALE
Voriconazole exhibits nonlinear pharmacokinetics due to saturable
CYP2C19 metabolism, causing unpredictable plasma concentrations
and necessitating TDM. Renal elimination, protein binding, and
autoinduction are not the main reasons for TDM.
Question 4
In a patient with penicillin allergy who requires prophylaxis for dental
procedures, which alternative is most appropriate according to current
guidelines?
A. Clindamycin 600 mg PO 1 hour before procedure
B. Azithromycin 500 mg PO 1 hour before procedure
C. Cephalexin 2 g PO 1 hour before procedure
Page 3
, D. Doxycycline 100 mg PO 1 hour before procedure
Correct Answer: B - Azithromycin 500 mg PO 1 hour before
procedure
RATIONALE
Current AHA guidelines recommend azithromycin or clarithromycin
for penicillin-allergic patients. Clindamycin is no longer preferred due
to C. difficile risk; cephalexin has cross-reactivity potential;
doxycycline is not recommended for prophylaxis.
Question 5
Which of the following best explains why rifampin is contraindicated with
certain protease inhibitors in HIV therapy?
A. Rifampin induces CYP3A4, significantly reducing protease inhibitor
levels.
B. Rifampin inhibits CYP3A4, increasing protease inhibitor toxicity.
C. Rifampin chelates protease inhibitors in the gut, reducing absorption.
D. Rifampin alters gastric pH, decreasing protease inhibitor solubility.
Correct Answer: A - Rifampin induces CYP3A4, significantly
reducing protease inhibitor levels.
RATIONALE
Rifampin is a potent CYP3A4 inducer, leading to subtherapeutic
protease inhibitor concentrations and risk of HIV resistance.
Inhibition, chelation, and pH effects are not the primary mechanisms.
Question 6
A patient on isoniazid for latent tuberculosis develops peripheral neuropathy.
Which intervention is most appropriate?
A. Discontinue isoniazid immediately
B. Add pyridoxine (vitamin B6) 25-50 mg/day
Page 4
