Quiz 4: 50S Protein Synthesis Inhibitors (Macrolides, Clindamycin,
Linezolid) Advanced Pharmacology NP Board Exam Preparation • 10 Practice Questions & Rationales
1. What is the mechanism of action of Macrolides (e.g., Azithromycin, Erythromycin)?
A. Binding 30S subunit and causing code misreading
B. Irreversibly binding 50S subunit (23S rRNA) and inhibiting translocation
C. Inhibiting topoisomerase IV
D. Cleaving the cell wall peptidoglycan layer
Correct Answer: B — Macrolides bind to the 50S ribosomal subunit (specifically 23S rRNA) and block translocation of the nascent
peptide chain.
2. Which macrolide antibiotic does NOT inhibit Cytochrome P450 3A4 enzymes and has minimal hepatic drug
interactions?
A. Erythromycin
B. Clarithromycin
C. Telithromycin
D. Azithromycin
Correct Answer: D — Unlike Erythromycin and Clarithromycin, Azithromycin does not significantly inhibit CYP3A4.
3. What cardiac safety warning applies to all Macrolide antibiotics?
A. Severe hypertension and reflex bradycardia
B. QTc prolongation and risk of Torsades de Pointes
C. Complete heart block
D. Acute pericarditis
Correct Answer: B — Macrolides can prolong the QTc interval and predispose patients to dangerous ventricular arrhythmias
including Torsades de Pointes.
4. What is the primary clinical indication for Fidaxomicin (Dificid)?
A. Systemic Pseudomonas aeruginosa sepsis
B. First-line oral treatment for Clostridioides difficile colitis
C. Methicillin-resistant Staphylococcus aureus bacteremia
D. Cryptococcal meningitis
Correct Answer: B — Fidaxomicin is a macrocyclic antibiotic with narrow spectrum bactericidal activity against C. difficile; minimal
systemic absorption allows targeted gut action.
NP Advanced Pharmacology Exam Practice Questions Page 1 of 3
Linezolid) Advanced Pharmacology NP Board Exam Preparation • 10 Practice Questions & Rationales
1. What is the mechanism of action of Macrolides (e.g., Azithromycin, Erythromycin)?
A. Binding 30S subunit and causing code misreading
B. Irreversibly binding 50S subunit (23S rRNA) and inhibiting translocation
C. Inhibiting topoisomerase IV
D. Cleaving the cell wall peptidoglycan layer
Correct Answer: B — Macrolides bind to the 50S ribosomal subunit (specifically 23S rRNA) and block translocation of the nascent
peptide chain.
2. Which macrolide antibiotic does NOT inhibit Cytochrome P450 3A4 enzymes and has minimal hepatic drug
interactions?
A. Erythromycin
B. Clarithromycin
C. Telithromycin
D. Azithromycin
Correct Answer: D — Unlike Erythromycin and Clarithromycin, Azithromycin does not significantly inhibit CYP3A4.
3. What cardiac safety warning applies to all Macrolide antibiotics?
A. Severe hypertension and reflex bradycardia
B. QTc prolongation and risk of Torsades de Pointes
C. Complete heart block
D. Acute pericarditis
Correct Answer: B — Macrolides can prolong the QTc interval and predispose patients to dangerous ventricular arrhythmias
including Torsades de Pointes.
4. What is the primary clinical indication for Fidaxomicin (Dificid)?
A. Systemic Pseudomonas aeruginosa sepsis
B. First-line oral treatment for Clostridioides difficile colitis
C. Methicillin-resistant Staphylococcus aureus bacteremia
D. Cryptococcal meningitis
Correct Answer: B — Fidaxomicin is a macrocyclic antibiotic with narrow spectrum bactericidal activity against C. difficile; minimal
systemic absorption allows targeted gut action.
NP Advanced Pharmacology Exam Practice Questions Page 1 of 3
