Quiz 9: Antiprotozoal & Anthelmintic Therapeutics Advanced Pharmacology NP Board Exam
Preparation • 10 Practice Questions & Rationales
1. What is the mechanism of action of Metronidazole (Flagyl)?
A. Inhibition of fungal ergosterol synthesis
B. Nitro group reduction forming cytotoxic radicals that break microbial DNA strands
C. Opening glutamate-gated chloride channels
D. Blockade of dihydrofolate reductase
Correct Answer: B — Metronidazole is reduced by nitroreductases in anaerobic organisms/protozoa to toxic free radical
intermediates that cause DNA strand breakage and cell death.
2. What clinical reaction occurs when Metronidazole is taken concurrently with Alcohol?
A. Rapid drug inactivation and treatment failure
B. Disulfiram-like reaction (flushing, severe nausea, vomiting, tachycardia, diaphoresis)
C. Sudden severe hyperkalemia
D. Acute renal tubular necrosis
Correct Answer: B — Metronidazole inhibits aldehyde dehydrogenase. Ingestion of alcohol causes accumulation of acetaldehyde,
precipitating a severe disulfiram-like reaction.
3. In treating invasive intestinal or extraintestinal Amebiasis (Entamoeba histolytica), why must Metronidazole be
followed by a Luminal Amebicide (e.g., Paromomycin or Iodoquinol)?
A. Metronidazole only treats lung lesions
B. Metronidazole cures tissue invasion but luminal amebicides are required to eradicate asymptomatic intestinal cysts
C. To prevent metronidazole-induced renal failure
D. Luminal amebicides cure systemic liver abscesses
Correct Answer: B — Metronidazole is completely absorbed systemically, curing tissue amebiasis, but achieves inadequate luminal
concentrations to clear intestinal cysts; luminal agents clear colonization.
4. What is the Drug of Choice for acute Giardiasis?
A. Chloroquine
B. Metronidazole (or Tinidazole / Nitazoxanide)
C. Ivermectin
D. Primaquine
Correct Answer: B — Metronidazole (5-day course) or single-dose Tinidazole is the drug of choice for Giardia lamblia.
NP Advanced Pharmacology Exam Practice Questions Page 1 of 3
Preparation • 10 Practice Questions & Rationales
1. What is the mechanism of action of Metronidazole (Flagyl)?
A. Inhibition of fungal ergosterol synthesis
B. Nitro group reduction forming cytotoxic radicals that break microbial DNA strands
C. Opening glutamate-gated chloride channels
D. Blockade of dihydrofolate reductase
Correct Answer: B — Metronidazole is reduced by nitroreductases in anaerobic organisms/protozoa to toxic free radical
intermediates that cause DNA strand breakage and cell death.
2. What clinical reaction occurs when Metronidazole is taken concurrently with Alcohol?
A. Rapid drug inactivation and treatment failure
B. Disulfiram-like reaction (flushing, severe nausea, vomiting, tachycardia, diaphoresis)
C. Sudden severe hyperkalemia
D. Acute renal tubular necrosis
Correct Answer: B — Metronidazole inhibits aldehyde dehydrogenase. Ingestion of alcohol causes accumulation of acetaldehyde,
precipitating a severe disulfiram-like reaction.
3. In treating invasive intestinal or extraintestinal Amebiasis (Entamoeba histolytica), why must Metronidazole be
followed by a Luminal Amebicide (e.g., Paromomycin or Iodoquinol)?
A. Metronidazole only treats lung lesions
B. Metronidazole cures tissue invasion but luminal amebicides are required to eradicate asymptomatic intestinal cysts
C. To prevent metronidazole-induced renal failure
D. Luminal amebicides cure systemic liver abscesses
Correct Answer: B — Metronidazole is completely absorbed systemically, curing tissue amebiasis, but achieves inadequate luminal
concentrations to clear intestinal cysts; luminal agents clear colonization.
4. What is the Drug of Choice for acute Giardiasis?
A. Chloroquine
B. Metronidazole (or Tinidazole / Nitazoxanide)
C. Ivermectin
D. Primaquine
Correct Answer: B — Metronidazole (5-day course) or single-dose Tinidazole is the drug of choice for Giardia lamblia.
NP Advanced Pharmacology Exam Practice Questions Page 1 of 3
