Drugs for protozoal infections: pharmacology MCQs With Answer

Drugs for protozoal infections: pharmacology MCQs With Answer is a focused study aid designed for M.Pharm students taking Advanced Pharmacology-II. This collection emphasizes mechanisms of action, pharmacokinetics, resistance, clinical indications, adverse effects and drug interactions of antiprotozoal agents used against malaria, leishmaniasis, trypanosomiasis, amoebiasis, giardiasis, toxoplasmosis and other protozoal diseases. Each question is crafted to test deeper conceptual understanding and clinical application rather than rote memorization, helping prepare for exams and practical therapeutics. Answers are provided clearly to facilitate self-assessment, and explanations are implied by option choice emphasis to encourage further reading on key topics such as radical cure, CNS penetration, and safety in pregnancy and G6PD deficiency.

Q1. Which of the following best describes the primary antiplasmodial mechanism of artemisinins?

• Inhibition of haem polymerization in the parasite food vacuole
• Intercalation into parasite DNA causing strand breaks
• Endoperoxide cleavage activated by ferrous heme generating free radicals that damage parasite proteins and membranes
• Selective inhibition of parasite dihydrofolate reductase

Correct Answer: Endoperoxide cleavage activated by ferrous heme generating free radicals that damage parasite proteins and membranes

Q2. Which antimalarial is most strongly associated with hemolytic anemia in patients with G6PD deficiency?

• Chloroquine
• Primaquine
• Atovaquone
• Doxycycline

Correct Answer: Primaquine

Q3. What is the recommended first-line parenteral therapy for severe Plasmodium falciparum malaria (including cerebral malaria) in current guidelines?

• Intravenous artesunate
• Intravenous quinidine
• Intramuscular artemether
• Oral artemether-lumefantrine

Correct Answer: Intravenous artesunate

Q4. Sulfadoxine-pyrimethamine acts by which pharmacological mechanism against Plasmodium species?

• Inhibition of heme detoxification by binding free heme
• Sequential inhibition of dihydropteroate synthase and dihydrofolate reductase in the folate synthesis pathway
• Disruption of parasite microtubule assembly
• Inhibition of mitochondrial cytochrome bc1 complex

Correct Answer: Sequential inhibition of dihydropteroate synthase and dihydrofolate reductase in the folate synthesis pathway

Q5. Which molecular mechanism most commonly mediates chloroquine resistance in Plasmodium falciparum?

• Mutations in dihydrofolate reductase decreasing drug binding
• Increased drug metabolism by parasite enzymes
• Mutations in pfcrt leading to decreased intravacuolar accumulation by enhanced efflux
• Alteration of parasite mitochondrial ribosomes

Correct Answer: Mutations in pfcrt leading to decreased intravacuolar accumulation by enhanced efflux

Q6. Which luminal amoebicide is preferred during pregnancy for eradication of Entamoeba histolytica cysts in the gut?

• Metronidazole
• Tinidazole
• Paromomycin
• Chloroquine

Correct Answer: Paromomycin

Q7. Which antiprotozoal drug commonly causes a disulfiram-like reaction if alcohol is consumed concurrently?

• Metronidazole
• Paromomycin
• Pyrimethamine
• Atovaquone

Correct Answer: Metronidazole

Q8. What is the main mechanism of action of atovaquone against Plasmodium and Babesia species?

• Inhibition of heme polymerization in the food vacuole
• Selective inhibition of parasitic dihydrofolate reductase
• Inhibition of mitochondrial electron transport at the cytochrome bc1 complex
• Interference with microtubule formation

Correct Answer: Inhibition of mitochondrial electron transport at the cytochrome bc1 complex

Q9. For late-stage human African trypanosomiasis (Trypanosoma brucei gambiense) with CNS involvement, which drug is specifically indicated and relatively preferred for its CNS efficacy?

• Suramin
• Melarsoprol
• Eflornithine (often in combination with nifurtimox)
• Pentamidine

Correct Answer: Eflornithine (often in combination with nifurtimox)

Q10. Which adverse metabolic effect is characteristically associated with pentamidine therapy?

• Renal tubular acidosis
• Pancreatic beta-cell toxicity leading to hypoglycaemia and possible subsequent diabetes
• Severe hyperlipidaemia
• Cholestatic liver injury

Correct Answer: Pancreatic beta-cell toxicity leading to hypoglycaemia and possible subsequent diabetes

Q11. Which antimalarial is used for radical cure of Plasmodium vivax and P. ovale by eliminating hepatic hypnozoites?

• Chloroquine
• Primaquine
• Mefloquine
• Proguanil

Correct Answer: Primaquine

Q12. Which antimalarial primarily acts by inhibiting heme polymerization in the parasite food vacuole?

• Chloroquine
• Artemisinin
• Atovaquone
• Doxycycline

Correct Answer: Chloroquine

Q13. Which antileishmanial agent is orally active and is contraindicated in pregnancy due to teratogenicity?

• Amphotericin B (liposomal)
• Sodium stibogluconate (pentavalent antimonial)
• Miltefosine
• Paromomycin (topical/systemic)

Correct Answer: Miltefosine

Q14. What is the principal mode of action of nifurtimox and benznidazole used in Chagas disease?

• Direct inhibition of parasite DNA gyrase
• Generation of reactive oxygen/nitrogen species via nitro-reduction causing oxidative damage to the parasite
• Inhibition of ergosterol synthesis in parasite membranes
• Blocking microtubule polymerization

Correct Answer: Generation of reactive oxygen/nitrogen species via nitro-reduction causing oxidative damage to the parasite

Q15. Artemisinin derivatives have clinically significant drug interactions because they primarily do which of the following to hepatic cytochrome P450 enzymes?

• Potently inhibit CYP2C9 leading to accumulation of warfarin
• Induce CYP3A4 and other CYPs, potentially reducing plasma concentrations of co-administered drugs
• Irreversibly inhibit CYP1A2 causing long-lasting interactions
• Do not interact with cytochrome P450 enzymes

Correct Answer: Induce CYP3A4 and other CYPs, potentially reducing plasma concentrations of co-administered drugs

Q16. Which of the following is the first-line treatment for symptomatic giardiasis in adults?

• Tinidazole single dose only
• Metronidazole (multiple-day regimen)
• Paromomycin (systemic)
• Chloroquine

Correct Answer: Metronidazole (multiple-day regimen)

Q17. Miltefosine exerts its antileishmanial effects primarily by which cellular mechanism?

• Inhibition of DNA topoisomerase II
• Alkylation of parasite proteins via a nitro group
• Disruption of membrane lipid metabolism and interference with phospholipid biosynthesis inducing apoptosis-like death
• Blocking calcium channels on parasite surface

Correct Answer: Disruption of membrane lipid metabolism and interference with phospholipid biosynthesis inducing apoptosis-like death

Q18. Which antiprotozoal can cause bone marrow suppression and megaloblastic anemia through folate antagonism and therefore often requires folinic acid rescue?

• Pyrimethamine
• Atovaquone
• Paromomycin
• Metronidazole

Correct Answer: Pyrimethamine

Q19. For short-term chemoprophylaxis against chloroquine-resistant Plasmodium falciparum in travelers, which regimen is often preferred for its rapid onset and short post-exposure dosing?

• Mefloquine weekly
• Atovaquone–proguanil daily
• Chloroquine weekly
• Doxycycline weekly

Correct Answer: Atovaquone–proguanil daily

Q20. Nitazoxanide exerts antiparasitic activity by inhibiting which metabolic pathway in anaerobic protozoa and some helminths?

• Parasite DNA synthesis through topoisomerase inhibition
• Pyruvate:ferredoxin oxidoreductase (PFOR)-dependent electron transfer required for anaerobic energy metabolism
• Heme polymerization in food vacuole
• Folate synthesis by inhibiting dihydrofolate reductase

Correct Answer: Pyruvate:ferredoxin oxidoreductase (PFOR)-dependent electron transfer required for anaerobic energy metabolism

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