Anthelmintics – classification and mechanism MCQs With Answer

Anthelmintics – classification and mechanism MCQs With Answer

Anthelmintics are drugs used to treat helminthic infections; understanding their classification, mechanisms, spectra, pharmacokinetics and resistance is essential for B. Pharm students. This concise, keyword-rich introduction covers major classes—benzimidazoles, macrocyclic lactones, praziquantel, imidazothiazoles, tetrahydropyrimidines and salicylanilides—and explains mechanisms such as β-tubulin binding, glutamate-gated chloride channel activation, nicotinic receptor agonism and tegumental Ca2+ disruption. Clinical indications, adverse effects, pregnancy cautions and common resistance mechanisms (β-tubulin mutations, P-glycoprotein efflux) are emphasized to deepen mechanistic insight. Clear MCQs will test pharmacology, drug choice for specific helminths and drug–host interactions. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. Which mechanism best describes how benzimidazoles (e.g., albendazole, mebendazole) exert their anthelmintic effect?

• Inhibition of cholinesterase at neuromuscular junctions
• Binding to β-tubulin to prevent microtubule polymerization
• Activation of glutamate-gated chloride channels
• Disruption of tegument by increasing Ca2+ influx

Correct Answer: Binding to β-tubulin to prevent microtubule polymerization

Q2. Which anthelmintic causes flaccid paralysis of nematodes by acting as a GABA agonist at inhibitory neuromuscular receptors?

• Levamisole
• Piperazine
• Praziquantel
• Ivermectin

Correct Answer: Piperazine

Q3. Levamisole’s primary mechanism of anthelmintic action involves:

• Inhibition of oxidative phosphorylation in helminths
• Agonism at nicotinic acetylcholine receptors causing spastic paralysis
• Blocking glutamate-gated chloride channels
• Interfering with DNA synthesis

Correct Answer: Agonism at nicotinic acetylcholine receptors causing spastic paralysis

Q4. Ivermectin targets which channels in invertebrates to produce paralysis and death of parasites?

• Voltage-gated sodium channels
• Glutamate-gated chloride channels
• Nicotinic acetylcholine receptors
• GABA transporters

Correct Answer: Glutamate-gated chloride channels

Q5. Praziquantel’s anthelmintic action is mainly due to:

• Inhibition of microtubule assembly
• Blockade of acetylcholinesterase
• Increase in Ca2+ permeability causing tegumental disruption
• Competitive inhibition of parasitic enzymes in glycolysis

Correct Answer: Increase in Ca2+ permeability causing tegumental disruption

Q6. Niclosamide’s principal mechanism against cestodes is:

• Inhibition of oxidative phosphorylation in the parasite mitochondria
• Activation of nicotinic receptors causing paralysis
• Inhibition of β-tubulin polymerization
• Disruption of parasite RNA synthesis

Correct Answer: Inhibition of oxidative phosphorylation in the parasite mitochondria

Q7. Which drug is the preferred oral treatment for intestinal tapeworms like Taenia saginata?

• Albendazole
• Niclosamide
• Metrifonate
• Piperazine

Correct Answer: Niclosamide

Q8. The drug of choice for onchocerciasis (river blindness) is:

• Diethylcarbamazine (DEC)
• Ivermectin
• Mebendazole
• Praziquantel

Correct Answer: Ivermectin

Q9. Diethylcarbamazine (DEC) reduces microfilarial burden primarily by:

• Directly inhibiting microtubule synthesis
• Altering microfilarial surface and enhancing host immune clearance
• Blocking parasite neuromuscular transmission via nicotinic receptors
• Inhibiting glutamate-gated chloride channels

Correct Answer: Altering microfilarial surface and enhancing host immune clearance

Q10. Which organophosphate used as an anthelmintic inhibits acetylcholinesterase?

• Trichlorfon
• Albendazole
• Praziquantel
• Niclosamide

Correct Answer: Trichlorfon

Q11. Between albendazole and mebendazole, which has better systemic absorption and improved bioavailability when taken with fatty meals?

• Mebendazole
• Albendazole
• Both have equal absorption
• Neither is absorbed systemically

Correct Answer: Albendazole

Q12. A common molecular mechanism of resistance to benzimidazoles in helminths involves:

• Overexpression of acetylcholinesterase
• Mutations in the β-tubulin gene reducing drug binding
• Upregulation of glutamate-gated chloride channels
• Increased tegumental Ca2+ influx

Correct Answer: Mutations in the β-tubulin gene reducing drug binding

Q13. Which anthelmintic is contraindicated or avoided during pregnancy due to teratogenic risk in animal studies?

• Piperazine
• Albendazole
• Praziquantel
• Ivermectin

Correct Answer: Albendazole

Q14. The Mazzotti reaction (fever, pruritus, lymphadenopathy) is classically associated with treatment of onchocerciasis using which drug?

• Praziquantel
• Diethylcarbamazine (DEC)
• Niclosamide
• Mebendazole

Correct Answer: Diethylcarbamazine (DEC)

Q15. Praziquantel is highly effective against which groups of parasites?

• Nematodes only
• Trematodes and cestodes
• Bacteria and protozoa
• Fungi and viruses

Correct Answer: Trematodes and cestodes

Q16. A serious adverse neurologic reaction (encephalopathy) after ivermectin administration is most likely in patients heavily infected with which parasite?

• Ascaris lumbricoides
• Loa loa
• Taenia solium
• Ancylostoma duodenale

Correct Answer: Loa loa

Q17. Albendazole is converted in the liver to an active metabolite known as:

• Albendazole sulphate
• Albendazole sulfoxide
• Albendazole glucuronide
• Albendazole phosphate

Correct Answer: Albendazole sulfoxide

Q18. The drug of choice for neurocysticercosis is:

• Piperazine
• Praziquantel
• Albendazole
• Niclosamide

Correct Answer: Albendazole

Q19. Parasite selectivity of benzimidazoles is largely due to:

• Higher affinity of the drugs for parasite β-tubulin than mammalian β-tubulin
• Inability of the drug to cross the parasite gut
• Selective activation by human liver enzymes
• Binding to mammalian receptors only at high doses

Correct Answer: Higher affinity of the drugs for parasite β-tubulin than mammalian β-tubulin

Q20. Schistosomiasis is best treated with which anthelmintic?

• Ivermectin
• Praziquantel
• Piperazine
• Mebendazole

Correct Answer: Praziquantel

Q21. Macrocyclic lactone resistance (e.g., to ivermectin) in helminths is frequently associated with:

• Mutations in acetylcholinesterase gene
• Increased expression of P-glycoprotein efflux pumps
• Enhanced tegumental Ca2+ influx
• Loss of β-tubulin

Correct Answer: Increased expression of P-glycoprotein efflux pumps

Q22. Which drug is preferred for treating Strongyloides stercoralis infection?

• Mebendazole
• Piperazine
• Ivermectin
• Praziquantel

Correct Answer: Ivermectin

Q23. Which anthelmintic is poorly absorbed from the gut and acts primarily within the intestinal lumen against nematodes?

• Albendazole
• Mebendazole
• Ivermectin
• Diethylcarbamazine (DEC)

Correct Answer: Mebendazole

Q24. Which drug is specifically effective against both adult and larval forms of many cestodes and trematodes by disrupting parasite tegument?

• Nicotinic agonists like levamisole
• Praziquantel
• Piperazine
• Trichlorfon

Correct Answer: Praziquantel

Q25. Benzimidazoles impair glucose uptake in helminths primarily by:

• Inhibiting glycolytic enzymes directly
• Preventing microtubule formation needed for vesicular transport of glucose
• Blocking glucose transporters in human enterocytes
• Stimulating parasite glycolysis to toxic levels

Correct Answer: Preventing microtubule formation needed for vesicular transport of glucose

Q26. Which salicylanilide derivative is used as an anthelmintic for cestodes?

• Niclosamide
• Albendazole
• Ivermectin
• Mebendazole

Correct Answer: Niclosamide

Q27. For which helminth infection is praziquantel the recommended therapy?

• Trichuris trichiura
• Schistosoma mansoni
• Enterobius vermicularis
• Strongyloides stercoralis

Correct Answer: Schistosoma mansoni

Q28. Which drug is most appropriate for cutaneous larva migrans or certain resistant nematode infections?

• Praziquantel
• Ivermectin
• Niclosamide
• Trichlorfon

Correct Answer: Ivermectin

Q29. Which of the following statements about niclosamide is correct?

• It is systemically absorbed and treats tissue cysts
• It is poorly absorbed and used for intestinal tapeworms
• It acts by stimulating nicotinic receptors
• It is the drug of choice for onchocerciasis

Correct Answer: It is poorly absorbed and used for intestinal tapeworms

Q30. Metrifonate, formerly used for Schistosoma haematobium, acts by:

• Inhibiting β-tubulin polymerization
• Inhibiting acetylcholinesterase
• Activating glutamate-gated chloride channels
• Disrupting parasite tegument via Ca2+ influx

Correct Answer: Inhibiting acetylcholinesterase

G S Sachin

I am a Registered Pharmacist under the Pharmacy Act, 1948, and the founder of PharmacyFreak.com. I hold a Bachelor of Pharmacy degree from Rungta College of Pharmaceutical Science and Research. With a strong academic foundation and practical knowledge, I am committed to providing accurate, easy-to-understand content to support pharmacy students and professionals. My aim is to make complex pharmaceutical concepts accessible and useful for real-world application.

Mail- Sachin@pharmacyfreak.com