Drugs for helminthiasis: pharmacology MCQs With Answer

Introduction: This collection of multiple-choice questions focuses on drugs for helminthiasis tailored to M.Pharm students studying Advanced Pharmacology-II. The quiz emphasizes pharmacodynamics, pharmacokinetics, resistance mechanisms, clinical uses, adverse effects, and important drug interactions of major anthelmintics such as benzimidazoles, praziquantel, ivermectin, levamisole, diethylcarbamazine and others. Questions are designed to probe in-depth understanding useful for exams and clinical pharmacology practice, including molecular targets (e.g., tubulin, glutamate-gated chloride channels), metabolic activation (albendazole sulfoxide), and therapy choices in special situations (pregnancy, co-infections like Loa loa). Use this set to test, revise and consolidate advanced concepts relevant to helminth therapy.

Q1. Which molecular mechanism best explains the primary mode of action of benzimidazole anthelmintics (e.g., albendazole, mebendazole)?

• Inhibition of parasite acetylcholinesterase causing continuous neuromuscular stimulation
• Binding to β-tubulin and inhibition of microtubule polymerization
• Activation of host immune-mediated cytotoxicity against microfilariae
• Increase in parasite membrane permeability to calcium ions

Correct Answer: Binding to β-tubulin and inhibition of microtubule polymerization

Q2. Albendazole requires hepatic metabolism to an active metabolite. Which hepatic metabolite mediates its anthelmintic activity?

• Albendazole sulfone
• Albendazole sulfoxide
• Albendazole glucuronide
• Albendazole N-oxide

Correct Answer: Albendazole sulfoxide

Q3. Praziquantel’s schistosomicidal effect primarily results from which pharmacological action?

• Inhibition of parasite microtubule assembly
• Blockade of GABA-mediated inhibitory transmission in the parasite
• Increase in tegumental permeability to calcium leading to spastic paralysis and tegumental disruption
• Interference with folate metabolism in helminths

Correct Answer: Increase in tegumental permeability to calcium leading to spastic paralysis and tegumental disruption

Q4. Ivermectin exerts its antiparasitic effect mainly by binding to which target in nematodes?

• Nicotinic acetylcholine receptors at the neuromuscular junction
• β-tubulin in microtubules
• Glutamate-gated chloride channels increasing chloride influx and causing paralysis
• Voltage-gated sodium channels causing hyperexcitability

Correct Answer: Glutamate-gated chloride channels increasing chloride influx and causing paralysis

Q5. Which statement is most accurate regarding the oral bioavailability of mebendazole compared with albendazole?

• Mebendazole has higher systemic bioavailability than albendazole when taken fasting
• Both drugs have nearly identical high oral bioavailability independent of diet
• Mebendazole has low oral bioavailability which increases with a fatty meal, whereas albendazole’s active metabolite formation is enhanced by fatty meals
• Albendazole is poorly absorbed and gives no active metabolite systemically

Correct Answer: Mebendazole has low oral bioavailability which increases with a fatty meal, whereas albendazole’s active metabolite formation is enhanced by fatty meals

Q6. A patient with suspected loiasis is being considered for ivermectin therapy. What is a key clinical concern with ivermectin in high Loa loa microfilarial loads?

• Risk of severe cholestatic jaundice
• Precipitation of fatal encephalopathy due to rapid microfilarial killing
• Ivermectin has no activity against Loa loa so treatment is ineffective
• Marked renal toxicity and acute tubular necrosis

Correct Answer: Precipitation of fatal encephalopathy due to rapid microfilarial killing

Q7. Diethylcarbamazine (DEC) is the drug of choice for certain filarial infections. Its primary proposed mechanism includes:

• Direct binding to parasite nicotinic receptors producing paralysis
• Microfilaricidal action by altering surface membranes making parasites susceptible to host immune attack
• Inhibition of parasite folate synthesis enzymes
• Blocking parasite calcium channels leading to paralysis

Correct Answer: Microfilaricidal action by altering surface membranes making parasites susceptible to host immune attack

Q8. Which anthelmintic is contraindicated or used with extreme caution in pregnancy, especially during the first trimester, due to teratogenicity observed in animal studies?

• Praziquantel
• Albendazole
• Piperazine
• Niclosamide

Correct Answer: Albendazole

Q9. Resistance to benzimidazoles in helminths is most commonly associated with which molecular change?

• Mutations in voltage-gated sodium channels
• Overexpression of P-glycoprotein efflux pumps only
• Point mutations in the β-tubulin gene reducing drug binding
• Altered glutamate-gated chloride channels

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

Q10. Which drug is preferred for treating Taenia saginata (adult beef tapeworm) infections and acts by inhibiting the parasite’s oxidative phosphorylation?

• Praziquantel
• Niclosamide
• Piperazine
• Diethylcarbamazine

Correct Answer: Niclosamide

Q11. Levamisole’s anthelmintic effect is primarily due to which pharmacodynamic action?

• GABA receptor agonism causing flaccid paralysis
• Agonism at nicotinic acetylcholine receptors causing spastic paralysis of nematodes
• Inhibition of microtubule polymerization
• Disruption of parasite tegument via calcium influx

Correct Answer: Agonism at nicotinic acetylcholine receptors causing spastic paralysis of nematodes

Q12. Which of the following is the most important clinical monitoring parameter after administering albendazole long-term for hydatid disease?

• Serum creatinine and renal function tests
• Complete blood count and liver function tests for hepatotoxicity and bone marrow suppression
• Serial ECGs for QT prolongation
• Blood glucose monitoring for induced hyperglycemia

Correct Answer: Complete blood count and liver function tests for hepatotoxicity and bone marrow suppression

Q13. Piperazine treats ascariasis by which mechanism of action?

• Blocking parasite calcium channels causing spastic contraction
• Acting as a GABA agonist at the neuromuscular junction causing flaccid paralysis
• Binding to β-tubulin inhibiting microtubule formation
• Disrupting scolex attachment in cestodes by tegument damage

Correct Answer: Acting as a GABA agonist at the neuromuscular junction causing flaccid paralysis

Q14. Which anthelmintic is known for significant first-pass hepatic metabolism and drug interactions via CYP450, and may have reduced efficacy with rapid CYP induction?

• Ivermectin
• Praziquantel
• Albendazole
• Niclosamide

Correct Answer: Albendazole

Q15. Which agent is most appropriate as the first-line drug for onchocerciasis (river blindness) control programs?

• Praziquantel
• Ivermectin
• Diethylcarbamazine
• Albendazole

Correct Answer: Ivermectin

Q16. Which side effect is characteristically associated with praziquantel therapy and often correlates with parasite burden?

• Peripheral neuropathy
• Immune-mediated reactions such as fever, headache and myalgia due to antigen release from dying parasites
• Severe agranulocytosis
• Nephrotic syndrome

Correct Answer: Immune-mediated reactions such as fever, headache and myalgia due to antigen release from dying parasites

Q17. In mass drug administration programs for lymphatic filariasis, combination therapy often includes albendazole plus which other agent to maximize microfilaricidal effect?

• Piperazine
• Diethylcarbamazine or ivermectin depending on co-endemic infections
• Praziquantel
• Niclosamide

Correct Answer: Diethylcarbamazine or ivermectin depending on co-endemic infections

Q18. Which of the following anthelmintics is effective against both adult tapeworms and hydatid cysts and requires careful dosage adjustment for hepatic impairment?

• Prazquantel
• Albendazole
• Levamisole
• Piperazine

Correct Answer: Albendazole

Q19. Nitazoxanide has broad activity but is primarily used for protozoal infections; which potential role does it have in helminth therapy?

• No role; it is solely an antibacterial
• Adjunctive activity against some cestodes and certain nematodes due to interference with pyruvate:ferredoxin oxidoreductase-dependent electron transfer
• Primary drug of choice for schistosomiasis
• Direct microtubule inhibitor like benzimidazoles

Correct Answer: Adjunctive activity against some cestodes and certain nematodes due to interference with pyruvate:ferredoxin oxidoreductase-dependent electron transfer

Q20. Which pharmacokinetic property of ivermectin is most relevant to its safety profile in humans and animals, particularly with respect to CNS toxicity?

• High penetration across the blood–brain barrier in humans leading to central effects
• P-glycoprotein (MDR1)–mediated exclusion from the CNS; dogs with MDR1 mutations show increased susceptibility to neurotoxicity
• Rapid hepatic metabolism to inactive water-soluble metabolites that accumulate in the CNS
• Renal excretion as unchanged drug causing accumulation in renal failure leading to neurotoxicity

Correct Answer: P-glycoprotein (MDR1)–mediated exclusion from the CNS; dogs with MDR1 mutations show increased susceptibility to neurotoxicity

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