Amoebicidal agents – Diloxanide, Iodoquinol MCQs With Answer

Amoebicidal agents – Diloxanide, Iodoquinol MCQs With Answer

Amoebicidal agents, particularly Diloxanide and Iodoquinol, are key luminal therapies for intestinal amoebiasis and carrier eradication. This concise, B. Pharm-focused overview covers mechanisms, pharmacokinetics, dosage forms, clinical uses, adverse effects, contraindications, drug interactions and monitoring essentials. Students will learn distinctions between luminal and tissue amoebicides, rationale for combination therapy with metronidazole, common toxicities such as gastrointestinal upset and iodoquinol-associated optic neuritis, and dosing considerations in adults, children and pregnancy. Emphasis is placed on pharmacology concepts relevant to formulation, absorption, metabolism and antimicrobial resistance. Mastering these topics prepares pharmacy graduates for rational prescribing and patient counselling. Now let’s test your knowledge with 30 MCQs on this topic.

Q1. What is the primary clinical use of diloxanide furoate?

• Eradication of intestinal Entamoeba histolytica cysts and treatment of asymptomatic carriers
• First-line therapy for amoebic liver abscess
• Systemic tissue trophozoite eradication
• Treatment of bacterial gastroenteritis

Correct Answer: Eradication of intestinal Entamoeba histolytica cysts and treatment of asymptomatic carriers

Q2. Which serious adverse effect is classically associated with prolonged iodoquinol therapy?

• Optic neuritis leading to visual impairment
• Bone marrow suppression
• Pulmonary fibrosis
• Severe hypoglycaemia

Correct Answer: Optic neuritis leading to visual impairment

Q3. Why is metronidazole often followed by a luminal agent such as diloxanide or iodoquinol in amoebiasis treatment?

• Because metronidazole eliminates tissue trophozoites but does not reliably eradicate luminal cysts
• Because metronidazole causes severe GI side effects unless followed by a luminal agent
• Because luminal agents potentiate metronidazole’s systemic absorption
• Because luminal agents prevent metronidazole resistance

Correct Answer: Because metronidazole eliminates tissue trophozoites but does not reliably eradicate luminal cysts

Q4. Standard adult dosing of diloxanide furoate for luminal amoebiasis is:

• 500 mg three times daily for 10 days
• 2 g once daily for 3 days
• 650 mg three times daily for 20 days
• 100 mg twice daily for 7 days

Correct Answer: 500 mg three times daily for 10 days

Q5. Which of the following is a contraindication for iodoquinol use?

• Pregnancy due to risk of fetal thyroid dysfunction
• Renal stones
• Hypertension
• Hyperlipidaemia

Correct Answer: Pregnancy due to risk of fetal thyroid dysfunction

Q6. The mechanism of action of iodoquinol is best described as:

• Not fully elucidated; presumed to interfere with protozoal metabolism possibly by metal chelation and local antiseptic action
• Inhibition of bacterial cell wall synthesis
• Inhibition of DNA gyrase
• Competitive antagonism of folate synthesis

Correct Answer: Not fully elucidated; presumed to interfere with protozoal metabolism possibly by metal chelation and local antiseptic action

Q7. Which drug is primarily a tissue amebicide used for invasive amoebiasis (e.g., liver abscess)?

• Metronidazole
• Diloxanide furoate
• Iodoquinol
• Paromomycin

Correct Answer: Metronidazole

Q8. The most common adverse effects reported with diloxanide furoate are:

• Gastrointestinal upset such as nausea, abdominal cramps and diarrhoea
• Severe cardiotoxicity
• Ototoxicity
• Bone marrow aplasia

Correct Answer: Gastrointestinal upset such as nausea, abdominal cramps and diarrhoea

Q9. Which statement about iodoquinol absorption and distribution is correct?

• Iodoquinol is poorly absorbed from the gastrointestinal tract and acts mainly within the intestinal lumen
• Iodoquinol is highly protein-bound and widely distributed to the CNS
• Iodoquinol achieves high hepatic concentrations and treats liver abscesses
• Iodoquinol is given parenterally for systemic infections

Correct Answer: Iodoquinol is poorly absorbed from the gastrointestinal tract and acts mainly within the intestinal lumen

Q10. Diloxanide furoate is a prodrug. Where is it primarily hydrolysed to the active moiety?

• Hydrolysed in the intestinal lumen/mucosa to active diloxanide by esterases
• Hydrolysed in the liver by CYP450 enzymes
• Converted to active drug in the bloodstream by plasma oxidases
• Activated within macrophages at the site of infection

Correct Answer: Hydrolysed in the intestinal lumen/mucosa to active diloxanide by esterases

Q11. Which monitoring is recommended during prolonged iodoquinol therapy?

• Periodic ophthalmic (visual) examination
• Frequent liver biopsy
• Daily ECG monitoring
• Serial serum lactate measurements

Correct Answer: Periodic ophthalmic (visual) examination

Q12. Which of the following is recommended to eradicate asymptomatic intestinal cyst carriers of Entamoeba histolytica?

• Diloxanide furoate or iodoquinol (luminal amoebicides)
• High-dose oral penicillin
• Oral fluconazole
• Topical metronidazole gel

Correct Answer: Diloxanide furoate or iodoquinol (luminal amoebicides)

Q13. Iodoquinol belongs chemically to which class?

• Halogenated hydroxyquinoline derivative
• Nitroimidazole derivative
• Macrolide antibiotic
• Aminoglycoside antibiotic

Correct Answer: Halogenated hydroxyquinoline derivative

Q14. Which of the following statements about diloxanide’s systemic activity is correct?

• Diloxanide has minimal systemic activity and is used primarily as a luminal agent
• Diloxanide is the drug of choice for hepatic amoebic abscess
• Diloxanide is highly effective against CNS amoebic infections
• Diloxanide is routinely given intravenously for systemic infections

Correct Answer: Diloxanide has minimal systemic activity and is used primarily as a luminal agent

Q15. For a patient with amoebic liver abscess, the most appropriate pharmacological approach is:

• Start metronidazole for tissue trophozoites then follow with a luminal agent (e.g., diloxanide) to eradicate cyst carriage
• Start iodoquinol alone to treat the liver abscess
• Use diloxanide alone as monotherapy
• Prescribe oral paracetamol only

Correct Answer: Start metronidazole for tissue trophozoites then follow with a luminal agent (e.g., diloxanide) to eradicate cyst carriage

Q16. Which luminal amoebicide is preferred in pregnancy due to minimal systemic absorption?

• Paromomycin
• Iodoquinol
• Diloxanide furoate
• Metronidazole

Correct Answer: Paromomycin

Q17. Which adverse effect should prompt immediate discontinuation of iodoquinol?

• Any new visual disturbance or vision loss
• Transient mild headache
• Self-limited nausea lasting one day
• Minor skin dryness

Correct Answer: Any new visual disturbance or vision loss

Q18. Which statement about drug interactions with iodoquinol is most accurate?

• Iodoquinol may interact with iodine/thyroid status and should be used cautiously with other iodine-containing products
• Iodoquinol strongly induces CYP3A4 leading to reduced steroid levels
• Iodoquinol causes irreversible antagonism of beta-blockers
• Iodoquinol increases digoxin renal clearance dramatically

Correct Answer: Iodoquinol may interact with iodine/thyroid status and should be used cautiously with other iodine-containing products

Q19. Which of the following best describes the rationale for using luminal amoebicides after tissue therapy?

• To eliminate residual intraluminal cysts and prevent recurrence or transmission
• To treat systemic bacterial co-infection
• To reduce metronidazole-associated metallic taste
• To enhance absorption of metronidazole

Correct Answer: To eliminate residual intraluminal cysts and prevent recurrence or transmission

Q20. Common laboratory or clinical monitoring for patients on diloxanide therapy includes:

• Monitoring for relief of symptoms and stool clearance; routine blood monitoring only if clinically indicated
• Daily serum transaminases and coagulation profile
• Weekly bone marrow biopsy
• Continuous ECG telemetry

Correct Answer: Monitoring for relief of symptoms and stool clearance; routine blood monitoring only if clinically indicated

Q21. Which of the following is a key counselling point for patients taking diloxanide furoate?

• Take with food to reduce gastrointestinal upset and complete the full course even if symptoms resolve
• Do not drink water while taking the dose
• Avoid sunlight completely while on therapy
• Stop the drug as soon as diarrhoea improves

Correct Answer: Take with food to reduce gastrointestinal upset and complete the full course even if symptoms resolve

Q22. Which luminal amoebicide is associated with iodine-related toxicity and should be avoided in patients with thyroid disease?

• Iodoquinol
• Diloxanide furoate
• Metronidazole
• Azithromycin

Correct Answer: Iodoquinol

Q23. The simplest pharmacological distinction between luminal and tissue amoebicides is that luminal agents:

• Act primarily within the intestinal lumen to eliminate cysts, while tissue agents penetrate tissues to kill trophozoites
• Are always administered intravenously, while tissue agents are oral
• Are effective against bacterial pathogens, while tissue agents only treat parasites
• Require renal dosing adjustments in all patients

Correct Answer: Act primarily within the intestinal lumen to eliminate cysts, while tissue agents penetrate tissues to kill trophozoites

Q24. Which adverse reaction is more commonly reported with diloxanide than with iodoquinol?

• Gastrointestinal disturbances such as flatulence and abdominal cramps
• Severe optic neuritis
• Marked iodine overload
• Acute pancreatitis

Correct Answer: Gastrointestinal disturbances such as flatulence and abdominal cramps

Q25. If a patient develops visual symptoms while on iodoquinol, the pharmacist should:

• Advise immediate discontinuation and urgent ophthalmologic assessment
• Recommend doubling the dose to overcome symptoms
• Suggest taking the drug with milk and continue therapy
• Ignore symptoms if they are mild

Correct Answer: Advise immediate discontinuation and urgent ophthalmologic assessment

Q26. Which statement is true regarding resistance to luminal amoebicides like diloxanide and iodoquinol?

• Resistance is uncommon but possible; proper therapy and combination with tissue agents reduce recurrence
• Resistance is universal and these drugs are no longer effective
• Resistance is mediated by beta-lactamase production
• Resistance is prevented by concurrent antacid use

Correct Answer: Resistance is uncommon but possible; proper therapy and combination with tissue agents reduce recurrence

Q27. Which luminal agent is effective but not recommended in pregnancy due to systemic iodine exposure?

• Iodoquinol
• Paromomycin
• Diloxanide furoate (preferred in pregnancy)
• Metronidazole (luminal use)

Correct Answer: Iodoquinol

Q28. Which of the following best describes diloxanide furoate’s formulation and activation?

• It is administered as a furoate ester prodrug that is hydrolysed in the gut to active diloxanide
• It is given as an active intravenous compound that bypasses the gut
• It is a topical ointment used for cutaneous amoebiasis
• It is an inhaled formulation targeting pulmonary amoebiasis

Correct Answer: It is administered as a furoate ester prodrug that is hydrolysed in the gut to active diloxanide

Q29. In a child weighing 20 kg with noninvasive intestinal amoebiasis, which general dosing consideration applies for luminal agents?

• Use weight‑based dosing according to pediatric guidelines and avoid agents contraindicated in children or pregnancy
• Give adult doses regardless of weight
• Do not treat children for amoebiasis; only observe
• Always use intravenous therapy in children

Correct Answer: Use weight‑based dosing according to pediatric guidelines and avoid agents contraindicated in children or pregnancy

Q30. Which statement summarises the pharmacist’s role regarding diloxanide and iodoquinol therapy?

• Ensure correct indication and dosing, counsel on adverse effects (especially visual symptoms with iodoquinol), and recommend appropriate follow-up or referral
• Advise patients to stop therapy if any minor side effect occurs without reporting
• Substitute any antibiotic for luminal amoebicides without checking indication
• Recommend increasing dose if symptoms persist after 24 hours

Correct Answer: Ensure correct indication and dosing, counsel on adverse effects (especially visual symptoms with iodoquinol), and recommend appropriate follow-up or referral

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