Antifungal agents – classification and mechanism MCQs With Answer
Antifungal agents are a diverse group of drugs used to treat fungal infections; understanding their classification and mechanisms is essential for B. Pharm students. This concise review covers major classes — azoles, polyenes, echinocandins, allylamines, and nucleoside analogues — and explains key mechanisms such as inhibition of ergosterol synthesis (14α‑demethylase), membrane binding to ergosterol, blockade of beta-(1,3)-D-glucan synthesis, squalene epoxidase inhibition, and disruption of fungal nucleic acid synthesis. Emphasis is placed on spectrum of activity, resistance mechanisms, pharmacokinetics, drug interactions, adverse effects, and clinical applications. Detailed MCQs will challenge recall, application, and clinical decision-making skills. Now let’s test your knowledge with 30 MCQs on this topic.
Q1. Which enzyme is the primary target of azole antifungals?
- Inhibition of squalene epoxidase
- Inhibition of lanosterol 14α‑demethylase (ergosterol synthesis)
- Inhibition of beta-(1,3)-D-glucan synthase
- Conversion of flucytosine to 5‑fluorouracil
Correct Answer: Inhibition of lanosterol 14α‑demethylase (ergosterol synthesis)
Q2. What is the principal mechanism of action of amphotericin B?
- Inhibition of ergosterol synthesis by blocking 14α‑demethylase
- Binding to ergosterol in fungal membranes and forming pores
- Inhibition of fungal DNA synthesis by alkylation
- Inhibition of microtubule formation
Correct Answer: Binding to ergosterol in fungal membranes and forming pores
Q3. Echinocandins (e.g., caspofungin) primarily inhibit which fungal component?
- Squalene epoxidase
- Beta-(1,3)-D-glucan synthase
- Lanosterol 14α‑demethylase
- Fungal DNA polymerase
Correct Answer: Beta-(1,3)-D-glucan synthase
Q4. Terbinafine, an allylamine, exerts antifungal activity by inhibiting which enzyme?
- Lanosterol 14α‑demethylase
- Squalene epoxidase
- Beta-(1,3)-D-glucan synthase
- Cytosine deaminase
Correct Answer: Squalene epoxidase
Q5. Flucytosine (5-FC) acts as an antifungal by which mechanism?
- Direct binding to ergosterol to form membrane pores
- Being converted to 5‑fluorouracil inside fungi and inhibiting nucleic acid synthesis
- Inhibiting beta-(1,3)-D-glucan synthesis
- Blocking squalene epoxidase
Correct Answer: Being converted to 5‑fluorouracil inside fungi and inhibiting nucleic acid synthesis
Q6. Which antifungal agent is most classically associated with nephrotoxicity?
- Fluconazole
- Amphotericin B deoxycholate
- Terbinafine
- Flucytosine
Correct Answer: Amphotericin B deoxycholate
Q7. Which azole is well known as a potent inhibitor of human CYP3A4, causing significant drug interactions?
- Fluconazole
- Ketoconazole
- Griseofulvin
- Terbinafine
Correct Answer: Ketoconazole
Q8. For initial therapy of severe invasive candidiasis, which class is recommended as first-line in many guidelines?
- Azoles (e.g., fluconazole) for all patients
- Echinocandins (e.g., caspofungin)
- Allylamines (e.g., terbinafine)
- Pyrimidine analogues (e.g., flucytosine) alone
Correct Answer: Echinocandins (e.g., caspofungin)
Q9. The oral antifungal of choice for onychomycosis caused by dermatophytes is:
- Fluconazole
- Terbinafine
- Caspofungin
- Amphotericin B
Correct Answer: Terbinafine
Q10. Which amphotericin B formulation is associated with reduced nephrotoxicity compared to conventional deoxycholate form?
- Amphotericin B deoxycholate
- Liposomal amphotericin B
- Oral amphotericin B suspension
- Amphotericin B combined with ketoconazole
Correct Answer: Liposomal amphotericin B
Q11. A common fungal resistance mechanism to azoles involves:
- Mutation or overexpression of efflux pumps decreasing intracellular drug
- Increased ergosterol content via upregulation of squalene synthase
- Inactivation of amphotericin B by fungal enzymes
- Phosphorylation of flucytosine to inactive metabolites
Correct Answer: Mutation or overexpression of efflux pumps decreasing intracellular drug
Q12. Combining flucytosine with amphotericin B for cryptococcal meningitis is recommended primarily because:
- Flucytosine prevents amphotericin B nephrotoxicity
- The combination is synergistic and reduces emergence of resistance
- They share the same mechanism of action for additive effects
- Amphotericin B enhances oral absorption of flucytosine
Correct Answer: The combination is synergistic and reduces emergence of resistance
Q13. Which antifungal frequently causes visual disturbances and photopsia as an adverse effect?
- Fluconazole
- Voriconazole
- Amphotericin B
- Terbinafine
Correct Answer: Voriconazole
Q14. Which azole is preferred for prophylaxis of invasive fungal infections in high‑risk neutropenic patients?
- Fluconazole
- Ketoconazole
- Posaconazole
- Nystatin
Correct Answer: Posaconazole
Q15. Nystatin is used topically or orally for superficial candidiasis because it:
- Inhibits fungal DNA synthesis
- Binds ergosterol and forms pores in fungal cell membranes
- Inhibits squalene epoxidase
- Blocks beta-(1,3)-D-glucan synthesis
Correct Answer: Binds ergosterol and forms pores in fungal cell membranes
Q16. Which antifungal class is most active by inhibiting fungal cell wall synthesis rather than targeting ergosterol?
- Azoles
- Polyenes
- Echinocandins
- Allylamines
Correct Answer: Echinocandins
Q17. Therapeutic drug monitoring (TDM) is most important for which antifungal due to variable pharmacokinetics and nonlinear metabolism?
- Fluconazole
- Voriconazole
- Nystatin
- Amphotericin B
Correct Answer: Voriconazole
Q18. Routine monitoring of liver function tests is most important during prolonged therapy with which class?
- Polyenes
- Azoles
- Echinocandins
- Nystatin
Correct Answer: Azoles
Q19. Which statement best describes the typical antifungal effect of azoles on Candida species?
- Azoles are typically fungicidal against Candida at all concentrations
- Azoles are generally fungistatic against many yeasts including Candida
- Azoles primarily inhibit fungal cell wall synthesis
- Azoles act by alkylating fungal DNA
Correct Answer: Azoles are generally fungistatic against many yeasts including Candida
Q20. For fungal meningitis where good CSF penetration is required, which antifungal is preferred?
- Amphotericin B deoxycholate (IV)
- Fluconazole (oral or IV)
- Caspofungin (IV)
- Terbinafine (oral)
Correct Answer: Fluconazole (oral or IV)
Q21. Which antifungal is contraindicated in pregnancy due to teratogenicity?
- Griseofulvin
- Fluconazole (single dose for vulvovaginal candidiasis)
- Nystatin topical
- Amphotericin B
Correct Answer: Griseofulvin
Q22. Inhibition of squalene epoxidase by allylamines leads to:
- Decreased ergosterol synthesis and accumulation of toxic squalene
- Direct pore formation in the fungal membrane
- Inhibition of fungal DNA polymerase
- Activation of fungal efflux pumps
Correct Answer: Decreased ergosterol synthesis and accumulation of toxic squalene
Q23. Which antifungal has poor oral absorption and is therefore used intravenously for systemic infections?
- Amphotericin B
- Fluconazole
- Voriconazole
- Terbinafine
Correct Answer: Amphotericin B
Q24. “Shake and bake” infusion-related reactions (fever, chills) are most commonly associated with:
- Fluconazole
- Amphotericin B deoxycholate
- Voriconazole
- Terbinafine
Correct Answer: Amphotericin B deoxycholate
Q25. Which antifungal is primarily used for superficial dermatophyte infections and not for systemic mycoses?
- Griseofulvin
- Fluconazole IV
- Caspofungin
- Amphotericin B
Correct Answer: Griseofulvin
Q26. Resistance to echinocandins in Candida species is most commonly due to mutations in which genes?
- ERG11 genes
- FKS genes encoding glucan synthase
- CYP51 genes
- Cytosine deaminase genes
Correct Answer: FKS genes encoding glucan synthase
Q27. Absorption of which azole is decreased when gastric pH is increased (e.g., with proton pump inhibitors)?
- Fluconazole
- Itraconazole
- Caspofungin
- Amphotericin B
Correct Answer: Itraconazole
Q28. Co-administration of warfarin with many azoles commonly results in which interaction?
- Decreased INR and reduced anticoagulation
- Increased warfarin effect and elevated INR due to CYP inhibition
- Activation of an alternative metabolic pathway for warfarin causing no change
- Complete antagonism of warfarin’s effect by azoles
Correct Answer: Increased warfarin effect and elevated INR due to CYP inhibition
Q29. Nystatin is the treatment of choice for which condition and why?
- Systemic candidemia because it is given IV and penetrates tissues
- Oral or cutaneous candidiasis because it binds ergosterol and is not absorbed orally
- Invasive aspergillosis because it inhibits 14α‑demethylase
- Cryptococcal meningitis because it crosses the blood‑brain barrier
Correct Answer: Oral or cutaneous candidiasis because it binds ergosterol and is not absorbed orally
Q30. Griseofulvin’s antifungal mechanism primarily involves:
- Inhibition of ergosterol biosynthesis at 14α‑demethylase
- Interference with microtubule function and inhibition of mitosis
- Formation of membrane pores by binding ergosterol
- Inhibition of beta-(1,3)-D-glucan synthase
Correct Answer: Interference with microtubule function and inhibition of mitosis
