Terbinafine acts by inhibiting squalene epoxidase, causing squalene accumulation. This mechanism makes it fungicidal against dermatophytes. The LEAST effective antifungal for tinea unguium caused by Trichophyton rubrum is:
- A Terbinafine
- B Griseofulvin ✓
- C Itraconazole
- D Fluconazole
Correct answer: B. Griseofulvin
Explanation
Griseofulvin is the least effective for tinea unguium because it only inhibits fungal mitosis by binding beta-tubulin and is fungistatic, requiring very long courses (12-18 months for toenails) with poor nail penetration and low cure rates (~50%). Terbinafine (fungicidal) and itraconazole pulse therapy are first-line for onychomycosis with cure rates of 70-80%. Fluconazole weekly is second-line. Griseofulvin is mainly used for tinea capitis in children due to its activity against T. tonsurans.
Reference: Neena Khanna Illustrated Synopsis of Dermatology & STD, 6th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.