Which antifungal is not typically effective against dermatophyte infections?

Fluconazole is not typically effective against dermatophyte infections because it primarily targets Candida species and certain systemic fungal infections, rather than the keratinophilic dermatophytes that cause superficial skin infections. Dermatophytes, such as Trichophyton, Microsporum, and Epidermophyton, are known to invade the keratin in hair, skin, and nails, and the most effective antifungals for these types of infections are those specifically active against dermatophytes.

Griseofulvin, terbinafine, and itraconazole are all effective against dermatophyte infections. Griseofulvin has been a mainstay for treating dermatophyte infections for decades, particularly for tinea capitis (scalp infections). Terbinafine is effective for both superficial and systemic dermatophyte infections and works by inhibiting the synthesis of ergosterol in fungal cell membranes. Itraconazole, while primarily an azole antifungal effective against systemic infections, is also recognized for its activity against dermatophytes, making it suitable for treating these infections.

Thus, fluconazole's spectrum of antifungal activity doesn't typically extend to dermatophytes, making it less suitable for treating these specific fungal infections.