Which of the following antifungals is predominantly effective against dermatophytes?

Terbinafine is predominantly effective against dermatophytes, which are the fungi responsible for causing superficial infections of the skin, hair, and nails, such as athlete's foot, ringworm, and nail infections. This medication belongs to the allylamine class of antifungals and works by inhibiting the enzyme squalene epoxidase, leading to a decrease in ergosterol synthesis, an essential component of fungal cell membranes. As a result, terbinafine is particularly effective against the types of fungi that fall under the dermatophyte category, including Trichophyton, Microsporum, and Epidermophyton species.

In contrast, other antifungals listed, such as amphotericin B and caspofungin, are generally used for systemic fungal infections and are not the first line of treatment for dermatophyte infections. Fluconazole, while effective against certain yeasts and some systemic fungal infections, is not primarily indicated for dermatophytes. Therefore, when treating dermatophyte infections, terbinafine is the preferred agent due to its targeted action and effectiveness in this specific group of fungi.