Fluconazole is an antifungal medication that effectively treats candidal vaginitis by inhibiting the fungal cytochrome P450 enzyme 14α-demethylase, crucial for ergosterol synthesis, a key component of the fungal cell membrane. This disruption leads to increased membrane permeability and ultimately fungal cell death. It is administered orally as a single dose or in multiple doses depending on severity, providing a convenient and effective treatment option. Fluconazole specifically targets fungal infections, unlike other options which are used for bacterial or viral infections.

Reference: Harrison's Principles of Internal Medicine, Fauci et al., 20th Edition.