Systemic Antifungals: Terbinafine, Itraconazole, Fluconazole
Systemic antifungals, including terbinafine, itraconazole, and fluconazole, are critical in the treatment of various fungal infections, particularly those affecting the skin and nails. Understanding their mechanisms, indications, and potential side effects is vital for effective patient management.
Topics: antifungals, systemic, drug interactions
Overview / Definition Systemic antifungals are a class of medications used to treat fungal infections that are not limited to the skin's surface, but can also involve deeper tissues, organs, and systemic circulation. The three major systemic antifungals discussed here are terbinafine, itraconazole, and fluconazole, each with unique mechanisms of action, indications, and side effect profiles. Epidemiology Fungal infections are increasing in prevalence, particularly in immunocompromised individuals. The epidemiology of infections treated by systemic antifungals includes: Terbinafine: Most commonly used for onychomycosis and dermatophyte infections. Itraconazole: Effective against a broad spectrum of fungi, including Aspergillus species and systemic mycoses. Fluconazole: Commonly used for Candida infections, especially in patients with HIV/AIDS. Pathophysiology / Mechanism The three antifungal agents work through different mechanisms: Terbinafine: Inhibits the enzyme squalene epoxidase, disrupting ergosterol synthesis, leading to fungal cell death. Itraconazole: Inhibits 14-alpha-lanosterol demethylase, a key enzyme in ergosterol biosynthesis, impairing cell membrane integrity. Fluconazole: Also inhibits 14-alpha-lanosterol demethylase, but has a broader spectrum of activity against yeasts. Clinical Presentation Clinical manifestations of fungal infections can vary widely based on the organism and site of infection: Onychomycosis: Thickened, discolored, and brittle nails. Dermatophyte infections: Pruritic, erythematous plaques with scaling (tinea corporis, tinea capitis). Candidiasis: Erythematous plaques, often with satellite lesions in skin folds. Aspergillosis: Can present with respiratory symptoms or systemic involvement in immunocompromised patients. Diagnosis / Workup Diagnosis of fungal infections involves a combination of clinical assessment and laboratory testing: Clinical examination: Evaluate the appearance of the skin, nails, or mucosal lesions. Microscopy: