## Tinea Cruris: First-Line Antifungal ### Clinical Context Tinea cruris is a dermatophyte infection of the groin and adjacent skin. It is one of the most common fungal infections in tropical and subtropical climates, particularly in males with poor hygiene or excessive sweating. ### Drug of Choice: Terbinafine **Key Point:** Terbinafine 250 mg once daily for 4 weeks is the first-line systemic antifungal for tinea cruris. **High-Yield:** Terbinafine is a fungicidal allylamine that inhibits squalene epoxidase, disrupting ergosterol synthesis. It achieves rapid clinical response and is superior to azoles in dermatophyte infections. ### Why Terbinafine Wins | Feature | Terbinafine | Griseofulvin | Fluconazole | Itraconazole | |---------|-------------|--------------|-------------|---------------| | **MOA** | Fungicidal (allylamine) | Fungistatic (microtubule inhibitor) | Fungistatic (azole) | Fungistatic (azole) | | **Duration** | 4 weeks | 6 weeks | 4 weeks | 4 weeks | | **Efficacy in dermatophytes** | Excellent | Good | Moderate | Good | | **Dosing** | Once daily | Twice daily | Once weekly | Once daily | | **Hepatotoxicity** | Rare | Rare | Rare | Rare | | **Drug interactions** | Moderate | High | High | High | **Clinical Pearl:** Terbinafine's fungicidal action (kills the organism) is superior to the fungistatic action of azoles and griseofulvin in tinea infections, resulting in faster cure and lower relapse rates. ### Topical vs. Systemic - **Topical agents** (azoles, allylamines, terbinafine cream) are first-line for localized tinea cruris - **Systemic therapy** is reserved for extensive disease, nail involvement, or treatment failure - In this case, the extent and duration suggest systemic therapy is appropriate **Mnemonic:** **TERBINAFINE for TINEA** — Terbinafine is the Topmost choice for dermatophyte infections (tinea pedis, cruris, corporis, unguium). [cite:KD Tripathi 8e Ch 57]
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