A 32-year-old man presents with pruritic, scaly patches on the groin and inner thighs for 3 weeks. KOH mount confirms branching septate hyphae. What is the drug of choice for tinea cruris?

Question

Accepted Answer

C. Terbinafine. ## First-Line Treatment of Tinea Cruris

**Key Point:** Terbinafine is the gold-standard first-line agent for dermatophyte infections, including tinea cruris, due to superior efficacy, shorter duration, and better tissue penetration.

### Mechanism & Pharmacokinetics

Terbinafine is an **allylamine antifungal** that inhibits squalene epoxidase, blocking ergosterol synthesis. It achieves high concentrations in skin, nails, and hair, making it ideal for dermatophytosis.

### Dosing & Duration

| Parameter | Terbinafine | Griseofulvin | Fluconazole |
|-----------|-------------|--------------|-------------|
| **Dose** | 250 mg once daily | 500 mg–1 g daily (divided) | 150–200 mg weekly |
| **Duration (tinea cruris)** | 2–4 weeks | 4–6 weeks | 3–4 weeks |
| **Fungistatic/Cidal** | Fungicidal | Fungistatic | Fungistatic |
| **Tissue penetration** | Excellent (skin, nails) | Moderate | Moderate |

**High-Yield:** Terbinafine achieves cure in 2–4 weeks for tinea cruris; griseofulvin requires 4–6 weeks and is now second-line.

### Clinical Advantages of Terbinafine

1. **Faster cure**: Fungicidal action (kills organisms) vs. fungistatic (inhibits growth)
2. **Shorter treatment**: 2–4 weeks vs. 4–6 weeks with griseofulvin
3. **Better CNS penetration**: Useful for severe/disseminated disease
4. **Oral bioavailability**: Not food-dependent (griseofulvin requires fatty meals)
5. **Single daily dose**: Improves compliance

**Clinical Pearl:** Tinea cruris, tinea corporis, and tinea pedis are all best treated with oral terbinafine 250 mg daily for 2–4 weeks. Topical azoles (miconazole, clotrimazole) are reserved for mild, localized disease.

### Why Terbinafine Over Alternatives

```mermaid
flowchart TD
  A[Dermatophyte infection diagnosed]:::outcome --> B{Extent & severity?}:::decision
  B -->|Localized, mild| C[Topical azole or terbinafine]:::action
  B -->|Extensive or nail involvement| D[Oral antifungal needed]:::action
  D --> E{First-line oral agent?}:::decision
  E -->|Terbinafine preferred| F[250 mg once daily, 2-4 weeks]:::action
  E -->|Allergy or contraindication| G[Griseofulvin or fluconazole]:::action
  F --> H[Cure in 2-4 weeks]:::outcome
  G --> I[Cure in 4-6 weeks]:::outcome
```

**Mnemonic:** **TALL** = **T**erbinafine is **A**llylamine, **L**ong-acting, **L**ow relapse — remember terbinafine as the tall choice (first-line, superior height of efficacy).

**Warning:** Griseofulvin is now relegated to second-line due to longer treatment duration and lower cure rates. Do not confuse it with terbinafine in modern NEET PG exams.

Answer

A. Fluconazole

Answer

B. Miconazole

Answer

D. Griseofulvin

A 32-year-old man presents with pruritic, scaly patches on the groin and inner thighs for 3 weeks. KOH mount confirms branching septate hyphae. What is the drug of choice for tinea cruris?

Explanation

First-Line Treatment of Tinea Cruris

Mechanism & Pharmacokinetics

Dosing & Duration

Clinical Advantages of Terbinafine

Why Terbinafine Over Alternatives

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Parameter	Terbinafine	Griseofulvin	Fluconazole
Dose	250 mg once daily	500 mg–1 g daily (divided)	150–200 mg weekly
Duration (tinea cruris)	2–4 weeks	4–6 weeks	3–4 weeks
Fungistatic/Cidal	Fungicidal	Fungistatic	Fungistatic
Tissue penetration	Excellent (skin, nails)	Moderate	Moderate