How to treat tinea
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I now have all the essential data needed for a comprehensive answer. The Fitzpatrick's treatment table had the key information for tinea pedis/manuum and onychomycosis rows in the truncated output. Let me now compile a thorough answer.
Treatment of Tinea (Dermatophytosis)
Tinea refers to superficial dermatophyte infections of the skin, hair, and nails. Treatment depends on the site of infection, extent of disease, and whether the hair follicle or nail is involved.
General Principles
- Topical therapy is sufficient for most localized skin infections (tinea corporis, cruris, pedis).
- Systemic therapy is required when infection involves hair follicles (tinea capitis, barbae), nails (onychomycosis), or when skin disease is extensive.
- Avoid combination corticosteroid-antifungal products (e.g., clotrimazole/betamethasone) — they cause widespread tinea and fungal folliculitis. — Fitzpatrick's Dermatology, p. 2963
- Correct predisposing conditions: reduce moisture, wear loose clothing, treat co-existing tinea pedis.
Treatment by Site
🦠 Tinea Capitis (Scalp)
Always requires systemic treatment — topical alone is ineffective.
| Agent | Adults | Children |
|---|---|---|
| Griseofulvin | 20–25 mg/kg/day × 6–8 weeks | Micro: 10–25 mg/kg/day; Ultramicro: 5–15 mg/kg/day × 8 weeks |
| Terbinafine | 250 mg/day × 2–8 weeks | <20 kg: 62.5 mg/day; 20–40 kg: 125 mg/day; ≥40 kg: 250 mg/day × 2–4 weeks |
| Itraconazole | 5 mg/kg/day × 2–4 weeks | 3–5 mg/kg/day × 2–4 weeks |
| Fluconazole | 6 mg/kg/day × 3–6 weeks | 6 mg/kg/day × 3–6 weeks (not standard) |
- Griseofulvin is first-line for Microsporum species (e.g., M. canis) — higher efficacy vs. terbinafine for this genus. — Fitzpatrick's, p. 2972
- Terbinafine is preferred for Trichophyton tonsurans (most common in the US/UK). Terbinafine granules are FDA-approved for children ≥4 years. — Red Book 2021
- Adjuvant topical therapy: selenium sulfide 2.5% or ketoconazole 2% shampoo reduces shedding and transmission but does not cure the infection.
🔴 Tinea Corporis & Tinea Cruris (Body / Groin)
Topical therapy is first-line for localized disease.
Topical agents (apply twice daily for 2–4 weeks; terbinafine can be used 1 week):
- Allylamines: terbinafine (Lamisil), naftifine (Naftin), butenafine (Mentax)
- Imidazoles: clotrimazole (Lotrimin), miconazole (Micatin), ketoconazole (Nizoral), econazole (Spectazole), oxiconazole (Oxistat), sulconazole (Exelderm)
- Others: ciclopirox olamine (Loprox), tolnaftate
Econazole, ketoconazole, oxiconazole, and terbinafine can be dosed once daily. — Andrews' Diseases of the Skin, p. 347
Systemic therapy (for extensive disease or folliculitis):
| Agent | Dose |
|---|---|
| Terbinafine | 250 mg/day × 2–4 weeks |
| Itraconazole | 100 mg/day × 1–6 weeks |
| Fluconazole | 150–300 mg/week × 4–6 weeks |
| Griseofulvin | 500 mg/day × 2–4 weeks |
Terbinafine is generally preferred systemically — fewer drug interactions than itraconazole. — Harrison's 22E, p. 225
🦶 Tinea Pedis (Athlete's Foot) & Tinea Manuum
Topical therapy as for tinea corporis. The moccasin (hyperkeratotic) type often requires systemic treatment.
Systemic (adults):
- Terbinafine 250 mg/day × 2–6 weeks
- Itraconazole 200 mg/day × 1–4 weeks (or pulse)
- Fluconazole 150–300 mg/week × 4–6 weeks
Whitfield's ointment (benzoic acid + salicylic acid) is a cost-effective option and has antibacterial properties useful for secondary Corynebacterium infection. — Tintinalli's EM
💅 Tinea Unguium / Onychomycosis (Nails)
Topical therapy alone is usually ineffective. Confirm diagnosis with KOH/culture or PAS staining before starting systemic antifungals.
Systemic agents (adults):
| Agent | Regimen |
|---|---|
| Terbinafine | 250 mg/day × 6 weeks (fingernails) or 12 weeks (toenails) — first-line |
| Itraconazole | Pulse: 200 mg twice daily × 1 week/month × 2 months (fingernails) or 3 months (toenails) |
| Fluconazole | 150–300 mg once weekly × 6–12 months |
- Terbinafine is considered first-line for dermatophyte onychomycosis; does not treat Candida onychomycosis.
- Itraconazole is preferred for Candida onychomycosis and nondermatophyte molds.
- Topical efinaconazole solution applied for up to 1 year has shown benefit in some trials (mild disease, <50% nail involvement). — Harrison's 22E
- Relapses occur in 25–30% of cases after treatment.
🧔 Tinea Barbae (Beard)
Requires systemic treatment (like tinea capitis).
- Terbinafine 250 mg/day × 2–4 weeks
- Itraconazole 200 mg/day × 4–6 weeks
- Add systemic glucocorticoids for the first week if severe inflammation (kerion-like). — Fitzpatrick's, p. 2970
Key Drug Mechanisms
| Drug | Class | Mechanism |
|---|---|---|
| Terbinafine | Allylamine | Inhibits squalene epoxidase → accumulation of toxic squalene |
| Itraconazole, fluconazole | Triazoles | Inhibit lanosterol 14α-demethylase → block ergosterol synthesis |
| Griseofulvin | — | Disrupts microtubule assembly → inhibits fungal mitosis |
| Clotrimazole, miconazole, ketoconazole | Imidazoles | Inhibit 14α-demethylase (same target as triazoles) |
⚠️ Emerging Resistance (2025 Update)
Two recent systematic reviews (PMID 39082800 and PMID 40704771) flag terbinafine-resistant Trichophyton indotineae spreading into Europe and Australia. For refractory tinea corporis/cruris that fails terbinafine, consider:
- Fungal culture and susceptibility testing
- Itraconazole or voriconazole as alternatives
- Avoid empiric re-treatment with terbinafine until resistance is excluded
Sources: Fitzpatrick's Dermatology (8th ed.), Andrews' Diseases of the Skin, Harrison's Principles of Internal Medicine (22E), Red Book 2021, Tintinalli's Emergency Medicine
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