What are the oral medication options for treating ringworm?

Oral Medication for Ringworm (Tinea Infections)

Oral terbinafine is the first-line systemic treatment for most dermatophyte ringworm infections requiring oral therapy, including tinea capitis and extensive tinea corporis/cruris, due to its superior efficacy, tolerability, and cost-effectiveness. 1, 2

When Oral Therapy is Indicated

Oral antifungal agents are necessary for:

• Tinea capitis (scalp ringworm) - always requires systemic therapy because topical agents cannot penetrate hair follicles adequately 3, 4
• Extensive tinea corporis or tinea cruris - when topical therapy fails or disease is widespread 1
• Immunocompromised patients - who may not respond adequately to topical treatment 1
• Hair follicle involvement - in any body location 1

First-Line Oral Treatment: Terbinafine

Oral terbinafine 250 mg daily is the preferred systemic agent for dermatophyte infections, achieving mycological cure rates exceeding 80% in most tinea infections 2, 5.

Dosing by indication:

• Tinea capitis: Terbinafine is first-line therapy, with weight-based dosing in children (62.5-250 mg/day for 4 weeks) 2, 3
• Tinea corporis/cruris: 250 mg daily for 2-4 weeks 2
• Tinea pedis: 250 mg daily for 2-6 weeks depending on severity 2
• Onychomycosis (nail involvement): 250 mg daily for 6 weeks (fingernails) or 12 weeks (toenails) 2, 5

Advantages of terbinafine:

• Fungicidal mechanism - kills dermatophytes rather than just inhibiting growth 2, 5
• Residual tissue effect - mycological cure rates continue to improve after treatment cessation 2
• Low drug interaction potential - safer in patients on multiple medications 2
• Superior to griseofulvin - more effective in onychomycosis, tinea pedis, and tinea corporis/cruris 2, 5
• Cost-effective - inexpensive compared to alternatives 1

Alternative Oral Agents

Itraconazole

Itraconazole is an acceptable alternative when terbinafine is contraindicated or not tolerated, though it has more drug interactions 6, 2, 3. Dosing varies by indication but typically 200 mg daily for 1-4 weeks for cutaneous infections 2.

Critical drug interaction warning: Itraconazole is contraindicated with numerous medications including certain statins (lovastatin, simvastatin), cisapride, and many cardiovascular drugs due to CYP3A4 interactions 6. Always review the patient's medication list before prescribing.

Fluconazole

Fluconazole is used for tinea capitis in children at weight-based doses, though it is less effective than terbinafine for dermatophyte infections 3. It has better activity against Candida species than dermatophytes 7, 8.

Griseofulvin

Griseofulvin is no longer considered first-line despite being the only FDA-approved agent specifically for tinea capitis in children 3, 4. It requires longer treatment courses (8-10 weeks) and is less effective than terbinafine 2, 5, 4.

Emerging Resistant Tinea Infections

Important caveat: Emerging resistant dermatophyte strains may not respond to standard first-line topical or oral antifungals 1. These infections:

• Are often more severe than classic tinea presentations 1
• May require prolonged oral antifungal therapy 1
• Need specialized diagnostic testing to identify the causative organism 1

If a patient fails to respond to appropriate first-line therapy, consider resistant organisms and refer for mycological culture and susceptibility testing 1.

Common Pitfalls to Avoid

• Never use combination antifungal-corticosteroid products - this promotes resistance and worsens outcomes through antifungal stewardship principles 1
• Don't rely on clinical diagnosis alone - other conditions (eczema, psoriasis, alopecia areata) can mimic tinea infections; confirm with KOH prep or culture when possible 1, 3
• Don't use topical therapy alone for tinea capitis - it cannot penetrate hair follicles and will fail 3, 4
• Check for drug interactions with itraconazole - it has extensive CYP3A4-mediated interactions that can be dangerous 6