What is the first‑line oral treatment for tinea capitis in an otherwise healthy 16‑year‑old?

Oral Treatment for Tinea Capitis in a 16-Year-Old

For a 16-year-old with scalp ringworm, start terbinafine 250 mg daily for 2-4 weeks if the infection is caused by Trichophyton species (the most common cause in North America), or griseofulvin 500 mg daily for 6-8 weeks if Microsporum species is confirmed or suspected. 1

Treatment Selection Algorithm

Step 1: Collect Specimens Before Starting Treatment

• Obtain scalp scrapings, hair pluck, brush sample, or swab for microscopy and culture to identify the causative organism 1
• However, if cardinal clinical signs are present (scale, lymphadenopathy, alopecia, or kerion), start empiric treatment immediately without waiting for culture results 1

Step 2: Choose First-Line Agent Based on Organism

For Trichophyton species (most common in North America):

• Terbinafine 250 mg daily for 2-4 weeks is the preferred first-line agent due to its fungicidal activity, superior efficacy, and shorter treatment duration 1
• At 16 years old and likely >40 kg, the adult dose of 250 mg daily applies 1
• Gastrointestinal disturbances and rashes occur in <8% of children 1
• A meta-analysis confirms terbinafine is at least as effective as griseofulvin for Trichophyton infections 2

For Microsporum species:

• Griseofulvin is the preferred first-line agent 1
• Dosing: 500 mg daily (or 15-20 mg/kg/day if <50 kg) for 6-8 weeks 1, 3
• Terbinafine fails against Microsporum because it cannot be incorporated into hair shafts adequately and doesn't reach the scalp surface where arthroconidia are located 1
• Eight weeks of griseofulvin is significantly more effective than 4 weeks of terbinafine for confirmed Microsporum infection 1

Step 3: Add Adjunctive Measures

• Prescribe topical antifungal shampoo (selenium sulfide or ketoconazole 2%) as adjunctive therapy only—never as monotherapy 1, 4
• Screen and treat all family members and close contacts, especially for T. tonsurans infections where >50% of household members may be affected 1
• Clean hairbrushes and combs with bleach or 2% sodium hypochlorite solution 1

Step 4: Special Considerations for Inflammatory Disease

If kerion is present:

• Start oral antifungal therapy immediately without waiting for culture results 1
• Add topical or oral corticosteroids to reduce severe inflammation 1
• Recognize this is a fungal-driven inflammatory response, not a bacterial abscess, though secondary bacterial infection should be evaluated if clinically indicated 1

Second-Line Options for Treatment Failure

If initial therapy fails after 2-4 weeks with no clinical improvement:

• Itraconazole 100 mg daily for 2-4 weeks (effective against both Trichophyton and Microsporum species) 1, 5
• Fluconazole as an alternative for refractory cases with favorable tolerability 1

If clinical improvement occurs but mycology remains positive, continue current therapy for an additional 2-4 weeks 1

Critical Treatment Principles

• The treatment endpoint is mycological cure, not just clinical improvement 1
• Repeat mycology sampling is mandatory until clearance is achieved 1
• Consider poor compliance, suboptimal drug absorption, organism insensitivity, or reinfection if treatment fails 1
• Baseline liver function tests are recommended before initiating terbinafine or itraconazole, especially with pre-existing hepatic abnormalities 5

Common Pitfalls to Avoid

• Never use topical therapy alone—oral antifungal therapy is mandatory for tinea capitis 1
• Never use terbinafine for Microsporum infections due to poor efficacy 1
• Avoid underdosing griseofulvin; higher doses (20-25 mg/kg/day) are needed due to increasing treatment failures with lower doses 1, 6
• Do not exclude the patient from school—children receiving appropriate systemic and adjunctive topical therapy can attend school 1