What is the appropriate treatment and dosage for a child with a history of tinea capitis, previously treated with griseofulvin and ketoconazole (antifungal) shampoo, and currently on itraconazole treatment?

Treatment of Tinea Capitis After Griseofulvin Failure

For a child with tinea capitis who has failed griseofulvin treatment, itraconazole at 5 mg/kg/day for 2-4 weeks is the appropriate second-line therapy, and the current treatment should be continued. 1

Understanding Treatment Failure with Griseofulvin

When griseofulvin fails, several factors must be considered before switching therapy:

• Assess compliance and absorption: Poor adherence or suboptimal drug absorption are common causes of treatment failure 1
• Verify adequate dosing: Griseofulvin requires 15-20 mg/kg/day (up to 20-25 mg/kg/day for resistant cases), and underdosing is a frequent pitfall 1, 2
• Confirm organism identification: The causative species determines optimal therapy—griseofulvin is preferred for Microsporum species but may fail against certain Trichophyton strains 1, 2
• Consider reinfection: Screen and treat family members and close contacts, especially for T. tonsurans infections, as over 50% of household members may be affected 3

Itraconazole as Second-Line Therapy

Itraconazole is the recommended second-line agent when griseofulvin fails, with proven efficacy against both Trichophyton and Microsporum species. 1

Dosing Protocol

• Standard dose: 5 mg/kg/day for 2-4 weeks 1, 2
• Alternative regimen: 50-100 mg/day for 4 weeks 1
• Administration: Can be given as oral solution or capsules; oral solution has 30% higher bioavailability when taken fasting 4

Efficacy Evidence

• Itraconazole achieves 87% mycological cure rate versus 57% for griseofulvin in comparative studies 3
• Effective against both major causative organisms (Trichophyton and Microsporum species) 1, 5
• Well-tolerated in children with minimal side effects 5

Critical Management Principles

Treatment Endpoint

• Mycological cure is mandatory, not just clinical improvement 1
• Repeat mycology sampling (scalp scrapings, hair pluck, brush, or swab) must be performed until clearance is documented 1
• Treatment failure occurs if no clinical improvement is seen after the initial course 1

When to Continue vs. Switch Therapy

• Continue current therapy for 2-4 additional weeks if clinical improvement is present but mycology remains positive 1, 2
• Switch to itraconazole immediately if no clinical improvement occurs after the initial treatment course 1, 2

Adjunctive Measures (Essential for Success)

• Antifungal shampoo: Continue ketoconazole or selenium sulfide shampoo as adjunctive therapy to reduce spore transmission 1, 6
• Environmental decontamination: Clean hairbrushes and combs with bleach or 2% sodium hypochlorite solution 1
• Screen household contacts: All family members and close contacts must be evaluated and treated if infected 1, 3
• School attendance: Children can attend school while on appropriate systemic and topical therapy 1

Important Drug Considerations for Itraconazole

Pharmacokinetics

• Peak plasma concentrations reached within 2.5 hours 4
• Steady-state achieved in approximately 15 days with repeated dosing 4
• Terminal half-life increases to 34-42 hours with repeated dosing 4
• Extensively metabolized by CYP3A4 4

Drug Interactions (Critical to Review)

• Enhanced toxicity with: warfarin, certain antihistamines, antipsychotics, midazolam, digoxin, and simvastatin 3
• Licensing note: Itraconazole is licensed for children over 12 years in the UK but used off-label in younger children in some countries 3

Monitoring

• Liver enzyme monitoring is generally unnecessary if therapy is limited to ≤4 weeks 6
• Most common adverse effects are gastrointestinal symptoms 6, 5

Alternative Third-Line Option

If itraconazole fails or is contraindicated:

• Fluconazole: Favorable tolerability profile, available in liquid form, particularly useful in younger children who cannot swallow tablets 1, 6
• Limitation: Not licensed for tinea in children under 10 years in the UK, less cost-effective than other options 3

Common Pitfalls to Avoid

• Never use topical therapy alone—it cannot eradicate scalp infections and must only be adjunctive 1
• Do not stop treatment based on clinical improvement alone—mycological cure must be documented 1
• Avoid switching therapy prematurely—if clinical improvement is occurring, extend current therapy rather than switching 1, 2
• Do not neglect household screening—failure to treat infected contacts leads to reinfection 1, 3