What is the recommended treatment for a 16-year-old with moderate to severe tinea corporis (ringworm)?

Treatment of Moderate to Severe Tinea Corporis in a 16-Year-Old

For moderate to severe ringworm (tinea corporis) in a 16-year-old, oral antifungal therapy is required, with terbinafine 250 mg daily for 2-4 weeks as the preferred first-line treatment, particularly if Trichophyton species are suspected. 1

First-Line Oral Antifungal Options

The evidence clearly indicates that topical therapy alone is insufficient for moderate to severe disease, necessitating systemic treatment 1. The choice between agents should be guided by the causative organism when known:

Terbinafine (Preferred for Trichophyton species)

• Dosing: 250 mg daily for 2-4 weeks (patient is >40 kg) 2
• Advantages: Superior efficacy against Trichophyton tonsurans (the most common cause in North America), shorter treatment duration improving compliance, and favorable safety profile 2, 1
• Efficacy: Achieves 94% effective treatment rates in clinical trials 3

Itraconazole (Broad-spectrum alternative)

• Dosing: 100 mg daily for 15 days, or 5 mg/kg/day for 2-4 weeks 1, 2
• Advantages: Effective against both Trichophyton and Microsporum species with 87% mycological cure rate 1
• Considerations: Licensed for children over 12 years in the UK; has important drug interactions with warfarin, certain antihistamines, antipsychotics, midazolam, digoxin, and simvastatin 2

Griseofulvin (Alternative, longer duration)

• Dosing: 500 mg daily (or 10 mg/kg/day) for 2-4 weeks for tinea corporis 4
• Disadvantages: Requires longer treatment duration (2-4 weeks minimum), less convenient dosing, and increasingly expensive 2
• Efficacy: Achieves 92% effective treatment rates but requires extended therapy 3

Treatment Algorithm

Step 1: Confirm diagnosis

• Obtain scrapings for KOH preparation or fungal culture before initiating therapy to identify the causative organism 4
• If moderate to severe disease with classic clinical signs (scaling, inflammation, extensive lesions), it is reasonable to start treatment while awaiting mycology results 2

Step 2: Select initial therapy

• If Trichophyton species suspected or confirmed: Terbinafine 250 mg daily for 2-4 weeks 2, 1
• If Microsporum species suspected or confirmed: Griseofulvin 500 mg daily for 2-4 weeks 2
• If organism unknown or mixed infection possible: Itraconazole 100 mg daily for 15 days 1

Step 3: Monitor for treatment failure

• If clinical improvement occurs but mycology remains positive: Continue current therapy for an additional 2-4 weeks 2
• If no initial clinical improvement: Switch to second-line therapy 2

Second-Line Therapy for Treatment Failure

If first-line treatment fails, consider:

• Itraconazole 100 mg daily for 4 weeks if not used initially 2
• Switch from terbinafine to griseofulvin for Trichophyton infections, or vice versa 2
• Fluconazole can be considered as a third-line option, though it is less cost-effective and has limited comparative efficacy data 2

Critical Management Considerations

Treatment Endpoint

• The definitive endpoint is mycological cure, not just clinical resolution 1
• Repeat mycology sampling is essential until mycological clearance is documented 2
• Clinical relapse will occur if medication is discontinued before the organism is eradicated 4

Prevention of Recurrence

• Screen and treat all family members, as over 50% may be affected with anthropophilic species like T. tonsurans 2, 1
• Clean all contaminated items (combs, brushes, towels) with disinfectant or 2% sodium hypochlorite solution 1
• Avoid skin-to-skin contact with infected individuals and do not share personal items 1

Common Pitfalls to Avoid

• Do not rely on topical therapy alone for moderate to severe disease—this will result in treatment failure 2
• Do not stop treatment based solely on clinical improvement—mycological cure must be confirmed 1
• Do not ignore family screening—failure to treat household contacts leads to reinfection 2, 1
• Consider compliance issues, suboptimal drug absorption, organism resistance, and reinfection if treatment fails 2

Safety Profile

All three first-line agents have favorable safety profiles 3:

• Gastrointestinal symptoms are the most common adverse effects, occurring in <8% of patients 2
• Monitoring liver enzymes is generally unnecessary for treatment courses ≤4 weeks 5
• Adverse effects requiring discontinuation are rare (0.8% with griseofulvin) 2