What is the appropriate treatment for cutaneous ringworm (tinea corporis, tinea cruris, or tinea pedis) in an otherwise healthy adult?

Treatment of Cutaneous Ringworm (Tinea Corporis, Tinea Cruris, Tinea Pedis)

For otherwise healthy adults with cutaneous ringworm, topical terbinafine 1% cream applied twice daily for 1 week is the first-line treatment for tinea corporis and tinea cruris, while tinea pedis requires the same regimen but should be extended to 2 weeks if needed. 1

First-Line Topical Therapy

Tinea Corporis and Tinea Cruris

• Terbinafine 1% cream twice daily for 1 week achieves approximately 94% mycological cure and is superior to all other topical agents 2
• The major advantage is the dramatically shorter treatment duration (1 week versus 4 weeks for other agents), which significantly improves adherence 2
• If terbinafine is unavailable, ciclopirox olamine 0.77% cream/gel twice daily for 4 weeks achieves approximately 60% cure at end of treatment and 85% two weeks after completion 1
• Clotrimazole 1% cream twice daily for 4 weeks is less effective but widely available over-the-counter 1

Tinea Pedis

• Terbinafine 1% cream twice daily for 1 week is more effective than 4 weeks of clotrimazole, with 93.5% mycological cure versus 73.1% 3
• For interdigital tinea pedis specifically, the American Academy of Pediatrics recommends terbinafine 1% cream twice daily for 1 week 1
• Ciclopirox olamine 0.77% cream/gel twice daily for 4 weeks is an alternative, achieving 60% cure at end of treatment 4, 1
• Naftifine 1% gel is FDA-approved for tinea pedis, cruris, and corporis caused by common dermatophytes 5

Oral Therapy Indications

Reserve oral antifungals for severe disease, failed topical therapy after 4 weeks, extensive or multiple lesions, concomitant onychomycosis, or immunocompromised patients. 1, 2

Oral Treatment Options

• Terbinafine 250 mg once daily for 1-2 weeks is the most effective oral treatment, with fungicidal action allowing shorter duration 1
• Oral terbinafine for 1 week has similar mycological efficacy to 4 weeks of topical clotrimazole but with faster clinical resolution 4
• Itraconazole 100 mg daily for 2 weeks (or 200 mg daily for 7 days) is an alternative with comparable efficacy but slightly higher relapse rates 1, 6
• Itraconazole 100 mg daily for 15 days showed 87% mycological cure in adolescents and adults, superior to griseofulvin 500 mg daily (57% cure) 4
• Fluconazole 50-100 mg daily or 150 mg once weekly for 2-3 weeks is less effective than terbinafine or itraconazole but has fewer drug interactions 1, 6
• Griseofulvin is not recommended as first-line therapy due to lower efficacy (30-40% cure rates) and longer treatment duration (2-4 weeks for tinea corporis, 4-8 weeks for tinea pedis) 1, 7

Critical Management Principles

Diagnosis Confirmation

• Confirm diagnosis with potassium hydroxide (KOH) preparation or fungal culture before initiating treatment, especially if diagnosis is uncertain 2, 7
• The endpoint should be mycological cure (negative microscopy and culture), not just clinical improvement 2

Common Pitfalls to Avoid

• Failing to examine for concomitant onychomycosis, which requires 12-16 weeks of oral terbinafine and serves as a reservoir for reinfection 1
• Neglecting to address contaminated footwear—shoes harbor large numbers of viable dermatophyte spores that cause recurrence 1
• Treating only the index patient without addressing subclinical infections in household members leads to repeated episodes 1
• Stopping treatment when symptoms resolve rather than continuing until mycological cure is achieved 7

Prevention Strategies

• Thoroughly dry interdigital spaces after bathing—this single measure significantly reduces recurrence risk 1
• Apply antifungal foot powder after bathing, which reduces infection rates from 8.5% to 2.1% 1
• Change to cotton, absorbent socks daily 1
• Decontaminate footwear by placing naphthalene mothballs in shoes sealed in a plastic bag for minimum 3 days, or spray terbinafine solution inside shoes periodically 1
• Treat all infected family members simultaneously to prevent reinfection cycles 1
• Cover active foot lesions with socks before wearing underwear to prevent spread to groin 1

Special Considerations

Use of Combination Antifungal/Corticosteroid Products

• Combination products containing low-potency nonfluorinated corticosteroids may be used initially for symptomatic inflamed lesions in otherwise healthy adults with good compliance 8
• Substitute with pure antifungal once symptoms are relieved—never exceed 2 weeks for tinea cruris or 4 weeks for tinea pedis/corporis 8
• Contraindications include application on occluded areas, facial lesions, children <12 years, and immunosuppressed patients 8

Monitoring for Oral Terbinafine

• Baseline liver function tests and complete blood count are recommended in adults with history of hepatotoxicity or hematologic abnormalities 1
• Monitor for rare but serious adverse events including isolated neutropenia and hepatic failure, particularly in patients with pre-existing liver disease 1
• Common adverse effects include headache, taste disturbance, and gastrointestinal upset 1

Athletes and Return to Competition

• Athletes require minimum 72 hours of topical or systemic antifungal therapy before return to contact sports 1
• Lesions must be covered with gas-permeable dressing followed by underwrap and stretch tape 1
• Exclude from swimming pools and discourage barefoot walking in locker rooms until treatment initiated 1