What is the recommended treatment for superficial dermatophyte infection (ringworm) in an adult, including tinea corporis, tinea cruris, tinea pedis, tinea capitis, and special considerations for pregnancy or breastfeeding?

Treatment of Ringworm (Superficial Dermatophyte Infections)

For most localized tinea corporis, tinea cruris, and tinea pedis, topical terbinafine 1% cream applied once or twice daily for 1-2 weeks is the first-line treatment, achieving mycological cure rates exceeding 80%. 1, 2

Topical Treatment for Localized Skin Infections

First-line topical agents:

• Terbinafine 1% cream: Apply once or twice daily for 1-2 weeks for tinea corporis/cruris, achieving >80% mycological cure 1, 2, 3
• Terbinafine 1% cream for tinea pedis: Apply twice daily for 1 week (interdigital type), which is more effective than longer courses of other agents 2
• Alternative topical options: Clotrimazole 1% cream twice daily for 2-4 weeks, miconazole cream twice daily for 2-4 weeks, or ciclopirox 0.77% cream/gel twice daily for 4 weeks 1, 2

Treatment duration specifics:

• Tinea corporis/cruris: 2-4 weeks of topical therapy 1, 4
• Tinea pedis: 4-8 weeks, though terbinafine requires only 1 week 2, 4
• Continue treatment for at least one week after clinical clearing 5

Oral Therapy for Extensive or Resistant Disease

Indications for systemic treatment:

• Extensive disease covering large body surface area 1, 2
• Failed topical therapy after appropriate duration 2
• Concomitant onychomycosis requiring longer treatment 2
• Immunocompromised patients 2
• Severe moccasin-type tinea pedis 6

First-line oral agents:

• Terbinafine 250 mg daily: 1-2 weeks for tinea corporis/cruris/pedis, particularly effective against Trichophyton species with 86% mycological cure rate 1, 7, 3
• Itraconazole 100 mg daily: 15 days achieves 87% mycological cure rate, effective against both Trichophyton and Microsporum species 1, 7

Alternative oral agents:

• Itraconazole pulse dosing: 200-400 mg daily for 1 week per month 2
• Fluconazole: Less effective than terbinafine or itraconazole, reserved for when other agents are contraindicated due to fewer drug interactions 2, 7
• Griseofulvin: Not recommended as first-line due to lower efficacy (30-40% cure rates) and longer treatment duration (2-4 weeks for tinea corporis) 2, 4

Tinea Capitis Treatment

Systemic therapy is mandatory for tinea capitis as topical agents cannot penetrate hair follicles adequately. 7

Organism-directed therapy:

• For Trichophyton species (including T. tonsurans): Terbinafine with weight-based dosing for 2-4 weeks: children <20 kg receive 62.5 mg daily, 20-40 kg receive 125 mg daily, >40 kg and adults receive 250 mg daily 7
• For Microsporum species: Griseofulvin is preferred: children <50 kg receive 15-20 mg/kg/day for 6-8 weeks, children >50 kg and adults receive 1 g/day for 6-8 weeks 7, 4
• Kerion management: Start systemic antifungals immediately without waiting for culture results; griseofulvin is preferred unless Trichophyton is documented 7, 6

Important considerations:

• Obtain mycological confirmation via KOH preparation or culture before treatment when possible, but start immediately if kerion, severe scaling, lymphadenopathy, or alopecia are present 7
• Topical or oral corticosteroids may provide symptomatic relief for severe kerion inflammation 7
• Failure to treat kerion promptly leads to scarring and permanent hair loss 6

Tinea Unguium (Onychomycosis) Treatment

Oral antifungal therapy is the treatment of choice for nail infections, as topical agents have poor nail penetration. 7

First-line systemic options:

• Terbinafine 250 mg daily: Fingernails require 6 weeks, toenails require 12-16 weeks, with superior efficacy and shorter duration than itraconazole 7, 3
• Itraconazole continuous therapy: 200 mg daily for 12 weeks 7
• Itraconazole pulse therapy: 400 mg daily for 1 week per month (2 pulses for fingernails, 3 pulses for toenails) 7

Safety Monitoring and Drug Interactions

Baseline laboratory monitoring:

• Obtain liver function tests and complete blood count before initiating terbinafine or itraconazole, especially with pre-existing hepatic abnormalities 1, 7

Itraconazole drug interactions (significant):

• Enhanced toxicity with warfarin, certain antihistamines, antipsychotics, midazolam, digoxin, cisapride, and simvastatin 1, 7
• Contraindicated in heart failure 7
• Fluconazole has weaker cytochrome P450 inhibition and fewer interactions, making it useful when other agents are contraindicated 2

Terbinafine advantages:

• Over 70% oral absorption unaffected by food intake 2
• Lower risk of drug interactions compared to azoles 2
• Preferred for diabetic patients due to lower hypoglycemia risk 2

Treatment Endpoints and Follow-Up

Mycological cure, not just clinical improvement, is the definitive treatment endpoint. 1, 7

• Repeat mycology sampling (KOH preparation and culture) at the end of standard treatment period 1, 7
• Continue monthly sampling until mycological clearance is documented 7
• If clinical improvement occurs but mycology remains positive, continue current therapy for an additional 2-4 weeks 7
• If no initial clinical improvement, switch to second-line therapy 7

Prevention of Recurrence

Environmental and personal hygiene measures are essential to prevent reinfection:

• Treat all infected family members simultaneously, as over 50% may be affected with anthropophilic species like T. tonsurans 1, 2
• Clean contaminated combs, brushes, and towels with disinfectant or 2% sodium hypochlorite solution 1
• Wear protective footwear in public bathing facilities, gyms, and hotel rooms 2, 7
• Apply antifungal powders (miconazole, clotrimazole, or tolnaftate) inside shoes or spray terbinafine solution periodically 2, 7
• Discard old, moldy footwear or seal with naphthalene mothballs in plastic bag for minimum 3 days 2
• Change socks daily, wear cotton absorbent socks, and thoroughly dry between toes after showering 2
• Cover active foot lesions with socks before wearing underwear to prevent spread to groin 2
• Avoid sharing toenail clippers and keep nails as short as possible 2

Common Pitfalls to Avoid

Critical errors that lead to treatment failure:

• Starting treatment without mycological confirmation, as 50% of nail dystrophy is non-fungal 8
• Using topical therapy alone for tinea capitis or onychomycosis, which require systemic treatment 7
• Discontinuing antifungals when dermatophytid reactions (pruritic papular eruptions) occur after treatment initiation; these represent cell-mediated host response to dying dermatophytes and should be treated symptomatically with topical corticosteroids while continuing antifungals 7
• Failing to examine for concomitant onychomycosis, which serves as a reservoir for reinfection and requires extended treatment 2
• Neglecting to address contaminated footwear as a source of reinfection 2
• Stopping medication before mycological cure is achieved, leading to clinical relapse 4
• Using corticosteroid-antifungal combinations for >2 weeks (tinea cruris) or >4 weeks (tinea pedis/corporis), or using them in children <12 years, on facial lesions, diaper areas, or immunosuppressed patients 9

Special Populations

Athletes:

• Require minimum 72 hours of antifungal therapy before return to contact sports 2
• Cover lesions with gas-permeable dressing followed by underwrap and stretch tape 2
• Exclude from swimming pools and discourage barefoot walking in locker rooms until treatment initiated 2

Diabetic patients:

• Terbinafine is preferred over itraconazole due to lower drug interaction risk and hypoglycemia risk 2
• Up to one-third of diabetics have onychomycosis, which significantly predicts foot ulcer development 2

Pregnancy and breastfeeding:

• Systemic antifungals are generally avoided; topical therapy is preferred for localized infections 7