Management of Skin Fungal Infections
For superficial dermatophyte infections (tinea corporis, cruris, pedis), use topical antifungals as first-line therapy; for tinea capitis and onychomycosis, oral terbinafine is the preferred systemic agent based on superior efficacy, tolerability, and cost-effectiveness.
Tinea Corporis and Tinea Cruris
First-Line Treatment
- Topical antifungals alone are appropriate for localized, treatment-naïve cases 1, 2
- Apply for 2-4 weeks minimum in naïve cases 2
- Topical azoles are preferred due to anti-inflammatory, antibacterial, and broad-spectrum activity 2
When to Escalate to Oral Therapy
Switch to combination systemic plus topical antifungals for:
- Extensive lesions
- Recalcitrant cases (failed topical therapy)
- Immunocompromised patients
- Hair follicle involvement 1, 2
Oral regimens:
- Terbinafine or itraconazole as preferred systemic agents 2
- Duration: >4 weeks for recalcitrant cases 2
Critical Pitfall
Never use topical corticosteroid-antifungal combinations - this practice was strongly discouraged as it can worsen infection and contribute to resistance 2
Tinea Capitis
Mandatory Oral Therapy
Topical therapy alone is NOT recommended - oral antifungals are required for clinical and mycological cure 3
Treatment Selection Based on Organism
For Trichophyton species (T. tonsurans, T. violaceum, T. soudanense):
- First-line: Terbinafine 3, 1
- <20 kg: 62.5 mg daily for 2-4 weeks
- 20-40 kg: 125 mg daily for 2-4 weeks
40 kg: 250 mg daily for 2-4 weeks
For Microsporum species (M. canis, M. audouinii):
- First-line: Griseofulvin 3
- <50 kg: 15-20 mg/kg/day for 6-8 weeks
50 kg: 1 g/day for 6-8 weeks
- Griseofulvin is more effective than terbinafine for Microsporum because terbinafine doesn't reach adequate concentrations in prepubertal children's hair shafts and scalp surface where Microsporum arthroconidia reside 3
Second-line (treatment failures):
- Itraconazole 50-100 mg daily or 5 mg/kg/day for 2-4 weeks 3
Treatment Failure Algorithm
- First assess: compliance, drug absorption, organism sensitivity, reinfection 3
- If clinical improvement but positive mycology: continue current therapy 2-4 more weeks 3
- If no clinical improvement: switch to second-line agent 3
Tinea Pedis
Treatment Approach
- Topical monotherapy may be insufficient 2
- Combination systemic plus topical antifungals recommended even for naïve cases due to higher treatment failure rates 2
- Duration: minimum 2-4 weeks for naïve cases, >4 weeks for recalcitrant disease 2
Onychomycosis
Dermatophyte Onychomycosis (Most Common)
First-line: Oral terbinafine - superior to all alternatives based on higher cure rates and lower relapse 4, 1
Dosing:
- Fingernails: 250 mg daily for 6 weeks 4
- Toenails: 250 mg daily for 12-16 weeks 4
- Re-evaluate at 3-6 months; continue if disease persists 4
Evidence: In head-to-head trials, terbinafine achieved 55% complete cure vs. 26% with itraconazole at 72 weeks, with significantly lower relapse rates (23% vs. 53%) at 5-year follow-up 4
Second-line: Itraconazole 4
- Continuous: 200 mg daily for 12 weeks
- Pulse therapy: 400 mg daily for 1 week/month (2 pulses for fingernails, 3 for toenails)
Third-line: Fluconazole (off-label) 4
- 450 mg weekly for 3 months (fingernails) or ≥6 months (toenails)
- Less effective than terbinafine or itraconazole but useful for intolerance 4
Candida Onychomycosis
First-line: Itraconazole - superior efficacy with shorter treatment duration 4
- 200 mg daily OR pulse therapy 400 mg daily for 1 week/month
- Minimum duration: 4 weeks for fingernails, 12 weeks for toenails 4
- Cure rates: 92% with itraconazole vs. 40% with terbinafine in 4-month pulse regimens 4
Alternative: Fluconazole (if itraconazole contraindicated) 4
- 50 mg daily OR 300 mg weekly
- Same duration as itraconazole
Important distinction: Terbinafine requires 48 weeks to achieve comparable cure rates (70-85%) for Candida species 4 - making it impractical as first-line
Nondermatophyte Molds
Preferred: Itraconazole - broader coverage than terbinafine 4
- Standard pulse regimen: 200-400 mg daily for 1 week/month for 3 months
- Terbinafine shows lowest activity against most nondermatophyte molds despite variable clinical outcomes 4
Monitoring Requirements
- Baseline liver function tests and CBC recommended for: heavy alcohol use, hepatitis history, hematological abnormalities, or pediatric patients 4
- Terbinafine contraindicated in active/chronic liver disease 4
Pediatric Considerations
Onychomycosis in Children
- Systemic therapy is effective and safe 4
- Terbinafine not licensed for pediatric onychomycosis - baseline monitoring essential 4
- Consider topical therapy given thinner, faster-growing nails, though clinical trial data lacking 4
- Examine for concomitant tinea capitis and pedis; screen family members 4
Emerging Resistant Infections
Critical alert: Terbinafine-resistant strains (T. indotineae, T. mentagrophytes genotype VII, resistant T. rubrum) are causing severe, difficult-to-treat infections globally 5
When to Suspect Resistance
- Lack of response to first-line topical or oral antifungals 1
- More severe presentation than classic tinea 1
- Chronic, recurrent, or relapse cases 2
Management Approach
- Obtain fungal culture for chronic/recurrent/recalcitrant cases 2
- Consider DNA sequencing or MALDI-ToF for species identification 5
- Perform antifungal susceptibility testing 5
- May require prolonged oral antifungal therapy with alternative agents 1
Key Practice Points
Diagnostic confirmation: KOH microscopy recommended as point-of-care testing; culture indicated for chronic/recurrent/multisite cases 2
Antifungal stewardship: Avoid combination antifungal-corticosteroids to prevent resistance and treatment failure 1, 2
Address non-adherence first: Before assuming resistance, evaluate compliance and other causes of treatment failure 6