What is the recommended treatment for tinea (dermatophyte infection of the skin, hair, or nails), including topical and oral options, dosing, duration, and precautions?

Treatment of Tinea (Dermatophyte Infections)

For localized tinea corporis or cruris, use topical terbinafine 1% cream once or twice daily for 1-2 weeks; for extensive disease, tinea capitis, or onychomycosis, oral terbinafine is first-line therapy with species-specific dosing and duration. 1

Diagnostic Confirmation Before Treatment

• Obtain mycological confirmation via KOH preparation or fungal culture before initiating systemic therapy. 2 This is critical because treatment duration is prolonged and expensive, particularly for onychomycosis.
• For tinea capitis with cardinal signs (scale, lymphadenopathy, alopecia, kerion), it is reasonable to start treatment while awaiting culture results. 2
• Identify the specific dermatophyte species, as this determines optimal drug selection—Trichophyton species respond best to terbinafine, while Microsporum species require griseofulvin. 2, 1

Topical Treatment for Localized Skin Infections

Topical therapy is appropriate for limited tinea corporis, tinea cruris, and tinea pedis without hair follicle involvement. 1, 3

First-Line Topical Agents

• Terbinafine 1% cream applied once or twice daily for 1-2 weeks achieves >80% mycological cure. 1, 4, 5
• Allylamines (terbinafine, naftifine) are superior to azoles because they are fungicidal and require shorter treatment duration. 1, 6, 5
• Continue treatment for at least one week after clinical clearing to prevent relapse. 5

When Topical Therapy Fails

• Topical treatment is inferior to systemic therapy except for very distal nail infection or superficial white onychomycosis. 2
• Switch to oral therapy for extensive infections, treatment failures, immunocompromised patients, or hair follicle involvement. 1

Oral Treatment: Species-Specific Selection

Tinea Capitis (Scalp Ringworm)

Oral therapy is mandatory for tinea capitis—topical treatment alone is ineffective. 2

For Trichophyton Species (T. tonsurans, T. violaceum, T. soudanense):

• Terbinafine is first-line: 2, 1
  • <20 kg: 62.5 mg daily for 2-4 weeks 2, 3
  • 20-40 kg: 125 mg daily for 2-4 weeks 2, 3

  • 40 kg: 250 mg daily for 2-4 weeks 2

• Terbinafine achieves cure in 2-4 weeks versus 6-18 weeks with griseofulvin, improving compliance. 2, 7

For Microsporum Species (M. canis, M. audouinii):

• Griseofulvin is first-line—terbinafine is significantly less effective for Microsporum. 2, 7
  • <50 kg: 15-20 mg/kg/day for 6-8 weeks 2

  • 50 kg: 1 g/day for 6-8 weeks 2

• Griseofulvin may require 12-18 weeks for Trichophyton infections at higher doses. 2
• Administer with fatty food to enhance absorption. 8

Second-Line for Tinea Capitis:

• Itraconazole 5 mg/kg/day is effective for both Trichophyton and Microsporum when first-line agents fail. 2

Tinea Corporis and Tinea Cruris (Body and Groin)

For extensive disease requiring systemic therapy:

• Terbinafine 250 mg daily for 1-2 weeks achieves 87% mycological cure, superior to griseofulvin's 57%. 1, 4
• Itraconazole 100 mg daily for 15 days is an alternative with 87% cure rate. 1
• Griseofulvin 500 mg daily for 2-4 weeks is less effective but remains an option. 8

Onychomycosis (Nail Infections)

Terbinafine is superior to itraconazole for dermatophyte onychomycosis and should be considered first-line treatment. 2, 7

Standard Dosing:

• Fingernails: 250 mg daily for 6 weeks 2, 7
• Toenails: 250 mg daily for 12 weeks (up to 16 weeks for severe cases) 2, 7
• Cure rates: 80-90% for fingernails, 70-80% for toenails 2

Pre-Treatment Requirements:

• Obtain baseline liver function tests (ALT, AST) and complete blood count before initiating terbinafine. 7
• Monitor LFTs throughout treatment in patients with history of hepatitis or heavy alcohol use. 7

For Candidal Onychomycosis:

• Itraconazole 400 mg daily for 1 week per month, repeated for 2 months (fingernails) or 3-4 months (toenails). 2
• Terbinafine is less effective against Candida species. 7

Treatment Failure Management:

• Re-evaluate 3-6 months after treatment initiation. 7
• If mycology remains positive but clinical improvement occurs, continue therapy for additional 2-4 weeks. 2
• Consider partial nail removal for subungual dermatophytoma (tightly packed fungal mass preventing drug penetration). 2
• Switch to itraconazole 200 mg daily for 12 weeks if second terbinafine course fails. 7

Critical Safety Considerations

Terbinafine Contraindications:

• Active or chronic liver disease (absolute contraindication) 7
• Lupus erythematosus 2, 3, 7
• Porphyria 3

Common Adverse Effects:

• Gastrointestinal disturbances (49%): nausea, diarrhea, abdominal pain 1, 7
• Rashes and dermatological reactions (<8% in children) 2
• Taste disturbance 1
• Headache 7
• Serious adverse events are rare (0.04% incidence), including Stevens-Johnson syndrome and toxic epidermal necrolysis. 1, 7

Griseofulvin Contraindications:

• Lupus erythematosus 2, 1
• Porphyria 2, 1
• Severe liver disease 2, 1

Drug Interactions:

• Terbinafine has minimal drug interactions compared to azoles, making it safer for patients on multiple medications. 1, 7
• Significant interactions involve drugs metabolized by cytochrome P450 2D6 (certain antidepressants, beta-blockers, antiarrhythmics). 1, 7
• Itraconazole has significant interactions with warfarin, certain antihistamines, antipsychotics, midazolam, digoxin, and simvastatin. 1
• Griseofulvin plasma concentration is decreased by rifampicin and increased by cimetidine. 2, 1

Prevention of Recurrence

• Screen and treat household contacts—over 50% may be affected with anthropophilic species like T. tonsurans. 1
• Clean all fomites (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
• Complete drying of skin folds after bathing prevents recurrence of tinea cruris. 3

Treatment Endpoint and Monitoring

• Mycological cure (negative microscopy and culture), not just clinical response, is the definitive treatment endpoint. 2, 1, 3
• Follow-up with repeat mycology sampling is recommended until clearance is documented. 1
• For onychomycosis, allow 48-72 weeks from treatment start for full evaluation, as terbinafine persists in nails for 6 months post-treatment. 7

Common Pitfalls to Avoid

• Do not start systemic therapy without mycological confirmation, especially for onychomycosis. 2 The expense, duration, and potential adverse effects mandate diagnostic certainty.
• Do not use terbinafine for Microsporum tinea capitis—it is significantly less effective than griseofulvin. 2, 7 Terbinafine is not excreted in sweat or sebum of prepubertal children and cannot reach scalp surface arthroconidia in Microsporum infections.
• Do not rely on topical therapy alone for tinea capitis or extensive onychomycosis. 2
• Do not prescribe terbinafine to patients with active liver disease. 7
• Consider poor compliance, suboptimal absorption, organism insensitivity, and reinfection when treatment fails. 2