What are the oral therapies for tinea (fungal) infections?

Oral Therapies for Tinea Infections

The most effective oral antifungal medications for tinea infections include terbinafine, fluconazole, itraconazole, and griseofulvin, with the choice depending on the specific type of tinea infection and patient factors. Oral therapy is generally required for tinea capitis, extensive tinea corporis/cruris, chronic or resistant tinea pedis, and tinea unguium (onychomycosis).

First-Line Oral Antifungal Options

Griseofulvin

• FDA-approved indication: Treatment of dermatophyte infections of skin, hair, and nails caused by various species including Epidermophyton, Microsporum, and Trichophyton 1
• Dosing:
  • Children <50kg: 20-25 mg/kg/day for 6-8 weeks
  • Adults: Standard dosing of 500-1000 mg daily
• Duration:
  • Tinea corporis/cruris: 2-4 weeks
  • Tinea capitis: 6-8 weeks (may require longer)
  • Tinea pedis: 4-8 weeks
  • Tinea unguium: 6+ months
• Best for: First-line for tinea capitis caused by Microsporum species and kerion (unless Trichophyton confirmed) 2, 3

Terbinafine

• Dosing:
  • Adults: 250 mg daily
  • Children: Weight-based dosing
• Duration:
  • Tinea corporis/cruris: 2 weeks
  • Tinea capitis: 4 weeks
  • Tinea pedis: 2-6 weeks
  • Tinea unguium: 6 weeks for fingernails, 12 weeks for toenails
• Best for: First-line for tinea capitis caused by Trichophyton species and onychomycosis 3, 4
• Advantage: Higher cure rates compared to griseofulvin (RR 2.26,95% CI 1.49-3.44) 4

Itraconazole

• Dosing:
  • Adults: 100-200 mg daily or pulse therapy
  • Children: 3-5 mg/kg/day
• Duration:
  • Tinea corporis/cruris: 1-2 weeks
  • Tinea pedis: 2-4 weeks
  • Tinea unguium: Pulse therapy (1 week per month) for 2-3 months
• Best for: Alternative for onychomycosis and extensive tinea infections 5

Fluconazole

• Dosing:
  • Adults: 150-300 mg weekly
  • Children: 6 mg/kg weekly
• Duration:
  • Tinea corporis/cruris: 2-4 weeks
  • Tinea pedis: 4-6 weeks
  • Tinea unguium: 3-6 months
• Best for: Alternative when other agents are contraindicated

Indications for Oral Therapy

1. Tinea capitis: Always requires oral therapy 2

   • First-line: Terbinafine for Trichophyton species; griseofulvin for Microsporum species
   • Duration: 4-8 weeks depending on agent and response

2. Extensive tinea corporis/cruris:

   • Consider oral therapy when infection covers large areas or is resistant to topical treatment 6
   • First-line: Terbinafine or fluconazole
   • Duration: 2-4 weeks

3. Severe or chronic tinea pedis:

   • Indicated for moccasin-type tinea pedis or when topical therapy fails 3
   • First-line: Terbinafine
   • Alternative: Itraconazole
   • Duration: 2-6 weeks

4. Tinea unguium (onychomycosis):

   • First-line: Terbinafine (higher cure rates)
   • Alternative: Itraconazole (pulse therapy)
   • Duration: 6-12 weeks for terbinafine; 2-3 months of pulse therapy for itraconazole 5, 4

Special Considerations

Immunocompromised Patients

• Oral therapy often preferred over topical due to more extensive disease 7
• Terbinafine may be preferred due to fewer drug interactions compared to azoles
• Longer treatment durations may be necessary

Drug Interactions

• Terbinafine: Relatively low potential for drug interactions, making it suitable for patients on multiple medications 7
• Azoles (fluconazole, itraconazole): Significant CYP450 interactions; caution with statins, anticoagulants, and other medications 8
• Griseofulvin: Fewer drug interactions but may reduce efficacy of oral contraceptives

Treatment Failures

• Consider culture and susceptibility testing
• Switch to alternative agent with different mechanism of action
• Extend duration of therapy
• Rule out reinfection sources (family members, pets)

Common Pitfalls and Caveats

1. Misdiagnosis: Always confirm diagnosis with KOH preparation or culture before starting oral therapy
2. Inadequate duration: Continue treatment until clinical clearing plus 1-2 additional weeks
3. Neglecting adjunctive measures: Address predisposing factors (moisture, occlusion)
4. Drug interactions: Screen for potential interactions, especially with azoles
5. Hepatotoxicity risk: Monitor liver function with prolonged therapy
6. Recurrence: Educate patients on proper hygiene and preventive measures

Oral antifungal therapy should be selected based on the specific tinea infection type, extent of disease, patient comorbidities, and potential drug interactions to maximize efficacy while minimizing adverse effects.