What is the recommended treatment for onychomycosis (fungal infection of the nail) of a single nail?

Treatment of Onychomycosis of a Single Nail

For onychomycosis of a single nail, oral terbinafine 250 mg daily is the first-line treatment, administered for 6 weeks for fingernail infections and 12 weeks for toenail infections. 1, 2

Diagnostic Confirmation

Before initiating treatment, it's essential to confirm the diagnosis:

• Obtain appropriate nail specimens for laboratory testing (KOH preparation, fungal culture, or nail biopsy) 3
• Identify the causative organism (dermatophyte, Candida, or non-dermatophyte mold) as this will guide treatment selection 2

Treatment Algorithm

First-Line Treatment (Dermatophyte Infection)

• Oral terbinafine 250 mg daily:
  • Fingernail infection: 6 weeks
  • Toenail infection: 12 weeks 1, 2
• Expected cure rates: 80-90% for fingernail infections and 70-80% for toenail infections 1, 2
• Terbinafine is fungicidal against dermatophytes with superior efficacy compared to other antifungals 1

Alternative Treatment Options

1. Itraconazole (if terbinafine is contraindicated):

   • Continuous therapy: 200 mg daily for 12 weeks
   • Pulse therapy: 400 mg daily for 1 week per month (2 pulses for fingernails, 3 pulses for toenails) 1

2. Fluconazole (third-line option):

   • 150-450 mg once weekly
   • 3 months for fingernail infections
   • 6 months for toenail infections 1, 2

3. Topical therapy (for superficial white onychomycosis or early distal lateral subungual onychomycosis with <80% nail involvement):

   • Amorolfine 5% lacquer: applied once or twice weekly for 6-12 months 1
   • Ciclopirox 8% lacquer: applied once daily for up to 48 weeks 1, 4
   • Tioconazole 28% solution: applied twice daily for 6-12 months 1

Special Considerations

For Candida Infections

• Itraconazole is the first-line treatment 1
• Use the same dosage regimen as for dermatophytes 1

For Non-dermatophyte Mold Infections

• Itraconazole has broader antimicrobial coverage for non-dermatophyte molds compared to terbinafine 1

For Patients with Comorbidities

• Diabetics: Terbinafine is preferred over itraconazole due to lower risk of drug interactions and no contraindication in cardiac disease 1, 2
• Immunosuppressed patients: Terbinafine or fluconazole is preferred over itraconazole due to fewer interactions with antiretrovirals 1, 2

Monitoring and Follow-up

• Baseline liver function tests and complete blood count before starting terbinafine, especially in patients with:
  • History of hepatotoxicity
  • History of hematological abnormalities
  • Concomitant use of hepatotoxic drugs 1, 2
• Re-evaluate 3-6 months after treatment initiation 2
• Follow-up for at least 48 weeks (preferably 72 weeks) from the start of treatment to identify potential relapse 1

Management of Treatment Failure

If treatment fails, consider:

1. Poor compliance
2. Poor drug absorption
3. Immunosuppression
4. Dermatophyte resistance
5. Subungual dermatophytoma preventing drug penetration 1

In cases of treatment failure:

• Consider partial nail removal for subungual dermatophytoma 1
• Try an alternative drug 1
• Consider nail removal in combination with further antifungal therapy 1

Adjunctive Measures

• Keep nails short
• Disinfect footwear
• Treat concomitant tinea pedis
• Treat infected family members 2

Surgical avulsion followed by topical antifungal therapy is not recommended based on available evidence 1.