What is the treatment for onychomycosis (fungal infection of the nail) in one nail?

Treatment of Single Nail Fungal Infection (Onychomycosis)

For a single nail with fungal infection, topical antifungal treatment with amorolfine 5% nail lacquer applied once or twice weekly for 6-12 months is the recommended first-line therapy. 1, 2

Diagnostic Confirmation

Before initiating treatment:

• Confirm diagnosis through microscopic examination with potassium hydroxide (KOH), mycological culture, or nail biopsy 2
• Only approximately 50% of nail dystrophies are actually caused by fungi, making confirmation essential

Treatment Algorithm

Step 1: Assess Severity and Extent

• Mild to moderate infection (suitable for topical therapy):
  • Less than 80% of nail plate affected
  • No lunula involvement
  • No longitudinal streaks
  • No matrix involvement

Step 2: First-line Treatment for Single Nail

• Topical antifungal options:
  • Amorolfine 5% nail lacquer - applied once or twice weekly for 6-12 months (50% efficacy) 1, 2
  • Ciclopirox 8% nail lacquer - applied daily for up to 48 weeks (34% mycological cure rate) 1, 2, 3
  • Tioconazole 28% solution - though less effective (22% cure rate) 1

Step 3: Application Technique

• File away as much diseased nail as possible before application
• Apply to affected nail and allow to dry
• For amorolfine: persists in nail for 14 days after application
• For ciclopirox: must be removed with alcohol once weekly before reapplication 3

When to Consider Oral Therapy

Consider oral antifungal therapy if:

• Topical treatment fails after adequate trial
• Infection involves >80% of nail plate
• Matrix/lunula involvement exists
• Longitudinal streaks are present

Oral options (in order of preference):

1. Terbinafine - 250mg daily for 6 weeks (fingernails) or 12 weeks (toenails) 2, 4
2. Itraconazole - 200mg twice daily for 1 week per month × 2-3 pulses 1, 2
3. Fluconazole - 150-450mg once weekly for at least 6 months 2

Special Considerations

• Causative organism matters:

  • Dermatophytes (most common): respond well to terbinafine
  • Candida infections: itraconazole is more effective 1, 2
  • Non-dermatophyte molds: may require different approaches

• Treatment failure causes:

  • Poor compliance
  • Poor drug absorption
  • Subungual dermatophytoma (may require partial nail removal)
  • Zero nail growth
  • Immunosuppression 2

Prevention of Recurrence

• Keep nails short and clean
• Dry feet thoroughly after bathing
• Wear cotton, absorbent socks and change daily
• Apply antifungal powders to shoes
• Avoid sharing nail clippers
• Wear protective footwear in public areas 2

Common Pitfalls to Avoid

• Not confirming diagnosis before treatment
• Inadequate treatment duration
• Unrealistic expectations about improvement speed
• Not addressing predisposing factors
• Neglecting preventive measures 2

For a single nail with fungal infection, topical therapy is appropriate and cost-effective, avoiding the potential side effects and drug interactions associated with systemic therapy.