What is the most effective treatment for onychomycosis (fungal infection of the nail)?

Treatment of Onychomycosis

Oral terbinafine is the most effective treatment for onychomycosis, with superior cure rates and lower relapse rates compared to other antifungal agents. 1 This should be considered first-line therapy for most cases of dermatophyte onychomycosis, which represents the majority of nail fungal infections.

Diagnostic Confirmation

Before initiating treatment:

• Obtain appropriate nail specimens for laboratory testing (KOH preparation, fungal culture, or nail biopsy) to confirm diagnosis 2
• Incorrect diagnosis is the most common cause of treatment failure 1
• Avoid treating based on clinical appearance alone

Treatment Algorithm

First-line therapy for confirmed dermatophyte onychomycosis:

• Oral terbinafine 250 mg daily for:
  • 6 weeks for fingernail infections
  • 12 weeks for toenail infections 1
• Terbinafine is fungicidal with very low minimum inhibitory concentration (MIC) of approximately 0.004 μg/mL 1
• Provides mycological cure rates of 80-90% for fingernail infections and 70-80% for toenail infections 1

Second-line therapy (if terbinafine contraindicated):

• Oral itraconazole either:
  • 200 mg daily for 12 weeks continuously, OR
  • 400 mg daily for 1 week per month ("pulse therapy"):
    • Two pulses for fingernail infections (21 days apart)
    • Three pulses for toenail infections 1
• Less effective than terbinafine for dermatophyte infections but better for Candida infections 1

Topical therapy options (for mild cases or when oral therapy contraindicated):

• Ciclopirox 8% nail lacquer applied daily for 48 weeks with monthly removal of unattached, infected nail 3
• Only appropriate for:
  • Mild to moderate onychomycosis
  • Cases without lunula involvement
  • When systemic therapy is contraindicated 3
• Mycological cure rates of 29-36% (compared to 9-11% with vehicle) 4

Special Populations

Immunosuppressed patients:

• Terbinafine or fluconazole preferred over itraconazole due to reduced risk of interactions with antiretrovirals 1
• Griseofulvin is least effective in immunosuppressed patients 1

Diabetic patients:

• Terbinafine is preferred over itraconazole due to contraindication of itraconazole in congestive heart failure (more common in diabetics) 1
• Topical treatments may be appropriate for mild-to-moderate infections when drug interaction risk is high 1

Management of Treatment Failures

If treatment fails despite appropriate therapy:

1. Consider presence of dermatophytoma (dense white lesion beneath nail) which may require mechanical removal 1
2. Evaluate for other factors:
   • Poor compliance
   • Poor drug absorption
   • Immunosuppression
   • Dermatophyte resistance
   • Nail thickness >2mm
   • Severe onycholysis 1
3. Options for treatment failures:
   • Alternative oral antifungal
   • Partial nail removal combined with antifungal therapy 1

Prevention of Recurrence

Onychomycosis has high recurrence rates (40-70%) 1. Prevention strategies include:

• Wearing protective footwear in public areas
• Applying antifungal powders to shoes and feet
• Keeping nails short
• Avoiding sharing nail clippers
• Discarding or disinfecting contaminated footwear 1

Common Pitfalls to Avoid

1. Treating without diagnostic confirmation - leads to unnecessary treatment and poor outcomes 1
2. Inadequate treatment duration - full nail regrowth takes up to 18 months for toenails 1
3. Overlooking dermatophytomas - these dense fungal masses require mechanical removal 1
4. Ignoring drug interactions - particularly with itraconazole which has numerous potential interactions 1
5. Failing to address prevention - high recurrence rates without preventive measures 1

Onychomycosis should not be considered a trivial disease, as it can significantly impact quality of life and may lead to complications such as cellulitis, particularly in elderly patients with diabetes or peripheral vascular disease 1.