How should onychomycosis of the fingernails and toenails be treated?

Treatment of Fungal Nail Infections (Onychomycosis)

Oral terbinafine is the first-line treatment for fungal infections of fingernails and toenails, with superior efficacy compared to all alternatives. 1

Diagnostic Confirmation Required

Before starting any treatment, you must obtain mycological confirmation through microscopy and/or culture 2, 1. Approximately half of nail dystrophies are not fungal, making empiric treatment inappropriate and wasteful.

Treatment Algorithm by Severity

Mild Disease (<50% nail involvement, no matrix involvement)

• Topical monotherapy can be considered for very distal infection or superficial white onychomycosis 2, 1
• Efinaconazole 10% topical shows highest cure rates among topicals 3
• Amorolfine 5% lacquer once-twice weekly for 6-12 months is an alternative 1
• Important caveat: Topical treatments are inferior to systemic therapy in most cases 2

Moderate to Severe Disease (>50% involvement or matrix involvement)

First-line: Oral Terbinafine 1

• Fingernails: 250 mg daily for 6 weeks
• Toenails: 250 mg daily for 12-16 weeks
• Complete cure rates: 55% at 72 weeks, with only 23% relapse at 5 years 1
• Re-evaluate 3-6 months after treatment initiation 1

Second-line: Itraconazole (if terbinafine contraindicated) 1

• Pulse therapy: 400 mg daily for 1 week per month
  • Fingernails: 2 pulses
  • Toenails: 3 pulses
• Complete cure rates: only 26% at 72 weeks, with 53% relapse at 5 years 1
• Critical difference: Terbinafine demonstrates more than double the long-term cure rate compared to itraconazole 1

Third-line: Fluconazole (off-label, when others not tolerated) 1

• 450 mg weekly for 3 months (fingernails) or 6+ months (toenails)
• Lower efficacy than terbinafine or itraconazole 1
• Advantage: once-weekly dosing may improve compliance 1

Special Considerations for Candidal Onychomycosis

Itraconazole is most effective for Candida nail infections 2

• Same pulse dosing as dermatophyte infections
• Fingernails: 2 pulses
• Toenails: 3-4 pulses
• Most yeast infections with paronychia can be treated topically with imidazole lotion 2

Mandatory Monitoring

Before Starting Terbinafine 1

• Baseline liver function tests and complete blood count in patients with:
  • History of heavy alcohol consumption
  • Hepatitis or liver disease
  • Haematological abnormalities
  • Children (terbinafine not licensed for pediatric use)

Contraindications

• Terbinafine: Active or chronic liver disease, severe renal impairment 1
• Itraconazole: Heart failure, hepatotoxicity 1

Critical Patient Warnings

• Terbinafine: Warn about rare but potentially permanent taste disturbance 1
• Itraconazole: Multiple drug interactions via cytochrome P450 enzymes 1

Treatment Failure Management

If treatment fails after appropriate duration 2:

1. Verify compliance and adequate absorption
2. Rule out immunosuppression
3. Consider subungual dermatophytoma (tightly packed fungal mass preventing drug penetration)
4. For dermatophytoma: Partial nail removal + systemic therapy achieves near 100% cure 2
5. Consider alternative oral agent or nail avulsion with repeat systemic therapy during regrowth period 2

Expected Outcomes

Realistic cure rates to communicate to patients 2, 1:

• Fingernail infections: 80-90% cure rate
• Toenail infections: 70-80% cure rate
• Consistent 20-30% failure rate exists even with optimal terbinafine therapy 2

Common Pitfalls to Avoid

1. Never start treatment without mycological confirmation 2, 1
2. Don't use topical monotherapy for moderate-severe disease - it will fail 2, 1
3. Don't assume treatment failure means drug resistance - most failures are kinetic (drug can't penetrate dermatophytoma) 2
4. Don't forget to treat concurrent tinea pedis - reinfection source 1
5. Don't use itraconazole as first-line when terbinafine is available - significantly inferior long-term outcomes 1