What is the recommended treatment for onychomycosis (fungal infection of the nails) in adults?

Treatment for Onychomycosis

Oral terbinafine 250 mg once daily is the first-line treatment for onychomycosis: 6 weeks for fingernails and 12 weeks for toenails. 1, 2, 3

Treatment Algorithm

Step 1: Confirm Diagnosis

• Obtain nail specimens for laboratory testing (KOH preparation, fungal culture, or nail biopsy) before initiating treatment 2, 3
• Treatment failure most commonly results from incorrect diagnosis made on clinical grounds alone without mycological confirmation 2

Step 2: Assess Disease Severity and Select Treatment Approach

For Limited Disease (Topical Therapy Candidates):

• Superficial white onychomycosis only 1, 2
• Very early distal lateral subungual onychomycosis with <80% nail plate involvement and no lunula involvement 1, 2
• When oral therapy is contraindicated 1, 2

For All Other Cases (Oral Therapy Required):

• Any infection beyond the above criteria requires oral therapy 2

Step 3: Select Specific Treatment

First-Line Oral Therapy:

• Terbinafine 250 mg daily (Strength A, Level 1+ evidence) 1, 2
  • Fingernails: 6 weeks 1, 2
  • Toenails: 12 weeks 1, 2
  • Highest efficacy for dermatophyte infections with complete cure rates of 38% and mycological cure rates of 70% 4

Alternative Oral Therapy:

• Pulse itraconazole 200 mg twice daily for 1 week per month 1, 2
  • Fingernails: 2 pulses (2 months) 1
  • Toenails: 3 pulses (3 months) 1
  • Preferred for Candida species infections 1, 2
  • Complete cure rates of 14% and mycological cure rates of 54% for dermatophytes 4

Topical Therapy Options (When Appropriate):

• Amorolfine 5% nail lacquer applied once or twice weekly for 6-12 months after filing diseased nail 1, 2

  • Approximately 50% effectiveness in distal nail infections 1, 2
  • Mycological cure rates typically 30% lower than clinical improvement 1

• Ciclopirox 8% nail lacquer applied once daily 1, 5

  • Fingernails: up to 24 weeks 1
  • Toenails: up to 48 weeks 1, 5
  • Mycological cure 34% vs. 10% placebo, but clinical complete cure only 8% vs. 1% placebo 1
  • Must be used with monthly removal of unattached infected nail by healthcare professional 5

• Efinaconazole 10% topical solution applied once daily for 48 weeks 1, 6

  • Mycological cure rates approaching 50%, complete cure in 15% 1

Special Population Considerations

Diabetic Patients:

• Terbinafine is strongly preferred over itraconazole 1, 2
• Low risk of drug interactions and hypoglycemia 1
• Itraconazole contraindicated in congestive heart failure, which has increased prevalence in diabetics 1
• Onychomycosis is a significant predictor for foot ulcer development in diabetes 1

Immunosuppressed Patients:

• Terbinafine or fluconazole preferred over itraconazole 1, 2
• Reduced drug interactions with antiretrovirals and immunosuppressants 1, 2
• Griseofulvin is least effective in HIV-positive patients 1

Pediatric Patients:

• Terbinafine daily dosing based on weight 1
  • <20 kg: 62.5 mg/day 1
  • 20-40 kg: 125 mg/day 1

  • 40 kg: 250 mg/day 1

  • Duration: 6 weeks for fingernails, 12 weeks for toenails 1
• Pulse itraconazole 5 mg/kg/day for 1 week per month 1
  • Fingernails: 2 months 1
  • Toenails: 3 months 1
• Pediatric cure rates are higher than adults (88-100% in studies) 1, 2

Critical Pitfalls to Avoid

Treatment Selection Errors:

• Using topical therapy for extensive disease results in predictable failure 2
• Underdosing or insufficient treatment duration leads to poor outcomes 2
• Cure rates are usually lower with ciclopirox compared to amorolfine despite no head-to-head trials 1

Drug Interaction Concerns:

• Monitor patients taking terbinafine with tricyclic antidepressants, SSRIs, atypical antipsychotics, beta blockers, or tamoxifen for drug-drug interactions 7
• Itraconazole has significant drug interactions, particularly with antiretrovirals and immunosuppressants 1, 2
• Concomitant use of ciclopirox topical solution with systemic antifungals is not recommended 5

Realistic Expectations:

• Treatment failure rates of 20-30% are common even with the most effective agents 2
• Recurrence rates are high (40-70%) requiring preventive strategies 2
• Complete cure takes time due to slow nail growth; mycological cure rates are typically 30% better than clinical cure rates 6
• Clinical improvement with topical antifungals may not equal mycological cure, which has invariably lower rates 1

Monitoring Requirements:

• Confirm diagnosis before treatment to avoid the most common cause of treatment failure 2
• For ciclopirox, monthly removal of unattached infected nail by healthcare professional is required 5
• Monitor for application site reactions with topical agents, including dermatitis 6