What are the treatment options for onychomycosis (fungal nail infection)?

Treatment for Fungal Nail Infection (Onychomycosis)

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

Confirm the Diagnosis First

• Always obtain mycological confirmation (KOH preparation, fungal culture, or nail biopsy) before starting treatment 3
• The most common cause of treatment failure is incorrect diagnosis made on clinical grounds alone 4, 5, 2

Treatment Algorithm

Step 1: Assess Disease Severity and Type

For Limited Disease (use topical therapy only):

• Superficial white onychomycosis (SWO) only 4, 1, 2
• Very early distal lateral subungual onychomycosis (DLSO) with <80% nail plate involvement and no lunula involvement 2
• When oral therapy is contraindicated 4, 1, 2

For All Other Cases (use oral therapy):

• Any infection beyond the above criteria requires systemic treatment 4

Step 2: Select Appropriate Treatment

First-Line Oral Therapy - Terbinafine:

• Terbinafine 250 mg once daily for 6 weeks (fingernails) or 12 weeks (toenails) 1, 2, 3
• Achieves mycological cure in 70% of toenail cases and 79% of fingernail cases 3
• Clinical cure rates are approximately 30% lower than mycological cure rates (38% for toenails, 59% for fingernails) 3
• Superior efficacy compared to azoles with similar adverse event profile 6
• Most effective against dermatophytes, which cause 90-95% of onychomycosis 7, 8

Alternative Oral Therapy - Itraconazole:

• Itraconazole 200 mg twice daily for 1 week per month (pulse therapy): 2 pulses for fingernails, 3 pulses for toenails 1
• Particularly effective for Candida infections 4, 1
• Broader antimicrobial coverage than terbinafine for yeasts and non-dermatophyte moulds 4

Topical Therapy (when appropriate):

• Amorolfine 5% nail lacquer - approximately 50% effective for distal nail infections 4, 2
• Ciclopirox 8% nail lacquer - 34% mycological cure rate versus 10% with placebo 2
• Tioconazole 28% solution - variable results (20-70% cure rates) 4, 2

Step 3: Special Population Considerations

Diabetic Patients:

• Strongly prefer terbinafine over itraconazole due to lower risk of drug interactions and hypoglycemia 1, 2
• Treatment is particularly important as onychomycosis is a significant predictor for foot ulcers in diabetics 1
• Can lead to cellulitis and further compromise limbs with peripheral vascular disease 4

Immunosuppressed Patients:

• Prefer terbinafine or fluconazole over itraconazole due to reduced drug interactions with antiretrovirals and immunosuppressants 1, 2

Pediatric Patients:

• Pulse itraconazole 5 mg/kg/day for 1 week per month: 2 months for fingernails, 3 months for toenails 1
• Terbinafine dosing by weight: 62.5 mg/day if <20 kg, 125 mg/day for 20-40 kg, 250 mg/day if >40 kg 1
• Pediatric cure rates are higher than adults (88-100% in studies) 2

Candida Onychomycosis:

• Itraconazole is first-line with 92% cure rates versus 40% for terbinafine with pulse therapy 4
• Itraconazole 200 mg daily or pulse therapy (400 mg/day for 1 week per month) for minimum 4 weeks (fingernails) or 12 weeks (toenails) 4
• Fluconazole is an alternative: 50 mg daily or 300 mg weekly 4

Important Monitoring and Side Effects

Terbinafine:

• Perform baseline liver function tests before prescribing 3
• Monitor for hepatotoxicity - discontinue if liver enzyme elevation occurs 3
• Warn patients to report persistent nausea, anorexia, fatigue, vomiting, right upper abdominal pain, jaundice, dark urine, or pale stools 3
• Taste disturbance (including loss) can be severe, prolonged (>1 year), or permanent - discontinue if occurs 3
• Smell disturbance may also occur and can be permanent 3
• Monitor for depressive symptoms 3

Itraconazole:

• Strong CYP3A4 inhibitor - significant drug interaction potential 7
• Higher risk of interactions with multiple medications compared to terbinafine 2

Critical Pitfalls to Avoid

• Underdosing or insufficient treatment duration leads to predictable failure 2
• Using topical therapy for extensive disease results in poor outcomes 2
• Not considering drug interactions, particularly with itraconazole in patients on multiple medications 2
• Failing to confirm diagnosis mycologically before treatment 4, 5, 2
• Treatment failure rates of 20-30% occur even with the most effective agents 2

Expected Timeline and Recurrence

• Optimal clinical effect is seen months after mycological cure due to the period required for outgrowth of healthy nail 3
• Mean time to overall success is approximately 10 months for toenails and 4 months for fingernails 3
• High recurrence rates (40-70%) necessitate preventive strategies 1, 2
• Clinical relapse rate is approximately 15% at one year after completing therapy 3

Prevention Strategies

• Wear protective footwear in public facilities 1
• Use absorbent and antifungal powders in shoes 1
• Keep nails short 1
• Avoid sharing nail clippers 1