What is the recommended treatment for proximal subungual onychomycosis?

Treatment for Proximal Subungual Onychomycosis

Oral terbinafine 250 mg daily is the first-line treatment for proximal subungual onychomycosis, administered for 6 weeks for fingernail infections and 12 weeks for toenail infections. 1

First-Line Treatment Options

Oral Terbinafine

• Dosage: 250 mg daily
• Duration:
  • Fingernail infections: 6 weeks
  • Toenail infections: 12 weeks
• Expected cure rates: 80-90% for fingernail infections and 70-80% for toenail infections 1
• Mechanism: Fungicidal action against dermatophytes
• Monitoring:
  • Baseline liver function tests and complete blood count recommended
  • Particularly important in patients with history of hepatotoxicity or hematological abnormalities 2
• Common adverse effects: Headache, taste disturbance, gastrointestinal upset 2

Why Terbinafine is Preferred

• Superior efficacy compared to other antifungals (55% complete cure rate vs. 26% for itraconazole at 72 weeks) 1
• Better long-term mycological cure rates (46% vs. 13% for itraconazole at 5-year follow-up) 1
• Continuous dosing is more effective than pulse dosing (70.9% vs. 58.7% mycological cure rate) 3

Second-Line Treatment Options

Oral Itraconazole

• Recommended when terbinafine is contraindicated or not tolerated 2
• Dosing options:
  • Continuous therapy: 200 mg daily for 12 weeks
  • Pulse therapy: 400 mg daily for 1 week per month (2 pulses for fingernails, 3 pulses for toenails) 2, 1
• Particularly effective for Candida onychomycosis (92% cure rate with pulse therapy) 2
• Contraindications: Heart failure, hepatotoxicity 2
• Monitoring: Liver function tests recommended in patients with pre-existing abnormalities or receiving continuous therapy for more than a month 2

Oral Fluconazole

• Third-line option when terbinafine and itraconazole are contraindicated or not tolerated 1
• Dosage: 150-450 mg once weekly
• Duration: 3 months for fingernail infections, 6 months for toenail infections 1
• Contraindications: Hepatic impairment, renal impairment 2

Special Considerations for Proximal Subungual Onychomycosis

• Proximal subungual onychomycosis is uncommon in immunocompetent individuals but frequently occurs in immunocompromised patients, particularly those with AIDS 4
• In immunocompetent patients with proximal subungual onychomycosis due to Microsporum canis, terbinafine 250 mg daily for 2 months has been shown to produce clinical and mycological cure 4
• For immunosuppressed patients, terbinafine or fluconazole is preferred over itraconazole due to fewer drug interactions with antiretrovirals 1

Adjunctive Measures

• Keep nails short and avoid sharing nail clippers
• Disinfect footwear (naphthalene mothballs in shoes enclosed in plastic bags for 3 days)
• Apply antifungal powders inside shoes
• Treat concomitant tinea pedis and infected family members 2

Follow-Up and Monitoring

• Follow-up recommended for at least 48 weeks from treatment initiation
• Re-evaluate 3-6 months after starting treatment
• Additional treatment may be needed if disease persists 1

Treatment Failure Management

• Identify potential causes: poor compliance, poor drug absorption, immunosuppression, dermatophyte resistance
• Consider:
  • Partial nail removal
  • Alternative antifungal drug
  • Complete nail removal in combination with further antifungal therapy 1

Important Caveats

• Identify the causative organism before initiating treatment to guide therapy decisions
• Continuous terbinafine treatment is superior to pulse dosing regimens 3
• Treatment efficacy may be lower than previously believed, particularly for achieving complete cure of all toenails 3