What is the recommended treatment for toenail fungus?

Treatment of Toenail Fungus (Onychomycosis)

Oral terbinafine 250 mg daily for 12 weeks is the first-line treatment for toenail fungus, with superior cure rates compared to all other antifungal agents. 1, 2, 3

Confirm the Diagnosis Before Treatment

• Do not initiate treatment without mycological confirmation through microscopy and culture, potassium hydroxide preparation, or histological examination 2, 4
• Clinical appearance alone is insufficient, as many nail conditions mimic fungal infection 5

First-Line Treatment: Oral Terbinafine

Terbinafine is the preferred first-line agent because it demonstrates superior efficacy to all alternatives for dermatophyte infections 1, 2, 3

Dosing and Duration

• 250 mg once daily for 12-16 weeks for toenail infections 1, 2, 4
• Expect clinical cure rates of 70-80% and mycological cure rates of 70-80% 2, 6
• Full nail regrowth takes up to 18 months after treatment completion 2

Pre-Treatment Requirements

• Obtain baseline liver function tests and complete blood count in patients with history of hepatotoxicity or hematological abnormalities 1, 4
• Contraindicated in active or chronic liver disease 4

Common Adverse Effects

• Headache, taste disturbance, and gastrointestinal upset are most common 1, 4
• Taste loss can be severe and permanent; discontinue if this occurs 4
• Monitor for hepatotoxicity: instruct patients to report nausea, anorexia, fatigue, vomiting, right upper abdominal pain, jaundice, dark urine, or pale stools 4

Drug Interactions

• Minimal interactions compared to azoles; only cytochrome P450 2D6 substrates require caution 3
• Monitor patients taking tricyclic antidepressants, SSRIs, atypical antipsychotics, beta blockers, or tamoxifen 7

Second-Line Treatment: Itraconazole

Use itraconazole when terbinafine is contraindicated or not tolerated 1, 2, 3

Dosing Options

• Continuous therapy: 200 mg daily for 12 weeks, OR 1
• Pulse therapy: 400 mg daily for 1 week per month for 3 pulses (3 months total) 1

Important Contraindications and Monitoring

• Absolutely contraindicated in heart failure 1, 3
• Must be taken with food and acidic pH for optimal absorption 1
• Monitor hepatic function tests in patients with pre-existing abnormalities, those on continuous therapy >1 month, or with concomitant hepatotoxic drugs 1

Efficacy

• Complete cure rates of approximately 26% at 72 weeks, significantly lower than terbinafine's 55% 3
• Long-term mycological cure without retreatment: 13% at 5 years versus 46% for terbinafine 3

Third-Line Treatment: Fluconazole

Consider fluconazole only when both terbinafine and itraconazole cannot be tolerated 1, 3

Dosing

• 150-450 mg once weekly for at least 6 months for toenail infections 1, 3
• Requires dose adjustment in renal impairment 3

Monitoring

• Baseline liver function tests and complete blood count required 1
• Monitor liver function in high-dose or prolonged therapy 1

Topical Treatments: Limited Role

Topical therapy is inferior to systemic treatment except in very distal infections or superficial white onychomycosis 2

Available Options

• Amorolfine 5% lacquer: Apply once or twice weekly for 6-12 months 1
• Ciclopirox 8% lacquer: Apply daily for up to 48 weeks 1, 8
• Efinaconazole 10% solution: Available option with fewer adverse effects 2, 5

Important Limitations

• Ciclopirox achieves only 5.5-8.5% complete cure rates even with monthly nail debridement 8
• Only indicated for mild to moderate disease without lunula involvement 8
• Do not use topical and systemic antifungals concurrently as this may reduce systemic agent effectiveness 8

Combination Therapy

Combination treatment is recommended if response to topical monotherapy is likely to be poor 1

• Nail trimming and debridement used concurrently with pharmacologic therapy improve treatment response 7
• Monthly removal of unattached, infected nail by a healthcare professional enhances outcomes 8

Managing Treatment Failure

Despite terbinafine being most effective, expect a 20-30% failure rate 2

Common Causes of Failure

• Poor compliance with medication regimen 2
• Presence of dermatophytoma (fungal ball within nail) 2
• Nail thickness >2 mm 2
• Severe onycholysis (nail separation) 2
• Slow nail outgrowth 2
• Poor drug absorption or immunosuppression 9

Re-evaluation Strategy

• Re-evaluate patients 3-6 months after treatment initiation 3, 9
• Provide additional treatment if disease persists 3

Special Populations

Diabetic Patients

• Terbinafine is preferred due to low risk of drug interactions and hypoglycemia 3
• Itraconazole is contraindicated because heart failure is more prevalent in diabetics 3
• Up to one-third of diabetics have onychomycosis, which significantly predicts foot complications 1

Immunosuppressed Patients

• Terbinafine is preferred due to fewer interactions with antiretrovirals and immunosuppressive medications 3

Candida Infections

• Itraconazole has significantly greater efficacy than terbinafine for Candida onychomycosis 1, 9
• Most yeast infections associated with paronychia can be treated topically 2

Prevention of Recurrence

Recurrence is common due to ubiquitous environmental exposure to T. rubrum 2

Essential Preventive Measures

• Wear protective footwear in public facilities (pools, gyms, showers) 2
• Apply absorbent antifungal powders in shoes and on feet 1, 2
• Wear cotton, absorbent socks 1, 2
• Keep nails as short as possible 1, 2
• Avoid sharing toenail clippers with family members 1, 2
• Treat all infected family members simultaneously 1, 2
• Discard old footwear or disinfect by placing naphthalene mothballs in shoes within sealed plastic bags for minimum 3 days 1

Recurrence Rates

• Approximately 25% of patients experience relapse 7
• Terbinafine and azoles may lower recurrence rate compared to placebo, but evidence is limited 6