What is the treatment for a patient with a thick toenail growing upward, potentially caused by a fungal infection?

Treatment of Thick Toenail Growing Upward

For a thick toenail growing upward potentially caused by fungal infection, confirm the diagnosis with laboratory testing (KOH preparation and fungal culture) before initiating treatment, then prescribe oral terbinafine 250 mg daily for 12 weeks as first-line therapy. 1, 2

Diagnostic Confirmation is Mandatory

• Never treat based on clinical appearance alone—50% of dystrophic nails are non-fungal despite similar presentation 1, 3
• Obtain subungual debris from the most proximal part of the infection using a dental scraper for KOH preparation and fungal culture on Sabouraud's glucose agar 1
• Laboratory confirmation prevents inappropriate treatment and allows proper assessment of treatment failure versus incorrect initial diagnosis 1

First-Line Systemic Treatment

Terbinafine is the preferred first-line agent for dermatophyte onychomycosis: 1

• Dosing: 250 mg orally once daily for 12 weeks for toenails (6 weeks for fingernails) 1, 2
• Efficacy: Achieves 70% mycological cure and 38% complete clinical cure at 48 weeks 2
• Monitoring: Obtain baseline liver function tests and complete blood count before starting treatment 1
• Common adverse effects include headache, taste disturbance, and gastrointestinal upset 1

Itraconazole is an equally effective alternative: 1

• Continuous dosing: 200 mg daily for 12 weeks 1
• Pulse therapy: 400 mg daily for 1 week per month for 3 pulses (3 months total) 1
• Optimally absorbed with food and acidic pH 1
• Contraindicated in heart failure; monitor hepatic function in patients with pre-existing abnormalities 1

Addressing Treatment-Resistant Features

Nail thickness >2 mm, dermatophytoma (dense white lesion beneath nail), and severe onycholysis predict treatment failure: 1

• Dermatophytomas require mechanical removal before antifungal therapy to achieve cure—systemic treatment alone will fail 1
• Consider daily application of urea-based keratolytic cream to reduce nail thickness 4
• File nail surfaces gently with an emery board after softening in warm water 4

Adjunctive Measures and Prevention

Implement these strategies to prevent recurrence (40-70% recurrence rate without preventive measures): 1

• Keep nails as short as possible and file regularly 1
• Apply antifungal powders (miconazole, clotrimazole, or tolnaftate) inside shoes and on feet daily 1
• Wear cotton, absorbent socks and protective footwear in public bathing facilities 1
• Discard old, moldy footwear or treat shoes by placing naphthalene mothballs inside and sealing in plastic bag for minimum 3 days 1
• Alternatively, spray terbinafine solution into shoes periodically 1
• Apply daily topical emollients to cuticles and periungual tissues 5, 4

Critical Pitfalls to Avoid

• Do not diagnose fungal infection without laboratory confirmation—treatment is long-term (12 weeks minimum) and expensive 1
• Do not assume treatment failure without considering reinfection—examine and treat all infected family members simultaneously 1
• Do not ignore nail thickness >2 mm or dermatophytoma—these require mechanical debridement before systemic therapy 1
• Warn patients that optimal clinical effect occurs months after treatment completion due to slow nail outgrowth (approximately 10 months for toenails) 2

When Systemic Therapy is Contraindicated

Topical amorolfine 5% lacquer may be used when systemic antifungals are contraindicated: 1

• Apply once or twice weekly for 6-12 months after filing diseased nail areas 1
• Effective in approximately 50% of distal nail onychomycosis cases 1
• Limited to early disease with <80% nail plate involvement and no lunula involvement 1