What is the recommended treatment for onychomycosis (fungal nail infection)?

Treatment of Onychomycosis

Oral terbinafine 250 mg daily for 12-16 weeks is the first-line treatment for toenail onychomycosis caused by dermatophytes, with significantly superior cure rates compared to all topical therapies. 1, 2, 3

Treatment Selection Algorithm

Step 1: Confirm the Diagnosis

• Obtain mycological confirmation before initiating any treatment through KOH preparation, fungal culture, or nail biopsy 2, 3
• This prevents unnecessary treatment of non-fungal nail conditions that mimic onychomycosis 2

Step 2: Assess Disease Severity and Extent

Use topical therapy ONLY if:

• Superficial white onychomycosis (SWO) is present 1, 2
• Early distal lateral subungual onychomycosis (DLSO) with <80% nail plate involvement, no lunula involvement, and no longitudinal streaks 1
• Systemic antifungals are contraindicated 1, 2

Use oral therapy for:

• Typical toenail onychomycosis with >80% involvement 1
• Any lunula involvement 1, 4
• Moderate to severe disease 2

Oral Treatment (First-Line)

Terbinafine

• Dose: 250 mg daily for 12-16 weeks for toenails 1, 2, 3
• Dose: 250 mg daily for 6 weeks for fingernails 1
• Oral terbinafine is the only oral fungicidal antimycotic agent 1
• Achieves mycological cure rates of approximately 70-80% 1
• Persists in the nail for 6 months after treatment completion due to long half-life 1
• Most effective against dermatophytes (T. rubrum, T. mentagrophytes) but has lower activity against Candida species 1
• Well tolerated, though rare serious reactions including Stevens-Johnson syndrome and toxic epidermal necrolysis have been reported 1

Alternative Oral Agents (When Terbinafine Contraindicated)

Itraconazole:

• Pulse therapy: 200 mg twice daily for 1 week per month × 2-3 pulses for fingernails, 3-4 pulses for toenails 1
• Contraindicated in congestive heart failure due to negative inotropic effects 1
• Preferred for Candida onychomycosis over terbinafine 1

Griseofulvin:

• 500-1000 mg daily for 12-18 months for toenails 1
• Mycological cure rates only 30-40% 1
• No longer recommended as first-line due to lower efficacy, long treatment duration, and availability of superior alternatives 1
• Only antifungal licensed for children with onychomycosis (10 mg/kg per day for age ≥1 month) 1

Topical Treatment (Limited Role)

When Topical Monotherapy is Appropriate

Topical antifungals have limited efficacy with mycological cure rates 30% lower than clinical improvement rates 1, 2

Amorolfine 5% lacquer:

• Apply once or twice weekly for 6-12 months after filing away diseased nail 1, 2
• Effective in approximately 50% of distal fingernail and toenail onychomycosis cases 1
• Once-weekly application is as effective as twice-weekly 1
• Side effects limited to local burning, pruritus, and erythema 1

Ciclopirox 8% lacquer:

• Apply once daily for up to 48 weeks on toenails, 24 weeks on fingernails 1, 4
• FDA-approved only for mild to moderate onychomycosis without lunula involvement 4
• Mycological cure rate 34% vs. 10% placebo; complete cure only 5.5-8.5% 1, 4
• Cure rates usually lower than amorolfine 1
• Must be used with monthly removal of unattached infected nail by healthcare professional 4

Efinaconazole 10% solution:

• Apply once daily for 48 weeks 1
• Mycological cure rates approaching 50%, complete cure in 15% 1

Tioconazole 28% solution:

• Mycological and clinical cure achieved in only 22% of patients 1
• Allergic contact dermatitis not uncommon 1
• Contraindicated in pregnancy 1

Special Populations

Diabetic Patients

• Terbinafine is the oral antifungal of choice due to low risk of drug interactions and hypoglycemia 1
• Onychomycosis is a significant predictor for foot ulcer development in diabetes 1
• Itraconazole should be avoided due to increased cardiac disease prevalence in diabetics 1

Pediatric Patients

• Higher cure rates and faster response than adults 1
• Pulse itraconazole: 5 mg/kg per day for 1 week per month × 2 months (fingernails) or 3 months (toenails) 1
• Daily terbinafine: 6.25 mg/day if <20 kg, 125 mg/day if 20-40 kg, 250 mg/day if >40 kg for 6 weeks (fingernails) or 12 weeks (toenails) 1

Critical Pitfalls to Avoid

• Failure to obtain mycological confirmation before treatment leads to unnecessary therapy for non-fungal conditions 2, 3
• Inadequate treatment duration results in treatment failure and recurrence 2
• Not addressing concurrent tinea pedis increases reinfection risk 1, 2
• Failure to remove diseased nail before topical application significantly reduces drug penetration 1
• Using topical terbinafine 1% cream as monotherapy is not recommended due to limited efficacy 2
• Concomitant use of topical ciclopirox with systemic antifungals is not recommended as no studies have evaluated this combination 4

Post-Treatment Monitoring

• Re-evaluate 3-6 months after treatment initiation 2
• Clinical improvement may not correlate with mycological cure 1
• Terbinafine persists in nail for 6 months post-treatment, allowing continued antifungal effect 1