How should I treat a fungal infection of the toes (tinea pedis or onychomycosis)?

Treatment of Fungal Toe Infections

For fungal infection of the toes, start with topical terbinafine cream applied once or twice daily for 2-4 weeks if the infection is limited to the skin between the toes; if nails are involved, oral terbinafine 250 mg daily for 12 weeks is the gold standard treatment. 1, 2, 3

Distinguishing Between Skin and Nail Involvement

Before initiating treatment, determine whether you are dealing with:

• Tinea pedis (skin infection): Affects the skin between toes, soles, or sides of feet, presenting with scaling, cracking, maceration, or vesicles 2, 4
• Onychomycosis (nail infection): Involves thickening, discoloration, or dystrophy of the toenails 5, 1
• Both conditions simultaneously: Common scenario requiring combined treatment approach 6, 2

Obtain mycological confirmation (microscopy and culture) when possible, as only about 50% of nail dystrophies are actually fungal, and clinical diagnosis of skin infections has low accuracy. 1, 2, 4

Treatment Algorithm for Tinea Pedis (Skin Infection Only)

First-Line: Topical Therapy

Apply terbinafine cream once or twice daily for 2-4 weeks, which achieves approximately 67% cure rate. 2

Alternative topical agents include:

• Azole antifungals (ketoconazole, clotrimazole, miconazole) applied once to twice daily for 1-6 weeks 4
• Ciclopirox, tolnaftate, or amorolfine for similar duration 4

When to Escalate to Oral Therapy for Tinea Pedis

Consider oral antifungals if:

• Severe or extensive skin involvement 4
• Failed topical therapy after 4 weeks 4
• Concurrent nail involvement (onychomycosis) is present 2
• Patient is immunocompromised 4

Oral terbinafine 250 mg daily for 2-6 weeks is the preferred systemic option for severe tinea pedis. 4

Treatment Algorithm for Onychomycosis (Nail Infection)

First-Line: Oral Terbinafine

Terbinafine 250 mg once daily for 12 weeks is the first-line treatment for toenail onychomycosis, achieving mycological cure rates of approximately 73% at 48 weeks post-treatment. 1, 3

For severe infections with extensive nail involvement, extend treatment duration to 16 weeks. 1

Baseline Monitoring Requirements

• Obtain liver function tests (ALT, AST) and complete blood count before starting 1, 3
• Ongoing monitoring is advised for patients with prior liver disease, heavy alcohol use, concurrent hepatotoxic medications, or pre-existing abnormal liver enzymes 1, 3

Common Adverse Effects

• Gastrointestinal upset (nausea, diarrhea, abdominal pain) 3
• Headache 3
• Reversible taste disturbance in approximately 1 in 400 patients (may be severe or permanent—discontinue if this occurs) 1, 3
• Rare but serious: hepatotoxicity, Stevens-Johnson syndrome, severe neutropenia 3

Drug Interactions

• Rifampin decreases terbinafine levels 3
• Cimetidine increases terbinafine levels 3
• Terbinafine inhibits CYP2D6, affecting metabolism of certain antidepressants, beta-blockers, and antiarrhythmics 3

Second-Line: Itraconazole

Use itraconazole when terbinafine is contraindicated, not tolerated, or when treating Candida onychomycosis (where itraconazole achieves 92% cure versus only 40% with terbinafine). 1, 6

Dosing options:

• Continuous: 200 mg daily for 12 weeks 1, 6
• Pulse: 400 mg daily (200 mg twice daily) for 1 week per month for 3 cycles (total 3 months) 1, 6

Critical considerations:

• Must be taken with food and acidic beverages for optimal absorption 1, 6
• Contraindicated in heart failure due to negative inotropic effects 1, 6
• Baseline and periodic liver function monitoring required 1, 6
• Significant drug interactions with statins (increases myopathy risk), warfarin, digoxin, ciclosporin, and many others 1

Third-Line: Fluconazole

Fluconazole 150-450 mg once weekly for at least 6 months is reserved for patients who cannot tolerate terbinafine or itraconazole. 1, 6

• Baseline liver function tests and complete blood count required 1, 6
• Fewer drug interactions with statins compared to itraconazole 6

Adjunctive Topical Therapy

Combining systemic and topical antifungals provides antimicrobial synergy, wider spectrum, improved cure rates, and suppression of resistant mutants. 5, 1

• Amorolfine 5% lacquer applied once or twice weekly for 6-12 months achieves approximately 50% cure when used alone for distal infections 1, 6
• Ciclopirox 8% lacquer applied once daily for up to 48 weeks 1, 6

Reserve topical-only therapy for mild-to-moderate disease affecting only the distal nail without lunula involvement, or when systemic therapy is contraindicated. 1

Combined Skin and Nail Infection

When both tinea pedis and onychomycosis are present:

1. Treat with oral terbinafine 250 mg daily for 12 weeks (addresses both conditions) 1, 2
2. Add topical terbinafine cream to affected skin areas for faster resolution of skin symptoms 2
3. Consider adding topical nail lacquer (amorolfine or ciclopirox) to enhance nail cure rates 1, 6

Essential Adjunctive Measures to Prevent Recurrence

Recurrence rates for onychomycosis range from 40-70%, making prevention strategies critical. 1

Footwear Decontamination

• Discard old contaminated footwear if possible, or decontaminate shoes by placing naphthalene mothballs inside and sealing in plastic bags for minimum 3 days 1, 6
• Apply antifungal powders (miconazole, clotrimazole, tolnaftate) inside shoes regularly 1, 6
• Consider periodic spraying of terbinafine solution into shoes 6

Hygiene Measures

• Wear protective footwear in public bathing facilities, gyms, and hotel rooms where Trichophyton rubrum is commonly found 1, 6
• Wear cotton, absorbent socks 6
• Keep nails short and clean 6
• Apply antifungal powders to feet regularly 1, 6
• Avoid sharing nail clippers 6

Household Management

• Treat all infected household members simultaneously to prevent reinfection 1
• Transmission amongst family members is the most common route 4

Special Clinical Scenarios

Nondermatophyte Mold Infections (Scopulariopsis, Aspergillus)

Itraconazole demonstrates superior efficacy against nondermatophyte molds compared to terbinafine, achieving 88% cure rates for Scopulariopsis infections. 5

Candida Onychomycosis

Itraconazole is the preferred agent, achieving 92% cure versus only 40% with terbinafine. 1

Dermatophytoma Present

Dermatophytomas (dense white hyphal masses beneath the nail) require mechanical removal before antifungal therapy can be effective, followed by systemic treatment. 1, 6

Pediatric Patients (Off-Label Dosing)

For children 1-12 years with toenail onychomycosis:

• <20 kg: terbinafine 62.5 mg daily for 12 weeks 1
• 20-40 kg: terbinafine 125 mg daily for 12 weeks 1

• 40 kg: terbinafine 250 mg daily for 12 weeks 1

Pediatric onychomycosis demonstrates higher cure rates (94-100%) and faster response than adult infections. 5

Diabetic Patients

Terbinafine is preferred in diabetic patients due to low risk of drug interactions and hypoglycemia. 1

Immunosuppressed Patients

Terbinafine or fluconazole are preferred due to reduced antiretroviral drug interactions. 1

Monitoring and Follow-Up

• Follow patients for at least 48 weeks (preferably 72 weeks) from treatment initiation to detect relapse 1
• Complete toenail regrowth requires up to 18 months due to slow growth patterns 1, 6
• End-of-therapy culture is recommended, especially in high-risk groups, to confirm mycological clearance 1
• Mycological cure rates are typically 30% higher than clinical cure rates 1

Common Pitfalls to Avoid

• Do not use topical nail lacquers for skin infections between toes—these are formulated for nail penetration and are inappropriate for skin 2
• Do not assume treatment failure means resistant infection—poor compliance and reinfection from contaminated footwear are more common causes 2
• Do not use terbinafine for suspected yeast infections—it has poor activity against Candida species; use fluconazole or itraconazole instead 2
• Do not skip mycological confirmation—clinical diagnosis alone leads to frequent treatment failure 1, 2
• Even with optimal terbinafine therapy, expect a consistent failure rate of 20-30% 1

Factors Predicting Poor Treatment Outcomes

• Nail thickness >2 mm 1
• Severe onycholysis 1
• Presence of dermatophytoma 1
• Slow nail outgrowth 1
• Immunosuppression 1
• Poor patient compliance 1