What is the recommended treatment for an adult patient with tinea, considering the severity of the infection and potential underlying medical conditions such as impaired renal function?

Treatment of Tinea in Adults

For most tinea infections (corporis, cruris, pedis), topical antifungal therapy with azoles or allylamines is first-line treatment, applied for 2-4 weeks depending on site; however, oral systemic therapy is required for tinea capitis, extensive disease, or nail involvement (onychomycosis). 1

Topical Therapy for Localized Tinea

First-Line Topical Agents

• Terbinafine 1% cream applied once or twice daily for 1-2 weeks is highly effective for tinea pedis, corporis, and cruris, achieving cure rates of 78% even with single application in some studies due to its fungicidal mechanism 2
• Azole antifungals (clotrimazole, miconazole) applied twice daily are effective alternatives, though typically require longer treatment duration (3-4 weeks) compared to terbinafine 1, 2

Duration by Site

• Tinea corporis and cruris: 2 weeks of topical therapy 1
• Tinea pedis: 4 weeks with azoles OR 1-2 weeks with allylamine agents (terbinafine) 1, 2
• Continue treatment for at least 1 week after clinical clearing to prevent relapse 1

Oral Systemic Therapy Indications

When Oral Therapy is Required

• Tinea capitis (scalp/hair involvement): Always requires oral therapy, as topical agents alone are inadequate 3
• Extensive skin involvement or resistance to topical therapy 1
• Onychomycosis (nail infections) 4

Oral Agent Selection for Non-Nail Tinea

For tinea corporis/cruris:

• Fluconazole 50-100 mg daily for 2-3 weeks OR 150 mg once weekly for 2-3 weeks 5
• Itraconazole 100 mg daily for 2 weeks OR 200 mg daily for 7 days 5
• Terbinafine 250 mg daily for 1-2 weeks 5

For tinea pedis:

• Fluconazole 150 mg once weekly (pulse dosing) 5
• Itraconazole 100 mg daily for 2 weeks OR 400 mg daily for 1 week 5
• Terbinafine 250 mg daily for 2 weeks 5

For tinea capitis:

• Griseofulvin 500 mg daily (or 10 mg/kg/day in divided doses) for 4-6 weeks is traditional therapy 6, 3
• Terbinafine and itraconazole are alternatives at similar dosing to other tinea infections 3

Onychomycosis (Nail Infections) Treatment

First-Line Systemic Options

Terbinafine 250 mg daily is generally preferred over itraconazole for dermatophyte onychomycosis due to superior efficacy and fewer drug interactions 4

• Fingernails: 6 weeks of treatment 4
• Toenails: 12-16 weeks of treatment 4
• Baseline liver function tests and complete blood count are recommended before initiating therapy 4

Itraconazole 200 mg daily for 12 weeks continuously is an alternative first-line option 4

• Pulse therapy alternative: 400 mg daily for 1 week per month (2 pulses for fingernails, 3 pulses for toenails) 4
• Best absorbed with food and acidic pH 4
• Monitor hepatic function in patients with pre-existing abnormalities or on continuous therapy >1 month 4

Alternative Agents

• Fluconazole 150-450 mg weekly: Useful for patients intolerant to terbinafine or itraconazole 4
  • 3 months for fingernails, ≥6 months for toenails 4
• Griseofulvin 500-1000 mg daily: Lower efficacy with higher relapse rates; requires 6-9 months for fingernails, 12-18 months for toenails 4, 6

Topical Therapy for Nails

Topical monotherapy is only useful for superficial and distal onychomycosis; combination with oral therapy is recommended when response to topical alone would be poor 4

• Amorolfine 5% lacquer once or twice weekly for 6-12 months 4
• Ciclopirox 8% lacquer daily for up to 48 weeks 4

Special Considerations for Renal Impairment

Terbinafine and itraconazole both require caution in renal impairment 4

• For patients with significant renal dysfunction, consider fluconazole with 50% dose reduction after loading dose 7
• Echinocandins require no dose adjustment for renal dysfunction but are not indicated for dermatophyte infections 7

Adjunctive Measures to Prevent Recurrence

Environmental decontamination is critical to prevent reinfection:

• Discard old, moldy footwear when possible 4
• Alternative: Place naphthalene mothballs in shoes, seal in plastic bag for minimum 3 days to kill fungal elements 4
• Apply antifungal powders (miconazole, clotrimazole, tolnaftate) in shoes and on feet regularly 4
• Wear cotton, absorbent socks 4
• Keep nails trimmed short and avoid sharing nail clippers 4
• Treat all infected family members simultaneously, as tinea pedis and onychomycosis are contagious 4

Critical Pitfalls to Avoid

• Do not use topical therapy alone for tinea capitis or onychomycosis—systemic therapy is required 4, 3
• Do not discontinue therapy prematurely—continue until organism is completely eradicated by clinical or laboratory examination to prevent relapse 6, 1
• Do not use terbinafine in patients with psoriasis without careful consideration, as it can aggravate the condition 4
• In immunocompromised patients, infections are more extensive and severe; consider oral therapy earlier and monitor closely 8
• For patients on multiple medications (especially HIV-positive or transplant patients), terbinafine has lower drug interaction potential than itraconazole, which is a potent CYP3A4 inhibitor 8