How should tinea pedis be treated in an otherwise healthy adult, and what adjustments are needed for pregnancy, lactation, liver disease, or interacting medications?

Treatment of Tinea Pedis

Topical terbinafine 1% cream applied twice daily for 1 week is the first-line treatment for tinea pedis in otherwise healthy adults, offering superior efficacy with the shortest treatment duration of any topical antifungal. 1

First-Line Topical Therapy

• Terbinafine 1% cream twice daily for 1 week achieves mycological cure rates of approximately 72% and is significantly more effective than 4 weeks of clotrimazole. 1, 2
• The fungicidal action of terbinafine allows for this abbreviated course, whereas fungistatic agents require longer treatment. 1
• If terbinafine is unavailable, ciclopirox olamine 0.77% cream/gel applied twice daily for 4 weeks achieves approximately 60% cure at end of treatment and 85% cure two weeks later. 1
• Clotrimazole 1% cream twice daily for 4 weeks is less effective but remains widely available over-the-counter as a third-line option. 1

Oral Therapy Indications

Reserve oral antifungals for severe disease, failed topical therapy, concomitant onychomycosis, or immunocompromised patients—not as routine first-line treatment. 1

• Oral terbinafine 250 mg once daily for 1-2 weeks is the most effective systemic option, with fungicidal action and higher efficacy against dermatophytes than itraconazole. 1
• Itraconazole 100 mg daily for 2 weeks offers comparable efficacy but has slightly higher relapse rates and a broader spectrum covering Candida and non-dermatophyte moulds. 1
• Fluconazole 150 mg once weekly is less effective than both terbinafine and itraconazole but may be useful when other agents are contraindicated due to fewer drug interactions. 1
• Griseofulvin is not recommended as first-line therapy due to lower efficacy (30-40% cure rates) and longer treatment duration. 1

Special Population Adjustments

Pregnancy

Use topical terbinafine 1% cream twice daily for 1 week as first-line therapy in pregnancy—avoid all oral antifungals, particularly in the first trimester, due to teratogenic concerns. 3

• Oral azole antifungals have documented teratogenic potential and should be avoided throughout pregnancy for non-life-threatening infections. 3
• Topical ciclopirox olamine 0.77% cream/gel is an alternative if terbinafine is unavailable. 3
• If topical therapy fails after 4 weeks, verify diagnosis with fungal culture before considering any escalation. 3
• Concomitant onychomycosis should be noted but treatment deferred until after pregnancy, as the nail serves as a reservoir but does not require immediate systemic therapy. 3

Lactation

• Topical antifungals are preferred during lactation due to minimal systemic absorption. 1
• If oral therapy is absolutely necessary, terbinafine has minimal excretion into breast milk, but the risk-benefit discussion should occur. 1

Liver Disease

Choose terbinafine over itraconazole in patients with liver disease, but obtain baseline liver function tests and complete blood count before initiating oral therapy. 1

• Oral terbinafine carries rare but serious risk of hepatic failure, particularly in patients with pre-existing liver disease. 1
• Monitor for common adverse effects including headache, taste disturbance, and gastrointestinal upset. 1
• Topical therapy avoids hepatic metabolism concerns entirely and should be maximized before considering oral agents. 1

Drug Interactions

Terbinafine is preferred over itraconazole in diabetic patients or those on multiple medications due to lower risk of drug interactions and hypoglycemia. 1

• Itraconazole has broader cytochrome P450 inhibition, leading to more drug interactions than terbinafine. 1
• Fluconazole has weaker cytochrome P450 inhibition than itraconazole, making it useful when other agents cause problematic interactions. 1

Prevention and Recurrence Management

Address contaminated footwear and examine for concomitant onychomycosis—these are the two most common causes of treatment failure and recurrence. 1

• Applying antifungal foot powder after bathing reduces infection rates from 8.5% to 2.1%. 1
• Discard old, moldy footwear when possible, or place naphthalene mothballs in shoes sealed in a plastic bag for minimum 3 days. 1
• Spray terbinafine solution inside shoes periodically or apply antifungal powders containing miconazole, clotrimazole, or tolnaftate. 1
• Change socks daily, preferably to cotton absorbent socks, and thoroughly dry between toes after showering. 1
• Treat all infected family members simultaneously to prevent reinfection cycles. 1
• Cover active foot lesions with socks before wearing underwear to prevent spread to the groin area. 1
• Examine the entire skin surface, particularly hands, groin, and body folds, as dermatophyte infections commonly occur at multiple body sites simultaneously. 1

Critical Pitfalls to Avoid

• Failing to examine for concomitant onychomycosis is the most common error—nail infection requires extended oral terbinafine therapy (12-16 weeks) and acts as a reservoir for foot reinfection. 1
• Assuming treatment failure is due to drug resistance alone is incorrect—poor compliance, inadequate drug penetration, bacterial superinfection, or reinfection from contaminated footwear are more common causes. 3
• Neglecting to address contaminated footwear as a source of reinfection leads to recurrence. 1
• Treating only the index patient without addressing subclinical infections in cohabitants leads to repeated episodes. 1
• Athletes require minimum 72 hours of antifungal therapy before return to contact sports, with lesions covered appropriately. 1