What is the recommended dose and duration of terbinafine (oral and topical) for treating uncomplicated dermatophyte skin infection (tinea corporis or tinea cruris)?

Terbinafine Dosing for Uncomplicated Tinea Corporis and Tinea Cruris

Topical Terbinafine (First-Line for Localized Disease)

For uncomplicated tinea corporis or tinea cruris, apply topical terbinafine 1% cream once or twice daily for 1-2 weeks, which achieves mycological cure in over 80% of patients. 1, 2

• Topical therapy is the preferred initial approach for limited, uncomplicated skin infections without hair follicle involvement 3
• Topical terbinafine 1% formulations demonstrate superior efficacy compared to clotrimazole 1% cream, bifonazole 1% cream, and oxiconazole 1% lotion 1
• Mycological cure rates typically improve after treatment cessation due to terbinafine's fungicidal mechanism and residual tissue effect 1

Oral Terbinafine (For Extensive or Refractory Disease)

When systemic therapy is indicated—for extensive infections, hair follicle involvement, or failure of topical treatment after 2 weeks—prescribe oral terbinafine 250 mg once daily for 2-4 weeks. 4, 3

Weight-Based Dosing for Children:

• Children <20 kg: 62.5 mg once daily for 2-4 weeks 3
• Children 20-40 kg: 125 mg once daily for 2-4 weeks 3
• Children >40 kg and adults: 250 mg once daily for 2-4 weeks 4, 3

Important Clinical Considerations:

• The treatment endpoint should be mycological cure (negative microscopy and culture), not merely clinical improvement 4, 3
• If clinical improvement occurs but mycology remains positive, continue therapy for an additional 2-4 weeks 4
• The shorter 2-4 week duration improves patient compliance compared to longer regimens 3

When to Choose Oral Over Topical:

• Extensive body surface area involvement 3
• Infections involving hair follicles 3
• No response to topical treatment within 2 weeks 3
• Rapidly spreading lesions 4

Contraindications and Safety Monitoring

Oral terbinafine is absolutely contraindicated in patients with active or chronic liver disease, lupus erythematosus, porphyria, or pregnancy. 4, 3

Pre-Treatment Assessment:

• Obtain baseline complete blood count in patients with history of heavy alcohol consumption, hepatitis, or hematological abnormalities 3
• Screen for liver disease before initiating therapy 4, 3

Common Adverse Effects:

• Gastrointestinal disturbances (49%): nausea, diarrhea, dyspepsia, abdominal pain 3
• Dermatological reactions (23%): rash, pruritus, urticaria 3
• Rare but potentially permanent taste disturbance (1:400 patients) 5, 4
• Serious adverse events occur in approximately 0.04% of patients 3

Drug Interactions:

• Terbinafine has minimal drug interactions compared to azole antifungals 3
• Plasma concentrations reduced by rifampicin, increased by cimetidine 5
• May interact with drugs metabolized by cytochrome P450 2D6 3
• Manufacturers caution against men fathering a child for 6 months after therapy 5, 3

Critical Pitfalls to Avoid

Do not rely solely on clinical appearance to determine treatment success—always confirm mycological cure with negative microscopy and culture. 4, 3 Clinical improvement can occur while infection persists, leading to early treatment discontinuation and relapse.

Avoid using higher doses (500 mg daily) for uncomplicated skin infections, as recent evidence shows no additional benefit over standard 250 mg dosing for tinea corporis/cruris, with cure rates remaining suboptimal at both doses after 4 weeks 6

Alternative Oral Therapy

If terbinafine is contraindicated or not tolerated, oral itraconazole 100-200 mg once daily for 15 days achieves 87% mycological cure rates in adolescents and adults with tinea corporis 4, though it requires liver function monitoring for treatment durations exceeding 1 month 5