What is the recommended dosage and treatment duration of Terbinafine (antifungal medication) for fungal infections?

Terbinafine Dosage and Treatment Duration for Fungal Infections

For fungal nail infections (onychomycosis), terbinafine should be administered as 250 mg once daily for 6 weeks for fingernail infections and 12 weeks for toenail infections. 1

Standard Dosing Regimens

Oral Terbinafine

• Fingernail onychomycosis: 250 mg once daily for 6 weeks 1
• Toenail onychomycosis: 250 mg once daily for 12 weeks 1
• Tinea capitis in children: Weight-based dosing 2
  • <20 kg: 62.5 mg/day
  • 20-40 kg: 125 mg/day

  • 40 kg: 250 mg/day

  • Duration: 6 weeks for fingernails and 12 weeks for toenails

Topical Terbinafine

For less extensive fungal skin infections:

• 1% formulation applied once or twice daily for up to 2 weeks 3
• Achieves mycological cure in >80% of patients with tinea pedis, tinea corporis/cruris, cutaneous candidiasis, and pityriasis versicolor 3

Efficacy and Evidence Base

Terbinafine is highly effective against dermatophyte infections with:

• 70-80% efficacy for toenail infections 2
• 80-90% efficacy for fingernail infections 2
• 73-94% mycological cure rate for onychomycosis 2

The British Association of Dermatologists rates terbinafine with an A-I level of evidence (highest quality) for dermatophyte onychomycosis 4. It is fungicidal rather than fungistatic, with a very low minimum inhibitory concentration (0.004 μg/mL) 4.

Advantages Over Other Antifungals

Terbinafine offers several advantages over other antifungal medications:

• Superior efficacy: Better cure rates and lower relapse rates than itraconazole for dermatophytes 4
• Fungicidal action: True fungicidal activity against dermatophytes 4
• Shorter treatment duration: Compared to griseofulvin (which may require 12-18 months of treatment) 2
• Fewer drug interactions: Compared to azole antifungals like itraconazole 2

Special Considerations

Pre-treatment Assessment

• Diagnostic confirmation: Laboratory diagnosis is essential before treatment initiation 2
• Liver function: Obtain pretreatment serum transaminases (ALT and AST) 1

Monitoring

• Monitor for potential side effects including:
  • Liver problems
  • Taste or smell disturbances
  • Depressive symptoms
  • Skin reactions
  • Neutropenia 1

Drug Interactions

Terbinafine may interact with:

• Desipramine
• Cimetidine (increases terbinafine plasma concentration)
• Rifampicin (decreases terbinafine plasma concentration)
• Caffeine
• Cyclosporine
• Fluconazole 1

Common Pitfalls to Avoid

1. Failure to confirm diagnosis: Always confirm fungal infection through microscopy, culture, or nail biopsy before initiating treatment 2
2. Inadequate treatment duration: Completing the full course is essential to prevent recurrence 2
3. Not monitoring liver function: Check liver enzymes before starting treatment 1
4. Ignoring concomitant infections: Treating concurrent tinea pedis is important to prevent reinfection 2
5. Unrealistic expectations: Improvement in nail appearance may take months even after mycological cure 2

Alternative Regimens

Some evidence suggests that pulse therapy may be effective with less medication:

• Weekly intermittent terbinafine (500 mg/day for 1 week each month for 4 months) 5
• Single-dose terbinafine (1000 mg per month for 4 months) 5

However, the FDA-approved regimen remains the standard 250 mg daily continuous dosing 1.

Terbinafine's high lipophilicity and keratophilicity allow it to remain in the stratum corneum, sebum, nails, and hair for months after discontinuation, contributing to its effectiveness 5.