What is the recommended dose of Terbinafine (oral antifungal) for treating toenail fungus?

Terbinafine Dosing for Toenail Fungus

For toenail fungus (onychomycosis), the recommended dose of oral terbinafine is 250 mg once daily for 12-16 weeks. 1, 2

Dosing Recommendations

• Toenail infections: 250 mg once daily for 12-16 weeks 1, 2
• Fingernail infections: 250 mg once daily for 6 weeks 1, 2
• Patients should be re-evaluated 3-6 months after treatment initiation, and further treatment should be given if the disease persists 1, 3

Evidence Supporting This Recommendation

• Terbinafine is considered first-line treatment for dermatophyte onychomycosis due to its superior efficacy and tolerability compared to other antifungals 1
• The FDA-approved dosing for terbinafine in toenail onychomycosis is 250 mg once daily for 12 weeks 2
• British Association of Dermatologists guidelines recommend 250 mg daily for 12-16 weeks for toenail infections 1
• Terbinafine is fungicidal against dermatophytes with very low minimum inhibitory concentrations (approximately 0.004 μg/mL) 1, 4

Comparative Efficacy

• Terbinafine has demonstrated higher efficacy than itraconazole in dermatophyte onychomycosis 1, 5
• In the L.I.ON. study, mycological cure rates at 72 weeks were approximately twice as high with terbinafine compared to itraconazole (81% vs 49%) 5
• Long-term follow-up studies show lower relapse rates with terbinafine (23%) compared to itraconazole (53%) 1, 5

Monitoring and Safety Considerations

• Baseline liver function tests (LFTs) are recommended before starting treatment 4, 3
• More vigilant LFT monitoring is advised in patients with:
  • Pre-existing liver disease 3
  • Concomitant hepatotoxic medications 3
  • Continuous therapy for more than one month 3
  • History of heavy alcohol consumption 3
• Terbinafine is contraindicated in patients with:
  • Active or chronic liver disease 4, 2
  • History of allergic reaction to oral terbinafine 2
  • Lupus erythematosus 4

Common Side Effects and Drug Interactions

• Common adverse effects include headache, diarrhea, rash, dyspepsia, liver enzyme abnormalities, taste disturbance, and nausea 2
• Terbinafine has minimal drug interactions compared to azole antifungals 3, 5
• The main interaction concern is with drugs metabolized by cytochrome P450 2D6 isoenzyme 3, 2

Treatment Duration Considerations

• While some studies have evaluated shorter treatment durations (6 weeks), these have shown inferior cure rates compared to the standard 12-week regimen 6
• In one study, mycological cure rates at 48 weeks were 59.7% with 6 weeks of treatment versus 72.4% with 12 weeks of treatment 6
• Clinical trials have not shown significant additional benefit of extending treatment beyond 12 weeks for most patients 7