Terbinafine Dosage and Treatment Duration for Fungal Infections
Terbinafine should be administered at 250 mg once daily for 6 weeks for fingernail infections and 12 weeks for toenail infections, as this regimen provides optimal mycological cure rates of 73-94% for dermatophyte onychomycosis. 1
Standard Dosing Recommendations
Onychomycosis (Nail Infections)
- Fingernail infections: 250 mg once daily for 6 weeks 1
- Toenail infections: 250 mg once daily for 12 weeks 1
Tinea Capitis (Scalp Infections)
- Weight-based dosing for children:
- <20 kg: 62.5 mg daily for 2-4 weeks
- 20-40 kg: 125 mg daily for 2-4 weeks
40 kg: 250 mg daily for 2-4 weeks 2
Other Superficial Dermatophyte Infections
- Tinea pedis/corporis/cruris: 250 mg once daily for 2-4 weeks 3
Mechanism and Efficacy
Terbinafine is an allylamine antifungal that works by inhibiting squalene epoxidase, blocking ergosterol synthesis in the fungal cell wall. This creates both a fungistatic effect through ergosterol depletion and a fungicidal effect through squalene accumulation 4. Its fungicidal mechanism provides several advantages:
- Extremely low minimum inhibitory concentration (MIC) of approximately 0.004 μg/mL 4
- Higher efficacy against dermatophytes compared to azole antifungals 4, 2
- Continued improvement in mycological cure rates even after treatment cessation 3
Terbinafine demonstrates superior efficacy for dermatophyte infections with mycological cure rates of 73-94% for onychomycosis 2, which is significantly higher than griseofulvin and comparable or superior to itraconazole 3.
Comparative Efficacy
- Terbinafine vs. Itraconazole: Terbinafine is more effective than itraconazole for dermatophyte onychomycosis (Grade A-I evidence) 4, 2
- Terbinafine vs. Griseofulvin: Significantly higher cure rates and lower relapse rates compared to griseofulvin for dermatophyte infections 4, 3
- Organism specificity: Most effective against Trichophyton species; for Microsporum infections, higher doses or longer treatment may be required 5
Special Considerations
Topical Therapy
- Topical 1% terbinafine formulations are effective for limited superficial infections 6
- Should only be used for superficial white onychomycosis or very early distal lateral subungual onychomycosis 2
- Apply once or twice daily for up to 2 weeks 3
Safety and Monitoring
Before starting treatment:
- Baseline liver function tests are recommended 1
- Consider drug interactions, particularly with medications metabolized by CYP2D6 1
Common side effects (>2%):
- Headache, diarrhea, rash, dyspepsia, liver enzyme abnormalities, pruritus, taste disturbance, nausea, abdominal pain, and flatulence 1
Serious adverse effects to monitor:
- Liver toxicity (discontinue if liver injury develops)
- Taste or smell disturbances (may be prolonged or permanent)
- Depressive symptoms
- Severe neutropenia
- Serious skin reactions including Stevens-Johnson syndrome 1
Treatment Failures
If treatment fails, consider:
- Poor compliance
- Poor absorption
- Relative insensitivity of the organism
- Reinfection 2
Management options include:
- Partial nail removal plus antifungal therapy
- Alternative antifungal drug
- Complete nail avulsion combined with antifungal therapy 2
Clinical Pearls
- Terbinafine can be taken with or without food 1
- The drug is highly lipophilic and keratophilic, allowing it to persist in nails for months after stopping treatment 6
- For Candida onychomycosis, itraconazole may be more effective than terbinafine 2
- Pulse therapy regimens (e.g., weekly intermittent terbinafine 500 mg/day for 1 week each month for 4 months) may be effective alternatives to reduce cost and drug exposure 6
Terbinafine's superior efficacy, shorter treatment duration, and relatively favorable safety profile make it the treatment of choice for dermatophyte onychomycosis and other superficial fungal infections.