Recommended Terbinafine Dosing for Fungal Infections
The recommended dose of terbinafine for treating fungal infections is 250 mg once daily, with duration varying by infection type: 6 weeks for fingernail infections and 12 weeks for toenail infections. 1
Dosing Guidelines by Infection Type
Onychomycosis (Nail Infections)
- Adults: 250 mg once daily 1
- Fingernail infections: 6 weeks
- Toenail infections: 12 weeks
Tinea Capitis (Scalp Ringworm)
- Children (weight-based dosing): 2, 3
- < 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
Cutaneous and Lymphocutaneous Sporotrichosis
- Adults: 500 mg twice daily 2
- Treatment should continue for 2-4 weeks after all lesions have resolved (typically 3-6 months total)
Superficial Skin Infections (Tinea Corporis/Cruris/Pedis)
- Adults: 250 mg once daily for 2 weeks 4, 5
- Topical application: 1% formulation applied once or twice daily for up to 2 weeks 4
Efficacy and Mechanism of Action
Terbinafine is an allylamine antifungal agent with primarily fungicidal activity against a wide variety of dermatophytes, moulds, and certain dimorphic fungi 4. It has shown superior efficacy compared to other antifungals:
- More effective than continuous or intermittent itraconazole in dermatophyte onychomycosis 4
- Greater efficacy than griseofulvin in dermatophyte onychomycosis, tinea pedis, and tinea corporis/cruris 4
- More effective than ketoconazole 200 mg/day in tinea corporis/cruris 4
Mycological cure rates typically exceed 80% for most superficial dermatophyte infections 4.
Special Considerations
Monitoring
- Liver function tests should be performed before starting treatment, as terbinafine can cause liver problems that may lead to liver transplant or death 1
- Monitor for taste or smell disturbances, which may be prolonged or permanent 1
Drug Interactions
Terbinafine is an inhibitor of CYP4502D6 isozyme and may interact with: 1
- Antidepressants
- Antihypertensives
- Cardiac medications
- Desipramine
- Caffeine
- Cyclosporine
- Fluconazole
- Rifampin
- Cimetidine
Alternative Dosing Regimens
For onychomycosis, a pulsed regimen (500 mg daily for 1 week every 4 weeks, over 16 weeks) has shown similar efficacy to continuous dosing with potentially lower cost and better convenience 6.
Common Pitfalls and Caveats
Confirm diagnosis before treatment: Laboratory diagnosis through microscopy and culture is essential before initiating treatment 3
Species-specific efficacy: Terbinafine is more effective against Trichophyton species than Microsporum species 2. For Microsporum infections, griseofulvin may be more appropriate.
Treatment failure considerations: 3
- Poor compliance
- Suboptimal absorption
- Immunosuppression
- Dermatophyte resistance
- Inadequate treatment duration
Adverse effects to monitor: 1
- Liver problems (monitor liver enzymes)
- Taste or smell disturbances
- Depressive symptoms
- Severe neutropenia
- Serious skin reactions (Stevens-Johnson syndrome, toxic epidermal necrolysis)
Terbinafine is generally well-tolerated with relatively low potential for drug interactions compared to azole antifungals, making it a first-line treatment option for many fungal infections, particularly dermatophyte onychomycosis 4.