Terbinafine (Lamisil) Dosing for Mild Fungal Infections
For mild fungal infections, terbinafine (Lamisil) is recommended at a dose of 250 mg once daily, with duration varying by infection site: 6 weeks for fingernail infections and 12 weeks for toenail infections. 1
Dosing Recommendations by Infection Type
Onychomycosis (Nail Infections)
- 250 mg oral terbinafine once daily for 6 weeks for fingernail infections 2, 1
- 250 mg oral terbinafine once daily for 12 weeks for toenail infections 2, 1
- For children weighing 20-40 kg: 125 mg/day; for children <20 kg: 62.5 mg/day; for children >40 kg: adult dose of 250 mg 3
Cutaneous Dermatophyte Infections
- 250 mg oral terbinafine once daily for tinea corporis/cruris (ringworm) for 2-4 weeks 4
- 250 mg oral terbinafine once daily for tinea pedis (athlete's foot) for 2-6 weeks 4
- For topical treatment of mild superficial infections: apply terbinafine 1% cream once or twice daily for up to 2 weeks 4
Efficacy and Mechanism of Action
- Terbinafine is an allylamine antifungal with fungicidal activity against dermatophytes 2
- It inhibits squalene epoxidase in the ergosterol biosynthesis pathway, causing both ergosterol depletion (fungistatic effect) and toxic squalene accumulation (fungicidal effect) 5
- Terbinafine has a very low minimum inhibitory concentration (MIC) of approximately 0.004 μg/mL against dermatophytes 2
- It is more effective than itraconazole and griseofulvin for dermatophyte infections, with mycological cure rates generally >80% 4, 5
Clinical Considerations
- Terbinafine persists in the nail for a considerable period after elimination from plasma, allowing for shorter treatment durations compared to other antifungals 2
- For mild fungal infections, terbinafine is generally well-tolerated with minimal side effects 4
- Common adverse effects include headache, diarrhea, rash, dyspepsia, liver enzyme abnormalities, and taste disturbance 1
- Mycological cure rates typically improve after treatment cessation due to terbinafine's fungicidal mechanism and residual effect in tissue 4
Important Precautions and Monitoring
- Liver function should be monitored as liver failure has been reported in rare cases 1
- Discontinue treatment if liver injury, taste disturbance, or smell disturbance develops 1
- Terbinafine is contraindicated in patients with a history of allergic reaction to the drug 1
- Drug interactions are possible as terbinafine inhibits CYP450 2D6 isozyme, affecting metabolism of certain medications 1
Special Populations
- Terbinafine is not recommended during pregnancy 2
- Manufacturers caution against men fathering a child for 6 months after therapy 2
- For children with tinea capitis, terbinafine has shown high efficacy (93% cure rate) with a 4-week treatment duration 3
Terbinafine's fungicidal mechanism of action makes it particularly effective for dermatophyte infections, with higher cure rates and lower relapse rates compared to azole antifungals like itraconazole 2, 5.