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 infections, terbinafine should be dosed based on infection type and patient weight, with 250 mg daily for 2-4 weeks for tinea capitis (Trichophyton species) and 250 mg daily for 6 weeks (fingernails) or 12 weeks (toenails) for onychomycosis. 1, 2

Dosing by Infection Type

Tinea Capitis (Scalp Fungal Infection)

• Weight-based dosing for 2-4 weeks 3, 1:

  • < 20 kg: 62.5 mg daily
  • 20-40 kg: 125 mg daily

  • 40 kg: 250 mg daily

• Note: Terbinafine is more effective against Trichophyton species than Microsporum species. For Microsporum infections, griseofulvin is preferred (15-20 mg/kg/day for 6-8 weeks) 3, 1

Onychomycosis (Nail Fungal Infection)

• FDA-approved dosing 2:

  • Fingernail infection: 250 mg daily for 6 weeks
  • Toenail infection: 250 mg daily for 12 weeks

• Clinical evidence shows that shorter treatment durations (6 weeks) for toenail infections are generally insufficient, especially when the proximal part of the nail is affected 4

Tinea Corporis/Cruris (Body/Groin Fungal Infection)

• Adults: 250 mg daily for 1-2 weeks 5, 1
• Children: Weight-based dosing as for tinea capitis

Tinea Pedis (Athlete's Foot)

• 250 mg daily for 2 weeks 5
• Topical 1% formulation is also effective when applied once or twice daily for up to 2 weeks 5, 6

Treatment Considerations

Efficacy

• Terbinafine is fungicidal (kills fungi) rather than fungistatic, which contributes to its high efficacy 3
• Mycological cure rates generally exceed 80% for dermatophyte infections 5
• For onychomycosis, clinical cure rates continue to improve after treatment cessation, reaching approximately 45-59% by week 72 7

Monitoring and Follow-up

• The endpoint of treatment should be mycological cure rather than just clinical improvement 3
• For onychomycosis, improvement may continue for months after treatment completion due to the drug's residual effect in tissue 5, 7
• Monitor for adverse effects, particularly liver function abnormalities 2

Contraindications and Precautions

• Contraindicated in individuals with history of allergic reaction to terbinafine 2
• Use with caution in patients with liver disease; obtain pretreatment serum transaminases 2
• Common side effects include headache, diarrhea, rash, dyspepsia, liver enzyme abnormalities, taste disturbance, and nausea 2
• Rare but serious adverse reactions include liver failure, Stevens-Johnson syndrome, and taste/smell disturbances that may be permanent 2

Special Populations

Children

• Terbinafine is effective and safe in children with tinea capitis at weight-based dosing 8
• For children with Microsporum infections, higher doses or longer treatment duration may be needed 8
• In the UK, terbinafine is not licensed for children ≤12 years with tinea capitis, though it is widely used 3

Treatment Failures

• For treatment failures, consider:
  • Lack of compliance
  • Suboptimal absorption
  • Relative insensitivity of the organism
  • Reinfection 3
• If clinical improvement occurs but mycology remains positive, continue current therapy for 2-4 additional weeks 3
• If no clinical improvement, consider switching to itraconazole (50-100 mg daily for 4 weeks) 3, 1

Terbinafine's lipophilic nature allows excellent penetration into hair, skin, and nails, making it particularly effective for dermatophyte infections 8. Its fungicidal mechanism provides continued improvement even after treatment cessation, which is a significant advantage over fungistatic agents 5.