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The unexpectedly rapid response of fungal nail infection to short duration therapy
C S Munro1, J L Rees, S Shuster
1University Department of Dermatology, Royal Victoria Infirmary, Newcastle upon Tyne, England.
Abstract:
To test our hypothesis that, by laying down a fungicidal barrier in the growing nail, a short course of antifungal therapy should be effective against onychomycosis, we treated 8 subjects with Trichophyton rubrum nail infection with terbinafine 125 mg b.d. for 14 days. All but one patient showed marked improvement, and 80% of fingernails and 37% of toenails were clinically cured after 6 months. Although this confirmed our prediction, the onset of response measured by outward movement of affected nail and negative cultures from distal nail clippings occurred after as little as 4 weeks. This was too soon for a fungicidal barrier to have grown out and indicates that the drug must have been carried directly into the diseased distal nail, presumably from newly formed ventral nail beneath it. The findings show that 1) short duration therapy, perhaps even a single dose, is possible in fungal nail infections; 2) the ventral nail provides unexpectedly rapid access of drugs to the site of distal disease.
Insights
Short antifungal therapy courses show promise for treating fungal nail infections (onychomycosis). The drug appears to reach the diseased nail rapidly from beneath, suggesting even single doses may be effective.
Area of Science:
- Dermatology
- Mycology
- Pharmacology
Background:
- Onychomycosis is a common fungal nail infection.
- Effective treatment often requires prolonged therapy.
- The mechanism of drug delivery to the infected nail site is not fully understood.
Purpose of the Study:
- To evaluate the efficacy of a short course of antifungal therapy for onychomycosis.
- To test the hypothesis that a fungicidal barrier in the growing nail is key to treatment success.
Main Methods:
- Eight subjects with Trichophyton rubrum nail infection were treated with terbinafine (125 mg twice daily) for 14 days.
- Clinical improvement and cure rates were assessed over 6 months.
- Nail clippings were cultured, and nail growth was monitored.
Main Results:
- Marked improvement was observed in all but one patient.
- Clinical cure rates were 80% for fingernails and 37% for toenails after 6 months.
- Response, including negative cultures, was noted as early as 4 weeks, suggesting rapid drug penetration.
Conclusions:
- Short-duration antifungal therapy, potentially even single-dose regimens, may be effective for onychomycosis.
- The ventral nail provides a rapid pathway for antifungal drugs to reach the site of distal nail infection.
- This challenges the 'fungicidal barrier' hypothesis, indicating direct drug transport is significant.