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Fungal toenail infections; definitions and results

Study
Results
Comment

Fungal infections of the toenails are difficult to cure. But one of the most vexing questions is what constitutes a cure. Nails may look normal, but still harbour the fungus that caused the problem, with the result that some time after the end of treatment the infection recurs, and the cycle of treatment has to start again.

Study


A new review of terbinafine, itraconazole and fluconazole [1] sought the answer by looking for evidence of disease-free nails one year or longer after the start of treatment. A disease-free nail was defined as one that both looked normal and had negative results from potassium hydroxide microscopy and culture. The search strategy was reasonably comprehensive, and found seven studies, only some of which appeared to be randomised. Studies had to describe results in toenails (distinct from fingernails), use both culture and microscopy and include a clinical evaluation. Case reports, series of fewer than 15 patients, those combining finger and toenails, and those reporting on nails rather than patients were excluded.

Results


There were no data for fluconazole. The results for terbinafine and itraconazole are shown in the Figure. For terbinafine, 217 of 491 patients (44%) had a disease-free nail at one year. Most studies used terbinafine 250 mg daily for longer than the recommended 12 weeks. For itraconazole, 99 of 291 patients (34%) had a disease-free nail at one year. These results were obtained whether 200 mg daily was given, or as 400 mg daily for one week each month.

Figure 1: Disease free nails at one year with terbinafine (open circles and half tone fill) and itraconazole (filled circles)


Comment


Fungal nail infection is one of those seemingly innocuous subjects that seems to get people vexed whenever it is raised. This interesting little paper poses an important question for patient and practitioner - when is a cure not a cure? Epstein points out the deficiencies in the definition - or lack of definition - of a cure.

Bandolier 26 examined this subject, and found two randomised trials comparing terbinafine with griseofulvin in toenails. One is in this review, but the other had 48-week outcomes that might have been included by Epstein, but perhaps were omitted because 48 weeks is less than one year (though one also had longer outcomes). Disease-free nails at 48 weeks occurred in 67% of patients receiving terbinafine. Including these trials (half-tone fill in the Figure) would increase the one-year result for disease-free nails with terbinafine to 48%

These are expensive treatments for a condition which is not rare, and more attention would seem to be needed. The concentration on suitable end-point is pertinent, but the execution may be flawed. Is it time to have a good systematic review, as we have for topical treatments from the Cochrane Library [2], and especially as more randomised studies are being published?

Reference:

  1. E Epstein. How often does oral treatment of toenail onychomycosis produce a disease-free nail? Archives of Dermatology 1998 134: 1551-4.
  2. F Crawford et al. Topical treatments for fungal infections of the skin and nails of the foot. Cochrane Library 1999, 3.
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