Abstract
Antimycotic nail lacquers are effective and safe for the treatment of onychomycosis. To assess the efficacy of three topical agents we studied the minimum inhibitory and fungicidal concentration of amorolfine, bifonazole and ciclopiroxolamine. Amorolfine showed the most effective fungistatic and fungicidal activity in vitro against seven clinical Trichophyton rubrum nail isolates, followed in descending order by ciclopiroxolamine and bifonazole. To mimic a nail infection more appropriately, the nail minimum fungicidal concentration (Nail-MFC) was determined in an onychomycosis model. Amorolfine and ciclopiroxolamine had Nail-MFCs ranging from 2–32 μg/ml and 16–32 μg/ml, respectively. In contrast, bifonazole was unable to kill T. rubrum in this model. Statistical analyses of the results show a significant difference between the two treatments with amorolfine and ciclopiroxolamine (P<0.001). For amorolfine a mean concentration of 12.28 μg/ml (95%-CI=[8.66, 17.41]) was sufficient to kill all strains, while for ciclopiroxolamine about twice that concentration was needed, i.e., 24.13 μg/ml (95%-CI=[17.06, 34.13]). The individual sensitivity of six of the seven T. rubrum strains was higher for amorolfine. These data demonstrate that both amorolfine and ciclopiroxolamine effectively kill T. rubrum growing on nail powder and suggest a better cidal action for amorolfine. Further investigation would be required to determine if these in vitro data can partially explain the clinical observation of significantly higher cure rates in onychomycosis following a therapy with an amorolfine-containing nail lacquer formulation.
Acknowledgements
The authors thank Prof. Walter Burgdorf (Department of Dermatology and Allergology, University of Munich) for critical reading of the manuscript.
The experiments have been financially supported by Galderma Laboratorium GmbH, Germany. A. Jäckel is an employee of Galderma Laboratorium GmbH, Germany. M. Schaller and C. Borelli contributed equally to the work.
Declaration of interest: The authors report no other conflicts of interest. The authors alone are responsible for the content and writing of the paper.
This paper was first published online on iFirst on 16 April 2009.