The effect of keratolytic agents on the permeability of three imidazole antimycotic drugs through the human nail.

The permeability of three imidazole antimycotics (miconazole nitrate, ketoconazole, and itraconazole) through the free edge of healthy human nail was evaluated in vitro using side-by-side diffusion cells. The influence of keratolytic substances (papain, urea, and salicylic acid) on the permeability of the antimycotics was also studied. The results suggested that the nail constituted an impermeable barrier for these antimycotics; it could be considered that the nail behaved as a hydrophilic gel membrane, through which drugs of low solubility could not permeate. The use of ethanol did not promote the passage of any of the antimycotic drugs. Although scanning electron microscopy indicated that the keratolytic substances had a significant effect on the nail surface (papain > salicylic acid > urea), the passage of the three antimycotics was not improved by pretreatment with salicylic acid alone (20% for 10 days), or by the application of the drug in a 40% urea solution. It was found that only the combined effects of papain (15% for 1 day) and salicylic acid (20% for 10 days) were capable of enhancing the permeability of the antimycotic.