Studies on the Affinity of Terbinafine with Keratine

Abstract

To obtain information on the pharmacokinetic property of a new antifungal drug terbinafine (TBF) in the honey layer of the epidermis absorbability of the drug added to the ambient buffered medium (pH5 or 7) to keratine and release of the keratine-preloaded drug to the medium was studied using human-derived keratine powder. Determination of the drug in an active from was made biologically using the conventional agar-well diffusion method with Trichophyton mentagrophytes as the testing organism.
The absorption rate of TBF to keratine was slightly influenced by pH of the medium; higher values were obtained at pH5 than pH7. The drug absorption rate was more highly dependent upon the ratio of the drug weight to keratine weight (D/K ratio) in the reaction mixture, showing values of approx. 48, 73 and 88% at pH7 in D/K ratios of 1: 100, 1: 1, 000 and 1: 10, 000, respectively. However, the drug activity was almost completely removed from keratine and recovered in the washing medium after TBF-bound keratine was washed thoroughly with buffered solution (pH5 or 7). These results proved that although TBF molecules can be absorbed to keratine at a relatively high rate, they are easily released without losing their activity. Therefore, we are led to the prossibility that the honey layer of the epidermis in the host acts as a reservoir for TBF administered topically to release the active drug efficiently into the tissue.