Amorolfine is effective in several dermatophytoses, selleck screening library especially tinea unguium (1, 3, 5, 6); however, it is only used topically. For systemic use, itraconazole or terbinafine is generally available. Lecha et al. [3] and Baran et al. [5] described satisfactory

results using combinations of amorolfine and terbinafine or itraconazole, respectively, in vivo. We selected amorolfine and itraconazole to investigate combinations of antifungal drugs. The former is a non-azole agent that is used topically (externally) and the latter an azole drug that is used systemically (internally). Both agents are commonly used for dermatomycoses. We observed a synergistic effect in 7 of 27 strains with FIC indexes ≤0.5. Using a checkerboard method, Santos et al. demonstrated synergistic interactions between azoles and cyclopiroxamine against T. rubrum and T. mentagrophytes [9]. Harman et al. also reported a synergistic effect (≤1) of a combination of amorolfine and itraconazole in 46% of all organisms tested, including dermatophytes and non-dermatophytes [6]. In the present study, we used a stricter criterion for determination of synergy (≤0.5)

selleck compound and confirmed that a combination of these drugs had a synergistic (≤0.5) effect in 25.9% of samples and an additive (FIC index ≥1 and ≤0.5) effect in 59.3% of samples. In total, these agents showed additive or synergistic effects on more than 85% of the strains examined. In particular, we found additive or synergistic effects in 19 of 21 Trichophyton strains (90%) and in three strains of M. gypseum (100%). We identified no additive or synergistic Phospholipase D1 effects in two of three strains of E. floccosum and detected no antagonistic effects in any of the 27 dermatophytes. These results suggest that the combination of these two drugs can be expected to act additively or synergistically in the treatment of dermatomycoses.

Further investigation is required to examine the effects of antifungal drug combination against these and other clinically important dermatophytes. Although several studies have examined the synergic effects of antifungal agents [34, 35], few have provided explanations for the mechanisms of drug synergy [36]. In this study, we found additive or synergistic effects of amorolfine and itraconazole in most of dermatophytes; we do not have an explanation for this. To ascertain the mechanisms of drug synergy between amorolfine and itraconazole, we need to profile changes in cellular environment after drug administration. The authors thank the participating laboratories and hospitals for their cooperation and for providing the fungal isolates described in this report. K.M. has received research grants from the following companies: Hisamitsu Pharmaceutical (Tokyo, Japan), Seikagaku Biobusiness (Tokyo, Japan), Kaken Pharmaceutical (Tokyo, Japan), Dai-Nippon Sumitomo Pharmaceutical (Tokyo, Japan), Sato Pharmaceutical (Tokyo, Japan), Galderma (Tokyo, Japan), and Japan Space Forum.