Gel Formulations with an Echinocandin for Cutaneous Candidiasis: The Influence of Azone and Transcutol on Biopharmaceutical Features

Caspofungin is a drug that is used for fungal infections that are difficult to treat, including invasive aspergillosis and candidemia, as well as other forms of invasive candidiasis. The aim of this study was to incorporate Azone in a caspofungin gel (CPF-AZ-gel) and compare it with a promoter-free caspofungin gel (CPF-gel). An in vitro release study using a polytetrafluoroethylene membrane and ex vivo permeation into human skin was adopted. The tolerability properties were confirmed by histological analysis, and an evaluation of the biomechanical properties of the skin was undertaken. Antimicrobial efficacy was determined against Candida albicans, Candida glabrata, Candida parapsilosis, and Candida tropicalis. CPF-AZ-gel and CPF-gel, which had a homogeneous appearance, pseudoplastic behavior, and high spreadability, were obtained. The biopharmaceutical studies confirmed that caspofungin was released following a one-phase exponential association model and the CPF-AZ gel showed a higher release. The CPF-AZ gel showed higher retention of caspofungin in the skin while limiting the diffusion of the drug to the receptor fluid. Both formulations were well-tolerated in the histological sections, as well as after their topical application in the skin. These formulations inhibited the growth of C. glabrata, C. parapsilosis, and C. tropicalis, while C. albicans showed resistance. In summary, dermal treatment with caspofungin could be used as a promising therapy for cutaneous candidiasis in patients that are refractory or intolerant to conventional antifungal agents.