Characterization of minoxidil/hydroxypropyl-β-cyclodextrin inclusion complex in aqueous alginate gel useful for alopecia management: Efficacy evaluation in male rat

Solid inclusion complex between hydroxypropyl-β-cyclodextrin (HP-β-CD) and minoxidil (MXD) was prepared by freeze-drying and characterized by yield, drug loading and dissolution rate. Moreover, the complex was formulated as alginate gel (GEL HP-β-CD)/MXD 3.5% w/w). The efficacy of the novel GEL HP-β-CD)/MXD 3.5% w/w and of MXD 3.5% w/w ethanolic/propylene-glycol solution (MXD solution) were evaluated by monitoring the hair growth of dorsal skin 1–4 weeks after depilation followed by histological analysis and gene expression in skin biopsies in male rat. Patch-clamp experiments and cell-dehydrogenase activity (CDA) were performed to evaluate the capability of the formulations to activate “in vitro” the ATP-sensitive K+-channels (KATP) and their effects on cell viability in skin fibroblasts. After 3 weeks, the MXD solution and MXD/HP-β-CD GEL enhanced the hair growth, respectively, of 80.1 ± 2% and 84.3 ± 4% vs controls. After 4 weeks, the MXD/HP-β-CD GEL significantly enhanced the hair length and bulb diameter vs others groups. The MXD/HP-β-CD GEL significantly enhanced the mRNA levels of the SUR2 and Kir6.1 subunits of the KATP channels and AKT2 vs other groups. The AR gene was down-regulated vs controls following the treatment with either MXD formulations. Either MXD (10−4 M) formulations were effective in potentiating the KATP currents. The MXD solution and its vehicle after 9 h of incubation time, but not MXD/HP-β-CD, reduced CDA in fibroblasts. In sum, the MXD/HP-β-CD GEL shows a favorable profile following topical long-term use.