Effect of topical nanoemulsion of minoxidil on animal hair growth: an in vivo study

Topical minoxidil is typically administered over an extended period for the therapeutic management of androgenic alopecia. Given the adverse effects of commercial preparations of minoxidil (i.e., minoxidil solution), researchers are increasingly looking for alternative preparations that offer enhanced efficacy and reduced side effects. To do so, in this study, nanoemulsions containing 1%, 2%, and 5% minoxidil were formulated, and their stability was studied. Then, ex vivo permeation as well as in vivo irritation test and hair growth effects were investigated against commercial minoxidil solutions (2% and 5%). The prepared nanoemulsion exhibited particle sizes in the range of 11-12 nm. Permeation studies revealed no significant differences between the nanoemulsion and commercial formulations for both 2% and 5% minoxidil. The nanoemulsion did not cause skin irritation. Plasma concentrations of minoxidil were below the quantifiable range of the analytical method applied under the experimental conditions. From the animal hair growth studies, the 5% minoxidil nanoemulsion demonstrated enhanced hair growth. From the findings, the nanoemulsion formulation improved in vivo hair growth and follicle count compared to commercial formulations, despite the absence of statistically significant differences in ex vivo permeation.