Compounded Hair Solutions and Foams Containing Minoxidil: Does the Color Change Impact Stability?

Abstract

An increasing number of pharmacies around the world are producing hair solutions and foams containing minoxidil for alopecia, commonly using ready-to-use vehicles such as TrichoSolTM or TrichoFoamTM. However, it is paramount to determine the chemical and microbiological compatibility of these formulations so they can be safely implemented as vehicles of choice. Also, these products usually suffer from a change of color over time, which leads to many patients prematurely discontinuing treatment. As long-term treatment is recommended, this study aimed to assess the physical–chemical and microbiological stability and investigate the color change of compounded minoxidil formulations. For that, HPLC analyses and antimicrobial effectiveness testing were conducted in a bracketed study covering concentrations from 1.0% to 7.0% of minoxidil. HPLC, pH, and metals in 5.0% minoxidil compounded products were determined using ICP-MS to evaluate the mechanisms involved in their color change. The stability of the products varied from 120 to 380 days. The color change was remarkably noticeable, but apart from this parameter, no other quality attribute was affected throughout this period, including minoxidil content, which presented only minor fluctuations. No precipitation was observed, and pH was relatively stable. It is not expected that this yellow color will impact effectiveness. Finally, we created an indicative color chart of the behavior of minoxidil in the studied vehicles.