Standardization, Validation, and Application of a Rapid and Reliable HPLC-UV Method for the Determination of Minoxidil in Hair Growth Products

Background: Minoxidil is a medication used for hypertension. Nevertheless, a significant side effect of hypertrichosis was observed, whereby, now it is widely used in formulation of topical medications for treatment of alopecia. However, international regulations prohibit its use in cosmetic products due to its antihypertensive activity and the potential for systemic absorption after application to the scalp. Despite these regulatory restrictions, various studies have reported the presence of minoxidil in cosmetic products. Objectives: to determine the presence of minoxidil in cosmetic products for hair growth, by means of a standardized and validated HPLC-UV method for different cosmetic matrices. Methods: the analytical method was statistically validated by parameters such as selectivity, linear-ity, precision, accuracy, precision, robustness, limit of detection and limit of quantification according to International Conference on Harmonisation (ICH) guidelines. Results: The validated method meets the ICH requirements. Additionally, it was found that presumably 2 of the 9 cosmetic products analyzed contained the banned analyte minoxidil, corresponding to 22.22 % of the products analyzed. Conclusions: It was possible to standardize and validate a HPLC-UV method for identification of minoxidil in cosmetic matrices, which gives reliability to results obtained. However, it is important to verify these results with other techniques such as HPLC-MS, to support these statements.