In Vitro and In Vivo Scalp Retention and Penetration of 99mTc-Minoxidil Solution

The study evaluated the retention and penetration of radiolabeled minoxidil (5% w/v) on ex vivo skin and in vivo scalp using three formulations. Formulation C, which included 10% hydroxypropyl cellulose (HPC), showed significantly higher ex vivo retention and permeation compared to formulations with just the vehicle or with 10% propylene glycol (PG). In vivo results confirmed that formulation C had nearly 2.8-fold and 2.2-fold higher scalp penetration than formulations A and B, respectively, after 8 hours. The absence of minoxidil in systemic circulation indicated safety. The study concluded that increasing the contact time of minoxidil with the scalp by enhancing viscosity improves efficacy and reduces the frequency of application.