Penetration of Minoxidil from Ethanol/Propylene Glycol Solutions: Effect of Application Volume and Occlusion

The study investigated the penetration of minoxidil from ethanol/propylene glycol solutions and the effect of application volume and occlusion. The results showed that increasing the ethanol fraction generally leads to increasing delivery, with the exception of 12.5 µL/cm² of 2% minoxidil in pure ethanol, which had notably low penetration. Penetration of minoxidil peaked at the 90% ethanol solution for all application volumes by the 24-hour recovery point. Larger application volumes tended to be associated with increased absorption of minoxidil, but the efficiency of delivery dropped off at all propylene glycol levels and most notably the 50% level. The study provides insights into the factors that affect the penetration of minoxidil and can inform the development of more effective hair loss treatments.