Minoxidil - How long should I leave it on?

Minoxidil - what's the minimum time to leave it on and still work?

Minoxidil has been in the market for about 25 years, receiving FDA approval in 1988. Many people recognize one of the popular brand names - Rogaine. Minoxidil is approved male pattern balding (androgenetic alopecia) as well as female pattern hair loss. It can also be used to treat several other conditions. In women, minoxidil can be used before and after a hair transplant to reduce the chances of post operative shedding. Some patients also use minoxidil after a transplant to speed up the rate of growth of the grafts.

How long should I leave the minoxidil on the scalp?

A common question I'm asked is how long to leave the minoxidil on the scalp. Ideally it is left on for 8 hours but the 'minimum' time I advise is 4-6 hours. After 4 hours, 75 % of the minoxidil is absorbed.

This advice comes from a 1990 study. In that study, twenty-two healthy male volunteers completed a four-way, multiple-dose, randomized crossover study to determine the relationship between contact time of applied drug on the scalp and minoxidil absorption from a 2% topical solution.  The researchers examined how much minoxidil is absorbed at 1 hr, 4 hr compared to 11.5 hours. Relative to the amount absorbed after a contact time of 11.5 h, absorption was approximately 50% complete by 1 h and greater than 75% complete by 4 h.

Conclusion:

Although minoxidil should ideally be left on 8 hours, tremendous benefit can still be achieved with 4 hour use. Understanding the absorption of minoxidil is important to help improve the ability of patients to 'stick with' the treatment. 

Reference

Ferry JJ et al. Relationship between contact time of applied dose and percutaneous absorption of minoxidil from a topical solution. J Pharm Sci. 1990 Jun;79(6):483-6.