Why is Tretinoin and Rogaine Combination Used ? Tretinoin is a form of retinoid. The reason a doctor might recommend using this prescription drug in conjunction with Minoxidil is to increase the skin’s permeability. Minoxidil is applied topically to the scalp’s surface. And in order to produce desired results, it needs to penetrate the skin and reach the surface blood vessels along with the hair follicles themselves.

Why is Tretinoin and Rogaine Combination Used, Is There a Benefit to Using it alone ?

Certain retinoids have been shown to enhance hair growth in subjects. In one study, this was found to occur in 58% of subjects. In another study, when retinoids were combined with Minoxidil, 66% of subjects grew more hair.

Other forms of medication besides rogaine can be prescribed like thyroid medications and tretinoin. (Creative Commons) Thyroid medications can restore the balance needed to reverse hair loss.

Can tretinoin grow hair ? Possible role in hair loss treatment

http://www.webmd.com/drugs/2/drug-3956/tretinoin-topical/details Read more about Tretinoin here.