Minoxidil was first approved as a hair loss treatment by the U.S. Food and Drug Administration in 1988. Minoxidil was originally used to treat high blood pressure, and researchers noticed the unintended side effect of slowing down hair loss, and in some cases, regrowing new hair. Minoxidil is still taken orally to treat high blood pressure, while the topical solution is used to treat hair loss.
The exact cause of hair growth with minoxidil remains a bit of a mystery, even to Pharmacia & Upjohn, the manufacturers of the product. Company spokesman John Ruane admitted as much when he said, "We're not exactly sure how it works."
Larger Hair Follicles
While the exact driving force behind minoxidil is still unclear, there are several things that are known to occur when using minoxidil, one of which is an increase in the size of the hair follicle, which results in larger hair diameter.
Hair Growth Cycle
There are three stages to the hair growth cycle. Most hair at any one time is in the anagen, or growing stage, which is followed by a brief stage known as the catagen stage. This is when the hair follicle declines; the stage marks the transition between the growing stage and the telogen, or resting stage. After the resting stage is complete, hair begins the whole cycle over again.
In studies on animals, minoxidil has been shown to shorten the resting stage, which leads to a prolonged growing stage. It is believed that the primary reason for minoxidil's success as a hair growth product resides in its ability to alter the hair growth cycle.