Minoxidil was originally used to lower blood pressure as a treatment for hypertension as it widens blood vessels (vasodilatator) that had an interesting side effect of increased hair growth. This led to the development of a topical version, now available as a lotion and a foam, to be applied to areas of hair loss of the scalp. Its mechanism of action is not fully understood. As a vasodilatator, it may supply hair follicles with more blood, oxygen and nutrients. While it has no effect on the level of dihydrotestosterone (DHT) or the enzyme 5-alpha reductase (important mediators of androgenetic alopecia), it may nonspecifically block DHT from binding to hair follicle receptors.
Rogaine comes as 2% and 5% solution approved for use in both men and women. It needs to be applied twice daily, massaged into a dry scalp. Earliest results are seen after 10-12 weeks, and it can be used indefinitely to support the hair follicles. Rogaine tends to work better in the crown than the frontal area, although we have seen it to be effective to treat frontotemporal and upper temporal thinning in women. Sudden hair loss can occur at the beginning of treatment as a side effect, mostly due to the shedding of hairs that are already in the telogen phase. In most cases, this shedding stops after four to six weeks.
The most common sides effects of Rogaine® are irritation of the scalp including dandruff, and hair growth in other areas (sideburns and beard, neck, and forearms), most of which are reversible upon cessation. This irritation of the treated areas can be minimized by dissolving the minoxidil in hamamelis lotion. Severe side effects (allergic reactions, chest pain, palpitations, dizziness) require immediate cessation and if necessary the intervention of a physician. If being terminated for non-emergent reasons, it is best to slowly taper the use of the minoxidil over a several week period to help minimize the potential rapid loss of hair that can result. As with any other medication for hair loss, minoxidil requires regular use which is easy, but is best supervised by a doctor experienced in treating hair loss to assure the best results.