Perhaps the most intriguing aspect of topical
minoxidil is the fact that this
drug can promote hair growth in two unrelated conditions:
alopecia areata (AA) and
androgenetic alopecia. The two conditions have quite different underlying mechanisms. In AA, hair follicles respond to some signal or cell injury by entering a state of aborted cyclical activity; this state can reverse itself spontaneously, or it can be temporarily circumvented with nonspecific
immunomodulating agents. In
androgenetic alopecia, genetically marked hair follicles undergo progressive,
androgen-mediated miniaturization;
antiandrogens have been conventionally sought to intercept this process. It is not known how
minoxidil promotes hair growth except that living follicles capable of stimulation and
hypertrophy are required. It may be that
minoxidil influences some fundamental signal to the follicular apparatus, irrespective of the pathophysiology involved. We have used topical
minoxidil solution in 90 patients, aged 7-63 years, with extensive AA affecting 25-100% of the scalp. One study was double-blind, and placebo-controlled for an entire year.
Minoxidil-treated patients responded better than placebo-treated patients. Both 3 and 5% topical
minoxidil solutions have been used, and treatment with the 3%
solution has continued for up to 3 years. The results of these studies will be discussed. While topical
minoxidil is not very effective for those with 100% scalp
hair loss, it is an effective, easy and safe treatment for those with AA affecting 25-99% of the scalp.