Minoxidil is the generic name for the brand name drugs Rogaine
and Loniten. Minoxidil is a potent vasodilator,
introduced originally as an anti-hypertensive medication.
Shortly thereafter, reports began coming in from users that long-lost
hairs were being found, i.e., bald men on the hypertension
drug found, to their great delight, that they started growing hair
again!
The money to be made selling a hair restorative that actually works is almost beyond imagination. Pharmaceutical firms don't become colossal multinational corporations by ignoring promising developments, so the owners of the Minoxidil patents started some new trials. Sure enough, they found that in a significant fraction of men showing male pattern baldness (about 40%) topically applied minoxidil causes regrowth of hairs. This is no comfort to the 60% for whom it doesn't work, but there's an unending supply of hopeful, balding men.
Apparently, in addition to causing vasodilation, minoxidil also blocks androgen binding sites. The proliferative cells of hair follicles have such sites, and the presence of the drug in sufficient concentration blocks those sites. Hence the testosterone induced suppression of growth is removed, and the hair begins to grow again.
