Minoxidil was developed as a blood pressure medication in the late 1960’s and is still used today for moderate to severe hypertension (high blood pressure). Even during development for high blood pressure the “side effect” of hypertrichosis (excessive hair growth) was reported but was minimized by the company doing the research. They felt that a drug for hair loss was not meaningful enough and did not want to jeopardize developing the use of minoxidil for blood pressure. But once the word got out to enough people, the company was convinced to start studies for the treatment of baldness in the late 1970’s.
The mechanism for the extra hair growth from minoxidil is not completely understood. One proposed mechanism is that by opening potassium channels it causes a hyperpolarization of cell membranes in hair follicles, which could cause hair follicles in the telogen phase to shed the hair and be replaced by stronger, thicker hair of the anagen phase of growth.
Minoxidil for hair loss has been approved by the FDA in only 2 concentrations: 2% and 5%. Both of these strengths have shown some effectiveness in treating various forms of hair loss. For patients with less than optimal response to the 5% formula, higher concentrations up to 14% have been prescribed by doctors seeking better results for those patients. Since the commercial drug companies do not make anything more than 5%, a compounding pharmacy has to make these stronger formulas. Additional hair growth has been reported with these formulas. It should also be noted that stronger formulas require more of the inactive solvents propylene glycol and/or alcohol, which could theoretically increase the irritation and redness from the application.
So for those patients who have experienced some effects but insufficient benefit from standard concentrations of minoxidil for hair loss, a trial of stronger formulations is reasonable.