Minoxidil (Loniten) is an antihypertensive agent which is reserved for patients who do not respond adequately to maximum therapeutic doses of other antihypertensive agents. The mechanism of action of Minoxidil is that it produces vasodilation by directly relaxing arteriolar smooth muscle, with little effect on veins. The discovery of the common adverse event of Minoxidil, hypertrichosis (excessive hair growth) led to the development of use in hair disorders. This drug increases cutaneous blood flow by the stimulation of resting hair follicles and is secondary to vasodilation. Minoxidil has been known as the “hair growth stimulator” but the exact mechanism of action is completely understood.
Studies have shown the efficacy of topically applied minoxidil in humans that it increases the hair follicle size. Androgenetic alopecia (AGA) is a common dermatological condition affecting both men and women. In men, up to 30% over the age of 30 and more than 50% over the age of 50 are affected. AGA also affects women, however, clinical signs and thinning of scalp hair are usually milder in women than men. The most favorable approaches to AGA are drug therapies such as topical minoxidil, finasteride administered systemically, or the synergistic combination of both finasteride and minoxidil.
Minoxidil is a pro-drug converted to its active form, minoxidil sulfate by the sulfotransferase enzyme expressed in the outer root sheath of hair follicles. Minoxidil sulfate is the active metabolite that promotes hair growth. While topical minoxidil has an excellent safety record, the efficacy of the drug remains low than low dose oral minoxidil. Minoxidil is the only topical drug that is used for the treatment of both male and female pattern hair loss. In the United States, Minoxidil is approved over-the-counter (OTC) at a maximum concentration of 5%. Minoxidil is typically packaged in 5% aerosol foam and 2% solution. Continuous therapy for 4 months may be necessary for hair growth.
- Goren, A.,McCoy, J., Kovacevic, M., Situm. Et.al. The effect of topical minoxidil treatment on follicular sulfotransferase enzymatic activity. Journal of Biological Regulators and Homeostatic Agents, 32(4),1051-1054.
This content was originally provided by Seena Mathew PharmD candidate 2021.