Minoxidil, sold under the brand name Rogaine among others, is a medication used for the treatment of high blood pressure and pattern hair loss. It is an antihypertensive vasodilator. It is available as a generic medication by prescription in oral tablet form and over the counter as a topical liquid or foam. Medical uses
Minoxidil, when used for hypertension, is generally reserved for use in severe hypertension patients who can not respond to at least two agents and a diuretic. Minoxidil is also generally administered with a loop diuretic to prevent the sodium and potassium retention. It may also cause a reflex tachycardia and thus is prescribed with a beta blocker. Minoxidil, applied topically, is widely used for the treatment of hair loss. It is effective in helping promote hair growth in people with androgenic alopecia regardless of sex. Minoxidil must be used indefinitely for continued support of existing hair follicles and the maintenance of any experienced hair regrowth.Low-dose oral minoxidil is used off-label against hair loss.Its effect in people with alopecia areata is unclear. However, the association of oral minoxidil with Janus Kinase inhibitors (JAK inhibitors), termed oral adjuvant minoxidil, seems to increase hair regrowth in patients refractory to JAK inhibitor monotherapy. Side effects
Topically applied minoxidil is generally well tolerated, but common side effects include itching of the eye, itching, redness or irritation at the treated area, and unwanted hair growth elsewhere on the body. Exacerbation of hair loss/alopecia has been reported.
This antiandrogenic effect of minoxidil, shown by significant downregulation of 5α-R2 gene expression in HaCaT cells, may be one of its mechanisms of action in alopecia.Minoxidil is less effective when the area of hair loss is large. In addition, its effectiveness has largely been demonstrated in younger men who have experienced hair loss for less than 5 years. Minoxidil use is indicated for central (vertex) hair loss only. Two clinical studies are being conducted in the US for a medical device that may allow patients to determine if they are likely to benefit from minoxidil therapy.Conditions such as Cantú syndrome have been shown to mimic the pharmacological properties of minoxidil. Chemistry
Minoxidil is an odorless, white to off-white, crystalline powder (crystals from methanol-acetonitrile). When heated to decomposition it emits toxic fumes of nitrogen oxides. It decomposes at 259-261 °C.Solubility (mg/ml): propylene glycol 75, methanol 44, ethanol 29, 2-propanol 6.7, dimethylsulfoxide 6.5, water 2.2, chloroform 0.5, acetone <0.5, ethyl acetate <0.5, diethyl ether <0.5, benzene <0.5, acetonitrile <0.5.