|Trade names||Rogaine, others|
|Main uses||High blood pressure, male-pattern hair loss|
|By mouth, topical|
|Elimination half-life||4 hours|
|Chemical and physical data|
|Molar mass||209.253 g·mol−1|
|3D model (JSmol)|
|Melting point||248 °C (478 °F)|
|Solubility in water||<1 mg/mL (20 °C)|
Minoxidil is a medication used to treat high blood pressure and male-pattern hair loss. For high blood pressure, it is only recommended when severe and not controllable with a diuretic and a beta blocker. For male-pattern hair loss it is effective in both males and females. For high blood pressure it is taken by mouth while for hair loss it is applied to the skin.
Common side effects when taken by mouth include swelling, pericardial effusion, hair growth, and nausea. Other side effects may include low white blood cells, Stevens-Johnson syndrome and angina. Common side effects when applied to the skin include itchiness and local irritation. Safety in pregnancy and breastfeeding is unclear and such use is not recommended. As a high blood pressure medication it works by dilating blood vessels. How it works in hair loss is not entirely clear.
Minoxidil was approved for medical use in the United States in 1979. In the United States it is available as a generic medication by prescription in tablet form and over the counter for use on the skin. At a dose of 5 mg per day it costs the NHS about 9 pounds per month as of 2020.
Minoxidil, applied topically, is widely used for 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. Its effect in people with alopecia areata is unclear.
High blood pressure
For high blood pressure, it is only recommended when severe and not controllable with a diuretic and a beta blocker. The starting dose is generally 5 mg a day which may be increased by 5 to 10 mg every 3 or more days to a maximum of 100 mg. It should be started at half that dose in the elderly.
Minoxidil is generally well tolerated, but common side effects include burning or irritation 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. Severe allergic reactions may include rash, hives, itching, difficulty breathing, tightness in the chest, swelling of the mouth, face, lips, or tongue, chest pain, dizziness, fainting, tachycardia, headache, sudden and unexplained weight gain, or swelling of the hands and feet. Temporary hair loss is a common side effect of minoxidil treatment. Manufacturers note that minoxidil-induced hair loss is a common side effect and describe the process as "shedding".
Side effects of oral minoxidil may include swelling of the face and extremities, rapid and irregular heartbeat, lightheadedness, cardiac lesions, and focal necrosis of the papillary muscle and subendocardial areas of the left ventricle. Cases of allergic reactions to minoxidil or the non-active ingredient propylene glycol, which is found in some topical minoxidil formulations, have been reported. Pseudoacromegaly is an extremely rare side effect reported with large doses of oral minoxidil.
Mechanism of action
The mechanism by which minoxidil promotes hair growth is not fully understood. Minoxidil is a potassium channel opener, causing hyperpolarization of cell membranes. Theoretically, by widening blood vessels and opening potassium channels, it allows more oxygen, blood, and nutrients to the follicles. This may cause follicles in the telogen phase to shed, which are then replaced by thicker hairs in a new anagen phase. Minoxidil is a prodrug that is converted by sulfation via the sulfotransferase enzyme SULT1A1 to its active form, minoxidil sulfate.
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.
Minoxidil was developed in the late 1950s by the Upjohn Company (later became part of Pfizer) to treat ulcers. In trials using dogs, the compound did not cure ulcers, but proved to be a powerful vasodilator. Upjohn synthesized over 200 variations of the compound, including the one it developed in 1963 and named minoxidil. These studies resulted in FDA approving minoxidil (with the trade name 'Loniten') in the form of oral tablets to treat high blood pressure in 1979.
When Upjohn received permission from the FDA to test the new drug as medicine for hypertension they approached Charles A. Chidsey MD, Associate Professor of Medicine at the University of Colorado School of Medicine. He conducted two studies, the second study showing unexpected hair growth. Puzzled by this side-effect, Chidsey consulted Guinter Kahn (who while a dermatology resident at the University of Miami had been the first to observe and report hair development on patients using the minoxidil patch) and discussed the possibility of using minoxidil for treating hair loss.
Kahn along with his colleague Paul J. Grant MD had obtained a certain amount of the drug and conducted their own research, since they were first to make the side effect observation. Neither Upjohn or Chidsey at the time were aware of the side effect of hair growth. The two doctors had been experimenting with a 1% solution of minoxidil mixed with several alcohol-based liquids. Both parties filed patents to use the drug for hair loss prevention, which resulted in a decade-long trial between Kahn and Upjohn, which ended with Kahn's name included in a consolidated patent (U.S. #4,596,812 Charles A Chidsey, III and Guinter Kahn) in 1986 and royalties from the company to both Kahn and Grant.
In August 1988, the FDA finally approved the drug for treating baldness in men under the trade name "Rogaine" (FDA rejected Upjohn's first choice, Regain, as misleading). The agency concluded that although "the product will not work for everyone", 39% of the men studied had "moderate to dense hair growth on the crown of the head".
In 1991, Upjohn made the product available for women.
On February 12, 1996, the FDA approved both the over-the-counter sale of the drug and the production of generic formulations of minoxidil. Upjohn replied to that by lowering prices to half the price of the prescription drug and by releasing a prescription 5% formula of Rogaine in 1997.
In 1998, a 5% formulation of minoxidil was approved for nonprescription sale by the FDA.
As of June 2017[update], Minoxidil was marketed under many trade names worldwide: Alomax, Alopek, Alopexy, Alorexyl, Alostil, Aloxid, Aloxidil, Anagen, Apo-Gain, Axelan, Belohair, Boots Hair Loss Treatment, Botafex, Capillus, Carexidil, Coverit, Da Fei Xin, Dilaine, Dinaxcinco, Dinaxil, Ebersedin, Eminox, Folcare, Guayaten, Hair Grow, Hair-Treat, Hairgain, Hairgaine, Hairgrow, Hairway, Headway, Inoxi, Ivix, Keranique, Lacovin, Locemix, Loniten, Lonnoten, Lonolox, Lonoten, Loxon, M E Medic, Maev-Medic, Mandi, Manoxidil, Mantai, Men's Rogaine, Minodil, Minodril, Minostyl, Minovital, Minox, Minoxi, Minoxidil, Minoxidilum, Minoximen, Minoxiten, Minscalp, Mintop, Modil, Morr, Moxidil, Neo-Pruristam, Neocapil, Neoxidil, Nherea, Noxidil, Oxofenil, Pilfud, Pilogro, Pilomin, Piloxidil, Recrea, Regain, Regaine, Regaxidil, Regro, Regroe, Regrou, Regrowth, Relive, Renobell Locion, Reten, Rexidil, Rogaine, Rogan, Si Bi Shen, Splendora, Superminox, Trefostil, Tricolocion, Tricoplus, Tricovivax, Tricoxane, Trugain, Tugain, Unipexil, Vaxdil, Vius, Womens Regaine, Xenogrow, Xue Rui, Ylox, and Zeldilon. It was also marketed as combination drug with amifampridine under the brand names Gainehair and Hair 4 U, and as a combination with tretinoin and clobetasol under the brand name Sistema GB.
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