minoxidil

Minoxidil, when used for hypertension, is generally reserved for use in severe hypertension patients who do not respond to at least two agents and a diuretic. Minoxidil is also generally administered with a loop diuretic to prevent sodium retention and potassium retention. It may also cause a reflex tachycardia and thus is prescribed with a beta blocker.

Minoxidil, when applied topically, is used for the treatment of hair loss. It is effective in helping promote hair growth in people with androgenic alopecia regardless of sex.{{cite journal | vauthors = Varothai S, Bergfeld WF | title = Androgenetic alopecia: an evidence-based treatment update | journal = American Journal of Clinical Dermatology | volume = 15 | issue = 3 | pages = 217–230 | date = July 2014 | pmid = 24848508 | doi = 10.1007/s40257-014-0077-5 }} Minoxidil must be used indefinitely for continued support of existing hair follicles and the maintenance of any experienced hair regrowth.

Low-dose oral minoxidil (LDOM) is used off-label against hair loss and to promote hair regrowth.{{Cite news |date=August 18, 2022 |title=An Old Medicine Grows New Hair for Pennies a Day, Doctors Say |work=The New York Times |url=https://www.nytimes.com/2022/08/18/health/minoxidil-hair-loss-pills.html |access-date= |archive-url=https://web.archive.org/web/20220819190113/https://www.nytimes.com/2022/08/18/health/minoxidil-hair-loss-pills.html |archive-date=August 19, 2022 |vauthors=Kolata G}} Oral minoxidil is an effective and well-tolerated treatment alternative for patients having difficulty with topical formulations.{{cite journal |vauthors=Randolph M, Tosti A |date=March 2021 |title=Oral minoxidil treatment for hair loss: A review of efficacy and safety |journal=Journal of the American Academy of Dermatology |volume=84 |issue=3 |pages=737–746 |doi=10.1016/j.jaad.2020.06.1009 |pmid=32622136 }}{{cite journal |vauthors=Jimenez-Cauhe J, Saceda-Corralo D, Rodrigues-Barata R, Moreno-Arrones OM, Ortega-Quijano D, Fernandez-Nieto D, Jaen-Olasolo P, Vaño-Galvan S |date=November 2020 |title=Safety of low-dose oral minoxidil treatment for hair loss. A systematic review and pooled-analysis of individual patient data |journal=Dermatologic Therapy |volume=33 |issue=6 |pages=e14106 |doi=10.1111/dth.14106 |pmid=32757405 | doi-access=free }}{{cite journal |vauthors=Sharma AN, Michelle L, Juhasz M, Muller Ramos P, Atanaskova Mesinkovska N |date=August 2020 |title=Low-dose oral minoxidil as treatment for non-scarring alopecia: a systematic review |journal=International Journal of Dermatology |volume=59 |issue=8 |pages=1013–1019 |doi=10.1111/ijd.14933 |pmid=32516434 }}

File:Minoxidil and Finasteride side effects.jpg

Topically applied minoxidil is generally well tolerated, but common side effects include itching of the eyes, general itching, irritation at the treated area, and unwanted hair growth elsewhere on the body.{{cite web |url=https://www.drugs.com/sfx/rogaine-side-effects.html |title=Rogaine Side Effects |publisher=Drugs.com |access-date=December 8, 2020 |archive-date=September 22, 2017 |archive-url=https://web.archive.org/web/20170922052041/https://www.drugs.com/sfx/rogaine-side-effects.html |url-status=live }}

Alcohol and propylene glycol present in some topical preparations may dry the scalp, resulting in dandruff and contact dermatitis.{{cite journal | vauthors = Pray WS |title=Dandruff and Seborrheic Dermatitis |journal=US Pharmacist |volume=26 |issue=4 |year=2001 |pages=16–24 |url=http://www.medscape.com/viewarticle/407641 |url-status=live |archive-url=https://web.archive.org/web/20101028074627/http://www.medscape.com/viewarticle/407641 |archive-date=October 28, 2010 }}

Side effects of oral minoxidil may include swelling of the face and extremities, rapid heartbeat, or lightheadedness. Cardiac lesions, such as focal necrosis of the papillary muscle and subendocardial areas of the left ventricle, have been observed in laboratory animals treated with minoxidil. Pseudoacromegaly is an extremely rare side effect reported with large doses of oral minoxidil.{{cite journal | vauthors = Nguyen KH, Marks JG | title = Pseudoacromegaly induced by the long-term use of minoxidil | journal = Journal of the American Academy of Dermatology | volume = 48 | issue = 6 | pages = 962–965 | date = June 2003 | pmid = 12789195 | doi = 10.1067/mjd.2003.325 }}

In 2013 or 2014, a seven-year-old girl was admitted to a children's hospital in Toulouse in France after accidentally ingesting a teaspoon of Alopexy (a brand name for minoxidil in France). The child vomited constantly after ingestion and showed hypotension and tachycardia for 40 hours.{{cite journal | vauthors = Claudet I, Cortey C, Honorat R, Franchitto N | title = Minoxidil topical solution: an unsafe product for children | journal = Pediatric Emergency Care | volume = 31 | issue = 1 | pages = 44–46 | date = January 2015 | pmid = 25426682 | doi = 10.1097/PEC.0000000000000301 }} The authors of the report on the incident stressed that the product should be kept out of reach of children, and urged manufacturers to consider more secure child-resistant packaging.{{cite news | vauthors = Neumann J | url = https://www.reuters.com/article/us-side-effects-children-minoxidil-idUSKBN0JO2DB20141210 | title = Hair loss treatment may be dangerous to kids | date = December 10, 2014 | work = Reuters | access-date = March 23, 2021 | archive-date = May 17, 2021 | archive-url = https://web.archive.org/web/20210517191609/https://www.reuters.com/article/us-side-effects-children-minoxidil-idUSKBN0JO2DB20141210 | url-status = live }}

The mechanism by which minoxidil promotes hair growth is not fully understood. Minoxidil is an adenosine 5'-triphosphate-sensitive potassium channel opener,{{cite journal | vauthors = Wang T | title = The effects of the potassium channel opener minoxidil on renal electrolytes transport in the loop of henle | journal = The Journal of Pharmacology and Experimental Therapeutics | volume = 304 | issue = 2 | pages = 833–840 | date = February 2003 | pmid = 12538840 | doi = 10.1124/jpet.102.043380 }} causing hyperpolarization of cell membranes. Theoretically, by widening blood vessels and opening potassium channels, it allows more oxygen, blood, and nutrients to the follicles. Moreover, minoxidil contains a nitric oxide moiety and may act as a nitric oxide agonist. 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. The effect of minoxidil is mediated by adenosine, which triggers intracellular signal transduction via both adenosine A₁ receptors and two sub-types of adenosine A₂ receptors (A_2A and A_2B receptors).{{cite journal | vauthors = Li M, Marubayashi A, Nakaya Y, Fukui K, Arase S | title = Minoxidil-induced hair growth is mediated by adenosine in cultured dermal papilla cells: possible involvement of sulfonylurea receptor 2B as a target of minoxidil | journal = The Journal of Investigative Dermatology | volume = 117 | issue = 6 | pages = 1594–1600 | date = December 2001 | pmid = 11886528 | doi = 10.1046/j.0022-202x.2001.01570.x | quote = The expression of sulfonylurea receptor 2B and of the adenosine A1, A2A, and A2B receptors was detected in dermal papilla cells by means of reverse transcription polymerase chain reaction analysis. | doi-access = free }} Minoxidil acts as an activator of the Kir6/SUR2 channel upon selective binding to SUR2.{{cite journal | vauthors = Fukushiro-Lopes D, Hegel AD, Russo A, Senyuk V, Liotta M, Beeson GC, Beeson CC, Burdette J, Potkul RK, Gentile S | title = Repurposing Kir6/SUR2 Channel Activator Minoxidil to Arrests Growth of Gynecologic Cancers | journal = Frontiers in Pharmacology | volume = 11 | pages = 577 | date = May 8, 2020 | pmid = 32457608 | pmc = 7227431 | doi = 10.3389/fphar.2020.00577 | doi-access = free }} The expression of SUR2B in dermal papilla cells might play a role in the production of adenosine. Minoxidil induces cell growth factors such as VEGF, HGF, IGF-1 and potentiates HGF and IGF-1 actions by the activation of uncoupled sulfonylurea receptor on the plasma membrane of dermal papilla cells.{{cite journal | vauthors = Otomo S | title = [Hair growth effect of minoxidil] | journal = Nihon Yakurigaku Zasshi. Folia Pharmacologica Japonica | volume = 119 | issue = 3 | pages = 167–174 | date = March 2002 | pmid = 11915519 | doi = 10.1254/fpj.119.167 | doi-access = free }}

A number of in vitro effects of minoxidil have been described in monocultures of various skin and hair follicle cell types including stimulation of cell proliferation, inhibition of collagen synthesis, and stimulation of vascular endothelial growth factor, prostaglandin synthesis and leukotriene B4 expression.{{cite journal | vauthors = Messenger AG, Rundegren J | title = Minoxidil: mechanisms of action on hair growth | journal = The British Journal of Dermatology | volume = 150 | issue = 2 | pages = 186–194 | date = February 2004 | pmid = 14996087 | doi = 10.1111/j.1365-2133.2004.05785.x }}

Minoxidil causes a redistribution of cellular iron through its apparent capacity to bind this metal ion. By binding iron in a Fenton-reactive form, intracellular hydroxyl radical production would ensue, but hydroxyl would be immediately trapped and scavenged by the minoxidil to generate a nitroxyl radical. It is presumed that this nitroxyl radical will be capable of reduction by glutathione to reform minoxidil. Such a process would cycle until the minoxidil is otherwise metabolized and would result in rapid glutathione depletion with glutathione disulphide formation and therefore with concomitant consumption of NADPH/NADH and other reducing equivalents.{{cite book | vauthors = Chung LY, Andrews AM, Schmidt RJ, Turner TD |chapter=Effects of minoxidil on cell proliferation and intracellular glutathione status of murine (L929) fibroblasts |pages=122–128 | veditors = Harding KG, Leaper DL, Turner TD |title=Proceedings of the 1st European Conference on Advances in Wound Management, Cardiff, 4-6 September 1991 |date=1992 |publisher=Macmillan Magazines |isbn=978-0-333-58645-7 }} Minoxidil inhibited PHD by interfering with the normal function of ascorbate, a cofactor of the enzyme, leading to a stabilization of HIF-1α protein and a subsequent activation of HIF-1. In an in vivo angiogenesis assay, millimolar minoxidil increased blood vessel formation in a VEGF-dependent manner. Minoxidil inhibition of PHD occurs via interrupting ascorbate binding to iron.{{cite journal | vauthors = Yum S, Jeong S, Kim D, Lee S, Kim W, Yoo JW, Kim JA, Kwon OS, Kim DD, Min DS, Jung Y | title = Minoxidil Induction of VEGF Is Mediated by Inhibition of HIF-Prolyl Hydroxylase | journal = International Journal of Molecular Sciences | volume = 19 | issue = 1 | page = 53 | date = December 2017 | pmid = 29295567 | pmc = 5796003 | doi = 10.3390/ijms19010053 | doi-access = free }} The structural feature of positioning amines adjacent to nitric oxide may confer the ability of millimolar minoxidil to chelate iron, thereby inhibiting PHD. Minoxidil is capable of tetrahydrobiopterin inhibition as a cofactor for nitric oxide synthase.{{Cite patent|country=US|number=5874433|title=Blocking utilization of tetrahydrobiopterin to block induction of nitric oxide synthesis|pubdate=1999-02-23|inventor = Gross SS }}

Minoxidil stimulates prostaglandin E₂ production by activating COX-1{{cite journal | vauthors = Hwang JH, Chu H, Ahn Y, Kim J, Kim DY | title = HMGB1 promotes hair growth via the modulation of prostaglandin metabolism | journal = Scientific Reports | volume = 9 | issue = 1 | pages = 6660 | date = April 2019 | pmid = 31040377 | pmc = 6491442 | doi = 10.1038/s41598-019-43242-2 | bibcode = 2019NatSR...9.6660H }} and prostaglandin endoperoxide synthase-1 but inhibits prostacyclin production. Additionally, expression of the prostaglandin E₂ receptor, the most upregulated target gene in the β-catenin pathway of DP cells, was enhanced by minoxidil, which may enable hair follicles to grow continuously and maintain the anagen phase.{{cite journal | vauthors = Suchonwanit P, Thammarucha S, Leerunyakul K | title = Minoxidil and its use in hair disorders: a review | journal = Drug Design, Development and Therapy | volume = 13 | issue = | pages = 2777–2786 | date = 2019 | pmid = 31496654 | pmc = 6691938 | doi = 10.2147/DDDT.S214907 | doi-access = free }}

Due to the anti-fibrotic activity of minoxidil inhibition of enzyme lysyl hydroxylase present in fibroblast may result in the synthesis of a hydroxylysine-deficient collagen. Minoxidil can also potentially stimulate elastogenesis in aortic smooth muscle cells, and in skin fibroblasts in a dose-dependent manner. In hypertensive rats, minoxidil increases elastin levels in the mesenteric, abdominal, and renal arteries by a decrease in elastase enzyme activity in these tissues. In rats, potassium channel openers decrease calcium influx which inhibits elastin gene transcription through extracellular signal-regulated kinase 1/2 (ERK 1/2)-activator protein 1 signaling pathway. ERK 1/2 increases, through elastin gene transcription, adequately cross-linked elastic fiber content synthesized by smooth muscle cells, and decreases the number of cells in the aorta.{{cite journal | vauthors = Kassai B, Bouyé P, Gilbert-Dussardier B, Godart F, Thambo JB, Rossi M, Cochat P, Chirossel P, Luong S, Serusclat A, Canterino I, Mercier C, Rabilloud M, Pivot C, Pirot F, Ginhoux T, Coopman S, Grenet G, Gueyffier F, Di-Fillippo S, Bertholet-Thomas A | title = Minoxidil versus placebo in the treatment of arterial wall hypertrophy in children with Williams Beuren Syndrome: a randomized controlled trial | journal = BMC Pediatrics | volume = 19 | issue = 1 | pages = 170 | date = May 2019 | pmid = 31138170 | pmc = 6537216 | doi = 10.1186/s12887-019-1544-1 | doi-access = free }}

Minoxidil possesses α₂-adrenergic receptor agonist activity,{{cite journal | vauthors = Sharma N, Mehta AA, Santani DD, Goyal RK | title = Evidence for alpha 2-adrenoceptor agonist activity of minoxidil | journal = The Journal of Pharmacy and Pharmacology | volume = 49 | issue = 9 | pages = 935–937 | date = September 1997 | pmid = 9306265 | doi = 10.1111/j.2042-7158.1997.tb06139.x | doi-access = free }} stimulates the peripheral sympathetic nervous system (SNS) by way of carotid and aortic baroreceptor reflexes. Minoxidil administration also brings an increase in plasma renin activity, largely due to the aforementioned activation of the SNS. This activation of the renin-angiotensin axis further prompts increased biosynthesis of aldosterone; whereas plasma and urinary aldosterone levels are increased early in the course of treatment with minoxidil, over time these values tend to normalize presumably because of accelerated metabolic clearance of aldosterone in association with hepatic vasodilation.{{cite journal | vauthors = Sica DA | title = Minoxidil: an underused vasodilator for resistant or severe hypertension | journal = Journal of Clinical Hypertension | volume = 6 | issue = 5 | pages = 283–287 | date = May 2004 | pmid = 15133413 | pmc = 8109604 | doi = 10.1111/j.1524-6175.2004.03585.x | doi-access = free }}

Minoxidil may be involved in the inhibition of serotonin 5-HT₂ receptors.{{cite journal | vauthors = Wasiński R, Godlewski G, Wróbel B, Buckzko W | title = Interactions of minoxidil with vasoconstrictive agents in isolated rat tail artery | journal = Acta Poloniae Pharmaceutica | volume = 52 | issue = 3 | pages = 253–256 | date = May 1995 | pmid = 8960256 }}

Minoxidil might increase blood-tumor barrier permeability in a time-dependent manner by down-regulating tight junction protein expression and this effect could be related to ROS/RhoA/PI3K/PKB signal pathway.{{cite journal | vauthors = Gu YT, Xue YX, Wang YF, Wang JH, Chen X, ShangGuan QR, Lian Y, Zhong L, Meng YN | title = Minoxidil sulfate induced the increase in blood-brain tumor barrier permeability through ROS/RhoA/PI3K/PKB signaling pathway | journal = Neuropharmacology | volume = 75 | pages = 407–415 | date = December 2013 | pmid = 23973310 | doi = 10.1016/j.neuropharm.2013.08.004 }} Minoxidil significantly increases ROS concentration when compared to untreated cells.{{medcn|date=August 2024}}

In vitro Minoxidil treatment resulted in a 0.22 fold change for 5α-R2 (p < 0.0001). 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.{{cite journal | vauthors = Pekmezci E, Türkoğlu M | title = Minoxidil Acts as an Antiandrogen: A Study of 5α-reductase Type 2 Gene Expression in a Human Keratinocyte Cell Line | journal = Acta Dermatovenerologica Croatica | volume = 25 | issue = 4 | pages = 271–275 | date = December 2017 | pmid = 30064598 | url = https://hrcak.srce.hr/192895 }}

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.{{cite journal | vauthors = Scow DT, Nolte RS, Shaughnessy AF | title = Medical treatments for balding in men | journal = American Family Physician | volume = 59 | issue = 8 | pages = 2189–94, 2196 | date = April 1999 | pmid = 10221304 | url = https://www.aafp.org/link_out?pmid=10221304 }} 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.{{ClinicalTrialsGov|NCT02198261|Minoxidil Response Testing in Males With Androgenetic Alopecia}}

Conditions such as Cantú syndrome have been shown to mimic the pharmacological properties of minoxidil.{{cite journal | vauthors = Ohko K, Nakajima K, Nakajima H, Hiraki Y, Kubota K, Fukao T, Miyatake S, Matsumoto N, Sano S | title = Skin and hair abnormalities of Cantu syndrome: A congenital hypertrichosis due to a genetic alteration mimicking the pharmacological effect of minoxidil | journal = The Journal of Dermatology | volume = 47 | issue = 3 | pages = 306–310 | date = March 2020 | pmid = 31907964 | doi = 10.1111/1346-8138.15216 }}

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.{{cite web | title=COMPOUND SUMMARY Minoxidil | website=PubChem - National Center for Biotechnology Information | url=https://pubchem.ncbi.nlm.nih.gov/compound/Minoxidil#section=Chemical-and-Physical-Properties | access-date=September 25, 2022 | archive-date=September 1, 2022 | archive-url=https://web.archive.org/web/20220901221023/https://pubchem.ncbi.nlm.nih.gov/compound/Minoxidil#section=Chemical-and-Physical-Properties | url-status=live }}

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.

$\backslash mathrm\{p\}K\_\backslash ce\{a\}\; =$ 4.61

Minoxidil, 6-amino-1,2-dihydro-1-hydroxy-2-imino-4-piperidinopyrimidine, is synthesized from barbituric acid, the reaction of which with phosphorus oxychloride gives 2,4,6-trichloropyrimidine. Upon reaction with ammonium, this turns into 2,4-diamino-6-chloropyrimidine. Next, the resulting 2,4-diamino-6-chloropyrimidine undergoes a reaction with 2,4-dichlorophenol in the presence of potassium hydroxide, giving 2,4-diamino-6-(2,4-dichlorophenoxy)-pyrimidine. Oxidation of this product with 3-chloroperbenzoic acid gives 2,4-diamino-6-(2,4-dichlorophenoxy)pyrimidine-3-oxide, the 2,4-dichlorophenoxyl group of which is replaced with a piperidine group at high temperature, giving minoxidil.{{cite book |doi=10.1016/B978-044452166-8/50022-4 |chapter=Antihypertensive Drugs |title=Synthesis of Essential Drugs |date=2006 |pages=295–310 |isbn=978-0-444-52166-8 | vauthors = Vardanyan R, Hruby V }}

Another synthesis approach is depicted here:

File:Minoxidil synthesis 1.svg

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 the U.S. Food and Drug Administration (FDA) approving minoxidil (with the brand name Loniten) in the form of oral tablets to treat high blood pressure in 1979.{{cite web | title=Loniten: FDA-Approved Drugs | website=U.S. Food and Drug Administration (FDA) | url=https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&ApplNo=018154 | access-date=August 15, 2021 | archive-date=December 28, 2021 | archive-url=https://web.archive.org/web/20211228114736/https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&ApplNo=018154 | url-status=live }}{{cite book | vauthors = Conrad P | date = 2008 | title = The Medicalization of Society: On the Transformation of Human Conditions into Treatable Disorders | chapter = Rogain | chapter-url = {{GBurl|cAE5hlP5YkAC|p=37}} | publisher = JHU Press | pages = 37–38 | isbn = 978-0-8018-9234-9 | doi = 10.56021/9780801885846 }}

When Upjohn received permission from the U.S. Food and Drug Administration (FDA) to test the new drug as medicine for hypertension they approached Charles A. Chidsey, at the University of Colorado School of Medicine.{{Cite news |url=https://www.nytimes.com/2014/09/20/business/guinter-kahn-inventor-of-baldness-remedy-dies-at-80.html |title=Guinter Kahn, Inventor of Baldness Remedy, Dies at 80 |vauthors=Martin D |newspaper=The New York Times |date=September 19, 2014 |archive-url=https://web.archive.org/web/20141011000754/http://www.nytimes.com/2014/09/20/business/guinter-kahn-inventor-of-baldness-remedy-dies-at-80.html |archive-date=October 11, 2014 |access-date=May 11, 2015 |url-status=dead }} He conducted two studies,{{cite journal | vauthors = Gilmore E, Weil J, Chidsey C | title = Treatment of essential hypertension with a new vasodilator in combination with beta-adrenergic blockade | journal = The New England Journal of Medicine | volume = 282 | issue = 10 | pages = 521–527 | date = March 1970 | pmid = 4391708 | doi = 10.1056/NEJM197003052821001 }}{{cite journal | vauthors = Gottlieb TB, Katz FH, Chidsey CA | title = Combined therapy with vasodilator drugs and beta-adrenergic blockade in hypertension. A comparative study of minoxidil and hydralazine | journal = Circulation | volume = 45 | issue = 3 | pages = 571–582 | date = March 1972 | pmid = 4401051 | doi = 10.1161/01.CIR.45.3.571 | doi-access = free }} 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.{{cn|date=August 2024}}

Kahn, along with his colleague Paul J. Grant, had obtained a certain amount of minoxidil 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.{{cite journal |url=https://firstclinical.com/journal/2006/0603_Patents.pdf |title=When Patents Became Interesting in Clinical Research | vauthors = Goldfarb NM |journal=The Journal of Clinical Research Best Practices |volume=2 |issue=3 |date=March 2006 |archive-url=https://web.archive.org/web/20150518091435/https://firstclinical.com/journal/2006/0603_Patents.pdf |archive-date=May 18, 2015 |access-date=May 11, 2015 |url-status=dead }} The two doctors had been experimenting with a 1% solution of minoxidil mixed with several alcohol-based liquids.{{cite web|url=https://news.google.com/newspapers?nid=1957&dat=19960513&id=dT5GAAAAIBAJ&pg=1622,3318023|title=Hair-raising tale: no fame for men who discovered Rogaine|vauthors=Lester W|publisher=The Daily Gazette|date=May 13, 1996|access-date=May 11, 2015|archive-date=July 4, 2022|archive-url=https://web.archive.org/web/20220704034504/https://news.google.com/newspapers?nid=1957&dat=19960513&id=dT5GAAAAIBAJ&pg=1622,3318023|url-status=live}} Both parties filed patents to use minoxidil 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.

Meanwhile, the effect of minoxidil on hair loss prevention was so clear that in the 1980s physicians were prescribing Loniten off-label to their balding patients.

In August 1988, the FDA approved minoxidil for treating baldness in men under the brand name "Rogaine" (FDA rejected Upjohn's first choice, Regain, as misleading{{cite book| vauthors = Kuntzman G |date=2001|title=Hair!: Mankind's Historic Quest to End Baldness|url=https://books.google.com/books?id=omYBD2Ncn4YC&pg=PT172|publisher=Random House Publishing Group|page=172|isbn=978-0-679-64709-6|access-date=May 11, 2015}} (Google Books)). 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". "Men's Rogaine", marketed by Johnson & Johnson went off-patent on January 20, 2006.{{Cite web |title=Generic MINOXIDIL INN equivalents, pharmaceutical patent expiry and freedom to operate |url=https://www.drugpatentwatch.com/p/generic-api/minoxidil |access-date=February 23, 2023 |website=Deep knowledge on small-molecule drugs and the global patents covering them |archive-date=February 23, 2023 |archive-url=https://web.archive.org/web/20230223093516/https://www.drugpatentwatch.com/p/generic-api/minoxidil |url-status=live }}

In 1991, Upjohn made the product available for women. "Women's Rogaine", marketed by Johnson & Johnson, went off-patent in February 2014.

Minoxidil has been implicated in causing pericardial effusionshttps://nctr-crs.fda.gov/fdalabel/services/spl/set-ids/032835ab-1c8b-418a-9009-b6ebe58676dc/spl-doc?hl=MINOXIDIL including life-threatening cases of cardiac tamponade.{{cite journal | vauthors = Oye M, Oye M, Ali A | title = Signs of early cardiac tamponade induced by Minoxidil | journal = The American Journal of Emergency Medicine | volume = 40 | pages = 226.e1–226.e2 | date = February 2021 | pmid = 32778436 | doi = 10.1016/j.ajem.2020.07.050 }} There have been case reports dating back to the 1980s describing this phenomenon, including topical and oral formulations.{{cite journal | vauthors = Houston MC, McChesney JA, Chatterjee K | title = Pericardial effusion associated with minoxidil therapy | journal = Archives of Internal Medicine | volume = 141 | issue = 1 | pages = 69–71 | date = January 1981 | pmid = 7447585 | doi = 10.1001/archinte.1981.00340010061014 }} The frequency of these occurrences has previously been reported at 3% but the true frequency is difficult to determine as a large proportion of patients in this cohort also had renal insufficiency and may have had an effusion preceding the use of minoxidil.{{cite journal | vauthors = Martin WB, Spodick DH, Zins GR | title = Pericardial disorders occurring during open-label study of 1,869 severely hypertensive patients treated with minoxidil | journal = Journal of Cardiovascular Pharmacology | volume = 2 Suppl 2 | pages = S217–S227 | date = 1980 | pmid = 6156358 | doi = 10.1097/00005344-198000022-00016 }}

In February 1996, the FDA approved both the over-the-counter sale 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.{{cite web | title=Drug Approval Package: Rogaine NDA# 020834 | website=U.S. Food and Drug Administration (FDA) | date=August 8, 2003 | url=https://www.accessdata.fda.gov/drugsatfda_docs/nda/97/020834_rogaine_toc.cfm | access-date=August 15, 2021 | archive-date=September 27, 2021 | archive-url=https://web.archive.org/web/20210927064555/https://www.accessdata.fda.gov/drugsatfda_docs/nda/97/020834_rogaine_toc.cfm | url-status=live }} In 1998, a 5% formulation of minoxidil was approved for nonprescription sale by the FDA.{{cite book|vauthors=Pray SW|date=2006|title=Nonprescription Product Therapeutics|url=https://books.google.com/books?id=XU1sMK1djVAC&pg=PA663|publisher=Lippincott Williams & Wilkins|page=663|isbn=978-0-7817-3498-1|access-date=May 11, 2015|archive-date=August 29, 2024|archive-url=https://web.archive.org/web/20240829033100/https://books.google.com/books?id=XU1sMK1djVAC&pg=PA663#v=onepage&q&f=false|url-status=live}} (Google Books) The 5% aerosol foam formula was approved for medical use in the US in 2006.{{cite web | title=Drug Approval Package: Men's Rogaine (5% Minoxidil) NDA #021812 | website=U.S. Food and Drug Administration (FDA) | date=May 6, 2008 | url=https://www.accessdata.fda.gov/drugsatfda_docs/nda/2006/021812s000TOC.cfm | access-date=August 15, 2021 | archive-date=August 6, 2021 | archive-url=https://web.archive.org/web/20210806161825/https://www.accessdata.fda.gov/drugsatfda_docs/nda/2006/021812s000TOC.cfm | url-status=live }}{{cite web | title=Rogaine: FDA-Approved Drugs | website=U.S. Food and Drug Administration (FDA) | url=https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&ApplNo=021812 | access-date=August 15, 2021 | archive-date=August 16, 2021 | archive-url=https://web.archive.org/web/20210816004253/https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&ApplNo=021812 | url-status=live }} The generic versions of the 5% aerosol foam formula were approved in 2017.{{cite web | title=Minoxidil: FDA-Approved Drugs | website=U.S. Food and Drug Administration (FDA) | url=https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&varApplNo=208092 | access-date=August 15, 2021 | archive-date=August 16, 2021 | archive-url=https://web.archive.org/web/20210816003429/https://www.accessdata.fda.gov/scripts/cder/daf/index.cfm?event=overview.process&varApplNo=208092 | url-status=live }}{{cite web | title=CDER 2017 First Generic Drug Approvals | website=U.S. Food and Drug Administration (FDA) | date=February 20, 2018 | url=https://www.fda.gov/drugs/first-generic-drug-approvals/2017-first-generic-drug-approvals | access-date=August 15, 2021 | archive-date=April 26, 2020 | archive-url=https://web.archive.org/web/20200426185216/https://www.fda.gov/drugs/first-generic-drug-approvals/2017-first-generic-drug-approvals | url-status=live }}

In 2017, a study of pharmacy prices in four states for 41 over-the-counter minoxidil products which were "gender-specified" found that the mean price for minoxidil solutions was the same for women and men even though the women's formulations were 2% and the men's were 5%, while the mean price for minoxidil foams, which were all 5%, was 40% higher for women. The authors noted this was the first time gender-based pricing had been shown for a medication.{{cite journal | vauthors = Wehner MR, Nead KT, Lipoff JB | title = Association Between Gender and Drug Cost for Over-the-Counter Minoxidil | journal = JAMA Dermatology | volume = 153 | issue = 8 | pages = 825–826 | date = August 2017 | pmid = 28593214 | pmc = 5817599 | doi = 10.1001/jamadermatol.2017.1394 }}

{{As of|June 2017}}, Minoxidil is sold under many brand names worldwide, including but not limited to: 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, Follixil, 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, Nioxin, Noxidil, Oxofenil, Pilfud, Pilogro, Pilomin, Piloxidil, Re-Stim, Re-Stim+, Recrea, Regain, Regaine, Regaxidil, Regro, Regroe, Regrou, Regrowth, Relive, Renobell Locion, Reten, Rexidil, Rogaine, Rogan, Scalpmed, Si Bi Shen, Splendora, Superminox, Trefostil, Tricolocion, Tricoplus, Tricovivax, Tricoxane, Trugain, Tugain, Unipexil, Vaxdil, Vius, Women's Regaine, Xenogrow, Xtreme Boost, Xtreme Boost+, Xue Rui, Ylox, and Zeldilon.{{cite web | work = Drugs.com | url = https://www.drugs.com/international/minoxidil.html | title = International brand names for minoxidil | archive-url = https://web.archive.org/web/20170808074434/https://www.drugs.com/international/minoxidil.html | archive-date = August 8, 2017 | access-date = June 26, 2017 }} It is also sold as a combination medication 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.

Minoxidil is being investigated as a potential treatment for ovarian cancer.{{ClinicalTrialsGov|NCT05272462|Oral Minoxidil for the Treatment of Recurrent Platinum Resistant Epithelial Ovarian Cancer}}

Minoxidil is highly toxic to dogs and cats, even in doses as small as a drop or lick.{{cite journal |vauthors=Tater KC, Gwaltney-Brant S, Wismer T |title=Topical Minoxidil Exposures and Toxicoses in Dogs and Cats: 211 Cases (2001-2019) |journal=J Am Anim Hosp Assoc |volume=57 |issue=5 |pages=225–231 |date=September 2021 |pmid=34370845 |doi=10.5326/JAAHA-MS-7154}}{{Unreliable source?|reason=The actual paper is hidden behind a paywall, there is no way to read it as a common man, its credibility is questionable and cannot be verified|date=April 2025}} There are reported cases of cats dying shortly after coming in contact with minimal amounts of the substance.{{cite journal | vauthors = DeClementi C, Bailey KL, Goldstein SC, Orser MS |title=Suspected toxicosis after topical administration of minoxidil in 2 cats |journal=Journal of Veterinary Emergency and Critical Care |date=November 2004 |volume=14 |issue=4 |pages=287–292 |doi=10.1111/j.1476-4431.2004.04014.x }}

There is no specific antidote, but lipid rescue has been used successfully.{{cite journal |vauthors=Johnson TE, Fick ME, Haraschak JL, Vernier ME, Kadotani S |title=Successful management of minoxidil 5% toxicosis in 2 cats from the same household |journal=J Vet Emerg Crit Care (San Antonio) |volume=33 |issue=4 |pages=454–459 |date=2023 |pmid=37222073 |doi=10.1111/vec.13296}}{{cite journal |vauthors=Jordan TJ, Yaxley PE, Culler CA, Balakrishnan A |title=Successful management of minoxidil toxicosis in a dog |journal=J Am Vet Med Assoc |volume=252 |issue=2 |pages=222–226 |date=January 2018 |pmid=29319439 |doi=10.2460/javma.252.2.222}}

{{Reflist}}

• {{cite web | title=Minoxidil Topical | website=MedlinePlus | url=https://medlineplus.gov/druginfo/meds/a689003.html }}

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