Clinical data | |
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Trade names | Loniten, Rogaine, others |
Other names | 2,4-Diamino-6-piperidinopyrimidine 3-oxide |
AHFS/Drugs.com | Monograph |
MedlinePlus | a682608 |
License data | |
Pregnancy category |
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Routes of administration | By mouth, topical |
ATC code | |
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Pharmacokinetic data | |
Metabolism | Primarily liver |
Elimination half-life | 4.2 h |
Excretion | Kidney |
Identifiers | |
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CAS Number | |
PubChem CID | |
IUPHAR/BPS | |
DrugBank | |
ChemSpider | |
UNII | |
KEGG | |
ChEBI | |
ChEMBL | |
PDB ligand | |
CompTox Dashboard (EPA) | |
ECHA InfoCard | 100.048.959 |
Chemical and physical data | |
Formula | C9H15N5O |
Molar mass | 209.253 g·mol−1 |
3D model (JSmol) | |
Melting point | 248 °C (478 °F) |
Solubility in water | <1 |
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Minoxidil is a medication used for the treatment of high blood pressure and pattern hair loss. [4] [5] [6] It is an antihypertensive and a vasodilator. [10] It is available as a generic medication by prescription in oral tablet form and over the counter as a topical liquid or foam. [8] [9] [11] [12]
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. [13] Minoxidil is also generally administered with a loop diuretic to prevent sodium and potassium retention. [13] It may also cause a reflex tachycardia and thus is prescribed with a beta blocker. [13]
Minoxidil, when applied topically, is used for the treatment of hair loss. [14] It is effective in helping promote hair growth in people with androgenic alopecia regardless of sex. [14] Minoxidil must be used indefinitely for continued support of existing hair follicles and the maintenance of any experienced hair regrowth. [5] [6]
Low-dose oral minoxidil (LDOM) is used off-label against hair loss and to promote hair regrowth. [15] Oral minoxidil is an effective and well-tolerated treatment alternative for patients having difficulty with topical formulations. [16] [17] [18]
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. [20]
Alcohol and propylene glycol present in some topical preparations may dry the scalp, resulting in dandruff and contact dermatitis. [21]
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. [8] Pseudoacromegaly is an extremely rare side effect reported with large doses of oral minoxidil. [22]
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. [23] 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. [24]
The mechanism by which minoxidil promotes hair growth is not fully understood. Minoxidil is an adenosine 5'-triphosphate-sensitive potassium channel opener, [25] 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 (A2A and A2B receptors). [26] Minoxidil acts as an activator of the Kir6/SUR2 channel upon selective binding to SUR2. [27] The expression of SUR2B in dermal papilla cells might play a role in the production of adenosine. [26] 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. [28]
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. [29]
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. [30] 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. [31] 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. [32]
Minoxidil stimulates prostaglandin E2 production by activating COX-1 [33] 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. [34]
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. [35]
Minoxidil possesses alpha 2-adrenoceptor agonist activity, [36] 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. [13]
Minoxidil may be involved in the inhibition of serotonergic (5-HT2) receptors. [37]
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. [38] Minoxidil significantly increases ROS concentration when compared to untreated cells.[ medical citation needed ]
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. [39]
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. [40] 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. [41]
Conditions such as Cantú syndrome have been shown to mimic the pharmacological properties of minoxidil. [42]
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. [43]
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.
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. [44]
Another synthesis approach is depicted here:
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. [46] 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. [47] [48]
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. [46] He conducted two studies, [49] [50] 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.[ citation needed ]
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. [51] The two doctors had been experimenting with a 1% solution of minoxidil mixed with several alcohol-based liquids. [52] 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. [51]
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. [48]
In August 1988, the FDA approved minoxidil for treating baldness in men [48] [52] under the brand name "Rogaine" (FDA rejected Upjohn's first choice, Regain, as misleading [53] ). 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". [53] "Men's Rogaine", marketed by Johnson & Johnson went off-patent on January 20, 2006. [54]
In 1991, Upjohn made the product available for women. [52] "Women's Rogaine", marketed by Johnson & Johnson, went off-patent in February 2014. [54]
Minoxidil has been implicated in causing pericardial effusions [55] including life-threatening cases of cardiac tamponade. [56] There have been case reports dating back to the 1980s describing this phenomenon, including topical. [56] and oral formulations. [57] 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. [58]
In February 1996, the FDA approved both the over-the-counter sale and the production of generic formulations of minoxidil. [48] Upjohn replied to that by lowering prices to half the price of the prescription drug [52] and by releasing a prescription 5% formula of Rogaine in 1997. [48] [59] In 1998, a 5% formulation of minoxidil was approved for nonprescription sale by the FDA. [60] The 5% aerosol foam formula was approved for medical use in the US in 2006. [61] [62] The generic versions of the 5% aerosol foam formula were approved in 2017. [63] [64]
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. [65]
As of June 2017 [update] , Minoxidil is sold under many brand 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, 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, Regain, 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. [66] 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. [66]
Minoxidil is being investigated as a potential treatment for ovarian cancer. [67]
Minoxidil is highly toxic to dogs and cats, even in doses as small as a drop or lick. [68] There are reported cases of cats dying shortly after coming in contact with minimal amounts of the substance. [69]
There is no specific antidote, but lipid rescue has been used successfully. [70] [71]
Adenosine (symbol A) is an organic compound that occurs widely in nature in the form of diverse derivatives. The molecule consists of an adenine attached to a ribose via a β-N9-glycosidic bond. Adenosine is one of the four nucleoside building blocks of RNA (and its derivative deoxyadenosine is a building block of DNA), which are essential for all life on Earth. Its derivatives include the energy carriers adenosine mono-, di-, and triphosphate, also known as AMP/ADP/ATP. Cyclic adenosine monophosphate (cAMP) is pervasive in signal transduction. Adenosine is used as an intravenous medication for some cardiac arrhythmias.
Alopecia areata, also known as spot baldness, is a condition in which hair is lost from some or all areas of the body. It often results in a few bald spots on the scalp, each about the size of a coin. Psychological stress and illness are possible factors in bringing on alopecia areata in individuals at risk, but in most cases there is no obvious trigger. People are generally otherwise healthy. In a few cases, all the hair on the scalp is lost, or all body hair is lost. Hair loss can be permanent, or temporary.
Hair loss, also known as alopecia or baldness, refers to a loss of hair from part of the head or body. Typically at least the head is involved. The severity of hair loss can vary from a small area to the entire body. Inflammation or scarring is not usually present. Hair loss in some people causes psychological distress.
Tretinoin, also known as all-trans retinoic acid (ATRA), is a medication used for the treatment of acne and acute promyelocytic leukemia. For acne, it is applied to the skin as a cream, gel or ointment. For acute promyelocytic leukemia, it is effective only when the RARA-PML fusion mutation is present and is taken by mouth for up to three months. Topical tretinoin is also the most extensively investigated retinoid therapy for photoaging.
Ketoconazole, sold under the brand name Nizoral, among others, is an antiandrogen, antifungal, and antiglucocorticoid medication used to treat a number of fungal infections. Applied to the skin it is used for fungal skin infections such as tinea, cutaneous candidiasis, pityriasis versicolor, dandruff, and seborrheic dermatitis. Taken by mouth it is a less preferred option and only recommended for severe infections when other agents cannot be used. Other uses include treatment of excessive male-patterned hair growth in women and Cushing's syndrome.
Adapalene, sold under the brand name Differin among others, is a third-generation topical retinoid primarily used in the treatment of mild-moderate acne, and is also used off-label to treat keratosis pilaris as well as other skin conditions. Studies have found adapalene is as effective as other retinoids, while causing less irritation. It also has several advantages over other retinoids. The adapalene molecule is more stable compared to tretinoin and tazarotene, which leads to less concern for photodegradation. It is also chemically more stable compared to the other two retinoids, allowing it to be used in combination with benzoyl peroxide. Due to its effects on keratinocyte proliferation and differentiation, adapalene is superior to tretinoin for the treatment of comedonal acne and is often used as a first-line agent. The Swiss company Galderma developed adapalene.
Alopecia universalis(AU), also known as alopecia areata universalis, is a medical condition involving the loss of all body hair, including eyebrows, eyelashes, chest hair, armpit hair, and pubic hair. It is the most severe form of alopecia areata (AA). People with the condition are usually healthy and have no other symptoms and a normal life expectancy.
Hypertrichosis is an abnormal amount of hair growth over the body. The two distinct types of hypertrichosis are generalized hypertrichosis, which occurs over the entire body, and localized hypertrichosis, which is restricted to a certain area. Hypertrichosis can be either congenital or acquired later in life. The excess growth of hair occurs in areas of the skin with the exception of androgen-dependent hair of the pubic area, face, and axillary regions.
The management of hair loss, includes prevention and treatment of alopecia, baldness, and hair thinning, and regrowth of hair.
Pattern hair loss is a hair loss condition that primarily affects the top and front of the scalp. In male-pattern hair loss (MPHL), the hair loss typically presents itself as either a receding front hairline, loss of hair on the crown and vertex of the scalp, or a combination of both. Female-pattern hair loss (FPHL) typically presents as a diffuse thinning of the hair across the entire scalp.
Sulfotransferase 1A1 is an enzyme that in humans is encoded by the SULT1A1 gene.
Anagen effluvium is the pathologic loss of anagen or growth-phase hairs. Classically, it is caused by radiation therapy to the head and systemic chemotherapy, especially with alkylating agents.
Scarring hair loss, also known as cicatricial alopecia, is the loss of hair which is accompanied with scarring. This is in contrast to non scarring hair loss.
Non scarring hair loss, also known as noncicatricial alopecia is the loss of hair without any scarring being present. There is typically little inflammation and irritation, but hair loss is significant. This is in contrast to scarring hair loss during which hair follicles are replaced with scar tissue as a result of inflammation. Hair loss may be spread throughout the scalp (diffuse) or at certain spots (focal). The loss may be sudden or gradual with accompanying stress.
A Janus kinase inhibitor, also known as JAK inhibitor or jakinib, is a type of immune modulating medication, which inhibits the activity of one or more of the Janus kinase family of enzymes, thereby interfering with the JAK-STAT signaling pathway in lymphocytes.
Alfatradiol, also known as 17α-estradiol and sold under the brand names Avicis, Avixis, Ell-Cranell Alpha, and Pantostin, is a weak estrogen and 5α-reductase inhibitor medication which is used topically in the treatment of pattern hair loss in men and women. It is a stereoisomer of the endogenous steroid hormone and estrogen 17β-estradiol.
Topilutamide, known more commonly as fluridil and sold under the brand name Eucapil, is an antiandrogen medication which is used in the treatment of pattern hair loss in men and women. It is used as a topical medication and is applied to the scalp. Topilutamide belongs to a class of molecules known as perfluoroacylamido-arylpropanamides.
Pyrilutamide is a nonsteroidal antiandrogen (NSAA) – specifically, a selective high-affinity silent antagonist of the androgen receptor (AR) – which is under development by Suzhou Kintor Pharmaceuticals, inc., a subsidiary of Kintor Pharmaceutical Limited, for the potential treatment of androgenic alopecia As of September 2022, it is in phase 3 clinical trials for androgenic alopecia and phase 2 trials for acne.
Tapinarof, also known as benvitimod and sold under the brand name Vtama, is a medication used for the treatment of plaque psoriasis. The medication is applied to the skin. Besides its use in medicine, tapinarof is a naturally occurring compound found in bacterial symbionts of nematodes which has antibiotic properties.
Minoxidil sulfate, also known as minoxidil sulfate ester or minoxidil N-O-sulfate, is an active metabolite of minoxidil and is the active form of this agent. Minoxidil acts as a prodrug of minoxidil sulfate. Minoxidil sulfate is formed from minoxidil via sulfotransferase enzymes, with the predominant enzyme responsible, at least in hair follicles, being SULT1A1. Minoxidil sulfate acts as a potassium channel opener, among other actions, and has vasodilating, hypotensive, and trichogenic or hypertrichotic effects. Its mechanism of action in terms of hair growth is still unknown, although multiple potential mechanisms have been implicated.
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.