Minoxidil
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Minoxidil
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| Systematic (IUPAC) name | |
| 6-piperidin-1-ylpyrimidine-2,4-diamine 3-oxide | |
| Identifiers | |
| CAS number | |
| ATC code | C02 D11 |
| PubChem | |
| DrugBank | |
| ChemSpider | |
| Chemical data | |
| Formula | C9H15N5O |
| Mol. mass | 209.251 g/mol |
| Pharmacokinetic data | |
| Bioavailability | ? |
| Metabolism | Primarily hepatic |
| Half life | 4.2 hours |
| Excretion | renal |
| Therapeutic considerations | |
| Pregnancy cat. |
C |
| Legal status |
P(UK) for topical use, otherwise POM. Cannot be prescribed on the NHS. |
| Routes | Oral / topical |
Minoxidil (trade names Rogaine and Regaine) is a vasodilator medication known for its ability to slow or stop hair loss and promote hair regrowth. It is available over the counter for treatment of androgenic alopecia, among other baldness treatments, but measurable changes disappear within months after discontinuation of treatment.
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[edit] History
Minoxidil was first used by (trade name Loniten) to treat high blood pressure. It was, however, discovered to have an interesting side-effect: the ability to reverse or slow down the balding process. Upjohn Corporation produced a topical solution that contained 2% minoxidil to be used to treat baldness and hair loss, under the brand name Rogaine in the United States and Canada, and Regaine in Europe and the Asia-Pacific. Treatments usually include a 5% concentration solution that is designed for men, whereas the 2% concentration solutions are designed for women. The patent on minoxidil expired on February 13, 1996.[1]
In 2007 a new foam-based formulation of 5% minoxidil was shown to be as effective as the liquid-based treatment for male pattern baldness.[2]
While the drug is available in the United Kingdom, it cannot be prescribed on the NHS, so patients must either buy it over-the-counter or have a private prescription for it.[3]
[edit] Results
Objective evidence shows that minoxidil is effective in frontal areas of the scalp, and not just in the vertex area in male-pattern hair loss[citation needed]. At the conclusion of a 48 week study, improvements were seen in the frontal scalp regions of 51% of men using 5% minoxidil, 42% using 2% minoxidil, and 13% of placebo users[citation needed]. Among these men, moderate to great increases in hair growth were seen in the frontal scalp regions of 19% of men using 5% minoxidil, 10% using 2% minoxidil, and 3% of placebo users.[citation needed]
One study in healthy males aged 18–50 years with androgenetic alopecia (male pattern baldness) found that compared to a baseline of 103 to 106 hairs/cm2, those who applied of a 5% solution of minoxidil for 32 weeks increased their non-vellus hair counts by an average of 39 hairs/cm2, in contrast to 5 hairs/cm2 in subjects who received a placebo.[4]
[edit] Mechanism
The mechanism by which minoxidil promotes hair growth is not fully understood. Minoxidil is a potassium channel agonist. It contains the chemical structure of nitric oxide (NO), a blood vessel dilator, and may be a nitric oxide agonist. This appears to explain its vasodilatory effects, but may also be linked to minoxidil's ability to stimulate hair growth and treat hair loss. Since minoxidil is a nitric oxide-related compound, it was suspected to act via activation of guanylate cyclase, an enzyme involved in vasodilation, however there are no reports of cGMP or PKG activation to date.[5]
Minoxidil is less effective when there is a large area of hair loss. In addition, its effectiveness has largely been demonstrated in younger men (18 to 41 years of age), the younger the better, and in those with balding in the central (vertex) portion of the scalp.[6]
[edit] Side-effects
As a drug to combat hair loss, the most common side effect is itchy scalp. Alcohol present in topical preparations may dry the scalp, resulting in dandruff.[7] In some cases minoxidil may initially cause an increase in hair loss. 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.[8] There have been cases of allergic reactions to minoxidil or the non-active ingredient propylene glycol, which is found in some forms of topical Rogaine.
[edit] Effects on animals
Minoxidil is highly toxic to cats and can cause death when applied to their skin.[9][10]
[edit] Application
Minoxidil is made available by Rogaine in three ways: foam, liquid (applied via a dropper) and a gel. All involve contact with hair strands, which may cause problems with hair styling since minoxidil must be in an alcohol solution. To keep the minoxidil solution from affecting normal hair styling applications, it can be washed out after at least 40 minutes, although this will decrease the hair regrowth effect. For maximum effect, the solution should be in contact with the scalp for four hours before being washed out. If the solution is not a problem, hair styling devices can be used as soon as the minoxidil solution has dried.
Minoxidil solutions are sold under many brand names, just one of which is Rogaine. Many generic brands of Minoxidil regrowth solutions exist and do not differ in their active ingredient.
[edit] References
- ^ "Grant v. Pharmacia & Upjohn Co.". http://ca10.washburnlaw.edu/cases/2002/12/01-1509.htm. Retrieved on 2009-01-17.
- ^ Olsen EA, Whiting D, Bergfeld W, Miller J, Hordinsky M, Wanser R, Zhang P, Kohut B (2007). "A multicenter, randomized, placebo-controlled, double-blind clinical trial of a novel formulation of 5% minoxidil topical foam versus placebo in the treatment of androgenetic alopecia in men". J Am Acad Dermatol. 57: 767. doi:. PMID 17761356.
- ^ Drug Tariff, retrieved 2009/04/11
- ^ Rogaine Topical Solution 5%, at Pharmcom, 27 June 2009.
- ^ "Alopecia & Free Radical "Redox" Signaling--Nitric Oxide and Superoxide". http://www.drproctor.com/Archd.htm. Retrieved on 2006-08-09.
- ^ Medical Treatments for Balding in Men American Family Physician April 15, 1999
- ^ "Dandruff and Seborrheic Dermatitis". USPharmacist.com. http://www.uspharmacist.com/oldformat.asp?url=newlook/files/Cons/ACF21C8.cfm. Retrieved on 2008-08-31.
- ^ "Minoxidil Official FDA information, side effects and uses". Drugs.com. http://www.drugs.com/pro/minoxidil.html.
- ^ Camille DeClementi; Keith L. Bailey, Spencer C. Goldstein, and Michael Scott Orser (December 2004). "Suspected toxicosis after topical administration of minoxidil in 2 cats". Journal of Veterinary Emergency and Critical Care 14 (4): 287–292. doi:.
- ^ "Minoxidil Warning". ShowCatsOnline.com. http://www.showcatsonline.com/x/minoxidil.shtml. Retrieved on 2007-01-18. "Very small amounts of Minoxidil can result [in] serious problems or death"
[edit] External links
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