Minoxidil

Systematic (IUPAC) name
6-piperidin-1-ylpyrimidine-2,4-diamine 3-oxide
Identifiers
CAS number	38304-91-5
ATC code	C02DC01 D11AX01
PubChem	4201
DrugBank	APRD00086
ChemSpider	10438564
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
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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.

[edit] History

Minoxidil was first used exclusively as an oral drug (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

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. 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). Minoxidil use is indicated for central (vertex) balding only.^[5]

[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.^[6] 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.^[7] 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.

Ironically, hair loss is a common side effect of minoxidil treatment.^[8] Manufacturers note that minoxidil-induced hair loss is a common side effect and describe the process as 'shedding'. Although this phenomenon demonstrates that minoxidil is indeed affecting hair follicles, manufacturers offer no guarantee that the new hair loss will be replaced with hair growth.

[edit] Toxic effects

Minoxidil is highly toxic to cats and may cause death.^[9][10]

[edit] Application

Minoxidil products 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. Many high priced as well as generic brands of minoxidil regrowth solutions exist and do not differ in their active ingredient or concentration (except differing versions within each brand).

[edit] References

[edit] External links

• Minoxidil entry at healthAtoZ.com
• MEDLINEplus Drug Information: Minoxidil (Topical)