Tuesday, August 24, 2010

Minoxidil



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 mechanism by which Minoxidil promotes hair growth is not fully understood. Minoxidil is a potassium channel opener, causing hyper polarization of cell membranes. 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), or top of head, balding only.

Minoxidil may cause increased growth or darkening of fine body hairs. If this is bothersome, consult your doctor. When the medication is discontinued, the hair will return to normal within 30 to 60 days.

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 Regained 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.

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.

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.

Minoxidil is also a vasodilator. It is speculated that by widening blood vessels and opening potassium channels, it allows more oxygen, blood and nutrients to the follicle. This can also cause follicles in the deluge phase to shed, usually soon to be replaced by new, thicker hairs (in a new anagen phase).

One study in healthy males aged 18–50 years with androgenic alopecia (male pattern baldness) found that compared to a baseline of 103 to 106 hairs/cm2, those who applied a 5% solution of Minoxidil for 32 weeks increased their non-vellums hair counts by an average of 39 hairs/cm2, in contrast to 5 hairs/cm2 in subjects who received a placebo.

Side effects

Alcohol present in topical preparations may dry the scalp, resulting in dandruff.

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.

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.

Pseudoacromegaly is an extremely rarely reported side effect.

Ironically, 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’. 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.

The speculated reason for this “shedding” is the encouragement of hairs already in the telogen phase to shed early, before often beginning a fresh, healthier anagen phase.

Toxic effects

Minoxidil is highly toxic to cats and may cause death.

Application

Minoxidil usually needs to be applied regularly (once or twice daily) for hair gained to be maintained. It does not seem capable of reducing DHT or the enzyme responsible for its accumulation around the hair follicle, 5-alpha reductive, which are the main causes of male pattern baldness in genetically susceptible individuals. Therefore, when treatment is stopped, the DHT already accumulated around the follicle has its expected effect, and the follicle usually shrinks again and eventually dies.

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 rewrote 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 rewrote solutions exist and do not differ in their active ingredient or concentration (except differing versions within each brand).

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