Minoxidil

Minoxidil

Systematic (IUPAC) nam

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.

History

Minoxidil was first used exclusively as an oral drug (trade name Loniten) to treat high blood pressure. It was, however, discovered to have the interesting side-effect of hair growth and reversing baldness, and in the 1980s, 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.

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, which is preferable for most men.

Mechanism

The mechanism by which minodixil 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.

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) and in those with balding in the central (vertex) portion of the scalp.

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. In some cases minoxidil may initially cause an increase in hair loss. This is called shedding and is seen as a long-term positive effect during hair loss treatment since the shedded hair strands will regrow within a few months with renewed strength.

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. Large amounts of minoxidil can cause hypotension, and it has been found that using petroleum jelly or tretinoin on the scalp with minoxidil can cause too much of the drug absorption by the scalp, as can using the drug on sunburned scalps.

If a person uses minoxidil to stop hair loss for a length of time and then stops taking the drug, hair loss will occur again.

Other side-effects include:

• acne on the area where it is being used as a topical solution
• headaches and/or lightheadedness
• very low blood pressure
• irregular or fast heart beat
• blurred vision or other vision problems
• decreased sexual desire
• partial, or complete, impotence
• numbness or tingling in the hands, feet or face
• rapid weight gain
• chest pain

All the side-effects in the above list except for acne may be an indicator that too much of the drug is being used. It has also been found that the drug can be passed from a mother to a child via breast milk.

Effects on animals

Minoxidil is highly toxic to cats and can cause death when applied to their skin.

Application

Minoxidil is made available by Rogaine in two ways: Foam and liquid (applied via a dropper). Both ways 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.