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Author: Hon A/Prof Amanda Oakley, Dermatologist, Hamilton, New Zealand,1998.
Minoxidil was originally marketed in a tablet form for the treatment of high blood pressure. One of the side effects of this treatment was unwanted hair growth. This side effect promoted researchers to produce a topical solution for treating hair loss. In some countries, it is available in other formulations such as foam.
Topical minoxidil is used in the treatment of male pattern hair loss in men, and female pattern hair loss in women. It is occasionally useful for other forms of hair loss (alopecia), including alopecia areata, and after hair replacement surgery or chemotherapy.
Minoxidil is marketed in New Zealand as Rogaine™ Topical Solution (5%) and Headway™ Topical Solution (2% and 5%). The 5% solution is probably more effective but it may result in greater irritation than the 2% solution. It is applied to the affected area of the scalp once or twice daily for a minimum of 6 months. If it is found effective, it may be continued long term.
Minoxidil solution dilates small blood vessels. When applied to the affected areas of the scalp twice daily it has been shown to stimulate hair regrowth probably by enhancing cell proliferation. It is possible it also has an effect on the immune cells in the hair follicle.
Increased hair growth is seen after approximately 4 months of treatment. Generally hair growth is thinner and finer than the original hair.
Local irritation may occur, most often resulting in irching or stinging. Contact allergy to minoxidil or propylene glycol (the main component of the solution) occurs rarely, and results in dermatitis.
Unwanted hair growth might occur ( hypertrichosis), for example if the solution is dripped onto the forehead.
Internal effects are not likely as there is minimal absorption into the system. However, hair growth in distant sites such as the arms, chest and lower back has occasionally been reported when the 5% solution has been used.
Minoxidil is best avoided during pregnancy and breastfeeding (Pregnancy Category C, i.e., Drugs that, owing to their pharmacological effects, have caused or maybe suspected of causing harmful effects on the human fetus or neonate without causing malformations. These effects may be reversible.)
If treatment is stopped, the pretreatment appearance will normally return within 3 or 4 months. If it is stopped after several years of use, the hair that was genetically programmed to be lost during that time will fall out.
Efficacy may be enhanced by concurrent use of a topical retinoid.
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