Mary Warner
Androgenetic alopecia (AGA), also known as male pattern baldness or female pattern hair loss, affects up to 80% of men and 50% of women over their lifetime, with white men and women more likely to experience hair loss than other ethnicities. Nonprescription minoxidil is available to help patients regrow hair lost to AGA.
AGA is thought to be caused by a progressive reduction in the diameter, length, and pigmentation of the hair by the testosterone metabolite dehydrotestosterone on androgen-sensitive hair follicles. The genetic basis for AGA isn’t well understood, but it is known to cluster in families, and the myth that male pattern baldness skips a generation may be related to the fact that the gene most commonly associated with AGA is found on the X chromosome, though several other genes are also thought to contribute to the likelihood of male pattern baldness. Research has shown that 80% of people who experience noticeable balding had a father who also had AGA.
Availability
Minoxidil (2,6-diamino-4-piperidinopyrimidine-1-oxide) was developed in the 1970s as an antihypertensive medication, but when patients and practitioners noticed hair growth as an unexpected result, it began to be used as a hair regrowth agent, and in 1987, a topical formulation was developed to treat AGA. Minoxidil is the only FDA-approved nonprescription treatment for AGA and is available as the brand name Rogaine as well as numerous generic formulations.
As with the cause of AGA, the means by which minoxidil stimulates hair growth is not well understood, but research indicates that minoxidil is converted into minoxidil sulfate on the scalp by sulfotransferase and that minoxidil sulfate shortens the telogen (rest) phase of the hair growth cycle and extends the anagen (growth) phase, resulting in hair growth. Research has shown that differences in enzyme activity among individuals can lead to inconsistent results.
Most patients for whom minoxidil is effective see hair growth after about 8 weeks of treatment, with maximum effect within several months. However, growth continues only while the medication is used, and hair loss will begin again within a few months of stopping minoxidil treatment.
Dosage and use
Minoxidil is available as 2% and 5% hydroalcoholic solutions and as a 5% solvent-free foam and can be applied by various methods, depending on the applicator (i.e., spray, dropper, capful). The 2% and 5% solutions are applied as 1 mL twice daily and the 5% foam is applied as ½ capful twice daily for men; only the 2% solution (1 mL twice daily) and 5% foam products (½ capful once daily) are approved for use by women.
Adverse effects associated with minoxidil are generally minimal (e.g., local itching, irritation, and dryness or scaling at the site of application) and are thought to be related to the propylene glycol in the preparation. Use of minoxidil foam, which doesn’t contain propylene glycol, can reduce irritation. Rare adverse effects include acne at the site of application, increased hair loss, inflammation (with soreness) of the hair roots, reddened skin, swelling of the face, and allergic contact dermatitis.
What to tell your patients
Advise patients that if minoxidil doesn’t appear to increase hair growth after 4 to 6 months, they should consider discussing other options, including prescription Propecia, with their health care provider. Also ensure that they understand that once minoxidil treatment is discontinued, hair loss may recur within a few months and that they must continue to use minoxidil indefinitely to maintain new growth.
If patients notice excess hair growth, particularly on the chest, back, forearms, and ear rims, too much minoxidil has likely been used and the patients should be advised to pay close attention to dosage.
Patients should avoid applying topical corticosteroids, petrolatum, or retinoids to the scalp in combination with minoxidil because of possible increased absorption and increased risk of adverse effects. Minoxidil should not be used for 24 hours before or after application of any hair permanent, hair color, or hair relaxant products. Finally, advise patients that minoxidil should not be used by those under 18 years or by pregnant or breastfeeding women.
For further information, see APhA’s Handbook of Nonprescription Drugs, available in print through the bookstore on pharmacist.com or online in PharmacyLibrary. ■