Minoxidil has been available in the USA as Rogaine since 1988. Rogaine has been marketed by Johnson&Johnson since 2006. Numerous other branded generics are sold on the Internet.
Minoxidil is available as a solution for rubbing into the scalp and as a foam for spraying on and massaging in. The product variants for men and women differ in their concentration of active ingredients (men: 5% – 50 mg/ml, women: 2% – 20 mg/ml). The lower concentration for women is a compromise, which is intended to minimise the risk of unwanted hair growth beyond the scalp hair. In contrast, in the case of the foam, which has also been available in a version for women since 2016, both product variants contain the same concentration of active ingredient (5 % – 50mg/g).
Minoxidil – for whom is it suitable?
Minoxidil is primarily recommended for men and women with early-stage androgenetic hair loss: It is best used to prevent further hair loss and to stimulate “weakened” but not yet fully miniaturized hair follicles to grow again.
The efficacy of Minoxidil has been tested mainly for hair loss in the parting area (beginning baldness). The application for receding hairline is of course also possible; although scientific evidence for this is scarce, there are numerous positive reports from everyday dermatological experience.
The application for other forms of hair loss does not correspond to the official approval of Minoxidil, but it has also been tested in many studies and is often used on a trial basis in the context of off-label use. The extended field of application of Minoxidil includes alopecia areata , traction alopecia  and hair loss induced by chemotherapy .
Many men – even men who do not suffer from hair loss – continue to use Minoxidil successfully to promote beard growth.
Application of Minoxidil
Men use the Minoxidil products (solution or foam) formulated for men twice a day – in the morning and evening.
Women should also apply the Minoxidil solution formulated for women twice a day. The higher dosage of Minoxidil foam should only be used once a day by women. Both forms of application have shown roughly the same results in several studies in women with androgenetic hair loss  – however, the 5% foam more often triggered side effects (unwanted hair growth, itching, irritation of the scalp) .
Minoxidil must be used regularly to maintain results once achieved. If the application is stopped, the effects disappear after some time.
The Minoxidil solution is applied to the skin with the supplied pipette or pump spray applicator and massaged in with the finger. A quantity of one millilitre is recommended for a single application. For Rogaine, this corresponds to six spray strokes of the applicator; for other products, the dosage may be different. If a pipette is supplied with the product, it has a corresponding mark for dosage. The correct dose for one application of Minoxodil in foam form is one gram. In the case of Rogaine, this corresponds to the half-filled cap of the packaging. The product is absorbed with the finger and rubbed on the scalp or beard area.
After each application, Minoxidil should act on the scalp for about four hours without interruption (no moistening of the scalp, no other care products).
Wash hands thoroughly after application to prevent transfer to unwanted parts of the body (alternatively, use latex gloves). Minoxidil that has spread to other parts of the body is best rinsed off with water.
Caution: Keep Minoxidil away from pets, do not touch your pet, even if you have Minoxidil on your hands – when ingested orally, the product can dangerously lower blood pressure and is therefore potentially toxic to dogs, cats and other animals .
In pilot studies the application of minoxidil was successfully combined with microneedling.
Mode of action of Minoxidil
The fact that minoxidil has an effect on hair growth has been proven in numerous clinical studies  This effect is not infallible – in about half of the male users and about three quarters  of the female users it is absent or limited to maintaining the status quo without renewed hair growth. Nevertheless, in all application studies, preparations containing minoxidil have clearly outperformed the placebo preparations with which a control group was treated in each case.
The effect of minoxidil is a fact of experience. But why Minoxidil is effective – this has not been exhaustively clarified. The drug has been proven to dilate the blood vessels (this is the basis for its use as an antihypertensive). Working hypothesis was therefore for a long time that Minoxidil improves the supply of oxygen and nutrients to the hair follicles. In the meantime, hair growth researchers have begun to doubt this point: studies have tried unsuccessfully to prove that Minoxidil improves blood circulation in the scalp. Instead, there are other hypotheses: The active ingredient could stimulate the synthesis of hair growth-promoting growth factors and/or prostaglandins .
It is now known that the effectiveness of minoxidil depends, among other things, on the enzyme sulfotransferase, which converts the active substance into its biologically active form, minoxidil sulphate. Several studies have shown that successful minoxidil application correlates with the amount of sulfotransferase in the hair follicles  In the future, a rapid test that measures the sulfotransferase content of some follicles could predict whether or not minoxidil is worthwhile for interested parties.
Minoxidil causes (if it is effective …) among other things a shortening of the resting phase and a lengthening of the growth phase of the follicles. The hair grows longer and stronger, and by increasing the number of follicles in the growth phase, the hair density increases.
The best results can be achieved with Minoxidil if the application is started in the early stages of androgenetic alopecia. When applied to bald areas of the scalp, whose follicles have been miniaturized for years, the results in terms of number, length and thickness of hair newly gained by Minoxidil usually remain modest .
From the start of application until the new situation is stabilised (a new balance in the distribution of follicles between the anagen and telogen phases), a few months will pass: whether the treatment is successful can and should therefore only be assessed after about half a year of continuous application.
“Shedding” in connection with Minoxidil
Two to three weeks after starting the Minoxidil application, temporary increased hair loss may occur. The phenomenon known as shedding is in most cases no cause for concern. It is interpreted as a sign that the treatment is working – one explanation would be that, triggered by the active ingredient, numerous follicles suddenly enter a new growth phase from their resting phase and new growing hairs push the old ones out of the follicles and cause them to fall out. The explanation is plausible – whether it is really correct has not yet been investigated. There are no scientific studies specifically devoted to the subject of shedding. However, most experience suggests that hair loss through shedding only lasts for two to three weeks and is compensated for in the following weeks.
Side effects of Minoxidil
As occasional side effects of Minoxidil may include itching, redness, inflammation and scaling of the scalp, further allergic sensitization – skin reactions that occur only after repeated use. Some dermatologists prescribe cortisone to their patients to suppress these symptoms and allow the continued use of Minoxidil. In the long term, however, this is certainly not a solution.
The application of Minoxidil on the scalp occasionally leads to conspicuous (and especially in women undesirable) growth of facial hair (conversion of vellus hair into terminal hair). Men continue to report hair growth on the neck and even increased growth of breast hair in connection with the local application of Minoxodil. In contrast to the hair growth on the head, which disappears again after the preparation is discontinued, experience shows that it cannot be assumed with the same certainty that this also applies to facial hair.
Even with local application, a small amount of Minoxidil enters the body via the bloodstream. This not only explains the hair growth in places where solution or foam has not been applied at all, but in rare cases it can also lead to temporary cardiovascular problems related to the blood pressure lowering effect of Minoxidil. These side effects include low blood pressure, palpitations, dizziness and weakness and edema (swelling due to fluid retention in the tissues).