An oral medication called minoxidil (Loniten) has been available for a number of years for the treatment of high blood pressure, but because of its serious side effects on the heart and general circulation, it is only indicated when the patient has been unsuccessfully treated with the maximum doses of a combination of a water pill plus two other hypertensive drugs. In addition, because of the serious side effects, such as fluid retention and heart failure, minoxidil is only to be used when the high blood pressure causes actual symptoms or causes damage to the patient’s internal organs such as the kidneys.

It was noted that these patients who were taking minoxidil began growing hair in unusual areas of the body, like the forehead and the backs of the hands. It was thought that applying minoxidil directly to a bald scalp might cause hair growth in this area as well. If this hair growth occurred without the other side effects of the medication, it might be useful in healthy balding men. It was then shown that when a topical solution of minoxidil was applied to bald scalps, some men did indeed regrow some hair in the area where it was applied.

Rogaine is the brand name for the topically applied minoxidil solution originally trademarked by Upjohn. It can now be purchased over-the-counter without a prescription in either 2% or 5% concentrations. It appears that the 5% is approximately 50% more effective than 2% solution. The greatest benefit from the medication is seen from 5 months to 2 years, with gradual decrease in effectiveness after that.

Although the mechanism by which minoxidil stimulates hair growth is not known, it probably works by prolonging the hair follicle growth cycle (increases the length of anagen). The effect of the medication is to increases the quality of the hair by increasing the diameter and length of miniaturized (fine) hair. It does not grow hair in areas that are bald.

The controlled studies on minoxidil showed that it grows hair in the vertex (back part) of a man’s scalp, and it probably works to a small degree in other parts of the scalp as well, although only in areas that still have some hair. In addition, it was not shown to regrow hair in the front part of a bald scalp (where the effects of balding are most obvious).

It appears that minoxidil’s effects may only be temporary. Since testosterone is always present in the blood stream, the hormone eventually overcomes the effects of the minoxidil so that with time, men using minoxidil continue to bald, although at a somewhat slower rate. The concomitant use of minoxidil and Propecia (see next section) may partially circumvent this problem and there is evidence that in some cases these drugs may act synergistically.

Prior to trying minoxidil, you should know that even if it is going to work for you, it may take 6-12 months before you see any results. In addition, unless the medication is used consistently twice a day, it will not be of any benefit. For most men, minoxidil does not grow any significant amount of new hair. The action of minoxidil is to thicken already existing hair that is miniaturized (thinned from genetic balding) and most patients who do grow hair, grow only short, thin fuzz.

The majority of patients who see an effect from minoxidil, see only a delay or decrease in the rate of hair loss. This is the most difficult effect to measure scientifically. For many men, the effects are first noticed when they stop using the medication. Once the drug is stopped, the previous pattern of hair loss resumes, and any effects are lost within two to three months, even if the medication had been used for many years. This same limitation applies to other drugs used for hair loss.

Many patients are attracted to minoxidil because of its seeming lower cost compared to other methods of hair replacement. But, because the effects of minoxidil are temporary, the lifetime cost of using minoxidil can be more expensive than the cost of hairpieces or surgical treatments for hair loss. Some doctors recommend minoxidil before and after hair transplantation to decrease or prevent the temporary loss of hair that sometimes occurs with newly placed grafts, but this theory has not been proven.

Minoxidil has been prescribed in conjunction with other medications such as topical retinoic acid (Retin-A) to increase its topical penetration. These medications can greatly increase the systemic absorption of minoxidil and may increase the risk of potential side effects including severe scalp irritation. The prescribing information of Upjohn specifically states “Rogaine should not be used in conjunction with other topical agents including topical corticosteroids, retinoids, and petrolatum or agents that are known to enhance cutaneous drug absorption.” In addition, Retin-A often causes significant skin irritation when used alone and in conjunction with minoxidil. The prescribing instructions clearly state “because absorption of minoxidil may be increased and the risk of side effects may become greater…you should not use Rogaine if your scalp becomes irritated or is sunburned.”

A problem unique to patients using the combined mixture of minoxidil/Retin-A occurs when scalp irritation begins and the patient is afraid to stop the Retin-A since this would also mean discontinuation of the minoxidil (and the risk of subsequent hair loss). These patients often continue the mixture in spite of the development of severe scalp irritation. This can result in infection, scarring and permanent hair loss.

Although it seems that the topical preparation of minoxidil is innocuous, the long-term safety is not known. As with many medications, the clinical trials with minoxidil were performed over a very limited time frame. Since the medication must be continued for years, there may be potential long-term problems that we are presently unaware of.

Rogaine Use in Women

The early studies with minoxidil were on balding men, but it appears that minoxidil may actually be more effective in women. This is probably because women usually exhibit a more diffuse type of hair loss so that areas thin rather than become totally bald. Thus, there is still hair present for minoxidil to “work on”. As with men, minoxidil is only modestly effective in restoring one’s hair and it does not seem to work in older, post-menopausal women.

Although the 5% solution seems to be more effective, it is also stickier due to it’s higher propylene glycol content (the 2% solution contains more alcohol). This makes it impractical for many women to use during the day. As a compromise, it is advised that women use the 2% alcohol based solution in the AM and the stronger 5% propylene based solution in the PM.

Side effects from minoxidil are also slightly different in women than in men. Women seem to be a little more sensitive to the medication and have an increased risk of developing contact dermatitis. A more significant local reaction is the development of facial hirsuitism. The development of facial hair slowly resolves when the medication is discontinued but can be a real nuisance when it occurs. Carefully trying to avoid the medication dripping down onto the temples and forehead seems to reduce but not totally prevent this problem from occurring.

Some women appear to get light-headed or hypotensive (develop low blood pressure) when using the medication, but the exact incidence and significance of this is unclear.