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Minoxidil / Retin-A Combinations
I am generally against the physician-based practice of combining Retin-A with minoxidil. The reason some doctors do this is to get around the law that prevents a doctor, who sells medication in his office, from marking up the price of an individual medication more than 10%. The doctor, however, has the ability to charge anything that he/she wants if he makes his own formulation. If the formulation benefits the patient that is OK, the price might be justified, but in the case of Retin-A/Minoxidil, it is often a scam that actually harms patients.
Here is why: Retin-A only needs to be applied once a day to exert its effects on the skin. That is why Retin-A is prescribed only once a day for acne, where all the other acne medications i.e. topical antibiotics and benzyl peroxide must be used multiple times. Retin-A works by altering the follicular epithelium (the outer layer of skin) so that it doesn't keratinize (form a hard compact layer). This is helpful in acne because it keeps the opening of the follicles from clogging (I am keeping the explanation very simple of course). By preventing keratinization, Retin-A also decreases the protective barrier of the skin and makes it more able to absorb medications (like minoxidil) and more sensitive to chemicals (like the propylene glycol and alcohol base of Rogaine).
Since Retin-A binds well to the skin and exerts it influence over 24 hours, it only needs to be applied once a day. Using it more than once a day causes unnecessary irritation, without increasing its effectiveness. Minoxidil, on the other hand, needs to be used twice a day to be effective. Since the base of minoxidil (the propylene glycol and alcohol) is irritating, minoxidil should not be used more than twice a day.
I am not overly enthusiastic about minoxidil because I do not think that it works well over the long-term and think that it is too fussy. I find that finasteride is far more effective both on the short and long-term. I will occasionally prescribe both to patient with early hair loss that are not yet candidates for a transplant, but for the most part, I use Propecia alone as my mainstay of medical treatment. That said, if patients are set on using minoxidil and want to increase its effectiveness, I suggest that they apply it to damp scalp as soon as they get out of the shower. Applying medication to hydrated (damp) skin can increase the absorption up to 5-fold, without introducing another medication and without causing excessive irritation. It also makes the hair more groomable.
For patients who insist on using Retin-A and minoxidil, I would use them separately and stop the Retin-A as soon as there was any sign off irritation. Remember, irritated skin has very little barrier to absorption, so when you apply medication to irritated skin you are essentially dumping it directly into the blood stream. We know that oral minoxidil is a very potent blood pressure medication that can have very significant adverse side effects of the cardio-vascular system. That is why it is not used either as a first line, or even second line blood pressure medication, but only as a medication for patients with severe hypertension that don't respond to other medications. If a person were not getting irritation, the only local damage would be that the Retin-A would make one more sensitive to the sun (and cause increased facial hair in women). The possible long-term systemic consequences, although probably remote, are unknown. Cardiac enlargement from minoxidil had been reported in a single animal study a number of years ago in England, but did not get much press here. To my knowledge, it has not been duplicated in humans. However, I am always concerned when minoxidil is used with medications that increase its systemic absorb ion such as Retin-A, since we know that minoxidil orally is a very potent and potentially dangerous medication.
The main problem with the combination is that when patients begin to get irritation, they are afraid to stop using the minoxidil for fear of losing their hair. Since the Retin-A and minoxidil are mixed, they are forced to continue both, i.e. they are in a Catch-22. When they call the prescribing doctor, they are often advised to do things to decrease the irritation, even sometimes to use steroids…but not stop the medication. The doctor doesn't generally give the proper advice and say to simply use over-the-counter minoxidil alone until the irritation subsides and then gradually re-introduce Retin-A as a separate medication a little at a time, since this would uncover the doctor's scam. Therefore, the doctor sticks to his speech about the importance of the combined mixture and the patient is sometimes left with scarring (if the inflammation is not treated properly) and always left with a jacked up bill. (Minoxidil is over-the-counter and very inexpensive and Retin-A just needs to be used very sparingly, no more than once a day. So the cost is very modest.)
I have seen patients that have been given a doctor's mixture of an expensive, in house combination of Retin-A solution (which is very potent) mixed with minoxidil 4%, and told that they must use the combination four times a day. When they got irritation, they were not advised to stop the medication. They continued using this potent medication on an irritated scalp, with the risk of both local scarring (which some actually got) and the risk of systemic toxicity from the increased absorption into the bloodstream.
In sum, the reason I do not like the combination is that it has some potential risk, it increases the irritancy and fussiness of a medication that I do not think is that effective to begin with, and most importantly, it is often abused.
Dr. Bernstein
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