A clinical study investigated the hair growth effects of high strength minoxidil - the only current MHRA-licensed and FDA-approved topical hair loss solution for both men and women with androgenetic alopecia.
The findings showed that, when patients with Male Pattern Baldness or Female Pattern Hair Loss were predicted to be unresponsive to the minoxidil alone, using the prescription acne medication tretinoin alongside it significantly increased the number of patients who responded to treatment after five days by almost 50 per cent.
Tretinoin is a prescription medication used in cream or lotion form for the treatment of acne; it is a vitamin A derivitive known as a retinoid.
This skincare ingredient was used in an April 2019 hair regrowth study designed to find a way to improve patients' response to minoxidil hair loss treatment by teams of researchers from America, India and Croatia.
The corresponding study author, John McCoy of the Department of Research and Development at Applied Biology in Irvine, California, USA, wrote in the Dermatologic Therapy journal (doi.org/10.1111/dth.12915) of the minoxidil and tretinoin relationship:
"Minoxidil sulfate is the active metabolite required to exert the vasodilatory and hair growing effects of minoxidil. For hair growth, sulfotransferase enzymes expressed in outer root sheath of the hair follicle sulfonate minoxidil...
Retinoids have been reported to increase minoxidil response. The purported mechanism of action was retinoid modulation of skin permeation to minoxidil; however, evidence to the contrary supports retinoids increase dermal thickness.
In order to elucidate the effect of topical retinoids on minoxidil response, we studied the effect of topical tretinoin on follicular sulfotransferase. In this study, we demonstrate that topical tretinoin application influences the expression of follicular sulfotransferase."
What researchers found was that, of their clinical trial participants who were initially predicted to be non-responders to minoxidil hair loss treatment for Male and Female Pattern Hair Loss, 43 per cent 'converted' to responders after 5 days of using additional topical tretinoin applications.
The researchers believe this novel study is the first to bring this interaction to light and, as such, its findings may be useful for the development of future pattern hair loss treatments for both men and women.
One consideration that is likely to need additional consideration, given we do not know the scope nor size of this multi-centre study, is the side effect profile of tretinoin.
Tretinoin is potent so is generally used in extremely small doses of 0.025% when treating acne. It is a known irritant which can cause side effects including skin redness, itching, dry skin, scaling and/or mild burning when applied to the skin.
However, many users tolerate this well, either straight away or after building up to the required daily dose in order to help increase their tolerance gradually.
Another aspect of Tretinoin's use which may be particularly of concern, given this method would require it to, presumably, be applied directly to the scalp, is the question of photosensitivity.
Tretinoin can increase users sensitivity to the sun, making them more likely to experience sunburn and potentially placing them at a higher risk of melanoma.
The recommendation is currently that users limit their time in the sun, wear sunscreen daily and wear protective clothing when outdoors. Given the scalp is so exposed, users would almost certainly need to wear a hat whilst outdoors whilst using any tretinoin-based hairloss treatments.
Although this trial has seen positive results, there is still a long way to go before it can be fully established whether or not a beneficial, safe and tolerable relationship between minoxidil and tretinoin exists for hair growth in cases of Male Pattern Baldness and Female Pattern Hair Loss.
It should go without saying but for the sake of clarity, Belgravia does not advise any current tretinoin users to try this as a hair loss treatment, certainly not without the recommendation and close supervision of a dermatologist or medical professional.
The Belgravia Centre is a world-renowned group of a hair loss clinic in Central London, UK. If you are worried about hair loss you can arrange a free consultation with a hair loss expert or complete our Online Consultation from anywhere in the world for home-use treatment.
View our Hair Loss Success Stories, which includes the world's largest gallery of hair growth photos and demonstrates the level of success that so many of Belgravia's patients achieve.