Adenosine: Is it true it works better for women than men? Why is that?

Adenosine has gained attention in the world of hair care as a promising active ingredient against hair loss. Its topical application has been reported to strengthen hair follicles and stimulate hair growth in small trials. But a question persists among readers: does it work better in women than in men? This article looks at what the published trials actually measured, and where the claim comes from.

Adenosine is a molecule naturally produced by the human body. It is a nucleoside involved in essential cellular functions such as energy transfer and intercellular signaling.

It is especially known for its role in the production of ATP, the cell's main energy source. Its relevance in hair-related contexts lies in its ability to interact with specific receptors in the hair follicle. Laboratory work by Iino and colleagues (J Invest Dermatol, 2007) reports that adenosine acts on A2b receptors on cultured dermal papilla cells, and that this signaling raises expression of fibroblast growth factor-7 (FGF-7), a growth factor that supports cell proliferation in the follicle bulb. The Oura trial group also reports that adenosine upregulates vascular endothelial growth factor in the same cells. The proposed effect is on the cellular environment around the follicle rather than on hormones, and the trials measured it mainly as a shift toward thicker hair shafts — that is, a partial reversal of the follicular miniaturisation typical of androgenetic alopecia.

Does adenosine work differently in men and women?

There is no published head-to-head trial that compares adenosine in men against adenosine in women, so the honest answer is that the difference has not been measured. What exists is one trial in women and one trial in men, run years apart, with different comparators, different durations and different endpoints. Any comparison between them is indirect and should be read as such.

The idea that the two sexes might respond differently is a hypothesis, not a finding. Androgenetic alopecia does present differently: in men it often starts with receding temples and thinning at the crown; in women the pattern is more diffuse, with progressive thinning across the top of the head but usually without completely bald areas. Whether that morphological difference changes the response to adenosine has not been tested.

The women's trial

The trial most often cited is Oura and colleagues, published in 2008 in the Journal of Dermatology (35(12):763–767). It was a pilot, double-blind, randomised, placebo-controlled study in 30 Japanese women with female pattern hair loss. Participants used either a 0.75% adenosine lotion or a placebo lotion twice daily for 12 months. Efficacy was assessed by dermatologists, by investigators, by participant self-assessment and by phototrichogram.

The authors report that adenosine was significantly superior to placebo on the dermatologist, investigator and self-assessments, and that it significantly increased the anagen hair growth rate and the thick-hair rate. They report that no side-effects were encountered during the trial. The limitations are the ones the design implies: it is described by its own authors as a pilot, the sample is small, it enrolled only Japanese women — which limits how far the result carries to women of other backgrounds — and it did not measure hormonal markers or genetic predisposition.

The men's trial

A separate study by Watanabe and colleagues, published in 2015 in the International Journal of Cosmetic Science (37(6):579–587), applied the same approach to men. 102 Japanese men used a lotion containing either adenosine or niacinamide twice daily for 6 months, in a double-blind, randomised design. The authors report that adenosine was significantly superior to niacinamide for global improvement, for the percentage of thick hairs (at least 60 µm) and for self-assessed hair thickness, with no causal adverse event attributed to the lotion.

Note what this means for the "better in women" question: the men's trial was positive too. It ran for half as long, against a different comparator, and its authors concluded that adenosine "is useful for the improvement of AGA" in men.

The comparison with minoxidil

Faghihi and colleagues (Acta Dermatovenerologica Croatica, 2013; 21(3):155–159) compared topical minoxidil 5% with adenosine 0.75% in 110 men with Hamilton grade II–V androgenetic alopecia, over 6 months. The authors report that adenosine had no statistical superiority to minoxidil on recovery rates — in fact neither arm produced complete recovery, and relative recovery was low in both (2.4% vs 1.9% at 3 months). What did differ was patient satisfaction, which was significantly higher in the adenosine group, which the authors attribute to faster perceived prevention of hair loss and appearance of new hairs. This trial enrolled men only, so it says nothing about a sex difference.

The influence of the female hormonal environment

One explanation offered for a possible sex difference is hormonal, though it should be read as a proposed mechanism rather than a demonstrated one. Androgenetic alopecia, especially in men, is strongly associated with dihydrotestosterone (DHT), a more active form of testosterone that shrinks hair follicles in sensitive areas of the scalp. In women, DHT also contributes to hair loss, but the hormonal environment differs, and the distribution of hair loss across the scalp differs with it.

Adenosine does not act on sex hormones and does not inhibit DHT the way finasteride or dutasteride do. Its proposed mechanism is local: improving the cellular environment of the follicle. The suggestion is that follicles under less intense androgenic pressure may retain more capacity to respond — but this is a hypothesis offered to explain a difference that has not itself been established in a trial.

The stance of health authorities

To date, the FDA (U.S. Food and Drug Administration) has not approved adenosine as a medical treatment for androgenetic alopecia. In Japan, adenosine hair lotions are sold as quasi-drug/cosmetic products on the basis of locally generated clinical evidence, and adenosine-containing products are widely available across Asian markets. Outside those markets it is sold, where it is sold at all, as a cosmetic ingredient rather than as a licensed medicine — which means the manufacturer, not a regulator, is the source of any efficacy claim on the packaging.

User Experiences

Community feedback from Tressless suggests that adenosine is viewed as a mild-to-moderate option with a comparatively easy side-effect profile, rather than as a replacement for more established treatments like minoxidil.

In a 2023 thread titled "Adenosine vs. Minoxidil, experiences/thoughts?", users shared that while adenosine may not be as potent as minoxidil, they found it easier to tolerate. Some male users reported changes in hair texture and minor thickening but not regrowth comparable to what they had seen with minoxidil. One user described adenosine as acting more gently and as a reasonable option for people who cannot tolerate minoxidil's irritation or shedding.

Female users, especially those describing early-stage thinning or female pattern hair loss (FPHL), tended to report more positively. Women described adenosine-based products such as Shiseido Adenovital and other Asian-market formulations as contributing to visible thickening over time, and reported little or no irritation. These are self-reports in a public forum, not measured outcomes. Another discussion examined combining adenosine with caffeine in a liposomal gel; some users speculated that because caffeine is an adenosine receptor antagonist it might blunt the effect, while others thought any conflict was minor in practice. There was no consensus, and users were relying on personal experimentation.

A 2018 community post discussed the Faghihi minoxidil-versus-adenosine trial described above, and the thread mirrored its finding: satisfaction ran higher with adenosine early on, while neither option produced dramatic regrowth. The limited availability of adenosine products outside Asia was a recurring complaint, with users in the UK and USA asking where to buy formulations without importing them.

Conclusion: Does adenosine work better in women than in men?

Not proven, and not really testable from the evidence that exists. Both published trials were positive — one in 30 women against placebo over 12 months, one in 102 men against niacinamide over 6 months — but they were never run against each other, so a "better in women" verdict cannot be drawn from them. The impression that it favours women appears to come from the women's trial being the longer, placebo-controlled one, and from the pattern of community reports.

What can reasonably be said is narrower: in small Japanese trials, topical 0.75% adenosine increased the proportion of thick hairs in both sexes, and the reported tolerability was good in both. Larger trials in more varied populations, and a direct comparison between men and women, would be needed to answer the question in the title.

Talk to a doctor or pharmacist before starting, stopping or combining any hair-loss treatment, including over-the-counter topicals, especially if you are already using minoxidil, finasteride or an anti-androgen.

References

Oura, H., Iino, M., Nakazawa, Y., Tajima, M., Ideta, R., Nakaya, Y., Arase, S., & Kishimoto, J. (2008). Adenosine increases anagen hair growth and thick hairs in Japanese women with female pattern hair loss: a pilot, double-blind, randomized, placebo-controlled trial. Journal of Dermatology, 35(12), 763–767. https://pubmed.ncbi.nlm.nih.gov/19239555/

Watanabe, Y., Nagashima, T., Hanzawa, N., Ishino, A., Nakazawa, Y., Ogo, M., Iwabuchi, T., & Tajima, M. (2015). Topical adenosine increases thick hair ratio in Japanese men with androgenetic alopecia. International Journal of Cosmetic Science, 37(6), 579–587. https://pubmed.ncbi.nlm.nih.gov/25925959/

Faghihi, G., Iraji, F., Rajaee Harandi, M., Nilforoushzadeh, M. A., & Askari, G. (2013). Comparison of the efficacy of topical minoxidil 5% and adenosine 0.75% solutions on male androgenetic alopecia and measuring patient satisfaction rate. Acta Dermatovenerologica Croatica, 21(3), 155–159. https://pubmed.ncbi.nlm.nih.gov/24183218/

Iino, M., Ehama, R., Nakazawa, Y., Iwabuchi, T., Ogo, M., Tajima, M., & Arase, S. (2007). Adenosine stimulates fibroblast growth factor-7 gene expression via adenosine A2b receptor signaling in dermal papilla cells. Journal of Investigative Dermatology, 127(6), 1318–1325. https://pubmed.ncbi.nlm.nih.gov/17301835/

U.S. Food & Drug Administration. (n.d.). Drugs@FDA: FDA-Approved Drugs. Retrieved from https://www.accessdata.fda.gov/scripts/cder/daf/

Reddit. (2023, August 7). Adenosine vs. Minoxidil, experiences/thoughts? https://reddit.com/r/tressless/comments/15l0eeu/adenosine_vs_minoxidil_experiencesthoughts/

Reddit. (2023, July 25). Is Adenosine + caffeine good combo or does caffeine cancels Adenosine affect? https://reddit.com/r/tressless/comments/1591f7d/is_adenosine_caffeine_good_combo_or_does_caffeine/

Reddit. (2018, June 28). Comparison of the efficacy of topical minoxidil 5% and adenosine 0.75% solutions on male androgenetic alopecia and measuring patient satisfaction rate. https://reddit.com/r/tressless/comments/8ui60m/comparison_of_the_efficacy_of_topical_minoxidil_5/

Reddit. (2022, August 13). Does anyone know where to buy adenosine shampoo or conditioner in the UK? https://reddit.com/r/tressless/comments/wnm3wf/does_anyone_know_where_to_buy_adenosine_shampoo/

Reddit. (2023, May 29). Anyone tried topical adenosine? https://reddit.com/r/tressless/comments/13v3468/anyone_tried_topical_adenosine/