Where a Metered Transdermal Spray Sits in All of This

This is the last episode of The T Files, and the honest place to end is with what is published rather than what is promised.

A metered transdermal spray is a daily topical: testosterone applied to skin, absorbed through it, bypassing the liver — the constraint that has shaped every testosterone product since 1935.[1] It sits in the same trade space as every other route, not outside it.

What is published

Three peer-reviewed papers on this delivery platform:

Pharmacokinetics in healthy males — 2006, British Journal of Clinical Pharmacology.[2]

Bioequivalence corrected for endogenous testosterone — 2009, International Journal of Clinical Pharmacology and Therapeutics, compared against AndroGel®.[3] The correction is the substance: measuring an administered testosterone product means measuring drug plus endogenous production, and ignoring that biases the comparison.

The platform with a percutaneous local anaesthetic — 2006, Anaesthesia.[4]

Full treatment: the published clinical evidence.

What is not published

No large randomised outcome trial. Nothing comparable to TRAVERSE's 5,204 participants and its cardiac endpoint.[5]

No comparative symptom outcomes against another formulation.

Saying so is the point of this page. The alternative — asserting superiority the evidence does not carry — is the failure mode this entire series documents.

What does not change

Transfer precautions. It is a topical. Wash hands after applying, let the site dry before skin-to-skin contact, keep it covered. The FDA boxed warning describes what secondary exposure does.[8] See gel transfer risk.

The diagnosis. Symptoms plus unequivocally, consistently low concentrations, confirmed on a repeat fasting morning draw.[9]

The target. Mid-normal.[9]

The monitoring. Symptoms, adverse effects, compliance, serum testosterone, hematocrit, prostate cancer risk in the first year.[9]

Where the series ends

Ninety years from a molecule nobody could deliver to a metered daily dose — and the clinical framework around it is a short, dull checklist that has not changed with any of it.

If you take one thing from The T Files: the delivery has improved enormously and the standard of proof has improved more. Cognition, null.[10] Erectile function, null.[11] Fractures, worse.[12] Cardiovascular, non-inferior.[5] A field that finally ran good trials got smaller, truer claims.

Keen connects you with a licensed clinical team for a telehealth consultation and lab review. If your testosterone is clinically low, treatment is Keen Testosterone Spray Rx — a once-daily topical spray powered by Hypospray® transdermal delivery.

Frequently asked questions

Is a spray better than a gel or injection? Not established by outcome trials, and not claimed here. The guideline names five factors and ranks none.[9]

What evidence exists? Three pharmacokinetic and delivery papers.[2][3][4]

Do transfer precautions apply? Yes, fully.[8]

Where do I start if I think my testosterone is low? Why one low result doesn't mean low testosterone.

References

12 sources

1. Nieschlag E, Nieschlag S. ENDOCRINE HISTORY: The history of discovery, synthesis and development of testosterone for clinical use. Eur J Endocrinol. 2019;180(6):R201–R212. doi:10.1530/EJE-19-0071 · PMID 30959485
2. Chik Z, Johnston A, Tucker AT, et al. Pharmacokinetics of a new testosterone transdermal delivery system, TDS®-testosterone in healthy males. Br J Clin Pharmacol. 2006;61(3):275–279. doi:10.1111/j.1365-2125.2005.02542.x · PMID 16487220
3. Chik Z, Johnston A, Tucker AT, et al. Correcting endogenous concentrations of testosterone influences bioequivalence and shows the superiority of TDS®-testosterone versus Androgel®. Int J Clin Pharmacol Ther. 2009;47(4):262–268. PMID 19356392
4. Tucker AT, Chik Z, Michaels L, et al. Study of a combined percutaneous local anaesthetic and the TDS® system for venepuncture. Anaesthesia. 2006;61(2):123–126. doi:10.1111/j.1365-2044.2005.04432.x · PMID 16430563
5. Lincoff AM, Bhasin S, Flevaris P, et al. Cardiovascular Safety of Testosterone-Replacement Therapy. N Engl J Med. 2023;389(2):107–117. doi:10.1056/NEJMoa2215025 · PMID 37326322
6. Cussons AJ, Bhagat CI, Fletcher SJ, et al. Brown-Séquard revisited: a lesson from history on the placebo effect of androgen treatment. Med J Aust. 2002;177(11-12):678–679. doi:10.5694/j.1326-5377.2002.tb05014.x · PMID 12463999
7. Schultheiss D, Denil J, Jonas U. Rejuvenation in the early 20th century. Andrologia. 1997;29(6):351–355. doi:10.1111/j.1439-0272.1997.tb00329.x · PMID 9430441
8. U.S. Food and Drug Administration. AndroGel (testosterone gel) 1% — prescribing information, including BOXED WARNING: secondary exposure to testosterone. Reference ID 021015s044. 2019. accessdata.fda.gov
9. Bhasin S, Brito JP, Cunningham GR, et al. Testosterone Therapy in Men With Hypogonadism: An Endocrine Society Clinical Practice Guideline. J Clin Endocrinol Metab. 2018;103(5):1715–1744. doi:10.1210/jc.2018-00229 · PMID 29562364
10. Resnick SM, Matsumoto AM, Stephens-Shields AJ, et al. Testosterone Treatment and Cognitive Function in Older Men With Low Testosterone and Age-Associated Memory Impairment. JAMA. 2017;317(7):717–727. doi:10.1001/jama.2016.21044 · PMID 28241356
11. Pencina KM, Travison TG, Cunningham GR, et al. Effect of Testosterone Replacement Therapy on Sexual Function and Hypogonadal Symptoms in Men with Hypogonadism. J Clin Endocrinol Metab. 2024;109(2):569–580. doi:10.1210/clinem/dgad484 · PMID 37589949
12. Snyder PJ, Bauer DC, Ellenberg SS, et al. Testosterone Treatment and Fractures in Men with Hypogonadism. N Engl J Med. 2024;390(3):203–211. doi:10.1056/NEJMoa2308836 · PMID 38231621