Each transdermal generation targeted a different variable. Patches were displaced by gels for patient acceptability and their non-occlusive nature.[1] A metered spray addresses a different axis again: the quantity of material deposited and the precision with which it is measured out.
Whether that matters clinically is a question for published pharmacokinetics, not for adjectives. Fortunately there are some.
What is actually published
Three peer-reviewed papers examined this transdermal delivery system:
Pharmacokinetics in healthy males. A 2006 study in the British Journal of Clinical Pharmacology characterised the pharmacokinetics of a new transdermal testosterone delivery system.[2]
Bioequivalence against a marketed gel. A 2009 study in the International Journal of Clinical Pharmacology and Therapeutics examined how correcting for endogenous testosterone concentrations influences bioequivalence assessment in a comparison against AndroGel®.[3]
The delivery platform in another application. A 2006 study in Anaesthesia examined the same delivery system combined with a percutaneous local anaesthetic for venepuncture.[4]
Those are the papers. The fuller treatment is in the published clinical evidence.
Why the bioequivalence paper is methodologically interesting
Its subject is partly a measurement problem, and that is worth understanding.
Testosterone is produced endogenously. When you measure serum testosterone after administering a testosterone product, you are measuring the drug plus whatever the body was already making. Comparing two products without accounting for that baseline compares two contaminated signals.
The 2009 paper addresses exactly this — correcting for endogenous concentrations, and what that correction does to the bioequivalence conclusion.[3] It is a study about how to compare fairly, which is a more careful thing than a study asserting a winner.
What a spray does not change
Transfer precautions. Still a topical, still a treated skin surface. Wash hands, let it dry, cover the site — see the problem with gels.
Monitoring. The guideline's first-year plan is the same regardless of formulation: symptoms, adverse effects, compliance, serum testosterone, hematocrit and prostate cancer risk.[5]
The target. Mid-normal.[5]
The diagnostic requirement. Symptoms plus unequivocally, consistently low concentrations confirmed on repeat fasting morning measurement.[5] Delivery does not change who should be treated.
Frequently asked questions
Is a spray better than a gel? The guideline ranks no formulation. It names five factors to weigh: pharmacokinetics, patient preference, formulation-specific adverse effects, treatment burden and cost.[5]
What does the published evidence show? Pharmacokinetics in healthy males,[2] a bioequivalence comparison correcting for endogenous testosterone,[3] and the platform in a separate anaesthetic application.[4]
Do transfer precautions still apply? Yes, in full.[1]
Next in this series
What the published pharmacokinetics support — and what they do not — deserves stating precisely.
Continue with the clinical case for a spray.
Treatment options for low testosterone
Low testosterone is treated with testosterone replacement therapy, prescribed and monitored by a licensed provider. It is not a single product. Testosterone replacement therapy is delivered as intramuscular or subcutaneous injections, topical gels and creams, transdermal patches, implanted pellets, and topical sprays.
Which form fits a given patient depends on dosing schedule, application routine, monitoring requirements and clinical history. That is a decision for a provider who has seen your lab work — not something to settle from an article, including this one. Testing establishes whether treatment is appropriate; it is the first step of treatment, not an alternative to it.
Keen prescribes testosterone replacement therapy as a once-daily topical transdermal spray, with at-home lab testing and ongoing physician oversight, in 30 states. Eligibility is assessed by a US-licensed physician from your labs and medical history.
References
5 sources- Hadgraft J, Lane ME. Transdermal delivery of testosterone. Eur J Pharm Biopharm. 2015;92:42–48. doi:10.1016/j.ejpb.2015.02.015 · PMID 25709060
- 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
- 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
- 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
- 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