The important study is an absorption study
Wilton and colleagues studied intravenous and intranasal GHRH(1–29)-NH2 in 30 healthy men aged 19–43. Their 1993 report found low nasal bioavailability, approximately 3–5%, alongside a dose-dependent growth hormone response.
This is relevant human evidence, so saying that nasal sermorelin has never been studied would be inaccurate. The result is also much narrower than saying a nasal spray improves sleep, reduces body fat, or replaces an injected prescription.
Pharmacokinetics describes what happens to a drug in the body. A hormone response shows biological activity. Neither is automatically evidence of an improvement someone can feel or use in daily life. Those clinical outcomes need to be tested separately.
Why the percentage is not a conversion rule
The reported absorption estimate belongs to the formulation, administration conditions, participants, and comparator in that study. It is not a universal percentage to apply to every bottle with “sermorelin” on its label.
You cannot use that number to calculate your own spray-to-injection substitution. Different products need their own supporting information, and a hormone response need not translate into identical clinical effects. The prescriber and pharmacist need to address the actual product being offered.
The useful question is whether a provider has data for its formulation. If the answer is only the 1993 paper, the evidence gap remains between that research preparation and the present prescription.
Not every nasal GHRH paper used sermorelin
A 1990 placebo-controlled study in 16 young men used GHRH(1–44), not GHRH(1–29). It also examined growth hormone release rather than long-term wellness outcomes. Similar wording in the titles can conceal this difference.
Read the intervention before accepting the result as support for sermorelin. A longer hormone sequence, another analog, or a different delivery route can contribute to scientific understanding without supplying interchangeable evidence.
This matters when a marketing page links several papers under a broad phrase such as “nasal peptide research.” A larger reference list is not necessarily a larger body of research on the medication you would receive.
Four questions a spray claim needs to answer
| Question | Relevant evidence |
|---|---|
| Does the ingredient reach the body? | Human absorption data for the formulation |
| Does the pathway respond? | Appropriately measured hormone effects |
| Does the desired benefit occur? | Controlled clinical outcomes in a relevant population |
| Is it comparable with an injection? | A suitable direct comparison, not a shared ingredient name |
FDA’s bioavailability guidance treats exposure as something to measure. A convenient route or a plausible explanation of the nose’s blood supply does not remove that requirement. Ask which of these questions the provider’s evidence actually answers.
Convenience belongs in the decision, with uncertainty
A spray may appeal to someone who wants to avoid needles. That preference matters, but it should be discussed alongside the uncertainty about exposure and benefit. Easier administration does not establish equal effectiveness.
Ask for the complete ingredient list, the prescribed route, the dispensing pharmacy, and product-specific handling information. If more than one active ingredient is included, evidence for one component cannot establish what the combination does.
A compounded spray is not FDA-approved merely because a clinician prescribes it. Our FDA-status guide explains the historical Geref distinction. Keep the formulation question separate from the general question of whether treatment is appropriate.
What a careful recommendation should sound like
A useful recommendation should identify the clinical goal, explain the evidence that fits it, and acknowledge where the proposed spray differs from the studied product. It should not promise an injection-equivalent result based solely on an old hormone-response experiment.
Before committing, ask what would count as benefit and when the clinician would reconsider the plan. A change in formulation should have a clinical explanation, not simply a more attractive subscription price.
For another route where the evidence needs careful handling, read sermorelin lozenges and absorption. For the distinction between hormone activity and a practical benefit, start with does sermorelin work?
Sources & further reading
Sources reviewed October 2026. Provider prices and terms may change.