Peptides and nasal sprays

Some peptides are injected, but users also put them up the nose. Intranasal is a real pharmaceutical route for a handful of peptides — and, for most of the rest, a way to swap a known problem (the needle) for an unknown one (how much actually gets in).

This page is plain pharmacology and harm reduction, not a recommendation and not a dose. It does not give nasal conversions or endorse using anything this way. Many of these compounds are not approved for human use, and nothing here is medical advice.

Yes, some peptides really are nasal

Intranasal delivery is not fringe in itself. Several peptides have a registered nasal form: desmopressin spray for diabetes insipidus and bed-wetting, salmon calcitonin spray for osteoporosis, the GnRH agonist nafarelin as a metered spray, oxytocin historically and throughout research, and — in Russia — Semax and Selank as nasal drops. Intranasal insulin is a long-standing research tool for studying the brain.

What those products have in common is that they are small enough, or formulated well enough, to cross the nasal lining — and that a manufacturer worked out and fixed the dose per spray. That second part is what a home-made spray throws away.

The catch: you cannot know the dose

The nasal lining is a barrier, not an open door. Even for a properly formulated nasal peptide, typically only a few percent of the dose reaches the bloodstream, and getting even that much depends on permeation and absorption enhancers built into the product — a 2022 review of nose-to-brain peptide delivery lists cyclodextrins, fatty acids, phospholipids, surfactants and bile salts as the tools needed to make it work at all [1]. A research peptide dissolved in bacteriostatic water has none of those, so what crosses the lining is a small, variable and unmeasurable fraction. A spray actuation is a volume, not a delivered dose — much of it runs off, is swallowed, or never absorbs. Two people, or the same person on two days, can get very different amounts.

Nose-to-brain is real, but oversold

The idea that a nasal spray goes “straight to the brain” is not made up: the olfactory and trigeminal nerves do offer a direct route from the nasal roof to the brain that bypasses the blood-brain barrier. But the fraction delivered that way is small and heavily dependent on formulation and on reaching the right patch of tissue high in the nose — which ordinary spraying largely misses [1]. And “reaches the brain” is not automatically a good thing: it means unstudied exposure of the central nervous system to an unapproved compound of uncertain purity, at a dose nobody can state.

Which peptides have a plausible nasal basis — and which don't

A rough, honest split. It is about whether the molecule is absorbed nasally at all, not about whether it works for anything.

Some real basis small or formulated: Desmopressin, calcitonin, nafarelin, oxytocin, Semax and Selank, intranasal insulin — small peptides or purpose-built nasal products. Even here, absorption is partial and the registered dose does not transfer to a home-made spray.
Little or no basis large or unstudied: BPC-157, TB-500, GHK-Cu, the GLP-1 drugs (semaglutide, tirzepatide and the rest), growth hormone and its secretagogues — large or poorly absorbed molecules with no nasal formulation. Sprayed, they mostly deliver an unknown trickle or nothing.

Harm reduction specific to the nose

The solution is not sterile, and it is going on a mucous membrane. A grey-market peptide reconstituted at home carries the same unknown sterility and endotoxin status set out on the testing page — now applied to the nasal lining rather than under the skin.
Preservative and local irritation. Bacteriostatic water contains benzyl alcohol, which irritates the nasal mucosa; repeated spraying causes dryness, crusting, burning and nosebleeds, and chronic use can damage the lining.
Contamination. A refilled or shared nasal device is a route for bacteria straight onto broken mucosa; the tip touches the inside of the nose and goes back in the bottle.
The dose is unknown, so an effect is hard to judge and an overdose hard to rule out. With an injection you at least know what went in; with a home-made spray you know neither the delivered amount nor the absorbed one.

What this page will not do. It gives no nasal dose, no injection-to-spray conversion, and no endorsement of using any of this intranasally. The point is only that the route is real for a few peptides and mostly illusory for the rest, and that “no needle” is not the same as “no risk”.

Alabsi et al., Nose-to-Brain Delivery of Therapeutic Peptides as Nasal Aerosols — Pharmaceutics, 2022 (review; nasal absorption of peptides and the enhancers needed)

Peptides and nasal sprays: common questions

Do peptide nasal sprays actually work — does anything get absorbed?

It depends entirely on the peptide and the formulation. The registered nasal products (desmopressin, calcitonin, nafarelin) are specifically formulated to cross the nasal lining, and even then only a few percent of the dose reaches the bloodstream. A research peptide simply dissolved in bacteriostatic water and sprayed has no such formulation, so absorption is poor, erratic and impossible to quantify.

Can you take BPC-157 (or TB-500, GHK-Cu) as a nasal spray?

People do, but there is no evidence any of them is meaningfully absorbed through the nose or works when given that way, and no way to know what dose is delivered. Using an injectable research peptide as a nasal spray does not make it better studied or safer — it just adds a second unknown (how much crossed the lining) on top of the first (what is actually in the vial). See what a lab test proves.

Is a nasal spray safer than injecting?

It avoids the needle and the injection-site infection risk, which is real. But it is not “safe”: a non-sterile grey-market solution is now going onto the nasal lining instead, repeated use irritates and can damage that lining, and the delivered dose is unknown. The unknown-product problem is identical either way.

Which peptides come as a genuine nasal spray?

The ones with a registered intranasal form include desmopressin, calcitonin (salmon), nafarelin, oxytocin (research and historically), and — in Russia — Semax and Selank as nasal drops. Intranasal insulin is a research tool. These are small or specially formulated; most injectables are neither.

Can you make semaglutide or another GLP-1 drug into a nasal spray?

No. GLP-1 drugs such as semaglutide and tirzepatide are large, and there is no nasal version because they are not absorbed through the nose in any useful amount. Spraying an injectable GLP-1 would waste it and deliver an unknown trickle at best.

Injection safety · What a lab test proves · The basics · Legal status