Why these two routes exist at all
Swallowed peptides meet the same enzymes that digest dietary protein, which is why the oral route is closed to almost everything in this catalogue. Any viable route has to go around the gut.
Injection goes around it completely: material enters subcutaneous tissue and reaches circulation with well-understood, broadly compound-independent efficiency. It is the default in research for that reason — the delivery variable is essentially removed.
The nasal mucosa offers a second bypass. It is permeable enough for small molecules to cross, needle-free, and fast to administer. But its permeability falls sharply as molecular size rises, which turns chain length into a gatekeeper.
Route against route
The comparison as the chemistry sees it.
| Nasal spray | Subcutaneous injection | |
|---|---|---|
| Digestive bypass | Yes — via the nasal mucosa | Yes — complete |
| Works for which peptides | Short sequences; viability drops with size | Any compound in this catalogue |
| Delivery efficiency | Lower and more variable between individuals | Higher and more consistent |
| Dose precision | Metered pump; per-spray consistency is good, absorption is the variable | Syringe or pen; both measured and absorbed predictably |
| Handling | No sharps, no reconstitution in our formats | Needles, technique, disposal |
| Research caveat | Whether intranasal delivery reaches the brain is a contested question | Few route-specific controversies |
| In this catalogue | Short compounds only: semax, selank, DSIP, NAD+, PT-141 blend | Everything else, as pens and vials |
Our spray list is short by chemistry, not by choice: only sequences short enough for credible mucosal absorption are offered in the format.
What each route cannot promise
The spray’s weakness is quantitative. Less material crosses, and how much varies with mucosal condition — a blocked nose is a changed experiment. Claims that intranasal peptides reach the brain directly along nasal nerves exist in the literature and remain genuinely contested; we sell sprays while saying so, because the alternative is selling them while not saying so.
Injection’s weakness is practical rather than pharmacological: sharps, technique, and the handling chain from reconstitution to disposal. Every step is well understood, which is different from every step being effortless.
What neither route changes is the compound or the evidence behind it. A weak literature does not improve because the delivery is convenient, and a strong one does not weaken because needles are involved.
Both routes, where both are viable
Semax and selank appear in each format; the choice between them is exactly this page.
Around the routes
The format pages and their practical background.
About the routes
The recurring questions when both formats exist.