Non-injectable routes: intranasal, oral and topical

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The subcutaneous route dominates for a reason: it delivers the molecule intact. But there are compounds whose literature was built on other routes, and each one has its own rules.

Intranasal

• Advantage: rapid absorption through a highly vascularized mucosa and, for some compounds, partial access to the central nervous system via the olfactory and trigeminal pathways, partly avoiding the blood-brain barrier.
• Typical compounds: Semax and Selank (developed and studied in Russia by this route), oxytocin in behavioral research.
• Limitations: small volume per application, variability depending on technique and the state of the mucosa, and mucociliary clearance that removes the product within minutes.

Oral

It is the most difficult route for a peptide: acidic pH, gastric and pancreatic proteases, and an intestinal epithelium that barely lets large, hydrophilic molecules through. It only works with special strategies:

• Absorption enhancers (the case of oral semaglutide with SNAC).
• Intrinsically stable peptides, such as BPC-157, whose stability in acidic medium made it possible to study it orally in animal models.
• Local action in the gut itself, where systemic absorption is not needed (the line of research on KPV in intestinal inflammation).

Topical

The skin is a barrier designed to let nothing through. The stratum corneum limits penetration to small, lipophilic molecules, and most peptides are neither. That is why cosmetic peptides that work on the skin (GHK-Cu, signaling peptides, SNAP-8) are usually short, sometimes modified with lipophilic chains (palmitoylation) to improve penetration, and act in superficial layers.

Educational content for scientific purposes. It distinguishes preclinical from clinical evidence and is not medical advice, diagnosis or a recommendation for use. NeoPeptidos products are sold labelled for research use only (RUO).