Glossary
Intranasal
Nasal delivery puts a peptide solution on the nasal lining, avoiding hepatic first-pass loss. Surface area, clearance time and the nose-to-brain question.
With intranasal delivery, a solution is deposited on the olfactory and respiratory lining of the nose; this thin mucosa, rich in blood vessels, lets substances pass straight into the systemic circulation without a first pass through the liver. The human absorptive area is small — roughly 150 cm² — and the cilia sweep deposited liquid back to the pharynx in some fifteen to twenty minutes, leaving a short window for uptake.
Why researchers use this route
Two features make it attractive. Firstly, skipping first-pass metabolism gives many peptides higher bioavailability than the oral route, although values stay well under subcutaneous figures and depend strongly on the formulation. Secondly, nerve routes along the trigeminal and olfactory tracts might give access to the brain while sidestepping the blood-brain barrier; animal work and a few small clinical studies have tested this with insulin, oxytocin and the regulatory peptides developed in Russia, and the data is still under active debate rather than resolved.
The formulation is the bottleneck. Research sprays are water-based solutions containing a preservative and a tonicity agent, and each pump stroke typically delivers 50 to 100 µL; after mixing they rely on the chosen excipients for stability. More in our overview of nasal spray formats, on the Semax spray product page and in the guide to formulating sprays.
Related terms
Hydrophilic compounds; also our nasal spray reconstitution kit