Is intranasal delivery better than injection for cognitive peptides?

Intranasal delivery offers a non-invasive route that can bypass the blood-brain barrier through the olfactory and trigeminal nerve pathways, potentially providing more direct brain access. Some peptides show excellent nasal bioavailability, such as Selank at 92.8%, while others remain below 5%. Injectable peptides generally provide higher systemic bioavailability and more predictable pharmacokinetics. The optimal route depends on the specific peptide, its molecular properties, and the therapeutic target, with nasal delivery often preferred for direct neurological effects and injection for systemic applications.