In psychiatry, we have been trying to reach the brain via various parenteral routes for a long time. Some historians claim that Neolithic ‘trephination’ observed in the Stone Age skulls may in fact be an attempt to treat psychiatric conditions 1. We have been spectacularly successful with some non-pharmacological parenteral therapies. Brain stimulation techniques are commonly employed ‘parenteral’ approaches forming a substantial portion of our prescribed treatments now.
The last decade has seen a less invasive pharmacological approach for parenteral therapy. Intranasal delivery of drugs seem to reach the central nervous system by directly crossing the blood-brain barrier via olfactory bulb pathways. For drugs that do cross this barrier effectively, intranasal delivery offers a means to circumvent the side effects of systemic administration.
What drugs look promising in this regard?
The 3 most promising agents at present are
- Intranasal ketamine for depression
- Intranasal oxytocin for various conditions where reduced empathy is prominent
- Intranasal insulin for various neurodegenerative and cognitive syndromes2
Of these 3, the one that is ready for clinical use is the s-enantiomer of ketamine. You can find more information about the evidence for intranasal esketamine use in our Qbank materials.