The nasal spray? An anesthesiologist told me that it's 1/10th as effective as IV therapy due to some aspect of bioavailability and how it ultimately didn't produce the same sort of norketamine levels required.

edit: For context, he subsequently complained of how big pharma was conspiring to destroy ketamine iv therapy access in order to better control the "legal ketamine" market.

IV is not 10x more effective than intranasal - it's maybe twice as effective.

IV bioavailability is 100%, intramuscular 93%, intranasal around 50%, and oral around 20%.

This is something I just don't understand about IV ketamine therapy - IV protocols vary wildly, and I haven't been able to find any reasons why IV would be more effective than any other route of administration with an increased dose.