I went with the IV ketamine treatment so I haven't used the nasal spray. From what I understand, the nasal spray just uses the S molecule of ketamine while the IV uses S and R. I used it as a treatment for my depression, not for pain though. I was told for the six sessions that I went to that the side effects are during the treatment, not after. I am heading in for another session tomorrow sort of as a 'booster' since my depression is coming back. I had been told that would happen within a few weeks and that I would need another session. The time between sessions is supposed to get longer and longer for preventing depression. My cousin hasn't been back for another session in over a year.
Good luck with the treatments for your pain.