Esketamine is also called Spravato. It's very similar to ketamine, but I believe it has an additional molecule, not exactly the same though they both help with untreatable depression.
The problem with Esketamine is that it's a nasal spray, so the dosage you get each time may not be exactly the same depending on factors such as how you spray I up your nose, how much mucus is present and a couple other factors but the bottom line is it depends on how much of the drug is absorbed by your nasal passages and at what rate.
I take Ketamine infusions once a month. The dosage is always accurate, both methods take time - about 1 1/2 hours.
Google Dr. Rachel Dalthorp at Mind Mood Pain in Moore Oklahoma. She's a pioneer in the treatment of depression and other disorders with Spravato and Ketamine.