I have experience with ketamine infusions, nasal spray, pill form, and lozenges.

For me the infusions I went through,I started with the 10 day infusion and went through 1 day a week infusions for 2 years, that helped to kind of slow the pain but it would come back. Since I have been given ketamine nasal spray and lozenges which has made a complete difference and I don't end up in the ER as often and when I do that's when I get infusions. As for the pill form that didn't help at all, it made no difference in reducing my pain. But we are all different on how we react to medications and how much it helps. My RSD at that time was at a severe state with full body and internal it took awhile for my doctor to figure a cocktail of meds that made a difference. Ketamine works by numbing the nerves so the burning isn't so intense or don't feel it at all. And for me its the nasal spray that helps so much more then the lozenges but like my friend she just needed to use the lozenges and it made her burning pain all go away she has it in her knee. So the ketamine like all the pain meds we react differently and the severity of the rsd I think matters a lot, I spent years doing infusions a week that was just enough to get me to use the nasal spray and lozenges. I still get infusions during flares where I am admitted and given the infusions as long as it takes to calm down the fire.
Those are my experience with the different forms, Iam sure there are others with different ones. I hope you get the answers your looking for to help you.

Samantha