I have no clue, the first time I read about ketamine was in a article [1] about upcoming partydrugs in The Netherlands. In that article they mention that ketamine is generally used as a anesthetic for horses. But having things done to your body while you cannot decide about that is just horrible and should be banned.

[1] https://www.parool.nl/nieuws/ketamine-steeds-populairder-gro... (Dutch)