Prolonged fasting and meditation can generate non-ordinary mental states (which you could call psychedelic trips if you like) but the mechanism and the effects are not the same. When it comes to psychoactive compounds, classification matters a lot, at least from a pharmacological perspective. For example, MDMA dependency is a lot more likely than LSD dependency from an abuse perspective as it hits the dopamine reward circuitry in the brain, and this is generally true of all the tryptamine-class psychedelics.

As far as ketamine, it's an organochlorine compound whose regular use is associated with liver and urinary toxicity, I can't believe anyone who knows about this would want to take it regularly or recreationally.

https://en.wikipedia.org/wiki/Ketamine