250mg seems exceptionally high (in reference to the OP's response below). The esketamine nasal spray that was just approved contains only 28mg per dose (1-2x/week). I don't know if that's because you need more if you take it sublingually. Snorting/nasal is almost certainly the most efficient/most effective way to take it.

1) The different ROAs have different bioavailability.

2) Ketamine is cheap. Convenience should be prioritized over efficiency.

It's not just about the expense, ketamine can damage liver and kidneys, and reduce iron uptake. Efficiency, in this case, is more about harm reduction than expense

I've read some of the most important papers and books and have never come across this. Please post a source.

Depression is a very serious illness and ketamine is a very safe drug. We need to give people more options.

Are you concerned about potential long term side effects of the drug?

Like MDMA, which has also garnered attention from researchers for potential medical benefits, I was under the impression K had nontrivial neurotoxic potential if abused.

Yes, and that's why I take small doses infrequently. I took a few months off because I was doing that much better, but the intrusive thoughts came back. But overall. No, my brain is fucked and tells me to kill myself every day; I don't need that abuse. Those brain cells deserve to die. More serious take: my quality of life is improved by an order of magnitude. I didn't want to survive another decade in that condition, but now I do. That's worth the risk