> But somewhat right because the antidepressant effect isn't very durable, so it's mostly useful in emergency situations (suicidal tendencies) and for kickstarting conventional therapy. Even the rare patients who convince their doctor to prescribe ketamine multiple times per week over the long term usually encounter diminishing effects as tolerance sets in.

This is the unfortunate reality with all depression treatments, including SSRIs, Tricyclics, ECT, TMS, and even MAOIs.

Most people who have treatment resistant depression that is "biological" i.e. not situational will end up requiring treatment for the rest of their lives. SSRIs are well known for "pooping-out" after some number of years, and most patients will end up cycling through different treatments, sometimes finding something that works well for a long time, and other times not finding lasting relief for years at a time while experimenting with "cocktails" of meds from different psychiatrists.

The only problem with Ketamine at this time is that it is quite expensive as commonly provided (patented formulations, in-clinic requirements e.g. REMs, fusion providers, etc). If it turns out to be safe to use in lower doses via lozenges or some other compounded route, without the current associated high costs of administration and procurement, then there's no reason Ketamine can't end up being given out as a generic prescription to be used once or twice a week at just a few dollars / month, similar to what generic SSRIs or Tricyclics now cost.

But I imagine the Pharma industry and the increasing number of very profitable infusion providers will do everything they can to ensure this doesn't become mainstream anytime soon.