Edit: looks like HN has been down this very same road before[0] when Ketamine was brought up; and I'm smiling to see that I'm not the only one to think of Tianeptine in contrast to the drastic use of Ketamine. Psychopharmacology is the tried and true drug pusher of our times.
Tianeptine is a mu-opioid receptor agonist, so it has abuse & addiction potential above therapeutic doses. It's also rx-only in many countries, according to Wikipedia.
Additionally, ketamine works for a week whereas it's not uncommon for people who use tianeptine to split their daily regimen into something like 3 separate doses throughout the course of the day.
At least neither require several weeks to reach efficacy while initially potentially increasing the severity of depression...
Those countries include parts of Europe, Asia and Latin America.
On the same Wikipedia page, "not available [as in, at all, even with a prescription] in Australia, Canada, New Zealand, the U.K. or the U.S."
Kind of a bummer, I was starting to think I might have something new to look into. Not surprised, though.