Dextromethorphan is available over the counter, and at the dose that's supposedly for suppressing a cough, (which it is clinically proven it does not do) it is a very effective antidepressant with practically no side effects after the first couple weeks. Because it's so weak compared to other NMDA receptor antagonists, you can dial in a very precise macrodose for anything from "I just think music is great" to "time loops" to "talking to the god in your head" to "kissing the void." It lasts six hours and has more of a body load than other such drugs, so it's not always fun, but if you need the vision quest kind of neuroplasticity, you can get there dirt cheap, completely legal, and very safely. You can also just take the normal dose twice a day and hold your suffering much more lightly.
The main problem is finding it without tylenol or antihistamines added. These days you usually have to order it online to get it pure.