Honestly most prescription ODs fail, and are not recommended. (Unless you're half dead and got a doctor to prescribe you Fentanyl haha). Antidepressant and other psych med ODs usually just end up in serotonin syndrome, making you very sick, but rarely ever fatal.
The only tried and true, quick and painless methods are N or Fentanyl unfortunately, and you just have to put the work in and research how to aquire either of them.