It could cause serotonin syndrome and iirc that can lead to painful migraines, nausea, vomiting, diarrhea. Unfortunately most medications available today are chosen because they're safe, and hard to OD on. Chances are you'll vomit before you absorb a lethal dose. If you do try this and vomit it up, I strongly suggest you call emergency services so you don't cause long term damage to organs that you then have to live with. Also, painful migraines will probably test your resolve, and you might end up calling emergency services for help with the pain. There are a lot of risks with any method that isn't euthanasia because the body and mind will fight to keep you alive, even if it means doing long term damage