Although I have no idea of what dosage you would need to off yourself from your drug of choice I can tell you that at any given time I have more than enough medicine in my house to OD two or three people at least. Especially because I am a polysubstance user, although all of my medications are prescribed. There are more days than I'd like to admit where I almost ended it because I I feel useless in this world.
I've been in pain management since ~2004. I was fine until 2 years ago when a nasty bacterial infection took over a lung, put me in a coma, and left numerous scars on me as they desperately tried to save me for several months. They thought I would wake up pretty much a vegetable. Because the infection was on my lungs my oxygen level was below 70% and they believe it was that way for at least 4 to 5 days with the infection being in place for at least 2 weeks.
Since I've gotten out of the hospital I absolutely know that I have brain damage but I cannot convince anyone in my family, and I have one heck of a large family. I feel slow, sluggish, my short-term memory is shot and I have lost pieces of my long-term memory.
Why am I saying all of this? The one thing that keeps my feet on this planet is my four children. When I was in a coma in the hospital my children were completely beyond console. My siblings were in meltdown and we are all in our mid-to-late fifties but it was my own children's response to their mother almost dying that stops me from ever od'ing on my medicine. I will never intentionally cause that kind of pain to them. They age from 23 to 34 and need me so I'll smile, laugh and be there for them.
I decided to make a plan to perhaps change my daily loneliness, although nothing can fix the dark place I lived and died in at the hospital.