Probably twenty hydrocodones (Vicodin) would do it on their own, but chugging a half bottle of 80 proof bourbon, vodka, or whatever would make sure.
I'm not an expert, but I doubt you'd be conscious long enough to wish any tummy pain would go away. One thing: if you're worried about tummy pain, don't go the aspirin route. It takes a LOT of aspirin to kill a person, but barbiturates will definitely do the trick with a much smaller number of pills.
That was my concern. Intestinal tearing and what-have-you. Barbiturates, hydrocodones, and 80 proof. Sounds solid. Easier to get than a gun, makes less of a mess (more considerate)... just have to make sure I don't soil myself.
Dealing with soiled underwear, despite the stink, beats scraping your brains off the ceiling with a razor blade and empty tin can.
I'll still try to empty my bowls first just in case. For pride's sake. I mean I know I'll be non-existent, but I don't currently like the idea of my loved ones thinking I hadn't developed a contingency for "poo-pants". This might be a moot point, as by the time I'm old enough to consider this assisted suicide may be more common (hoping that's not wishful thinking).
I am a baby boomer, and I am for euthanasia. I am not into pain, and I will choose when I go, and it will be with dignity. That is my main thing, dignity. I have no fear of death, and I don't want anybody feeling sorry for me, and I am willing my body to a University, so would be doctors can cut me up :)
People will have a choice, legal or not. It has ti be planned, not involving my partner, so he doesn't get charged with murder, or whatever. Party first, lots of 70 and 80's music, lots of champers. Way to go.
When doctors know pain cannot always be controlled, I am out of here. And I am sure the overdoses of morphine, are to kill, but it is kept quiet.