I will answer the OP's question because I think it's legitimate and this topic shouldn't be taboo. When I was really sick this past spring and I had no options, I researched suicide methods extensively. I gave myself a cut off date for when I should be better by, and if things weren't better I would be offing myself. I was in absolute horrible pain that I wouldn't wish on my worst enemy. No one should have to suffer, if they've exhausted all options and the problem is long-term. It's a person's sovereign right to end it.
Killing yourself with pills is a poor choice. The success rate is very low (less than 20 percent), despite what popular media would have us believe. What ends up happening is that the person survives but has severe damage to various organs, usually the liver, which ends up entailing a much slower and painful death down the road. The brain is usually in tact, unless you use RX anti-depressants, in which case you'll survive but with brain damage. To me the most horrible suicide methods are the ones that you are more likely to survive, but with incapacitating disabilities that prevent you from making another attempt.
I've known several people who attempted suicide with pills, one of them was an opiate user. Their description of the experience sounded horrible. You don't just go to sleep and die, you are aware of what's happening on some level and you struggle. The ones who survived said it felt like their entire body was oppressed and it was like a hallucination from hell. Thinking about the various psychedelic trips I've been on, I wouldn't want to experience a stereoscopic death of any kind, especially if the dose isn't high enough and you linger for a long time. Ugh.
The only drug that is guaranteed to kill you peacefully is pentobarbitol, which is what they use for human euthanasia. You need a doctor's RX to get it, and to get an RX you need to be terminally ill. Though, if I recall correctly, there was a high profile media case recently where a person with horrible depression got the OK to be euthanized. Was it in the UK? *can't remember*
My spiritual beliefs prevent me from committing suicide unless there is clearly, absolutely no way to continue on my soul's path in this life. In general, suicide leads to lingering spirits who can't cross over. From all the spiritual work I've done over the years, it's an unfortunate reality that when people die unresolved, they take their shit with them. You don't just go to the light and it's all happy happy. You just become a messed up spirit with all the same problems as when you were alive, except you have no means to fix it.