Why SN is so appealing is that, in most places still, it is a legal substance. Someone discovered that a certain amount of it can be lethal. As far as substances that work like SN, I don't know of any, or haven't heard of any. You could probably kill yourself with all kinds of substances, if you can get enough of it down and keep it there. That's where the problem is. With SN the amount needed to CTB was a relatively small amount, but even so, other measures needed to be taken in order to help keep the "poison" down long enough, and still more measures to increase the efficacy of it. There's no perfect pill. Another thing you might want to consider is peacefulness. Who is to say how peaceful a SN CTB is? I can't because I've never taken it. And those that were successful with it can't tell you, either, since dead men tell no tales. Getting Nembutal (N), or other derivatives of it, is difficult, unless you head down to S. America and try your luck there. If you do happen to get it in S. America, you may very well have to CTB right down there, since bringing it back may be difficult. And it's a controlled substance, unlike SN, which is still mostly legal. Maybe someone will discover another legal substance on the market that can kill you using only a small amount eventually.