Just to add to what 6ixxy said...
N is an old school barbiturate, meaning a strong sedative. Too much equals overdose and death. That is why they developed newer sedatives - benzodiazepines like Xanax, Ativan, Valium, klonopin, etc. those are considered safer and a lot harder to ctb on if at all posssible. This is why N is used in euthanasia here in the US and other countries. It will cause your entire system to slow down so abruptly that you end up passing out very quickly then you stop breathing. This is the most peaceful way to die. If you watch the dignity's and exit international videos of old people dying, you can see how quickly it works.
SN is a poison to the body, not a sedative. Large amounts cause Methemoglobinemia, "Methemoglobinemia is an unusual and potentially fatal condition in which hemoglobin is oxidized to methemoglobin and loses its ability to bind and transport oxygen." So basically by taking a large enough amount we deprive the body from proper oxygen transportation, meaning all kinds of things start going bad. That's why there are the side effects like headaches, dizziness, drowsiness..etc. your brain can't function without oxyagen so eventually you pass out. But let's be clear here, although it has been reported peaceful by the Pph, and people who passed here during their goodbye threads, it's still a totally different approach to killing the body vs N. The nice thing about Sn it's fraction of the cost and easily available.
I'm not trying to scare you as I believe Sn is pretty peaceful esp compared to other methods, I just find it funny when people try to compare the 2. They are two totally different modes of action.