TLDR: If you ingest wayyyy more than the recommended you'll have an insanely harder time keeping all of it down and will probably be in a lot more pain.
This was a long tangent with no clear goal and this was all written top down so please do not judge any mistakes I made (I literally only proof read for spelling errors) and correct me on any info I might have gotten wrong (I am not a doctor or chemist and I am a high school drop out so trust me I don't know as much as some of you probably do)
Long version: First we need to talk about 25g of Sodium Nitrite which I will refer to as its chemical name from now on NaNO2 and how it works in your body. The protein in your blood (hemoglobin) uses iron to almost grab oxygen. If your blood is in a healthy state, it will be ferrous (Fe2+), and when it is carrying oxygen it will appear bright red. Since NaNO2 is an oxidizing agent, it will steal an electron from your iron and cause it to be ferric (Fe3+), this new form is now called methemoglobin. Ferric iron kinda acts like a delivery truck with a flat tire. It can no longer carry any of its oxygen to your vital organs causing hypoxia. And to top it all off it blocks any of that hemoglobin from delivering any of its oxygen to those organs either (kinda like a traffic jam). This is one of the forms of what is called chemical suffocation. In this ordeal ~70-90% of the victims hemoglobin will be converted into methemoglobin.
Another phenomenon beyond the chemistry of it is that NaNO2 acts like a power off button for blood pressure. This is because nitrites are very effective vasodilators. They basically tell the muscles wrapping around your blood vessels to just completely relax. This is the same phenomenon as when you put your thumb over a garden hose, just imagine on top of taking off your thumb the hose also grows 2x larger. The water will barely flow through and it will look more like a leaky faucet than a hose. 25g of NaNO2 in a 100kg person is enough to effectively do this to every vessel in your body at once. This is almost this self-sabotaging cycle where your blood pressure is near zero so your heart begins to pump faster to compensate, but since the blood carries no oxygen, the heart muscle uses up all its resources even faster and eventually gives up.
One final note on 25g of NaNO2 is because it is a pretty large amount (about 5 teaspoons) it causes direct damage to the stomach. When NaNO2 reaches the hydrochloric acid in the stomach, it causes a highly irritating reaction. This usually causes violent vomiting but assuming you're lucky and followed everything right, this does not occur. In an autopsy the pathologists will note tiny pin point sized red spots around your stomach lining. These are actually small hemorrhages where your capillaries burst. Your brain will also show signs of swelling. Your blood will keep its brown color even when exposed to oxygen. Your nails and skin will be cyanotic and have a brown undertone. And finally your lungs will be full of fluid called a pulmonary edema because the heart couldn't keep up with the pressure drop.
Also after reading all of this I know some of you might be very skeptical of the peaceful aspect of this method but a lot of this is post-mortem and/or occurs while unconscious.
If lets say 100g of sodium nitrite was consumed and it was all absorbed. You would likely experience cellular hypoxia before your body is even able to attempt any countermeasures. The transition would be insanely sudden and violent. Your blood would be immensely darker maybe even nearly black. This method would likely be extremely more painful, unforgiving, and violent. Once you reach territory of 100-200g (i just used this number as an assumption of what you meant) you're going further than just a very lethal overdose and it just becomes excessive chemical consumption. The cause of death still remains the same (chemical suffocation i think), however, the pathology aspect changes completely from a straight biochemical process to a sudden corrosive systemic shock situation.
Usually at 25g the stomach may be irritated but when you reach levels of NaNO2 like 100-200g it becomes severely chemically burned. While, yes, NaNO2 is a salt, when it reacts with the hydrochloric acid in our stomach it forms nitrous acid (HNO2) and nitrous oxide gas (NO). Ingesting 200g would cause a sudden violent chain of a chemical reaction in the gut. It would be less of poisoning and more similar to swallowing some sort of caustic agent (bleach is a caustic agent i believe). Instead of the tiny red spots (petechiae) the pathologist would observe (sorry for the fancy words) sloughing of the gastric mucosa (and in simple terms, the lining literally peeling off). The stomach would appear very leathery and very hardened due to nitrites acting as a mild tissue fixative (this is used in its meat curing practices).
This reaction of 200g would also likely be so fast that the conversion of hemoglobin the methemoglobin and the "chocolate blood" phenomenon might even fully take effect while you're still taking your final breaths. And also since the vasodilation would be so sudden and extreme the headache you'd get would be excruciating before your blood pressure rapidly drops to near-zero and you lose consciousness.
For more pathology stuff, the myocardial (heart) toxicity levels would be immensely different. Because while 25g might kill by starving of oxygen, 200g might even kill you just by the direct toxic shock. High levels of any sort of nitrites in the system can directly harm the way the heart utilizes electric signals. So instead of you dying from the oxygen deprivation, someone who takes 200g might suffer a sudden cardiac arrest or a lethal arrhythmia (basically when the heart just freaks out and does whatever) because of how imbalanced your electrolytes would be in your blood because of how much sodium and nitrite ions have just suddenly emerged.
Anyways I hope this helps at least someone with any questions or curiosity about this. I'm not encouraging or discouraging this I mainly just wanted to get all the facts out on the table for y'all to decide because I assumed (and hopefully was correct) that nobody else would write a long ass tangent about this B)
Have a lovely day everyone!
