There is a lot of medical information on SN precisely because of it's use as a suicider. Info on KN as a suicider should be available somewhere, but i don't know. I did manage to find this morsel
"Body weight, food intake and food efficiency were decreased at 3000-mg/litre level in males, while liquid intake was decreased in males given 1000 and 3000 mg/litre and in females given 3000 mg/litre. There was significant increase in the methaemoglobin concentration in animals given 3000 mg/litre, while slight decreases in red blood cell variables occurred at the 1000- and 3000-mg/litre dose. No impaired renal function was observed in any of the test groups, although the relative weight of the kidneys and the plasma urea nitrogen level was increased at 3000 mg/litre."
(this is about potassium nitrite given to rats in drinking water)