This is an interesting question. I wonder if it would work, or if it would increase a person's tendency to panic if they felt the urge to vomit after ingesting SN.
Personally I feel that an attempt would have the greatest chance to succeed if, the person drinks a lethal 50 gram dose of liquid and then administers another liquid 50 gram dose rectally.
I expect this has been discussed here on the forum before, and I am not sure what the consensus wisdom is on this idea.
But having administered drugs rectally in liquid form before, I can say that it works effectively for other things.
I'm pretty sure that if I choose SN, this will be part of my process to make it successful. Thank you for your thought-provoking question, and good luck to you.