SN is a neuroprotectant so it protects the brain, if you want to back out after taking it you can call the hospital and they can help you with little effects. But obviously you can't call if you fall unconscious, so uh, don't fall unconscious.
I think that is why sn is popular, not many physical consequences if things go wrong. But if you are somehow resuscitated after, say 8 hours (very unlikely), things might turn out differently.
I think there was a member that took SN and went to the hospital. They made a thread I think.