Depends on the poison. Some will be more painful and it varies as to what the symptoms are. Some poisons take much longer than others to get into your system and do it's thing. One thing that's fairly consistent with any poison, synthetic or plant/fungus derived, is gastric distress in the form of abdominal pain, nausea and vomitting. There's also the fact that people sometimes respond differently. Without more details, this isn't something anyone can answer with a definitively. Unfortunately, as far as I know, there isn't something you can drink/swallow whole that will allow you to ctb and not feel any side effects whatsoever.
