It depends on the type of the suspected poison. If a minor one, and you have the ingredients for P&B shakes take a shake and water. The charcoal in the Dr Schulze products will absorb too. I would take a spoonful hourly for two or three doses with a large glass of water. PS, if your body needs to reject food or anything, you will vomit it up. Then you need to replace fluids. I take a glass of very dilute juice, a spoonful of maple syrup or sugar, and a big pinch of real Sea Salt . This fluid is sorta like gatorade to replace fluids that you lose to vomiting or diarrhea.
Of course, if you think it is a serious type of poison, you need to call the poison control center and get advice quickly.