In Poland charcoal is a popular medicine for upset stomach... My mom used to give it to me when I was little. Now my preffer method is alkaseltzer

... If I remember correctly they were 500 mg tablets.
Everyone knows it's binding properties for toxins. Charcoal also adsorbs gastrointestinial gas and may cause mild constipation which is good ico diarrhea.
Great link on charcoal:
http://en.wikipedia.org/wiki/Activated_carbon