Disclaimer: This is not medical advice.
It can be used preventatively. Personally, I’d take 2 tabs, 2 hours before your meal, then pop another one, after the meal, if I start to get crampy. Cramps can signal diarrhea, so I’d use it as an indicator to take more.
Drink lots, otherwise you’ll have severe constipation. You’ll urinate a lot but, it’s better than dry constipation, trust me.
Obligatory not a medical proffesional…
Im pretty sure diarrhea right after your breaking meal implies you have a sensitivity to what you just consumed… fasting amplifies sensitivity reactions, thats part of the reason why its offten suggested to break a multi-day fast with a lean piece of meat and nothing else.