Pancreatin causes bad diarrhea

Hi,

Two days ago I went and bought an over-the-counter digestive enzyme preparation from a health food store. I took one with dinner the night before last and yesterday I felt pretty bad (tired and brain-fog, but didn't think too much of it as I often feel that way). I took 3 yesterday, one with each meal and last night I woke up with bad heartburn. I got up and had an antacid and went back to bed. This morning I felt terrible with bad diarrhea, stomach cramps, nausea, headache and fatigue.

The tablets contain:
Betain Hychloride 300mg
L-Glutamic Acid 200mg
Magnesium Ascorbate 100mg
Potassium Ascorbate 100mg
Pepsin 1:15000 8.33mg
Pancreatine(porcine) 100mg

The only gastro problem I have had in the past is chronic constipation (although I have always had a 'pot-belly' which seems out of proportion to the rest of me as I am not overweight).

What would cause this reaction? This stuff should be safe if you can buy it over the counter. The only info I can find on the web is for prescription pancreatine products which list the symptoms I have as rare side-effects and to see you doctor. Could this sort of reaction point to some sort of problem?

Any info much appreciated.

Cheers
Johnno