My first recommendation for treatment of irritable bowel (and it won't cause any interaction with your other medications) eliminate the caffeine.
http://digestive.niddk.nih.gov/ddiseases/pubs/ibs_ez/
If you drink LOTS of caffeine, it is likely that you might develop withdrawal symptoms if you stop if cold turkey. What I recommend is to wean the concentration of the caffeine - For coffee drinkers - starting today you mix your regular coffee 3 parts to 1 part decaf in the coffee maker, next week it is 2 parts regular to 2 parts decaf, next week 1 to 3 parts and finally ALL decaf.
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