I also have IBS-D/C and GERD. I have Lomotil for the "D" and Prevacid for the GERD. I haven't noticed any obvious side effects. Initially I had to take Prevacid every day, but only occasionally now, if I'm "stoopid" about what I eat, or eat after dinner time.The Lomotil has been a Godsend for thr "D". I'm actually tapering off on the amount that I'm taking, and have had no relapses.I wish you well, and hope everything works out for you.Luilu