I take lamotrigine 75mg twice daily. My gallbladder was removed in 2014 but all AEDs can cause diarrhea and constipation. I have been on an AED since may 2014. I have alternating dusrthea and constipation so I requested a dose reduction from neurologist. Went from 100mg twice daily to 75mg twice daily. I am working on my diet too. Spicy food has to go. I am just now seeing meditation for GI issues helps. I need to reduce my diet soda intake more because caffeine i think is an issue. I may have to discuss a further reduction on dosage of lsmotrigine.