I've been on Zelnorm for about 3 months, but I don't take it twice a day, everyday, like I'm supposed to! When I started it, I was taking it religiously, 6mg in the morning before breakfast and 6mg before dinner. My GI doc said I could play around with the dosage after I had been on it for about a month or so. He said if it helped a lot, I could cut it down to one pill in the morning and see if it still helps. I've had no side effects, except for when I first started it, I didn't get diarrhea, but I did get a bad, crampy feeling in my gut. It went away after I took the pill for a few more days. My neurologist started me on doxepin, which is an antidepressant with a side-effect of constipation (just what I need!!!), but nothing else has really helped my horrible migraines, so now I am back to taking my Zelnorm more as I should (along with my citrucel that my GI doc said I should be taking everyday, too!) I haven't had any drug interactions with these pills. Zelnorm is really expensive without insurance, and since the pill is so new, not many insurance companies even cover it as of yet. However, you can most likely get your insurance to cover it if you have the exact symptoms that Zelnorm helps (IBS with constipation, bloating, and abdominal pain.) If they initially don't approve it, have your pharmacy call your doctor's office to get a prior-authorization for the drug. If they wouldn't have done it for me, they wanted to charge me about $175 for a month's supply, and I definitely don't have that kind of money! Now it's $25. The doctor probably has samples and could have vouchers for a free month's worth of Zelnorm, too.Also, US doctors cannot prescribe Zelnorm to men yet because there were not enough men recruited to the initial drug study to prove that it works for them.