I have been on Entyvio for 4 years now and have never had a reaction to it nor do I take anything before the infusion. Yesterday I had my infusion at noon and by 4 pm I was having cramping and pain and felt like I would like to throw up but didn't. I know I have a narrowing area where they took out the valve between the large and small and some intestine on each side back in 2007 which is were the narrowing is at. Has anyone else had a reaction like this or is this just a coincidence with the timing to have a problem with the narrowing? Today at 1 pm I am still uncomfortable but not near to what I was feeling last night.