Hi Hopeful2, Nasuea and vomiting are side effects of lactulose, so is the gas problem. From what I understand that is quite common and should only be temporary. As far as the diarreha goes I would suspect that alot depends on the doses he's taking. Remember that Lactulose was originally intended to be given to relieve constipation. So you can only imagine when given in hgh doses what it does. If the taste is too horrible for him to take it you can mix it with water or juice. In my moms case they decreased the dose a couple times because she was having watery stools about 8 times a day. They eventually increased the dose again as her amonia levels were so high. It varies from case to case. Don't hesitate to call the Dr's office and speak to him/her or the nurse to report what is going on. They won't have a clue unless you tell them. Good luck and keep us posted.