If your baby or toddler is using reflux medicine, maybe it’s time to quit. Here’s why, and how. This is one of my least favorite findings in a little one’s history. Along with its needed effects, lansoprazole (the active ingredient contained in Prevacid) may cause some unwanted effects. Although not all of these side effects may occur, if they do occur they may need medical attention. For the constipation, what works for me best is a drug called Amitiza. It is not cheap, but it is less expensive than it used to be. I just take it every 3 days or so. I also use Miralax, which seems to be the same thing as your macrogol. Ranitidine didn't work for our son or for our current foster baby. Could you see if 7.5 mg of Prevacid works? Maybe it is just too much of it at 15 mg. PPIs are often the preferred GERD treatment. They can heal the esophageal lining and treat GERD symptoms, but they can cause constipation. There are a few ways to manage constipation caused by PPIs. Prevacid (lansoprazole) is a proton pump inhibitor. Lansoprazole decreases the amount of acid produced in the stomach. Prevacid is used to treat and prevent stomach and intestinal ulcers, erosive esophagitis (damage to the esophagus from stomach acid), and other conditions involving excessive stomach acid such as Zollinger-Ellison syndrome. Most people have the opposite problem with Prevacid. Actually, it is used off-label to treat constipation. So it most likely isn't the prevacid causing the constipation. Quoting Bonnie: Prevacid and constipation Has anyone had problems with their baby and constipation while they were on prevacid? My daughter is 8 weeks old and it seems that since she has had the prevacid she has been constipated. Some of those problems before taking the prevacid was occasional bouts of constipation or diarreah because of the acid and indigestion. Since the prevacid I have had none of that. Was wondering if your LO got constipated after starting Prevacid, and if so, what did you do/start that helped them out? My daughter is an ex-25 weeker, 5 months actual, 1.5 months adjusted, and since.