To :Laurie Re :PREVACID Lansoprazole. This drug is in my '97 edition if you need more specifics. Basically it is a proton pump inhibitor that blocks formation of acid in the stomach. We have no data on its transfer into human milk, nor its effect on newborns/infants. But basically, these drugs are really quite safe, and tend to have almost no side effects. Perhaps the mom could ask her doctor if Pepcid would work...this one penetrates milk poorly, is commonly used in pediatric patients, and is a suitable alternative. If she needs the big gun or another proton pump inhibitor, then Prilosec(omeprazole) may be substituted, as it is extremely unstable in acid mileu, and would be destroyed in the infants stomach prior to being absorbed. Regards Tom Hale, Ph.D.