They definately can. My two year old has been on Zantac for about a year now and I can tell a difference at night when I forget to give it to her. The doctors also have her on Prilosec during the day but I really don't think that helps a whole lot. If I forget that one then I don't see any difference. When it comes to Zantac, I don't leave home without it. If I do, I won't be getting any good sleep because she'll be up 4 and 5 times fussing.