My son started on zantac one week ago. He takes 2 ml/ day. When he first started it, I though that it was heaven sent. He was sleeping better and seemed more content. This only lasted 4 days. Over the weekend, he started crying excessively and he nursed from 11 pm to 4:30 am for comfort. Is it common for zantac to work for a few days when it is first administered and then stop working just days after starting it? This is obviously not because he gained weight since it was over the course of a week. Why would he improve immediately after starting the zantac and then regress just 4 days later? My doctor said that zantac can take up to 2 weeks to have a full effect. Should I wait that long or should I call and ask for a different medication? My poor baby is clearly suffering.