Zantac usually takes a week to show slight progress and at then end of 2 you will see a huge difference. I am soooooo glad they finally got you meds for him. I actually worry about you guys because of how horribly you have been treated by doctors. Good job sticking with it and getting them to take care of your son.
My DS was on Zantac when he was baby also for Reflux it took closer to 2 weeks but he still had some breakthrough reflux even after being on Zantac for awhile. Remember it doesn't last forever even though it sometimes feels like it does. ENjoy your LO.