Hi, P.! My son was on Zantac for about 6 months. I'll just list a few things the doc told us to do, not to do, etc. and other recommendations that worked for us.
Make sure you give him the prescribed dosage. My son was on it 3 times daily and if he even missed one dose, he paid the price for around 24 hours. I also learned to give him the meds 1/2 hour to an hour before feeding him. Seemed to take a little time to work so he would spit up less after eating.
Burp, burp and burp him some more! Seriously, like every half ounce.
Do not lay him down immediately after eating. Keep him upright 1/2 hour to an hour after eating.
Let him sleep in his bouncy chair or even a swing if he's really fussy. When you lay him down the acid comes up into his throat and is really painful. I used to call Jack "my little upright baby". If you held him or kept him sitting up he was perfectly content. The second you laid him flat on his back he would start crying.
Get a sleep wedge or roll up towels and put under his mattress to keep him elevated when he is sleeping.
Don't keep feeding him. Jack would cry his hungry cry after he would spit up his whole bottle and I would think he's hungry, I can't deprive him. The milk feels good going down but then it just mixes with the acid in his tummy and he will throw it back up. It took me a while and the doc telling me a couple times to stop doing this cuz I just couldn't get past thinking he was hungry.
And, last, hang in there Mama. You will get it figured out and get your own routine of what to do and not to do. GL!!!