Zantac question

My nb was put on Zantac and the instructions are to give it to him half an hr before he is going to eat. The problem I am having is that he has no real feeding schedule, sometimes he wants to eat before 3hrs and sometimes he will go 4 or 5. So sometimes he starts to act hungry, I give him his medicine and then he falls asleep and doesn't want to eat in half an hr. Will it hurt his stomach if he doesn't eat after half an hr? Or does it just need to be in him for at least that long to work? I cannot call his Dr. and ask until Monday morning.

If its like adult zantac, u can use it before meals to prevent or u can use it when symptoms start, id just give it to him at the start of feeding or right after.