We just got through with this problem with our daughter. At first I thought it was the formula.. but thought it was weird because it was the most gentle formula. Then the Dr. ordered an ultrasound of her stomach to make sure everything was well-formed.
The culprit?? She eats WAY too much!! She was eating about 2X as much as other kids her age.. and in about half the time. So the Dr. reccommended about how often to feed her, and how much.. and how to fill her up more on cereal. We also try to keep her upright for 20 minutes after she eats.
I was just wondering if it's possible that your daughter is having the same problem because she is gaining weight well.
Also.. she was forcefully spitting up.. and it was projectile by about a foot even. (Reminded me of the exorcist!) But she just had too much milk in her little belly! She is a greedy eater!
I would try this first and use Zantac only as a last resort! Also check with your Dr. first.
I think sometimes rushing to medications only masks the underlying cause of a problem.