Antacids that might be used:
Antacids like Pepcid, Zantac, Tagamet, Prilosec are intended to change the pH or degree if acidity in the esophagus.

The benefit is to decrease discomfort, inflammation and scarring, but they don’t have a direct effect on reducing regurgitation per se (maybe a secondary one from the above benefits).

The choice seems to vary by vet and patient convenience. However there seems to be some additional benefit with ranitidine (Zantac) in the following way.

One of the things that would be hugely helpful for our megaE pups is if we could speed up the transition of food from their esophagus and stomach into their intestine where it wouldn’t be able to come up. There are meds like Metachlopramide and Cisapride that in humans do so. In dogs they are much less effective because of the specifics of esophagus muscle anatomy. These pro-movement (pro-kinetic) meds are still used (honestly because we are desperate).

Zantac, unlike all the other antacids, may possess a small degree of prokinetic effect as well. So often it’s a good choice if possible, with the hope that it might offer this small potential benefit.

Prolonged use of antacids as commented by Dr Kathy Morris:
Even in human medicine there is controversy in long term (longer than 2 weeks) use of any acid neutralizers. Some megae dog owners feel that their pets do better WITH acid neutralizers, but, it is probably best not to use it long term if at all possible. I don’t remember saying that Zantac should not be used in dogs; in fact, besides the acid neutralization effect it can have some pro-motility activity. Tums and Tagamet are the ones that are pretty useless. Acid neutralizers may best be used with the initial diagnosis of megae as that is when there is more of a likelihood of esophagitis. Once an adequate management protocol is found for a particular dog, stopping the acid neutralizer may be something to consider. Then, if an owner finds that their pet has increased regurgitation or appetite loss whenever the acid neutralizer is eliminated, THAT particular pet may indeed need it daily.