I don't think that Zantac has any calcium in it. It's just Ranitidine. Just don't buy the souped up versions like Pepcid AC, which do contain it. The plain stuff (like plain old Zantac and plain old Pepcid) have no calcium.

But they are H-2 Blockers. For bad heartburn, you need a PPI, like the list outlaw gave you - the nexium, prevacid, etc.

P.S. Don't take Prilosec OTC, it's very weak. If you want Prilosec, get the prescription version that is actually made by Astrazeneca, or the generic prescription.