Aluminum hydroxide gel is an anti gas and acid medication. Magnesium is an acid neutralizer. Neither of these is the actual active ingredient in Gaviscon, although different countries restrict what they can call "active" on the label. The alginic acid is what forms the protective raft on top of your stomach contents, sealing off your throat from acid.
But if you find the above 2 ingredients are what is helping you the most, then you might want to look at anti gas medications like Maalox and similar brands. They commonly contain both of these in one form or another.
It doesn't contain either of these ingredients, but you might also want to try Life Extension Esophageal Guardian as a Gaviscon replacement.
Post Edited (rjdriver) : 8/21/2017 6:16:30 AM (GMT-6)