The small antacid effect in Gaviscon Advance liquid (if you are buying the UK version) is from 200 milligrams of potassium bicarbonate. It is a very low dose and will not neutralize much acid. To put it in perspective, a single tablet of Tums has 750 milligrams of calcium, and the recommended dose is 2-4 tablets. There is no "rebound" from this like there is from PPIs or H2 blockers. The effect does wear off after a few hours, but it is essentially just an alkaline substance used to counteract an acid.
The potassium bicarbonate is really in there to activate the sodium alginate, causing it to bubble up and form the raft on top of your stomach contents. Kind of like oil on top of water. They don't mix. That too goes away after a few hours, but it should be there long enough to accompany the stomach contents out. But it may not be as effective at night as it is during the day unless you are very diligent about
not lying down until 3-4 hours after your last food or drink (especially drink). When you go horizontal, the raft goes horizontal with you, exposing the esophagus to what's underneath.
I know you have the head of your bed raised, but you would have to sleep standing up to completely avoid this. So the time between last meal and lying down becomes the critical factor.
Post Edited (rjdriver) : 3/3/2014 4:12:25 PM (GMT-7)