There ae two differences here let me explain, now I dont know all the technically terms of whats is blocking what ect... However this is what I do know...
Antacids don't really "potentiate" or make the narcotics stronger, but they do specific things with the way they are absorbed and metabolized with in the body and different antacids work differently to do this depending on the ROA (route of administration) and perceivably, it may seem as though your getting a stronger dosage.
For example, and this works on any narcotic but mostly the morphine based...
Tums or chewable anti acids taken roughly 30-45 minutes prior to Oral ingestion of the narcotic will lower the acid in the stomach which will slow the breakdown and digestion of the narcotic through first pass metabolism. Meaning that when you swallow the pill, less will be removed by the digestion process allowing more of the drug to enter your bloodstream. But again this only works for the drugs that are swallowed only...
The second is Tagement, if you take that about the same time, around 45 minutes prior to any ROA of the narcotic has the potential to block the enzymes in the liver that break down the morphine to remove it from you system. That means that if you are snorting, plugging, railing, whatever the drug, the tagament will help keep more of it in your system for a longer period of time as the liver doesn't produce as much of the enzymes responsible for breaking them down so you potentially can stay high for longer. Now I did read in the box of tagament that this is mostly based on the morphine type narcotics, I dont know about others. Infact the tagament drug info warns of potential overdose of those drugs if you take the tagament with them continually.
So the ROA and the type of anti acid is what makes the difference..
Oral - Narc + Tums (t -45) + tagament (t -45) = potentially longer high
Any other ROA and this step is useless, it must be oral administration for the tums to do anything useful.
All ROA's - Narc + tagement (t -45) = potentially longer high (tums will have no effect here as your not swallowing the drug)
There is a thread somewhere are this site I believe that goes into much greater technical explanations, but this is my simplified version.
Hope it was helpful and you understand that the ROA and the anti acid is what makes the difference.