When an oral product, usually a tablet or capsule, is taken, it almost instantaneously goes into the stomach (gastric compartment). The gastric environment can be described as an acidic (mostly HCl based) aqueous solution (pH 1 to 3) with a churning (moving and mixing) process. Assuming a disintegrating type product, the product will disintegrate into solid particles/aggregates. Once in this disintegrated form, the drug will behave exactly like granules in dilute acidic solution with mild stirring in a beaker or flask. In case of non-disintegrating type tablets, the drug will be released or leaked-out from the unit into the acidic solution.
If the drug is soluble then it will move into the intestine as a solution, otherwise as a slurry or suspension. The important thing to note here is that with some delay, the drug will move into the intestinal component. Here the acid solution or suspension will be mixed with a strong buffer turning the acidic liquid to basic, more accurately less acidic in the pH range of 5 to 7. Considering the variability in contents and the rates of entrance of the two solutions i.e. slurry from the stomach and the buffer from pancreas, it is almost impossible to accurately determine or establish the pH of the soup. However, it is a well-established fact that pH in this area of intestine ranges between 5 and 7. Therefore, for all practical and standardization purposes one can use pH of 6, an average of 5 and 7.
