An artificial stomach-duodenum model for the in-vitro evaluation of antacids.

To improve the dynamic in-vitro evaluation of the effects of antacids, we have developed the 'artificial stomach' model by adding a 'duodenal reservoir' to receive the gastric emptying flux and simulated bicarbonate secretion, thus constituting an 'artificial stomach-duodenum' model. With this model we measured antacid-induced resistance to gastric acidification, and simultaneously evaluated the effect of antacid activity on the duodenal milieu. The model also permitted evaluation of the antacid effects of proteins (as natural antacids), and of drugs containing aluminium phosphate, alone or combined with magnesium oxide, or aluminium and magnesium hydroxides. At the gastric site, these drugs, as well as the proteins (that is, meat extract), induced a strong resistance to acidification due to the gastric emptying flux and to antacid composition. At the duodenal site, the decrease of the acid load penetrating into the duodenum varied, depending on the efficacy of gastric antacid activity. Duodenal pH was related to the equilibrium between bicarbonate secretion and the emptying of acid load. Proteins and aluminium phosphate induced the same duodenal pH as in the control tests without antacids, but magnesium-containing antacids increased it, thus decreasing bicarbonate consumption. The antacid mechanisms within the stomach, and the fate of antacids in the duodenal milieu, might explain the variation in duodenal pH in response to antacid administration.