A model of an ‘artificial stomach’ for assessing the characteristics of an antacid

SUMMARY A model of an ‘artificial stomach’ has been constructed in order to take into account some of the parameters lacking in conventional in vitro antacid evaluation, namely the interaction between secretory flux and variation in emptying fluxes, the presence of proteins, and the use of human gastric juice instead of an aqueous solution of hydrochloric acid. The ‘artificial stomach’ has two elements, the ‘stomach’ and the pH recording system. The ‘stomach’ includes a ‘gastric’ reservoir receiving secretory flux and is emptied by variable fluxes. Aluminium phosphate gel has been studied in 100 ml of 0.1 n HCl, without and with 1 or 5% meat extracts and also in 100 ml of human gastric juice. The antacid effect of 1 or 5% meat extracts has also been assessed. The antacid effect of aluminium phosphate was characterized by the pH rise of the ‘gastric’ contents, the buffering capacity, and the dilution of gastric contents. These factors were modulated by emptying fluxes. The same characteristics were found when antacid was studied in gastric juice. Proteins exerted a neutralizing effect and modified aluminium phosphate's antacid capacity. A mechanism for buffering capacity by cation aluminium is suggested.