Background Antacids are intended to neutralise the gastric H⁺ ions without interfering with the secretory process. They are generally administered 1 h 30 min after the beginning of a meal.

Given the multitude of antacids on the market, it would be interesting to have quantitative techniques to compare these products and to demonstrate their physiological behaviour.

Purpose To evaluate the behaviour of antacids in the presence of an increasing amount of acidity in vitro and to predict their use depending on the importance and periodicity of gastric acidity in vivo.

Material and methods We studied the in vitro behaviour of six antacid drugs. For this, a therapeutic dose was diluted in 100 ml of distilled water, to which were added increasing amounts of 0.1 N HCl in increments of 0.2 ml every 30 s up to a total acid volume of 25 ml. The variation in pH of the mixture was followed by pH-metry. Each test was repeated three times.

The composition of the studied antacids is shown in table 1.

Results The in vitro behaviour of the six antacid drugs in the presence of increasing amounts of 0.1 N HCl is represented in figure 1.

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Abstract DI-071 Figure 1

Conclusion The proposed method allowed us to quantitatively compare the studied antacids.

According to the results, drug C slightly neutralised stomach acid without an extended effect. It can be prescribed for low and temporary gastric acidity.

Drugs A, B and F had an average and extended neutralising action (pH stabilisation around 5). They can be prescribed for moderate and prolonged gastric acidity.

Regarding drugs D and E which had a strong neutralising and long acting action that stabilised the pH around 7.5, they can be prescribed for high and prolonged gastric acidity.

No conflict of interest.