The site of action of a high-power Al-Mg antacid gel (buffering capacity 70 meq/10 ml) and its interaction with food was examined in 10 healthy volunteers. Combined pH-metries in antrum and corpus were performed in each volunteer on four occasions. In a randomized study design, antacid or placebo were given 1 hr after either a protein or a carbohydrate pancake, of which only the former had any acid-buffering capacity. Before the meal, pH was higher in the antrum than in the corpus (median antrum: 3.2, corpus 1.5). In the corpus, a protein pancake but not a carbohydrate pancake raised the pH (median pH after protein pancake: 3.5; after carbohydrate pancake: 1.4). In the antrum, the protein pancake had no effect, but the carbohydrate pancake decreased the pH (median pH after protein pancake: 3.1; after carbohydrate pancake: 2.0). The antacid had no effect in the corpus after either pancake. It raised intraluminal pH markedly in the antrum after a carbohydrate pancake (median antral pH before antacid: 2.0; after antacid: 3.3), whereas its effect in the antrum was weak after a protein pancake. In vitro experiments were conducted to explain the in vivo results: in contrast to a carbohydrate pancake, a protein pancake reduced the buffering capacity of the antacid by direct interaction. In conclusion, the effect of an antacid gel on intragastric pH is predominantly localized in the antrum and is attenuated in the presence of proteins.(ABSTRACT TRUNCATED AT 250 WORDS)
Adult Antacids