Background: Proton pump inhibitors including omeprazole and lansoprazole inhibit gastric acid secretion by selectively and non-competitively inactivating the H+, K+ ATPase molecules of the parietal cell, but possibly only those that are actively secreting acid. This might imply that stimulation of acid secretion by a meal is necessary for optimal inhibition of gastric secretion.
Aim: To quantify and compare the effect on daytime gastric acidity of omeprazole 20 mg or lansoprazole 30 mg daily taken 15 min before breakfast, with that of the same drug taken without a meal.
Methods: Twenty-one healthy volunteers were randomized to receive either omeprazole or lansoprazole. They were given the drug for two separate periods of 7 days in randomized order and at least 7 days apart. During one period the study medication was taken before breakfast; during the other it was taken at the same hour, but with no meal until 12:00 hours. Lunch was standardized. On day 7, intragastric pH-metry was performed, starting at 08:00 hours. Tracings were analysed for the 8-h period from 08:00 hours until 16:00 hours with regard to percentage time for which gastric pH was below 4.0 and 3.0, and median gastric pH. Tracings were also analysed after removing the 1 h breakfast period, to exclude the buffering effect of the meal.
Results: When taking the drug with breakfast, the median percentage time for which gastric pH < 4.0 was 17.2 (interquartile range 4.6-45.5), compared with 42.0 (interquartile range 31.4-48.8) when taken without food (P=0.01). Fifteen subjects had better control of gastric acidity when the medication was taken with breakfast. A pH threshold of 3 and median pH showed similar differences. When the breakfast period was removed, the differences were no longer statistically significant.
Conclusions: When therapy with omeprazole or lansoprazole is indicated, medication should be taken before a meal for optimal control of daytime gastric acidity.