Background: Little is known about the best regimen of omeprazole 40 mg/day for suppressing gastric acid and distal esophageal acid exposure. In addition, the relationship between the level of serum gastrin and gastric pH and this therapy is still uncertain.
Methods: Nineteen healthy male volunteers (mean age 25 yr) had a baseline fasting serum gastrin and 24-h ambulatory combined distal esophageal and gastric pH monitoring. Subjects underwent a 7-day course of each of three specific regimens of omeprazole 40 mg (20 mg b.i.d., 40 mg qAM, 40 mg qPM) with repeat pH and gastrin on day 6. Meals and activity patterns were constant for each subject during the test series. Medications were taken before meals.
Results: All dosing regimens caused significant (p < 0.01) acid reduction compared with baseline in both the stomach and the distal esophagus. There was no significant difference in the amount of acid exposure (time pH < 4) among the three dosing regimens in the esophagus and between qAM and qAM dosing in the stomach. However, b.i.d. dosing gave better (p < 0.05) gastric acid suppression compared with single daily dosing in 15 of 19 subjects. When the baseline was compared with all regimens of omeprazole 40 mg, there was a significant difference with both the serum gastrin (p < 0.01) and the percentage time gastric pH was < 4 (p < 0.01). The correlation between change in serum gastrin and change in percentage time gastric pH was < 4 was poor (r = 0.26).
Conclusions: Divided dosing of omeprazole 20 mg b.i.d. provides superior gastric acid suppression to either once a day regimen of omeprazole 40 mg in most individuals. Serum gastrin levels do not correspond well to gastric pH, necessitating the use of gastric pH monitoring to accurately determine the response to gastric acid suppression.