Influence of chronic omeprazole treatment on gastric endocrine function.

The influence of a 4-week treatment with the substituted benzimidazole omeprazole (20 mg daily) or placebo on gastric endocrine function was tested in healthy male volunteers. Compared with placebo-treated subjects basal serum gastrin levels were slightly but significantly increased after treatment with omeprazole from 10 to 22 pg/ml (medians; P less than 0.05) but returned to pretreatment values after 2 weeks recovery (9 pg/ml). Antral gastrin tissue concentration increased and was still elevated after recovery; however, antral gastrin concentrations also increased in placebo controls, and increments immediately after cessation of omeprazole treatment (2.58 micrograms/g; median) were not significantly over control values (1.92 micrograms/g; P greater than 0.1). Postprandial gastrin release, basal and food-stimulated insulin release, antral somatostatin concentration, and volume densities of antral G and D cells were unaffected. It is concluded that, due to incomplete inhibition of gastric acid secretion at the omeprazole dose studied, only slight effects on the endocrine stomach are to be expected after 4 weeks of administration of omeprazole.