EFFECT OF OMEPRAZOLE ON INTRAGASTRIC BACTERIAL COUNTS, NITRATES, NITRITES, AND N-NITROSO COMPOUNDS

Previous studies have suggested that profound inhibition of gastric ac id secretion may increase exposure to potentially carcinogenic N-nitro so compounds. The aim of this study was to find out if the proton pump inhibitor omeprazole (20 mg daily) is associated with increased conce ntrations of potentially carcinogenic N-nitroso compounds in gastric j uice. The volume of gastric contents, number of bacteria, and concentr ations of nitrates, nitrites, and N-nitroso compounds was determined i n gastric aspirates obtained after an overnight fast in 14 healthy vol unteers (7M:7F) after one week of treatment with placebo, and one and two weeks' treatment with omeprazole. Median bacterial concentrations were 1.0 X 10(4) (range 5.0 X 10(3)-5.0 X 10(6)) colony forming units (CFU)/ml after one weeks' treatment with placebo and increased signifi cantly to 4.0 x 10(5) (0-3.3 x 10(7)) CFU/ml after two weeks' treatmen t with omeprazole (p<0.05). A similar increase was seen in the concent ration of nitrate reducing bacteria. There was no difference in the vo lume of gastric aspirates after treatment with omeprazole when compare d with placebo (65 (29-155) ml v 42 (19-194) ml). The concentration of N-nitroso compounds was 0.13 (0-1.0) mumol/l after two weeks of omepr azole, which was not significantly different from that seen with place bo (0.15 (0-0.61) mumol/l). There was also no increase in the concentr ations of nitrates or nitrites. It is concluded that omeprazole (20 mg once daily) for two weeks in healthy volunteers is associated with ga stric bacterial proliferation but does not increase concentrations of N-nitroso compounds.