Background & Aims: This study evaluated the effect of long-term gastric aci
d suppressive therapy with omeprazole on intragastric levels of carcinogeni
c N-nitrosamines and related parameters. Methods: Forty-five patients on lo
ng-term omeprazole medication (mean, 35 months) and :13 healthy subjects wi
thout medication participated. Volatile N-nitrosamines were determined in g
astric juice and urine. Intragastric pH, nitrite, nitrate, and H. pylori st
atus were determined. DNA isolated from gastric biopsy specimens was analyz
ed for precarcinogenic alkyl-DNA adducts. Results. The intragastric pH in p
atients was significantly higher compared with controls (P = 0.0001). Gastr
ic nitrite levels in patients were nonsignificantly higher. There was no di
fference in total levels of intragastric volatile N-nitrosamines between pa
tients and controls, however, urinary N-nitrosodimethylamine excretion was
higher in patients (P = 0.001). On omeprazole, Helicobacter pylori-positive
vs. -negative patients had a nonsignificantly higher intragastric nitrite
level and higher urinary N-nitrosodimethylamine excretion. No alkyl-DNA add
ucts could be detected in gastric epithelium. Conclusions: Increased intrag
astric pH caused by long-term treatment with omeprazole does not result in
increased intragastric levels of nitrite and volatile N-nitrosamines. The s
ignificantly higher urinary N-nitrosamine excretion implies the risk of inc
reased endogenous formation of N-nitrosamines during long-term omeprazole t
reatment. This risk may be higher in H. pylori-positive patients.