Prolonged effect of omeprazole on the 14C-urea breath test.

OBJECTIVES We investigated omeprazole's effect on 14C-urea breath testing. We also determined the duration of omeprazole's effect on the breath test. Finally, we studied whether effects on breath testing were dose dependent. METHODS Fifty-seven employees and outpatients were screened for Helicobactor infection. Those positive for serology, CLO, or histology were asked to undergo baseline breath testing. Those with a positive breath test took omeprazole 20 mg/day for 14 days followed by repeat breath testing, 1, 3, and 5 days after therapy. Subjects with persistently positive breath tests despite omeprazole 20 mg/day were asked to take omeprazole 20 mg b.i.d. for 14 days. Repeat breath tests were performed as above. RESULTS Thirteen of 57 had HP infection. Ten of 13 underwent a baseline breath test. Eight of 10 with baseline breath test experienced a significant decrease in expired 14CO2 after omeprazole 20 mg/day. Five of 13 with active HP infection developed a negative breath test after omeprazole. All subjects had a positive breath test within 5 days of stopping omeprazole 20 mg/day. Five of eight with persistently positive breath tests despite omeprazole 20 mg/day took omeprazole 40 mg/day. Four of five developed a significant decrease in 14CO2 excretion after omeprazole. All subjects had a positive breath test within 5 days of stopping omeprazole 40 mg/day. CONCLUSIONS Recent treatment with omeprazole 20 mg/day led to a false-negative breath tests in 38.5%. This effect appeared to be dose dependent and lasted up to 5 days after cessation of omeprazole.