Omeprazole‐induced leukopenia. A case report

Summary Background: Omeprazole has been marketed in France since 1989, for the healing of peptic ulcers, erosive reflux oesophagitis, and the Zollinger–Ellison syndrome. However, the drug has been associated with serious adverse reactions, including haemolytic anaemia and acute interstitial nephritis. More recently, an autoimmune syndrome induced by omeprazole has been described. Objective: We present here a clinical history and an in vitro test of cytotoxicity linking leukopenia to omeprazole. Results: A 37‐year‐old woman was hospitalized in the intensive care unit of our hospital with acute pulmonary insufficiency secondary to pneumonia. 72 h after starting omeprazole treatment, a decrease in leucocyte count was observed. The leukopenia was maximal on day 22: total white cell count was 2·1×109/l, and neutrophil count was less than 0·75×109/l. In order to find the cause of this leukopenia, an in vitro cytotoxicity test was performed. The test was positive only when patient neutrophils and patient serum were in the presence of omeprazole. This cytotoxicity seems to be complement‐dependent, as in the presence of heated serum, the omeprazole toxic effect was substantially reduced. Conclusion: This case report suggests that the leukopenia was associated with omeprazole.