• P A Galindo, J Borja, F Feo, E Gómez, R García, M Cabrera, and C Martínez.
• Allergy Section, Hospital Complex, Ciudad Real, Spain.
• Ann. Allergy Asthma Immunol. 1999 Jan 1;82(1):52-4.

BackgroundOmeprazole is a non-competitive inhibitor of the parietal cell enzyme H+-K--adenosine triphosphatase. To date, two cases of angioedema and urticaria and two cases of anaphylaxis from omeprazole have been published.ObjectiveTo report a new patient with omeprazole-induced anaphylaxis demonstrated by skin tests and increased serum tryptase levels.Methods And ResultsElevated serum tryptase levels (5.1 U/L) were detected 6 hours after the onset of the anaphylaxis. Skin intradermal tests were positive with omeprazole i.v. (4 mg/mL), omeprazole capsules diluted in saline serum (20 mg/ mL), and lansoprazole (30 mg/mL). Serum specific IgE anti-omeprazole was negative.ConclusionsAccording to the elevated serum tryptase levels and the positive skin test results, anaphylaxis was due to use of omeprazole. We think the adverse reaction to omeprazole was induced by an IgE-mediated hypersensitivity mechanism to omeprazole itself and not to a metabolite. We have also demonstrated crossreactivity, at least by skin tests, between omeprazole and lansoprazole.

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