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  • Poster presentation
  • Open Access

Evaluation of the inhibitory effect of various drugs / active ingredients on the activity of human diamine oxidase in vitro

  • 1,
  • 2 and
  • 3
Clinical and Translational Allergy20144 (Suppl 3) :P23

  • Published:


  • Histamine
  • Ibuprofen
  • Verapamil
  • Cimetidine
  • Active Ingredient


In this study the influence of active ingredients of certain drugs on the activity of human diamine oxidase (DAO; EC was quantified. DAO is the main enzyme in catabolism of biogenic amines in the intestine. Ingestion of food containing high amounts of biogenic amines in case of reduced activity of DAO leads to an accumulation of histamine which causes symptoms of histamine intolerance. Many drugs are suspected to inhibit DAO-activity, nevertheless, only few scientific data are available to support this thesis.


Therefore, based on a selection of drugs / active ingredients by literature research, the interaction with purified human diamine oxidase is determined and quantified in vitro with an activity test. Various drugs at pharmacologic concentrations were incubated with human diamine oxidase. Inhibition of diamine oxidase activity was calculated as the percentage of inhibition versus control (no inhibitor). To exclude drug formulation specific influences active ingredients (AI) of drug products (D) in pure form were examined.


Chloroquine and clavulanic acid showed greatest inhibition potential on diamine oxidase (> 90%). Cimetidine and verapamil showed inhibition of about 50%. Moderate influence on DAO was caused by isoniazid and metamizole, acetyl cysteine and amitriptyline (>20%). Diclofenac, metoclopramide, suxamethonium and thiamine have very low inhibition potential (<20%). Interestingly cyclophosphamide and ibuprofen displayed no effect on DAO.


Since even levels of about 30% inhibition may be critical, most of the observed substances, can be designated as DAO inhibitors. Other drug components than active ingredients did not affect DAO activity or its interaction with a specific drug.

Authors’ Affiliations

Scientific Association for Research and Education in the field of food-intolerances, Austria
University of Applied Sciences, FH Campus Wien, Molecular Biotechnology Program, Austria
SCIOTEC Diagnostic Technologies GmbH, R&D, Austria


© Leitner et al; licensee BioMed Central Ltd. 2014

This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The Creative Commons Public Domain Dedication waiver ( applies to the data made available in this article, unless otherwise stated.