Medications that Block Histamine Catabolizing Enzymes
Medications that Block Diamine Oxidase:
Medications that Block Histamine N-Methyl Transferase:
Medications that Might Enhance Histamine Catabolism:
—Inhibition of histamine-N-methylation by some antihistamines. K.J. Netter, K. Bodenschatz , In vivo blocking of HMT by antihistamines of the benzimidazole and ethylene diamine types such as clemizole and tripelennamine wasn't achieved because of toxicity of high doses required for HMT inhibition.
—Inhibition of in vivo histamine metabolism in rats by foodborne and pharmacologic inhibitors of diamine oxidase, histamine N-methyltransferase, and monoamine oxidase. Hui JY, Taylor SL., When [14C]histamine was administered orally to rats, an average of 80% of the administered radioactivity was recovered in the urine at the end of 24 hr. About 10% of the total dose was excreted via the feces. Analysis of 4-hr urine samples found imidazoleacetic acid to be the predominant metabolite (60.6%), with N tau-methylimidazoleacetic acid (8.6%), N tau-methylhistamine (7.3%), and N-acetylhistamine (4.5%) to be the minor metabolites. Histamine metabolism was inhibited by simultaneous oral administration of aminoguanidine, isoniazid, quinacrine, cadaverine, putrescine, tyramine, and beta-phenylethylamine. The administration of inhibitors resulted in an increased amount of unmetabolized histamine and a decreased amount of metabolites reaching the urine. Pharmacologic inhibitors were found to be more potent and have a longer duration of action than foodborne ones. The inhibitors could potentiate food poisoning caused by histamine by inhibiting its metabolism.
—Structural basis for inhibition of histamine N-methyltransferase by diverse drugs. Horton JRSawada K Nishibori M, Cheng X., The histamine receptor H1 antagonist diphenhydramine, the antimalarial drug amodiaquine, the antifolate drug metoprine, and the anticholinesterase drug tacrine (an early drug for Alzheimer's disease) are surprisingly all potent HNMT inhibitors, having inhibition constants in the range of 10-100nM. We have determined the structural mode of interaction of these four inhibitors with HNMT. Despite their structural diversity, they all occupy the histamine-binding site, thus blocking access to the enzyme's active site.