<chemical> A thiamine antagonist due to its inhibition of thiamine pyrophosphorylation. It is used to produce thiamine deficiency. ... Pharmacological action: antimetabolites. ... Chemical name: Pyridinium, 1-((4-amino-2-methyl-5-pyrimidinyl)methyl)-3-(2-hydroxyethyl)-2-methyl-, bromide, monohydrobromide ... (12 Dec 1998) ...