Table 3.

Effects of drugs and antithiamine agents on thiamine^{32,34,41,54,59,61,68,71}

Drug family/antithiamine agent	Drug	Effect on thiamine
Alcohol	Ethanol	Decreased intestinal thiamine transport
Antibiotic	Metronidazole	Production of thiamine antimetabolites
Antibiotics	β-lactams, aminoglycosides, trimethoprim, quinolones	Decreased production of thiamine by intestinal microbiota
Chemotherapy	5-fluorouracil	Decreased production of hepatic thiamine, decreased TKT activity
Polyphenols (coffee, tea)	Caffeic acid, tannic acid	Oxidation of thiazole ring
Diuretics	Furosemide, thiazides	Increased renal excretion, decreased intestinal absorption
Flavonoids	Quercetin, rutin	Oxidation to thiamine disulfide
Food preservatives	Sulfites	Disruption of thiamine methylene bridge
Oral hypoglycemics (biguanide)	Metformin	THTR2 inhibitor, prevents active transport of thiamine
Proton pump inhibitors	Omeprazole	Inactivation of PDH, erythrocyte transketolase, and H/K ATPase

Abbreviations: H/K ATPase, hydrogen/potassium adenosine triphosphatase; PDH, pyruvate dehydrogenase; TKT, transketolase; THTR2, thiamine transporter 2.