title: Phenytoin-folate interactions: differing effects of the sodium salt and the free acid of phenytoin.
abstract: Chronic phenytoin (PHT) treatment has long been associated with folate deficiency. It has been suggested that pH changes in the gut associated with PHT ingestion may be responsible for decreased folate uptake either by direct inhibition of folate transport into the intestinal mucosa or by inhibition of folate conjugase activity. To examine these possibilities, rats were gavaged chronically with PHT using either the sodium salt (NaPHT) or the free acid (HPHT) in the presence of folic acid as the dietary source of folate. The NaPHT caused a greater depletion of folate in the liver and brain and a significant increase in methylenetetrahydrofolate reductase activity in the liver. The HPHT caused a significantly decreased weight gain over the 8 weeks of treatment and resulted in a much higher liver PHT concentration and a slightly lower plasma PHT concentration. These data support the hypothesis that PHT-induced changes in pH in the gut affect the enterohepatic circulation of folate.
authors.affiliation: Medical Research, VA Medical Center, Augusta, Georgia 30910.
authors.forename: G F
authors.initials: GF
authors.lastname: Carl
authors.forename: M L
authors.initials: ML
authors.lastname: Smith
mesh_terms: D000818:Animals; D001923:Brain Chemistry / Q000187:drug effects; D004195:Disease Models, Animal; D004764:Enterohepatic Circulation / Q000187:drug effects; D005492:Folic Acid / Q000032:analysis / Q000378:metabolism* / Q000493:pharmacokinetics; D005494:Folic Acid Deficiency / Q000139:chemically induced; D005744:Gastric Acid / Q000378:metabolism; D006801:Humans; D006863:Hydrogen-Ion Concentration / Q000187:drug effects; D008099:Liver / Q000737:chemistry / Q000187:drug effects; D010672:Phenytoin / Q000009:adverse effects / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D015430:Weight Gain / Q000187:drug effects
chemical_list: D010672:Phenytoin; D005492:Folic Acid