title: Homocysteine concentrations and methionine loading in patients on antiepileptic drugs.
abstract: OBJECTIVE
  A few reports have shown elevated fasting total plasma homocysteine (tHcy) in patients taking antiepileptic drugs (AEDs). In this study we determined the influence of AEDs on plasma tHcy levels prior to and following methionine loading.
  
  
  METHODS
  Thirty-four patients on different AEDs and 34 matched controls were recruited. Blood samples were drawn prior to and 6 h post-methionine loading (6h-PML).
  
  
  RESULTS
  The patients on AEDs inducing the cytochrome P450 (carbamazepine, phenytoin, phenobarbital, primidone), had higher fasting and 6h-PML plasma tHcy concentrations than the controls (P = 0.01 and P<0.001). Patients on AED inhibiting the cytochrome P450 (valproate [VPA]), had lower 6h-PML p-tHcy concentrations than controls (P = 0.01).
  
  
  CONCLUSIONS
  Our data indicate that not only fasting but also 6h-PML tHcy levels should be determined in order to identify hyperhomocysteinemia among patients on AEDs. Inducer AEDs seem to have an opposite effect than the inhibitor VPA on plasma tHcy, erythrocyte folate and serum folate levels.
authors.affiliation: Department of Internal Medicine, The Central Hospital of Rogaland, Stavanger, Norway.
authors.forename: T
authors.initials: T
authors.lastname: Apeland
authors.forename: M A
authors.initials: MA
authors.lastname: Mansoor
authors.forename: R E
authors.initials: RE
authors.lastname: Strandjord
authors.forename: O
authors.initials: O
authors.lastname: Kristensen
mesh_terms: D000328:Adult; D000368:Aged; D000927:Anticonvulsants / Q000009:adverse effects / Q000494:pharmacology*; D002220:Carbamazepine / Q000494:pharmacology; D016022:Case-Control Studies; D003577:Cytochrome P-450 Enzyme System / Q000187:drug effects*; D004827:Epilepsy / Q000188:drug therapy; D005260:Female; D005492:Folic Acid / Q000097:blood; D006710:Homocysteine / Q000097:blood* / Q000187:drug effects*; D006801:Humans; D020138:Hyperhomocysteinemia / Q000097:blood / Q000139:chemically induced* / Q000201:enzymology; D008297:Male; D008715:Methionine; D008875:Middle Aged; D010634:Phenobarbital / Q000494:pharmacology; D010672:Phenytoin / Q000494:pharmacology; D011324:Primidone / Q000494:pharmacology; D016896:Treatment Outcome; D014635:Valproic Acid / Q000494:pharmacology; D014805:Vitamin B 12 / Q000097:blood
chemical_list: D000927:Anticonvulsants; D006710:Homocysteine; D011324:Primidone; D002220:Carbamazepine; D014635:Valproic Acid; D010672:Phenytoin; D003577:Cytochrome P-450 Enzyme System; D005492:Folic Acid; D008715:Methionine; D014805:Vitamin B 12; D010634:Phenobarbital