Homocysteine concentrations and methionine loading in patients on antiepileptic drugs

(C) Munksgaard 2000. Objectives - 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. Material and 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 Gh-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.