Folate, homocysteine and methionine loading in patients on carbamazepine

Objectives - Some antiepileptic drugs (AEDs) are associated with low levels of serum (S-FA) and erythrocyte folate (E-FA) and high levels of plasma total homocysteine (p-tHcy). We have explored the concentrations of S-FA, E-FA and p-tHcy in patients on carbamazepine (CBZ). The methionine loading test was applied for better assessment of mildly impaired homocysteine metabolism. Material and methods - The study comprised 42 adult patients on CBZ and 42 matched healthy controls. Blood samples were drawn prior to and 6 h post methionine loading (6 h-PML) (0.1 g/kg body weight). Results - The patients on CBZ had significantly lower concentrations of fasting S-FA and E-FA than the controls (P = 0.0004, P = 0.003, respectively). Fasting and 6 h-PML p-tHcy concentrations were significantly higher in the patients than in the controls (P = 0.03 and P = 0.0001, respectively). The methionine loading test identified additional patients with hyperhomocysteinemia undetected by fasting p-tHcy. Conclusion - CBZ therapy may be associated with low folate and high p-tHcy levels.