Mechanism for reduction of serum folate by antiepileptic drugs during prolonged therapy.
To determine whether the induction of liver enzymes by antiepileptic drugs play a major role in folate depletion, serum concentrations of folate were measured in age-matched control subjects without anemia and in epileptic outpatients who were being treated with a single antiepileptic drug. Two of the four drugs being administered were enzyme inducers. A protein binding radioassay was used to measure folate levels. Compared with serum folate levels in controls (5.14 +/- 1.88 ng/ml: n = 74), mean serum folate levels were reduced significantly in patients treated with phenobarbitone (3.91 +/- 1.73 ng/ml, p < 0.01: n = 33) and carbamazepine (3.85 +/- 1.02 ng/ml, p < 0.01: n = 36): both of which are enzyme-inducing agents. In contrast, patients treated with the non-enzyme-inducer valproate (5.39 +/- 1.71 ng/ml: n = 41) or zonisamide (5.59 +/- 2.60 ng/ml: n = 25) exhibited serum folate levels that did not differ significantly from values in controls. Findings showed that a reduction in serum folate is associated with the induction of enzymes by antiepileptic drugs. Thus, the induction of microsomal liver enzymes may be critical to the depletion of folate by antiepileptic drugs.
Kishi
T
T
Department of Pediatrics, National Kure Hospital, Hiroshima, Japan.
Fujita
N
N
Eguchi
T
T
Ueda
K
K
D000293:Adolescent; D000328:Adult; D000927:Anticonvulsants / Q000008:administration & dosage / Q000009:adverse effects* / Q000097:blood; D002220:Carbamazepine / Q000008:administration & dosage / Q000009:adverse effects / Q000097:blood; D002648:Child; D002675:Child, Preschool; D003710:Demography; D004827:Epilepsy / Q000097:blood / Q000188:drug therapy*; D005260:Female; D005492:Folic Acid / Q000097:blood*; D005494:Folic Acid Deficiency / Q000139:chemically induced*; D006801:Humans; D007223:Infant; D007555:Isoxazoles / Q000008:administration & dosage / Q000009:adverse effects / Q000097:blood; D008297:Male; D010634:Phenobarbital / Q000008:administration & dosage / Q000009:adverse effects / Q000097:blood; D013997:Time Factors; D014635:Valproic Acid / Q000008:administration & dosage / Q000009:adverse effects / Q000097:blood; D000078305:Zonisamide
D000927:Anticonvulsants; D007555:Isoxazoles; D002220:Carbamazepine; D000078305:Zonisamide; D014635:Valproic Acid; D005492:Folic Acid; D010634:Phenobarbital