Effect of anticonvulsant therapy on serum 25-hydroxyvitamin D level.

Serum 25-hydroxyvitamin D levels in young patients receiving anticonvulsants were assayed. They had neither retardation of physical and psychomotor development nor malnutrition. The patients treated with phenobarbital alone revealed rather high levels of serum 25-hydroxyvitamin D during 2 months after institution of the therapy, then they gradually returned to the normal level by the end of 3 to 5 months and thereafter decreased further, while a marked decrease of serum 25-hydroxyvitamin D levels was observed in patients receiving combined anticonvulsant (phenobarbital, diphenylhydantoin and others) therapy even during 1 to 2 months after initiation of the treatment. Our results suggest that the patients who have combined anticonvulsant therapy will have more tendency to suffer from osteomalacia than those who have phenobarbital alone.