Reduced 2,25-dihydroxyvitamin D and 24,25-dihydroxyvitamin D in epileptic patients receiving chronic combined anticonvulsant therapy.

Thirty-one adult epileptic outpatients on chronic combined anticonvulsant therapy were investigated. Eleven patients took vitamin D2 supplementation 400-1200 IU/day as multivitamin tablets. Mean serum calcium and renal calcium excretion were reduced. Serum alkaline phosphatase and urinary hydroxyproline excretion were increased. Forearm bone mineral content was reduced. Serum concentrations of 25-hydroxyvitamin D (25-OHD), 24-25-dihydroxyvitamin D (24,25-(OH)2D) and 1,25-dihydroxyvitamin D (1,25-(OH)2D) were reduced (p less than 0.001). A positive correlation was found between the serum 25-OHD and 24,25-(OH)2D concentrations (p less than 0.05) with the highest levels in those receiving vitamin D2 supplementation (p less than 0.01). Serum 1,25-(OH)2D correlated positively with renal calcium excretion (r = 0.65, p less than 0.001) suggesting that the intestinal calcium absorption in epileptic patients depends on 1,25-(OH)2D levels.