Effect of phenytoin on bone and vitamin D metabolism

Authors

  • Dr. Rodney D. Bell MD,

    Corresponding author
    1. Division of Neurology, The University of Texas Health Science Center at San Antonio, TX
    2. Department of Neurology and the Section on Mineral Metabolism, Department of Internal Medicine, The University of Texas Health Science Center at Dallas Southwestern Medical School, Dallas, TX
    • Division of Neurology, The University of Texas Health Science Center at San Antonio, 7703 Floyd Curl Dr, San Antonio, TX 78284
    Search for more papers by this author
  • Charles Y. C. Pak MD,

    1. Division of Neurology, The University of Texas Health Science Center at San Antonio, TX
    2. Department of Neurology and the Section on Mineral Metabolism, Department of Internal Medicine, The University of Texas Health Science Center at Dallas Southwestern Medical School, Dallas, TX
    Search for more papers by this author
  • Joseph Zerwekh PhD,

    1. Division of Neurology, The University of Texas Health Science Center at San Antonio, TX
    2. Department of Neurology and the Section on Mineral Metabolism, Department of Internal Medicine, The University of Texas Health Science Center at Dallas Southwestern Medical School, Dallas, TX
    Search for more papers by this author
  • Donald E. Barilla MD,

    1. Division of Neurology, The University of Texas Health Science Center at San Antonio, TX
    2. Department of Neurology and the Section on Mineral Metabolism, Department of Internal Medicine, The University of Texas Health Science Center at Dallas Southwestern Medical School, Dallas, TX
    Search for more papers by this author
  • Michael Vasko PhD

    1. Division of Neurology, The University of Texas Health Science Center at San Antonio, TX
    2. Department of Neurology and the Section on Mineral Metabolism, Department of Internal Medicine, The University of Texas Health Science Center at Dallas Southwestern Medical School, Dallas, TX
    Search for more papers by this author

Abstract

Calcium and vitamin D metabolism were evaluated in 5 adult epileptic patients before and during treatment with phenytoin. Significant decreases occurred in serum concentrations of calcium, albumin, and 25-hydroxycholecalciferol. The decreases in serum calcium paralleled those in serum albumin. Significant increases occurred in serum alkaline phosphatase and 1α,25-dihydroxycholecalciferol, in urinary hydroxyproline, and in the fractional gastrointestinal absorption of calcium. Urinary cyclic adenosine monophosphate and serum parathyroid hormone did not change.

The results suggest that the bone disease resulting from phenytoin therapy may be associated with a deficiency of 25-hydroxycholecalciferol and not of 1α,25-dihydroxycholecalciferol, and that reduced gastrointestinal absorption of calcium or changes in parathyroid function may not be necessary for the development of bone disease.

Ancillary