Anticonvulsant Therapy and Vitamin D

Excerpt

To the editor: The excellent article by Dr. Sotaniemi and colleagues, "Radiologic Bone Changes and Hypocalcemia with Anticonvulsant Therapy in Epilepsy" (Ann Intern Med 76:389-394, 1972), was read with interest. With regard to the questions the authors raise concerning the pathogenesis of osteomalacia after anticonvulsant therapy, it should be noted that chronic phenobarbital therapy in humans has produced a marked decrease in plasma vitamin D₃-³H (D₃-³H) half-life, with increased formation of polar, apparently biologically-inactive, vitamin D metabolites (1). This increased catabolism appears to occur in the liver, since in vitro incubation of D₃-³H with liver microsomes from phenobarbital-treated rats results