Effect of Chronic Anticonvulsant Therapy on Serum 25-Hydroxycalciferol Levels in Adults

Abstract

A survey of 48 adult epileptic outpatients receiving chronic combined phenobarbital and diphenylhydantoin therapy demonstrated significant hypocalcemia in 19 per cent, and significantly decreased serum 25-hydroxycalciferol in 33 per cent of patients, as compared to 38 untreated controls. Similar but less marked changes were seen in a group of 13 patients given chronic therapy with either phenobarbital or diphenylhydantoin alone. Elevation of serum alkaline phosphatase in the patients receiving chronic therapy with either or both of these agents was attributable to increases in both the hepatic and bone isoenzyme fractions. Serum calcium correlated positively with serum 25-hydroxycalciferol in both the patient and the control groups. Serum 25-hydroxycalciferol also correlated positively with vitamin D intake in the patient and control groups, but at any given intake of vitamin D, mean serum levels were lower in the patient group. Lowest serum calcium and 25-hydroxycalciferol levels were seen in the patients with lowest vitamin D intake and least exposure to sunlight. These data suggest that adults receiving chronic combined-drug anticonvulsant therapy should be maintained on supplemented vitamin D intake.