Serum calcium balance during early phase of diphenylhydantoin therapy.

The timing of anticonvulsant-induced disturbances of calcium metabolism was investigated in ten epileptics before diphenylhydantoin therapy and during it for up to three years. There was a significant decrease in average serum calcium and an increase in average serum alkaline phosphatase one month after the commencement of the therapy, these values remaining constant thereafter. Decreased serum inorganic phosphate and elevated hydroxyproline levels were also seen in the patients during the followup. At any time after the start of the drug therapy, 10 to 40 per cent of the patients had abnormalities in one or more of these parameters. The findings suggest that prophylactic therapy with vitamin D is indicated from the earliest phase of anticonvulsant therapy to prevent the development of bone disease.