A Prospective Study to Evaluate the Dose of Vitamin D Required to Correct Low 25-Hydroxyvitamin D Levels, Calcium, and Alkaline Phosphatase in Patients at Risk of Developing Antiepileptic Drug-Induced Osteomalacia

摘要

The dose of vitamin D3required to maintain normal serum 25-hydroxyvitamin D levels in epileptic patients was evaluated in a prospective study. Patients were divided into two groups, comprising 14 institutionalized and 18 non-institutionalized subjects; they were taking carbamazepine, phenytoin and phenobarbitone, alone or in combination. The study was divided into a dose titration stage and a further period of assessment on a fixed dose after attainment of normal serum 25-hydroxyvitamin D levels. Seventeen of the 18 non-institutionalized patients achieved normal levels over a period of 12 months; the remaining patient became normal after 15 months. The dose required to achieve normal levels ranged from 400 to 4000 IU/day; three patients required2400 IU. All institutionalized patients achieved normal levels over a period of 12 months, six patients required2400 IU vitamin D3.Raised alkaline phosphatase levels occurred in 11 patients, and reverted to normal in six patients during the initial return of 25-hydroxyvitamin D levels to normal. During the second 12 months, when patients were taking a fixed dose of vitamin D3alkaline phosphatase increased in five patients who had achieved normal levels. During this phase normal 25-hydroxyvitamin D levels were not maintained in five patients. There was a significant seasonal variation of 25-hydroxyvitamin D levels in institutionalized patients, being highest in June and lowest in December. Our findings show that while there was a wide range in the dose required to achieve normal serum 25-hydroxyvitamin D levels—between 400 and 4000 IU/day—78 per cent of patients responded to a dose of 2400 IU/