Prevalence of hypocalcemia and elevated serum alkaline phosphatase in patients receiving chronic anticonvulsant therapy.

Residents of an institution for the developmentally disabled in northwest Ohio receiving anticonvulsant therapy for six months or more with phenobarbital or phenytoin or both were studied for the prevalence of hypocalcemia and elevated alkaline phosphatase level. Fifty-six residents were identified. Sixteen (29 percent) were hypocalcemic. Fifteen (27 percent) had elevated serum alkaline phosphatase levels. Twenty-three residents received vitamin D supplementation (400 IU/d) in addition to a normal dietary intake of calcium and vitamin D. The mean serum calcium level was identical (8.65 mg/dL) for those receiving and not receiving additional vitamin D. This study corroborates the findings of prior studies suggesting an association between anticonvulsant usage and mineral and bone abnormalities. The causal nature of this association, its clinical significance, and its management require further investigation.