Rickets associated with long-term anticonvulsant therapy in a pediatric outpatient population

Over a 12-month period, an ambulatory pediatric population receiving long-term anticonvulsants was surveyed for the presence of biochemical and radiologic rickets. There were 74 treated children and 95 matched controls. Elevations of serum alkaline phosphatase activity occurred in 31 of the 74 (42%) treated children (23 of 47 children between 2 and 10 years and 8 of 21 children between 10 and 16 years). This frequency of abnormal values was significantly greater than that which occurred in our control population. Calcium and phosphorus abnormalities were minimal in both treated and control populations. Radiologic rickets occurred in 6 of the 74 (8%) of the treated children and in none of the control population. Neither the severity of the rickets nor the degree of hyperalkaline phosphatasemia were correlated with age of the patient, duration, and/or dose of anticonvulsant therapy.