The effect of carbamazepine and valproate monotherapy on bone mineral density was measured by dual-energy x-ray absorptiometry in 27 healthy children and 26 children with uncomplicated idiopathic epilepsy treated with an anticonvulsant for longer than 18 months at the Memorial University of Newfoundland, St John’s, Canada. Mean serum trough levels for carbamazepine and valproate were 6.88 and 72.04 mcg/ml, respectively. Dietary calcium was similar in treated and control patients. Valproate caused a 10 to 14% reduction in bone mineral density, and the percent reduction was related to treatment duration. Carbamazepine had no significant effect on bone mineral density. 
COMMENT. Valproate but not carbamazepine causes reduction in mineralization of bone in children and adolescents, aged 8 to 20 (mean 15 years) and may predispose to osteoporotic fractures. The mechanism of decreased mineralization is undetermined. The authors suggest possible preventive measures including calcium dietary supplements, weight-bearing exercises, and avoidance of smoking.