Effect of carbamezapine and valproic acid on bone mineral density, IGF-I and IGFBP-3

To examine the effect of carbamezapine and valproate on bone mineral density (BMD), IGF-I and IGFBP-3 levels in children.The effects of at least 2 years valproic acid and carbamazepine therapy on BMD were evaluated in a cross-sectional and retrospective study. All children were ambulatory, prepubertal, and had normal activity and nutritionally adequate diets. Ambulatory epileptic patients were divided into two groups. Thirty-three patients (group 1; 17 boys, 16 girls; mean age: 8.8 +/- 2.0 years) were treated with valproic acid and 33 patients were treated with carbamazepine (group 2; 20 boys, 13 girls; mean age: 9.7 +/- 1.6 years). The control group consisted of 22 healthy children (13 boys, 9 girls; mean age: 8.9 +/- 2.3 years), who were age- and sex-matched with the patient groups. Children with metabolic bone disease, growth and neurological impairment, signs of malnutrition, or any chronic disease were excluded from the study.BMD values at lumbar spine in both the carbamazepine (-1.69 +/- 0.85 mean L1-4 BMD z-scores, mean 35.5 +/- 12.8 months treatment, and 19,478.6 +/- 6,301.3 mg/kg cumulative dose) and valproic acid (-1.28 +/- 0.80 mean L1-4 BMD z-scores, mean 33.7 +/- 15.0 months treatment, and 22,852.4 +/- 12,477.4 mg/kg cumulative dose) groups were significantly lower than that of the control group (-0.23 +/- 0.87 mean L1-4 BMD z-score). Serum ALP and PTH levels were significantly higher in the carbamazepine-treated group (65.4 +/- 21.1 pg/ml, 767 +/- 267 U/l, respectively) than those of the valproic acid-treated (39.1 +/- 12.8 pg/ml, 561 +/- 166 U/l, respectively) and control groups (36.3 +/- 4.9 pg/ml, 487 +/- 82 U/l, respectively). Serum 25-hydroxyvitamin D of the carbamazepine-treated group (9.8 +/- 3.2 microg/l) was significantly lower than the other groups (15.1 +/- 3.5, 16.6 +/- 4.7 microg/l, respectively). There were eight and 13 patients with plasma intact PTH above reference values in groups 1 and 2, respectively. Valproic acid and carbamazepine therapy results in a hyperparathyroid state and altered vitamin D metabolism, respectively.BMD values at lumbar spine were significantly reduced in both carbamezapine and valproic acid treated groups. Valproic acid and carbamazepine therapy do not change IGF-I and IGFBP-3 levels. Altering the hepatic conversion of vitamin D may be the mechanism of carbamazepine-associated reduction in BMD, but the mechanism of decreased BMD in valproate therapy remains unclear.