Abstracts

Several antiepileptic drugs (AEDs) have been associated with disorders of bone mineral metabolism, in particular liver enzyme-inducing AEDs including carbamazepine (CBZ). In addition, postmenopausal women are a vulnerable population for bone loss due to estrogen deficiency. We therefore wanted to study the effect of chronic CBZ treatment in a group of postmenopausal women and to compare the results with individually age-matched controls to reduce possible confounding factors regarding age and lifestyle. 13 postmenopausal women with epilepsy on CBZ monotherapy for [gt]4 years and 13 age-matched controls consisting of close female friends of the patients were studied. Blood samples were drawn and serum analyzed for indices of bone metabolism including calcium, phosphate, vitamin D (S-25(OH)Vit D), PTH and thyroid hormones. In addition, bone formation markers including alkaline phosphatase (ALP), bone-specific alkaline phosphatase (bALP) and osteocalcin, and CrossLaps (CTX-1) as a marker for bone resorption were analyzed. ALP and bALP were significantly higher in CBZ treated patients versus controls (61.4 U/l and 22.0 U/l in controls versus 93.2 U/l and 33.4 U/l in CBZ treated women, respectively). Both osteocalcin and CrossLaps were higher in the CBZ treated, although this was not statistically significant (0.95 nmol/l and 0.47 mg/ml in controls compared to 1.13 nmol/l and 0.58 ng/ml in CBZ treated, respectively). Vitamin D was lower in CBZ treated patients vs. controls (67.4 vs 97.7 nmol/l, p=0.039) as was PTH (3.8 vs 5.2 pmol/l, p=0.28). Serum calcium, ionized calcium and phosphor were the same in both groups. Free thyroxine level was slightly, but significantly lower in CBZ treated women. The increase in bALP and ALP indicates an effect of CBZ on bone formation, possibly related to an increased bone turnover as there was an increase in both osteocalcin and CrossLaps. The lack of significance for the last two parameters may be related to the low number of patients. An alternative explanation if turnover should not be increased would be a direct effect on the enzyme bALP of the drug. The observed changes in bone parameters may be associated with CBZ induced disorders of bone metabolism including osteoporosis.