Abstracts

Rationale: Bone metabolism abnormalities are commonly observed in patients taking antiepileptic drugs (AED). Magnesium (Mg) is a cofactor for the enzyme cytochrome P450 (CYP450), an enzyme responsible for the metabolism of many AEDs and activation of the vitamin D metabolite 25-dihydroxyvitamin D (25OHD). Patients taking AEDs may be deprived of body Mg stores. Poor Mg stores may impair both osteoblastic activity and activation of 25OHD, further increasing risk of bone loss. The usage of AEDs may also impair vitamin D metabolism, thereby attenuating the ability of 25OHD to suppress PTH production  and leading to higher bone-turnover and systemic inflammation. The objective of this study is to determine the associations between Mg status, bone mineral density (BMD), bone regulating nutrients, bone turnover markers and markers of inflammation in adults on AED. Methods: A total of 7 men and women currently taking antiepileptic medications participated in this study. Blood samples were obtained for analyses of serum ionized Mg, 25-hydroxyvitamin D (25OHD), parathyroid hormone, c-terminal telopeptide and makers of inflammation. Bone mineral density (BMD) (total body BMD, L2 – L4 BMD, mean hip BMD, non-dominate wrist 33% BMD) were measured using dual energy x-ray absorptiometry (DXA). Results: The mean, standard deviation and range age of this cohort was 45.4 ± 15.9 (26.0, 63.0) years, body mass index was 26.5 ± 4.6 (19.5 ± 33.6) kg/m², serum 25OHD concentration was 34.6 ± 14.2 (23.24, 60.01) ng/mL, serum PTH concentration was 68.4 ± 17.5 (53.22, 99.9) pg/mL and serum ionized Mg concentration was 0.54 ± 0.04 (0.50, 0.60) mmol/L. Serum ionized Mg concentration was significantly and positively associated with serum osteocalcin concentration (r = 0.846, p = 0.034), while negatively associated with total body BMD (r = -0.833, p = 0.040). There were no statistically significant relationships between serum 25OHD and serum PTH concentration with any variables. Conclusions: The classic negative relationship between 25OHD and PTH may be altered in patients on AED. Future research should focus on investigating the potential benefits of Mg therapy on restoring the normal 25OHD/PTH axis in patients on AEDs. Funding: Not applicable