Epilepsy and bone health in adults.
ABSTRACT Adults taking antiepileptic drugs (AEDs) have an augmented risk for osteopenia and osteoporosis because of abnormalities of bone metabolism associated with AEDs. The increased fracture rates that have been described among patients with epilepsy may be related both to seizures and to AEDs. The hepatic enzyme-inducing AEDs phenytoin, phenobarbital, and primidone have the clearest association with decreased bone mineral density (BMD). Carbamazepine, also an enzyme-inducing drug, and valproate, an enzyme inhibitor, may also adversely affect bone, but further study is needed. Little information is available about specific effects of newer AEDs on bone. Physicians are insufficiently aware of the association between AEDs and bone disease; a survey found that fewer than one-third of neurologists routinely evaluated AED-treated patients for bone disease, and fewer than 10% prescribed prophylactic calcium and vitamin D. Physicians should counsel patients taking AEDs about good bone health practices, and evaluation of bone health by measuring BMD is warranted after 5 years of AED treatment or before treatment in postmenopausal women.
- SourceAvailable from: Xi Emily Zheng[Show abstract] [Hide abstract]
ABSTRACT: Oxidative catabolism of 1α,25-dihydroxyvitamin D(3) [1α,25(OH)(2)D(3)] is mediated by either CYP24A1 or CYP3A4. In this paper, we tested whether induction of CYP3A4 in the LS180 intestinal cell model enhances clearance of 1α,25(OH)(2)D(3) and blunts its hormonal effect on expression of the apical membrane calcium transport protein, TRPV6. Treatment with the hPXR agonist rifampin significantly increased CYP3A4 mRNA content and catalytic activity, but had no effect on CYP24A1 or TRPV6 mRNA content. Pre-treating cells with rifampin for 48h, prior to a 24h 1α,25(OH)(2)D(3) treatment phase, was associated with a subsequent 48% increase in the elimination of 1α,25(OH)(2)D(3) and a 35% reduction of peak TRPV6 mRNA. Introduction of the CYP3A4 inhibitor, 6',7'-dihydroxybergamottin, an active inhibitor in grapefruit juice, reversed the effects of rifampin on 1α,25(OH)(2)D(3) clearance and TRPV6 expression. Over-expression of hPXR in LS180 cells greatly enhanced the CYP3A4 responsiveness to rifampin pretreatment, and elicited a greater relative suppression of TRPV6 expression and an increase in 1α,25(OH)(2)D(3) disappearance rate, compared to vector expressed cells, following hormone administration. Together, these results suggest that induction of CYP3A4 in the intestinal epithelium by hPXR agonists can result in a greater metabolic clearance of 1α,25(OH)(2)D(3) and reduced effects of the hormone on the intestinal calcium absorption, which may contribute to an increased risk of drug-induced osteomalacia/osteoporosis in patients receiving chronic therapy with potent hPXR agonists. Moreover, ingestion of grapefruit juice in the at-risk patients could potentially prevent this adverse drug effect.Biochemical pharmacology 05/2012; 84(3):391-401. DOI:10.1016/j.bcp.2012.04.019 · 4.65 Impact Factor
Article: Antiepileptics and bone health.[Show abstract] [Hide abstract]
ABSTRACT: In recent years there has been increasing evidence suggesting that epilepsy and its treatment can have adverse effects on bone mineralization and calcium metabolism. Many studies have shown a significant reduction in bone mineral density (BMD) and an increased fracture risk in patients treated with enzyme-inducing antiepileptics (phenobarbital, carbamazepine, phenytoin). It is assumed that CYP450-inducing antiepileptic drugs (AEDs) upregulate the enzymes which are responsible for vitamin D metabolism, with the effect of converting 25(OH) vitamin D into inactive metabolites, resulting in reduced calcium absorption with consecutive secondary hyperparathyroidism. Data on bone-specific effects of newer AEDs are limited; nevertheless, alterations of bone metabolism have been reported for oxcarbazepine, gabapentin and, in preclinical studies, for levetiracetam. Prophylactic administration of adequate amounts of calcium and vitamin D is recommended for all patients. For patients with long-term AED exposure, BMD measurement is recommended as part of osteoporosis investigation (especially for patients treated with enzyme-inducing AEDs and where there are major risk factors for fractures). Drug therapy (bisphosphonates) is reserved for the treatment of patients who have a high fracture risk; there are no specific intervention studies available in patients with epilepsy.Therapeutic advances in musculoskeletal disease 10/2011; 3(5):235-43. DOI:10.1177/1759720X11410769
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ABSTRACT: To investigate the effect of topiramate on bone mass and metabolism in premenopausal women with epilepsy. Thirty-six women on long-term (at least 1 year) topiramate monotherapy were compared with 36 women taking carbamazepine, 32 women taking valproate, and 36 age- and sex-matched controls. Subjects completed bone mineral density (BMD) studies. Serum was analyzed for indices of bone metabolism. BMD Z-scores, and serum 25-hydroxyvitamin D and 1alpha,25-dihydroxyvitamin D(3) concentrations did not differ among the groups. Serum calcium concentrations were significantly lower in patients receiving topiramate than in those receiving valproate, and in patients receiving carbamazepine than in those receiving valproate and controls. Patients taking topiramate had lower levels of parathyroid hormone compared with controls and those taking carbamazepine or valproate. Patients receiving topiramate had higher levels of bone-specific alkaline phosphatase and osteocalcin when compared with controls and higher levels of C-terminal telopeptide of type 1 collagen when compared with those taking carbamazepine or valproate. Patients receiving carbamazepine had higher levels of bone-specific alkaline phosphatase compared with controls and those receiving valproate. Serum bicarbonate concentrations were significantly lower in patients receiving topiramate than in the other groups. Our results demonstrate that use of topiramate is associated with lower parathyroid hormone and bicarbonate concentrations along with mild hypocalcemia and increased bone turnover, which suggests that topiramate may have long-term effects on bone.Epilepsia 06/2011; 52(10):1884-9. DOI:10.1111/j.1528-1167.2011.03131.x · 4.58 Impact Factor