Valproate therapy: predisposition to bone fracture?

Slipped capital femoral epiphysis in a 5-year-old boy with cerebral palsy on valproic acid and levetiracetam for epilepsy: a case report

This study presents a rare case of unilateral slipped capital femoral epiphysis treated surgically in a 5-year-old boy with cerebral palsy who was born at 27 weeks' gestation and developed grade III intraventricular haemorrhage and periventricular leucomalacia and was on antiepileptic drugs, including valproic acid and levetiracetam for >3 years. The patient had no history of endocrine, renal, and significant familial diseases.

Enzyme-inducing antiepileptic drugs and fractures in people with epilepsy: A systematic review

OBJECTIVE

People with epilepsy (PWE) have an increased fracture risk, independent of seizures. Antiepileptic drugs are thought to increase this risk, particularly those that induce the hepatic cytochrome P450 enzyme system. We aimed to determine whether PWE treated with enzyme-inducing antiepileptic drugs (EIAEDs) have decreased bone mineral density (BMD), or increased fracture incidence, versus those treated with non-EIAEDs.

METHODS

We searched MedLine, EMBase, CENTRAL, and CINAHL prior to November 2014 for all studies comparing fracture risk, or BMD change, in PWE treated for ≥ 1 year with EIAEDs versus non-EIAEDs.

RESULTS

Thirteen observational studies met eligibility criteria. These studies, representing 68,973 adult PWE, were significantly heterogeneous, making meta-analysis impossible. Study results were split, with 5 studies showing decreased BMD in EIAED users, 5 studies showing no effect of EIAED on BMD, 2 studies showing increased fracture incidence in EIAED users, and 1 study showing no difference in fracture risk. The largest study (n = 63,259), which was also the most methodologically rigorous, showed an increased hazard ratio of 9-22% for any fracture, and 49-53% for hip fracture, in EIAED users.

SIGNIFICANCE

The literature is divided regarding the bone effects of EIAEDs; however, current best evidence supports an increased fracture risk in PWE treated with an EIAED compared to those treated with non-EIAEDs. A single article dominated our review, and other large methodologically rigorous studies are needed to confirm or refute its results. Further small studies, with limited power to control for multiple potentially confounding variables, are not likely to help.

Inhibition of Histone Acetylation as a Tool in Bone Tissue Engineering

Our approach to bone tissue engineering is the in vitro expansion and osteogenic differentiation of bone marrow-derived human mesenchymal stem cells (hMSCs) and their subsequent implantation on porous ceramic materials. Current osteogenic differentiation protocols use dexamethasone to initiate the osteogenic process, thus ignoring the multiple signaling pathways that control osteogenesis in vivo. Supporting osteogenesis at multiple stages might further enhance the bone-forming capacity of hMSCs. As reported previously, inhibition of so-called histone deacetylases (HDACs) stimulates osteoblast maturation, and in this report, we investigated whether trichostatin A (TSA), a widely used HDAC inhibitor, can be implemented in bone tissue engineering. We confirmed that TSA treatment of hMSCs results in increased expression of alkaline phosphatase (ALP) with concomitant increase in mineralization. Flow cytometry demonstrated that TSA increases the percentage of ALP-positive hMSCs as well as their average ALP expression level, but the robustness of the response differs between donors. Unfortunately, TSA has a profound negative effect on cell proliferation, so we investigated whether hMSCs respond to TSA after reaching confluence. Confluent hMSCs on tissue culture plastic displayed enhanced ALP expression. Therefore, we seeded TSA-treated hMSCs onto ceramic particles and analyzed ectopic bone formation upon implantation in immune-deficient mice. Unfortunately, TSA-treated hMSCs did not display better bone formation in vivo than control cells. Finally, we observed that TSA treatment strongly enhanced bone formation of ex vivo cultured mouse calvaria, which warrants further exploration of TSA in bone tissue engineering.

Bone mineral status in pediatric outpatients on antiepileptic drug monotherapy

Drug-induced osteopenia has been reported in institutionalized children on chronic antiepileptic drug therapy. The aim of this study was to assess longitudinally bone mineral status in pediatric outpatients on antiepileptic drug monotherapy. The study group consisted of 30 ambulatory children on a normal diet: 15 on valproic acid, 11 on carbamazepine, and 4 on phenobarbital monotherapy. Bone mineral density, serum active vitamin D (1,25-dihydroxyvitamin D), and certain biochemical markers of bone formation (calcium, phosphorus, alkaline phosphatase, intact parathyroid hormone, osteocalcin, calcitonin, and urinary calcium to serum creatinine and urinary phosphorus to serum creatinine ratios) were studied at the beginning of antiepileptic drug monotherapy and at the end of 2 years of treatment. Age- and sex-specific Z-scores of bone mineral density were measured at anterior-posterior L2-L4 by dual-energy x-ray absorptiometry. Drug-induced osteopenia was defined in only two patients (one on carbamazepine and the other on phenobarbital monotherapy), with Z-scores of bone mineral density less than -1.5. Serum levels of active vitamin D and biochemical markers were not significantly correlated with the Z-scores of bone mineral density. We detected a frequency of antiepileptic drug-induced osteopenia of 6.7% in pediatric outpatients after 2 years of monotherapy. However, osteopenia was not attributed to a defect in serum active vitamin D production owing to hyperparathyroidism in children on antiepileptic drug monotherapy.

Antiepileptic drugs and reduced bone mineral density

There is a growing interest in recognizing the association between antiepileptic drugs and reduced bone mineral density. Although the literature regarding this association has been available for more than three decades, the management of this complication remains unclear. We review the relevant literature regarding antiepileptic drugs and reduction in bone mineral density with the aim of developing some guidelines for practical management of this problem. This review focuses on the mechanism of antiepileptic drug-induced bone loss, its recognition, and its management.

Bone health in pediatric epilepsy

Childhood and adolescence are critical periods of skeletal mineralization. Peak bone mineral density achieved by the end of adolescence determines the risk for later pathological fractures and osteoporosis. Chronic disease and medication often adversely affect bone health. Epilepsy is one of the most common neurological conditions occurring in persons under the age of 21. Epilepsy may affect bone in a number of ways. Restrictions of physical activity imposed by seizures; limitations on physical activity resulting from cerebral palsy, frequently present in patients with symptomatic epilepsy; and medications used to treat seizures can all adversely affect bone health. It has long been observed that treatment with phenytoin and phenobarbital can be associated with rickets. More recently, established agents such as carbamazepine and valproate have been shown to be associated with a lowering of bone mineral density. The literature related to bone health in pediatric epilepsy is reviewed, although it should be noted that these data are limited.

Factors influencing bone fractures in severely disabled persons

OBJECTIVES

Factors affecting bone fracture in severely disabled persons were evaluated.

DESIGN

Bone mineral density was measured, and the ratio against the average values in healthy subjects was calculated. Seventy-three subjects were selected from among 113 inpatients with severe mental and physical handicaps. The subjects were classified into four levels of mobility.

RESULTS

Multiple logistic regression analysis was conducted to determine the contribution of variables to the history of bone fracture. Age, medication of sodium valproate, and bone mineral density percentage were found to significantly affect bone fracture.

CONCLUSIONS

Increase of bone mineral density is the protective or preventive factor in bone fracture.

Bone mineral status in ambulatory pediatric patients on long-term anti-epileptic drug therapy

BACKGROUND

For ambulatory pediatric outpatients,reports of abnormalities of bone metabolism associated with anti-epileptic drugs are inconsistent and may be difficult to interpret.

METHODS

The effects of long-term anti-epileptic therapy (mainly valproic acid and/or carbamazepine) on bone mineral status were evaluated in ambulatory epileptic patients(seven males and 11 females) aged 5.5-15.9 years. Bone mineral density (BMD) at the lumbar spine was measured by dual-energy X-ray absorptiometry and markers of bone and mineral metabolism were determined.

RESULTS

The mean BMD was decreased by 9% in our patients relative to the control, and five patients (all males)showed osteopenia, defined as BMD SD scores less than - 1.5. Serum levels of minerals, intact parathyroid hormone and 1alpha,25(OH)2 vitamin D were within the normal ranges. In most patients, serum levels of intact osteocalcin, carboxyterminal propeptide of type I procollagen and pyridinoline cross-linked telopeptide of type I collagen were reduced relative to the corresponding mean control values. The BB genotype by BsmI restriction fragment length polymorphism, associated with low BMD, was not found in our patients. The dietary calcium intake in the osteopenic patients was significantly lower than that of the non-osteopenic patients.

CONCLUSIONS

Our results indicate that long-term anti-epileptic treatment induces a state of decreased bone turnover in children, resulting in osteopenia preferentially in males. The alterations may be due, at least in part, to direct effects of the drugs on bone cells; and that low calcium intake could be an aggravating factor for anti-epileptic-associated osteopenia.