The effect of phenytoin on parathyroid hormone stimulated cAMP activity in cultured murine osteoblasts

Markers of bone turnover in patients with epilepsy and their relationship to management of bone diseases induced by antiepileptic drugs

Data from cross-sectional and prospective studies revealed that patients with epilepsy and on long-term treatment with antiepileptic drugs (AEDs) are at increased risk for metabolic bone diseases. Bone diseases were reported in about 50% of patients on AEDs. Low bone mineral density, osteopenia/osteoporosis, osteomalacia, rickets, altered concentration of bone turnover markers and fractures were reported with phenobarbital, phenytoin, carbamazepine, valproate, oxcarbazepine and lamotrigine. The mechanisms for AEDs-induced bone diseases are heterogeneous and include hypovitaminosis D, hypocalcemia and direct acceleration of bone loss and/or reduction of bone formation. This article reviews the evidence, predictors and mechanisms of AEDs-induced bone abnormalities and its clinical implications. For patients on AEDs, regular monitoring of bone health is recommended. Prophylactic administration of calcium and vitamin D is recommended for all patients. Treatment doses of calcium and vitamin D and even anti-resorptive drug therapy are reserved for patients at high risk of pathological fracture.

Neuroendocrinological aspects of epilepsy: important issues and trends in future research

Neuroendocrine research in epilepsy focuses on the interface among neurology, endocrinology, gynecology/andrology and psychiatry as it pertains to epilepsy. There are clinically important reciprocal interactions between hormones and the brain such that neuroactive hormones can modulate neuronal excitability and seizure occurrence while epileptiform discharges can disrupt hormonal secretion and promote the development of reproductive disorders. An understanding of these interactions and their mechanisms is important to the comprehensive management of individuals with epilepsy. The interactions are relevant not only to the management of seizure disorder but also epilepsy comorbidities such as reproductive dysfunction, hyposexuality and emotional disorders. This review focuses on some of the established biological underpinnings of the relationship and their clinical relevance. It identifies gaps in our knowledge and areas of promising research. The research has led to ongoing clinical trials to develop hormonal therapies for the treatment of epilepsy. The review also focuses on complications of epilepsy treatment with antiepileptic drugs. Although antiepileptic drugs have been the mainstay of epilepsy treatment, they can also have some adverse effects on sexual and reproductive function as well as bone density. As longevity increases, the prevention, diagnosis and treatment of osteoporosis becomes an increasingly more important topic, especially for individuals with epilepsy. The differential effects of antiepileptic drugs on bone density and their various mechanisms of action are reviewed and some guidelines and future directions for prevention of osteoporosis and treatment are presented.

Influences of bone and mineral metabolism in epilepsy

INTRODUCTION

Patients with epilepsy are at increased risk for metabolic bone disease, low bone mineral density and fractures.

AREAS COVERED

This article reviews the predictors and mechanisms of bone loss in patients with epilepsy. It provides information regarding the basic bone biology, evidences of osteopathy with epilepsy and the potential mechanisms of its pathogenesis. This review shows that long-term use of antiepileptic drugs (AEDs) is associated with the risk of osteopathy. However, age, gender, low body mass, severity of epilepsy, co-morbid conditions, institutionalization and calcium and vitamin D deficiencies are additional and modified risk factors. AEDs may indirectly accelerate bone loss through hypovitaminosis D, hypocalcemia and hyperparathyroidism or reduce bone accrual through decreasing the levels of calcitonin, growth factors and vitamin K. Also, AEDs may directly accelerate osteoclastic (bone loss) and/or reduce osteoblastic (bone formation) activities, the main cells involved in bone remodeling.

EXPERT OPINION

Understanding the basic bone biology and the pathophysiology of the disturbed bone and mineral metabolism in epilepsy will aid in identification and monitoring of patients at risk and in planning appropriate prophylactic and therapeutic measures.

Bone health in young women with epilepsy after one year of antiepileptic drug monotherapy

OBJECTIVE

Antiepileptic drugs (AEDs) may have adverse effects on bone mineral density (BMD) and metabolism. We previously reported biochemical evidence of increased bone turnover in premenopausal women with epilepsy on phenytoin monotherapy compared with those on carbamazepine, lamotrigine, and valproate. We therefore hypothesized that rates of bone loss would be higher in young women treated with phenytoin.

METHODS

Ninety-three premenopausal women with epilepsy receiving a single AED (carbamazepine, lamotrigine, phenytoin, or valproate) participated. Subjects completed nutritional and physical activity questionnaires. Biochemical indices of bone and mineral metabolism and BMD of the proximal femur and lumbar spine were measured at baseline and 1 year.

RESULTS

Participants reported high calcium intake (>1,000 mg/day) and were physically active. Significant loss (2.6%) was seen at the femoral neck in the phenytoin group. BMD remained stable in the other AED groups. Bone turnover markers and calciotropic hormones were unchanged after 1 year in all groups except for a significant decline in urine N-telopeptide in the phenytoin group. In women receiving phenytoin, lower serum 25-hydroxyvitamin D concentrations were associated with higher parathyroid hormone, bone alkaline phosphatase, and urine N-telopeptide levels, a biochemical pattern consistent with secondary hyperparathyroidism and increased remodeling.

CONCLUSION

In this study, young women treated with phenytoin had significant femoral neck bone loss over 1 year. In contrast, those treated with carbamazepine, lamotrigine, and valproate did not have detectable adverse effects on bone turnover or bone mineral density. These results raise concerns about the long-term effects of phenytoin monotherapy on bone in young women with epilepsy.

Pathophysiology of bone loss in patients receiving anticonvulsant therapy

Many studies have shown that patients taking antiepileptic drugs (AEDs) are at increased risk for metabolic bone disease and low bone mineral density. Although early reports of bone disease in patients with epilepsy often involved institutionalized patients, who may be at risk because of lack of physical activity, reduced sunlight exposure, and poor nutrition, low bone density has also been reported in well-nourished, ambulatory outpatients with epilepsy. Traditionally, attention to the problem of AED-induced bone loss has been focused on those drugs that induce the hepatic cytochrome P450 enzyme system, thereby increasing the metabolism of vitamin D. However, the mechanisms of AED-induced bone loss appear to be multiple, and all types of AEDs are potentially implicated. Besides hepatic enzyme induction, mechanisms may include direct effects of AEDs on bone cells, resistance to parathyroid hormone, inhibition of calcitonin secretion, and impaired calcium absorption. An understanding of bone biology and the pathophysiology of bone loss can aid in the identification and monitoring of patients at risk and in the planning of appropriate prophylactic and therapeutic measures, by which most of the morbidity associated with AED-induced bone loss can be prevented.

The effect of phenytoin medication on dentin apposition, root length, and caries progression in rat molars

To determine the effect of phenytoin (PHT) on dentin apposition and the rate of caries progression in dentin, 40 Wistar rats were treated daily for 35 days with intraperitoneal injections of 5,5-diphenylhydantoin. Twenty-eight controls received saline with pH adjusted to that of PHT. One PHT and one control group were fed a 43% sucrose diet, and the others a non-cariogenic pellet diet. Streptococcus sobrinus was inoculated to induce caries. Schiff staining was used to determine caries. The areas of dentin apposition and dentinal caries lesions were quantified after tetracycline staining. The root lengths were measured. PHT reduced slightly the dentin apposition and activated significantly the progression of the dentinal carious lesions. No difference in caries initiation was found. The high-sucrose diet reduced dentin apposition and increased the rate of progression of existing caries greatly. Our study suggests that both the high-sucrose diet and PHT have an effect on secreting odontoblasts, which can be seen as an alteration in dentin apposition and caries progression rates in dentin.