Bone status of children receiving anticonvulsant therapy

The bone mineral content alterations in pediatric patients medicated with levetiracetam, valproic acid, and carbamazepine

AIM

The negative effect of antiepileptic drugs on bone health has been previously documented. However, which antiepileptic drug is safer in regard to bone health is still questionable. Our aims were to investigate the bone mineral density alterations in pediatric patients who receive antiepileptic medication for a minimum of two years and to compare the results of these drugs.

MATERIALS AND METHODS

Fifty-nine patients (32 males, 27 females; mean age: 8.6±4.6years) and a control group (13 males, 7 females; mean age: 7.6±3.3years) were included in the study. The patients were receiving necessarily the same antiepileptic drugs (AEDs) for at least two years, and none of the patients had mental retardation or cerebral palsy. The patients were divided into three groups: group 1 (patients receiving levetiracetam (LEV), n=20), group 2 (patients receiving carbamazepine (CBZ), n=11), and group 3 (patients receiving valproic acid (VPA), n=28). Plasma calcium (Ca), phosphorus (P), parathyroid hormone (PTH), alkaline phosphatase (ALP), vitamin D levels, and bone mineral density (BMD) values of femur and vertebras (L1-4) and z-scores (comparative results of BMD values of the patients with the age- and gender-matched controls in device database) of the groups were compared.

RESULTS

The differences between P, PTH, ALP and age, Ca and BMD results, and vitamin D levels of the patients in all four groups was not statistically significant according to Kruskal-Wallis test (p>0.05). The z-score levels of all the patient and control groups were also not statistically significantly different compared with each other.

CONCLUSION

In contrast to previous reports in pediatric patients, our study has documented that there is not a considerable bone loss in patients receiving long-term AED medication. Although levetiracetam has been proposed as bone-protecting medication, we did not observe any difference between AEDs regarding bone mineral density after two years of treatment.

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 drug-induced osteopenia in ambulatory epileptic children receiving a standard vitamin D3 supplement

Dual energy X-ray absorptiometry (DEXA) is a non-invasive, rapid, accurate and highly reproducible method for the assessment of antiepileptic drug (AED)-induced osteopenia in epileptic children. In this study, we investigated bone mineral density (BMD) using DEXA in 56 epileptic children receiving long-term AED treatment for at least 2 years. All children received AED monotherapy or polytherapy plus a standard vitamin D3 supplement (400 U/day). BMD measurements were made from lumbar spine (L2-L4) regions. Age- and sex-specific BMD SD scores were calculated for each child. Osteopenia was defined as SD scores less than -1.5. There was no significant difference in mean BMD values between epileptic children receiving monotherapy or polytherapy. The results were also compared to the age- and sex-specific BMD SD scores obtained from healthy Turkish children. Only three patients (5%) receiving AED therapy had a BMD SD score less than -1.5. This rate is relatively lower than the rates of previous studies conducted on ambulatory children on long-term AED treatment without vitamin D3 supplementation.

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.

High incidence of significant bone loss in patients with severe congenital neutropenia (Kostmann's syndrome)

OBJECTIVE

Clinical observation of bone pain, unusual fractures in two patients, and diffuse osteopenia/osteoporosis led us to assess bone mineral content and density in 30 patients with severe congenital neutropenia who were treated with recombinant-methionyl-human granulocyte colony-stimulating factor (r-metHuG-CSF).

STUDY DESIGN

We reviewed roentgenograms in 29 of these 30 patients to evaluate bone loss before and during treatment. In addition, in 17 of the 30 patients, bone mineral status could be assessed by both quantitative computed tomography (Q-CT; n = 16) and dual energy x-ray absorptiometry (DXA; n = 1). In one patient, Q-CT was not possible because of severe vertebral fractures.

RESULTS

Of the 30 patients investigated, 15 had evidence of osteopenia/osteoporosis observed on spine radiographs (n = 5), on Q-CT/DXA (n = 1/n = 1), or on radiographs and Q-CT (n = 8). In 13 of the 30 patients, only a lateral radiograph of the lumbar spine was available, 5 of 13 showing either increased kyphosis and wedging of the vertebrae or compression fractures of the vertebral bodies, indicating severe established osteoporosis. In eight patients, the findings of the spinal radiographs were normal. In nine patients, spinal radiographs were taken before r-metHuG-CSF treatment. Osteoporotic vertebral deformation (n = 3) or reduced bone mass (n = 3) was seen in six of these nine patients. The levels of serum biochemical markers of bone metabolism were all within normal ranges except for mild elevation of the serum alkaline phosphatase level. The degree of spinal bone mineral loss did not correlate with dose and duration of r-metHuG-CSF treatment or with the age or sex of the patients.

CONCLUSIONS

These data indicate a high incidence of bone mineral loss in children with severe congenital neutropenia. The underlying pathogenesis of bone demineralization is not clear. It is more likely that the bone loss was caused by the pathophysiologic features of the underlying disease, but it is possible that r-metHuG-CSF accelerates bone mineral loss.

Bone-mineral density in children and adolescents who have spastic cerebral palsy

Bone-mineral density was studied in a heterogeneous group of 139 children (mean age, nine years; range, three to fifteen years) who had spastic cerebral palsy. The evaluation included serum analyses and a nutritional assessment based on a dietary history and anthropometric measurements. The bone-mineral density of the proximal parts of the femora and the lumbar spine was measured with dual-energy x-ray absorptiometry and was normalized for age against a series of ninety-five normal children and adolescents who served as controls. Bone-mineral density varied greatly but averaged nearly one standard deviation below the age-matched normal means for both the proximal parts of the femora (-0.92 standard deviation) and the lumbar spine (-0.80 standard deviation). Ambulatory status was the factor that best correlated with bone-mineral density. Nutritional status, assessed on the basis of caloric intake, skinfolds, and body-mass index, was the second most significant variable. The pattern of involvement, durations of immobilization in a cast, and a calcium intake of less than 500 milligrams per day were additional factors of less significance. The age when the child first walked, previous fractures, use of anticonvulsants, and serum vitamin-D levels did not correlate with bone-mineral density after adjustment for covariance with the ambulatory status and the nutritional status. Serum levels of calcium, phosphate, alkaline phosphatase, and osteocalcin were not reliable indicators of low bone-mineral density.

Radiographic absorptiometry of the phalanges in healthy children and in girls with Turner syndrome

Although bone mineral status in children has been measured with various techniques, information about development of the actual bone mass density during childhood and adolescent growth is scarce. Our modified radiographic absorptiometry (RA) determines bone mass density (BMaD) three dimensionally at the diaphyseal and metaphyseal site of the middle phalanx of the left second digit, representing predominantly cortical (50% site) and trabecular bone compartments (25% site), respectively. The objectives of this study were to establish reference curves with 95% prediction intervals of BMaD in relation to bone age (BA) during childhood and adolescence (N = 303) determined by RA. The specific effects of female puberty on BMaD were studied comparing the values of 110 untreated girls with Turner syndrome (TS) with those of the female reference group. For either sex, a piecewise linear model with one inflection point (IP) was postulated for the relationship of both the 25% and 50% site with BA. The IPs appeared at exactly the same BA (11.5 "years") for both the 25% and 50% site in boys and for the 25% site in girls. However, in girls the 50% site IP appeared 0.25 "years" later. All BMaD values to the left of the IPs showed little increase with age. In contrast, the slopes to the right of the IPs showed in both genders regression coefficients of approximately 0.05 for the 25% site. For the 50% site, the regression coefficient in girls was markedly higher (0.075) than in boys (0.058), resulting only in girls in a significant difference between the 25% and the 50% site to the right of the IP (p = 0.03).(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of anti-epileptic drug therapy on bone mineral density in ambulatory epileptic children

In order to assess the bone changes in the subjects receiving anti-epileptic drugs (AEDs), bone mineral densities (BMDs) of the arms, legs, ribs, pelvis, spine, and the whole body were scanned in 78 epileptic children and in 78 controls using dual photon absorptiometry. The study subjects were classified according to the duration of the monotherapy with phenobarbital (PB) or phenytoin (PHT); those who received AEDs for less than 12 months as Group I, for 13-23 months as Group II, and for 24 months as Group III. Group III was subclassified according to the kind of AEDs administered, into those receiving PB as Group IIIp, and those receiving PHT as Group IIId. There was no significant differences in the BMDs of each area, when compared to each control in Groups I and II. In Group III, there were significant differences in ribs and spine, according to the duration of administration. In Group IIIp, there was a significant difference in ribs and spine, and, in Group IIId, there was a significant difference in most of the areas. These results show that the measurement of BMDs in the ribs and spine is necessary for the early detection of subtle bone loss, and it is recommended that vitamin D be administered to children with epilepsy receiving AEDs over 24 months.

Reference values for radial bone width and mineral content using single photon absorptiometry in healthy children aged 4 to 10 years

Bone width and mineral content were measured in 420 healthy Cambridge children aged 4 to 10 years using single photon absorptiometry. The results are expressed first in the form of standard centile charts, with additional prediction charts which provide body-size-adjusted estimates for the measurements, and interpretation centiles for comparing these estimates with the actual measurements. The values obtained are similar to those reported for American children aged five to six years after adjusting for body-size differences. We suggest that appropriate application of these prediction charts will facilitate the use of single photon absorptiometry in monitoring and treating children who have disorders of bone growth and mineralization.

Physiological and pharmacological regulation of biological calcification

Biological calcification is a highly regulated process which occurs in diverse species of microorganisms, plants, and animals. Calcification provides tissues with structural rigidity to function in support and protection, supplies the organism with a reservoir for physiologically important ions, and also serves in a variety of specialized functions. In the vertebrate skeleton, hydroxyapatite crystals are laid down on a backbone of type I collagen, with the process being controlled by a wide range of noncollagenous proteins present in the local surroundings. In bone, cells of the osteoblast lineage are responsible for the synthesis of the bone matrix and many of these regulatory proteins. Osteoclasts, on the other hand, are continually resorbing bone to both produce changes in bone shape and maintain skeletal integrity, and to establish the ionic environment needed by the organism. The proliferation, differentiation, and activity of these cells is regulated by a number of growth factors and hormones. While much has already been discovered over the past few years about the involvement of various regulators in the process of mineralization, the identification and functional characterization of these factors remains an area of intense investigation. As with any complex, biological system that is in a finely tuned equilibrium under normal conditions, problems can occur. An imbalance in the processes of formation and resorption can lead to calcification disorders, and the resultant diseases of the skeletal system have a major impact on human health. A number of pharmacological agents have been, and are being, investigated for their therapeutic potential to correct these defects.(ABSTRACT TRUNCATED AT 250 WORDS)

Risk of age-related fractures in patients with unprovoked seizures

The incidence of age-related fractures was determined in a cohort of 467 Rochester, Minnesota residents with unprovoked seizures. The 30 initial hip fractures observed were significantly more than the 13.19 expected [standardized morbidity ratio (SMR) = 2.3; 95% confidence interval (CI) 1.5-3.3]. The overall incidence of distal forearm (Colles) fractures was not significantly increased (SMR = 1.6; 95% CI 0.9-2.5), based on 17 cases. Hip fracture incidence was increased during the first 10 years after seizure diagnosis but was not related to anti-epileptic drug (AED) use. In contrast, the increase in Colles' fracture incidence was associated with duration of therapy, as the SMR for greater than or equal to 10 years of AED use was 2.4 (95% CI 1.0-5.0). The incidence of vertebral fractures was slightly higher among treated patients but was not associated with duration of AED use. Thus, there was no consistent pattern to support the contention that fracture incidence is greatly increased by long-term AED use.

Bone status in nonambulant, epileptic, institutionalized youth. Improvement with vitamin D therapy

This study was conducted to determine if the adverse effects of anticonvulsant drug therapy and nonambulancy on bone status could be overcome with vitamin D therapy in severely handicapped individuals. Six male and five female gastrostomy fed, nonambulant, epileptic, profoundly mentally retarded individuals ranging in age from 7 to 17 years were given vitamin D therapy at a dosage of 4,000 IU/m2 body surface area/day for 6 months. Photon absorptiometry and biochemical indices of bone status were measured to follow the effects of therapy. Bone mineral content expressed as a percentage of normal improved by 11 percent (p less than 0.01), from 59.6 to 66.1 percent. Tartrate-resistant acid phosphatase, total alkaline phosphatase, and the bone isoenzyme activities declined 11 percent, 18 percent, and 11 percent respectively. These reductions were not statistically significant but they were consistent with the improvements observed by photon absorptiometry. The results of our study suggest that a conservative supplement of vitamin D will improve the bone status of severely disabled youths.

Bone densitometry in infants

Bone mineral mass and density can be measured noninvasively by various absorptiometric procedures. Two methods, dual-photon absorptiometry (DPA) and quantitative computed tomography, have widespread application in adults but only limited use in children. One method, single-photon absorptiometry (SPA), has been used extensively in adults and children and has been modified for use in infants. The radius shaft has been used for most research on infants. However, the difficulty of using older SPA methods on this small bone (4 to 7 mm width) has led a few investigators to measure the shaft of the humerus. The typical precision of measurement in a newborn is about 5% with the use of computerized rectilinear scanners for the radius; older linear scanners have a precision error of 5% to 10% on the humerus. Linear scanners cannot measure precisely the radius in individual neonates. The SPA scans typically take about 5 minutes. The DPA technique using 153Gd has been modified for use on smaller animals (5 to 10 kg monkeys and dogs), but it has not been used on infants because DPA scans take 20 minutes. New methods using x-ray absorptiometry allow rapid (1 minute), precise (1%) measurements in the perinate. The need for a soft tissue bolus is eliminated, and both the axial and peripheral skeletons can be measured with dual-energy x-ray absorptiometry. Ultrasonic measurements do not yet offer adequate precision in the neonate, given the limited biologic range of values.

Long term follow-up of bone mineral status in children with renal disease

Bone mineral content (BMC) was measured by photon absorptiometry in the non-dominant forearm of children with chronic renal failure followed for a total of 2472 months. From 48 children, 302 measurements were made, and changes which occurred in BMC over time were correlated with several factors. Patients were divided into those who had received glucocorticoids (group 1) and those who had not (group 2). Group 1 patients had a lower mean serum creatinine (Cr) (p less than 0.05), a lower growth velocity (p greater than 0.02) and were more demineralized than group 2 patients. There was no correlation between BMC and height velocity or estimated creatinine clearance. BMC and height Z-score (SDS) were highly correlated. Over the period of study, group 1 patients remained shorter, had a lower height velocity, a lower BMC Z-score and a lower BMC for each serum creatinine level. Long-term therapeutic intervention with oral 1,25(OH)2D improved bone mineral status in three children in the nonsteroid group, but none of those in the steroid group. This study demonstrates that steroid administration is probably the most important factor causing bone demineralization, possibly even more important than renal failure.

Direct effects of diphenylhydantoin (phenytoin) on the ion-transporting ATPases of cultured osteoblast-like cells

Diphenylhydantoin (phenytoin) added to cultures of osteoblast-like cells at a concentration of 10 microM, at the high end of the therapeutic range in plasma of unbound phenytoin (4-8 microM), caused reductions in Na+, K+-ATPase and alkaline phosphatase activities and increases in Ca2+-ATPase and HCO3--ATPase activities in homogenates of whole cells and in subcellular fractions of cultured osteoblast-like cells. These data suggest that, if these changes occur in vivo, the osteomalacia associated with treatment with diphenylhydantoin may be mediated in part by direct effects on the ability of bone cells to transport ions.