Factors causing rickets in institutionalised handicapped children on anticonvulsant therapy

A Literature Review of the Potential Impact of Medication on Vitamin D Status

In recent years, there has been a significant increase in media coverage of the putative actions of vitamin D as well as the possible health benefits that supplementation might deliver. However, the potential effect that medications may have on the vitamin D status is rarely taken into consideration. This literature review was undertaken to assess the degree to which vitamin D status may be affected by medication. Electronic databases were searched to identify literature relating to this subject, and study characteristics and conclusions were scrutinized for evidence of potential associations. The following groups of drugs were identified in one or more studies to affect vitamin D status in some way: anti-epileptics, laxatives, metformin, loop diuretics, angiotensin-converting enzyme inhibitors, thiazide diuretics, statins, calcium channel blockers, antagonists of vitamin K, platelet aggregation inhibitors, digoxin, potassium-sparing diuretics, benzodiazepines, antidepressants, proton pump inhibitors, histamine H2-receptor antagonists, bile acid sequestrants, corticosteroids, antimicrobials, sulphonamides and urea derivatives, lipase inhibitors, hydroxychloroquine, highly active antiretroviral agents, and certain chemotherapeutic agents. Given that the quality of the data is heterogeneous, newer, more robustly designed studies are required to better define likely interactions between vitamin D and medications. This is especially so for cytochrome P450 3A4 enzyme (CYP3A4)-metabolized medications. Nevertheless, this review suggests that providers of health care ought to be alert to the potential of vitamin D depletions induced by medications, especially in elderly people exposed to multiple-drug therapy, and to provide supplementation if required.

Valproic Acid Impacts the Growth of Growth Plate Chondrocytes

A range of bone abnormalities including short stature have been reported to be associated with the use of antiepileptic drugs (AEDs) in children. Exactly how AEDs impact skeletal growth, however, is not clear. In the present study, rat growth plate chondrocytes were cultured to study the effects of AEDs, including valproic acid (VPA), oxcarbazepine (OXA), levetiracetam (LEV), lamotrigine (LTG), and topiramate (TPM) on the skeletal growth. VPA markedly reduced the number of chondrocytes by apoptosiswhile other AEDs had no effect. The apoptosis associated noncleaved and cleaved caspase 3, and caspases were increased by exposure to VPA, which up-regulated cyclooxygenase 2 (COX-2) mRNA and protein levels likely through histone acetylation. The COX-2 inhibitor NS-398 attenuated the effects of VPA up-regulating COX-2 expression and decreased VPA-induced caspase 3 expression. The use of VPA in children should be closely monitored or replaced, where appropriate, by AEDs which do not apparently affect the growth plate chondrocytes.

Effect of impaired ambulation and anti-epileptic drug intake on vitamin D status of children with cerebral palsy

BACKGROUND

Children with cerebral palsy (CP) are vulnerable to developing vitamin D deficiency. There is little information on the prevalence and severity of vitamin D deficiency in these patients.

OBJECTIVE

To study vitamin D status in children with CP with special reference to their intake of anti-epileptic drugs (AED) and ambulatory status.

METHODS

The relative effects of AED use and ambulatory status on the vitamin D status of 120 children with CP aged 2-10 years were examined in this observational study. The patients were classified into four groups (30 in each) on the basis of AED use and ambulatory status: ambulatory (CPA), ambulatory receiving AED (CPAD), non-ambulatory (CPNA) and non-ambulatory receiving AED (CPNAD). A control group of 30 age-matched healthy children was also included. Parameters assessed included dietary calcium intake, sun exposure, serum total and ionised calcium (tCa, iCa), inorganic phosphate (iP), alkaline phosphatase (ALP), parathormone (PTH), 25 hydroxy vitamin D [25(OH)D] levels and a wrist radiograph to detect rickets. Vitamin D status was defined on the basis of serum 25(OH)D levels as normal (>50 nmol/L), mild deficiency (25-50 nmol/L), moderate deficiency (12.5-25 nmol/L), severe deficiency (<12.5 nmol/L).

RESULTS

Median (IQR) serum 25 (OH)D levels in patients with CP were 35.6 (26.75-64) nmol/L compared with 60 (37-69.25) nmol/L in controls (p = 0.04). Sixty per cent of children with CP and 36.7% of controls were vitamin D-deficient [25(OH)D < 50 nmol/L]. Children with CP had a significantly lower dietary calcium intake and sun exposure than controls (p < 0.0001 each). Serum tCa and iCa levels were significantly lower (p = 0.01 and p < 0.001, respectively) and PTH and ALP levels significantly higher (p = 0.04 and p = 0.001, respectively) in children with CP than in controls. Patients in the CPNAD group were the worst affected, 83.3% of them being vitamin D-deficient with median (IQR) 25(OH)D levels of 33.5 (12.5-45.25) nmol/L. Also, 53.3% of them had raised ALP and 17.2% raised PTH levels.

CONCLUSION

Children with CP are highly vulnerable to vitamin D deficiency. In these patients, AED use and lack of sun exposure contribute towards poor vitamin D status, the effect being more pronounced when they co-exist.

The Impact of Anti-Epileptic Drugs on Growth and Bone Metabolism

Epilepsy is a common neurological disorder worldwide and anti-epileptic drugs (AEDs) are always the first choice for treatment. However, more than 50% of patients with epilepsy who take AEDs have reported bone abnormalities. Cytochrome P450 (CYP450) isoenzymes are induced by AEDs, especially the classical AEDs, such as benzodiazepines (BZDs), carbamazepine (CBZ), phenytoin (PT), phenobarbital (PB), and valproic acid (VPA). The induction of CYP450 isoenzymes may cause vitamin D deficiency, hypocalcemia, increased fracture risks, and altered bone turnover, leading to impaired bone mineral density (BMD). Newer AEDs, such as levetiracetam (LEV), oxcarbazepine (OXC), lamotrigine (LTG), topiramate (TPM), gabapentin (GP), and vigabatrin (VB) have broader spectra, and are safer and better tolerated than the classical AEDs. The effects of AEDs on bone health are controversial. This review focuses on the impact of AEDs on growth and bone metabolism and emphasizes the need for caution and timely withdrawal of these medications to avoid serious disabilities.

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.

The impact of the use of antiepileptic drugs on the growth of children

BACKGROUND

This study investigated whether long-term treatment with antiepileptic drugs (AEDs) had negative effects on statural growth and serum calcium levels in children with epilepsy in Taiwan.

METHODS

Children with epilepsy treated with one prescription of AEDs (monotherapy) for at least 1 year were selected. The AEDs included valproic acid (VPA; Deparkin) in 27 children (11 boys and 16 girls) aged 4-18 years, oxcarbazepine (Trileptal) in 30 children (15 boys and 15 girls) aged 5-18 years, topiramate (Topamax) in 19 children (10 boys and 9 girls) aged 6-18 years, and lamotrigine (Lamicta) in eight children (5 boys and 3 girls) aged 5-13 years. Patients with a history of febrile convulsions were selected as the controls.

RESULTS

One year of VPA treatment significantly impaired the statural growth of pediatric patients with epilepsy (p < 0.005) compared with the control group. The underlying mechanism may have been due to the direct effect of VPA on the proliferation of growth plate chondrocytes rather than alterations of serum calcium.

CONCLUSIONS

These results raise serious concerns about the growth of pediatric epilepsy patients who use AEDs, and potentially the need to closely monitor growth in children with epilepsy and adolescents under AED treatment, especially VPA.

Drug-vitamin D interactions: a systematic review of the literature

Extensive media coverage of the potential health benefits of vitamin D supplementation has translated into substantial increases in supplement sales over recent years. Yet, the potential for drug-vitamin D interactions is rarely considered. This systematic review of the literature was conducted to evaluate the extent to which drugs affect vitamin D status or supplementation alters drug effectiveness or toxicity in humans. Electronic databases were used to identify eligible peer-reviewed studies published through September 1, 2010. Study characteristics and findings were abstracted, and quality was assessed for each study. A total of 109 unique reports met the inclusion criteria. The majority of eligible studies were classified as class C (nonrandomized trials, case-control studies, or time series) or D (cross-sectional, trend, case report/series, or before-and-after studies). Only 2 class C and 3 class D studies were of positive quality. Insufficient evidence was available to determine whether lipase inhibitors, antimicrobial agents, antiepileptic drugs, highly active antiretroviral agents, or H2 receptor antagonists alter serum 25(OH)D concentrations. Atorvastatin appears to increase 25(OH)D concentrations, whereas concurrent vitamin D supplementation decreases concentrations of atorvastatin. Use of thiazide diuretics in combination with calcium and vitamin D supplements may cause hypercalcemia in the elderly or those with compromised renal function or hyperparathyroidism. Larger studies with stronger study designs are needed to clarify potential drug-vitamin D interactions, especially for drugs metabolized by cytochrome P450 3A4 (CYP3A4). Healthcare providers should be aware of the potential for drug-vitamin D interactions.

Elevated Alkaline Phosphatase in Children: An Algorithm to Determine When a "Wait and See" Approach is Optimal

Due to the possibility of underlying hepatobiliaryor bone diseases, the diagnostic work up of a child with elevated alkaline phosphatase (AP) levels can be quite costly. In a significant proportion of these patients, elevated AP is benign, requiring no intervention: hence, known as transient hyperphosphatasemia (THP) of infants and children. A 27-month old previously healthy Caucasian female was found to have isolated elevation of AP four weeks after the initial symptoms of acute gastroenteritis. One month later, when seen in hepatobiliary clinic, signs and symptoms of gastrointestinal, hepatobiliary, or bone disease were absent and physical examination was normal. The diagnosis of THP was made, and, as anticipated, AP levels normalized after four months. Using this case as an example, we suggest an algorithm that can be utilized as a guide in a primary care setting to arrive at the diagnosis of THP and avoid further tests or referrals.

Nutrition in neurologically impaired children

Malnutrition, either under- or overnutrition, is a common condition among neurologically impaired children. Energy needs are difficult to define in this heterogeneous population, and there is a lack of information on what normal growth should be in these children. Non-nutritional factors may influence growth, but nutritional factors such as insufficient caloric intake, excessive nutrient losses and abnormal energy metabolism also contribute to growth failure. Malnutrition is associated with significant morbidity, while nutritional rehabilitation improves overall health. Nutritional support should be an integral part of the management of neurologically impaired children, and should focus not only on improving nutritional status but also on improving quality of life for patients and their families. When considering nutritional intervention, oromotor dysfunction, gastroesophageal reflux and pulmonary aspiration must be addressed and a multidisciplinary team should be involved. Children at risk for nutrition-related problems should be identified early. An assessment of nutritional status should be performed at least yearly, and more frequently in infants and young children, or in children at risk for malnutrition. Oral intake should be optimized if safe, but enteral tube feedings should be initiated in children with oromotor dysfunction, leading to clinically significant aspiration, or in children unable to maintain an adequate nutritional status with oral intake. Nasogastric tube feeding should be used for short-term intervention, but if long-term nutritional intervention is required, a gastrostomy should be considered. Antireflux procedures should be reserved for children with significant gastroesophageal reflux. The patient's response to nutritional intervention should be carefully monitored to avoid excessive weight gain after initiation of enteral nutrition, and paediatric formulas should be used to avoid micronutrient deficiencies.

[Not Available]

Malnutrition, either under- or overnutrition, is a common condition among neurologically impaired children. Energy needs are difficult to define in this heterogeneous population, and there is a lack of information on what normal growth should be in these children. Non-nutritional factors may influence growth, but nutritional factors such as insufficient caloric intake, excessive nutrient losses and abnormal energy metabolism also contribute to growth failure. Malnutrition is associated with significant morbidity, while nutritional rehabilitation improves overall health. Nutritional support should be an integral part of the management of neurologically impaired children, and should focus not only on improving nutritional status but also on improving quality of life for patients and their families. When considering nutritional intervention, oromotor dysfunction, gastroesophageal reflux and pulmonary aspiration must be addressed and a multidisciplinary team should be involved. Children at risk for nutrition-related problems should be identified early. An assessment of nutritional status should be performed at least yearly, and more frequently in infants and young children, or in children at risk for malnutrition. Oral intake should be optimized if safe, but enteral tube feedings should be initiated in children with oromotor dysfunction, leading to clinically significant aspiration, or in children unable to maintain an adequate nutritional status with oral intake. Nasogastric tube feeding should be used for short-term intervention, but if long-term nutritional intervention is required, a gastrostomy should be considered. Antireflux procedures should be reserved for children with significant gastroesophageal reflux. The patient's response to nutritional intervention should be carefully monitored to avoid excessive weight gain after initiation of enteral nutrition, and paediatric formulas should be used to avoid micronutrient deficiencies.

Bone mineral density in children, adolescents, and young adults with epilepsy

PURPOSE

The aim of this study was to assess bone mineral density (BMD) in a large population of children, adolescents, and young adults with epilepsy alone or in association with cerebral palsy and/or mental retardation.

METHODS

Ninety-six patients were enrolled in the study. The group comprised 50 males and 46 females, aged between 3 and 25 years (mean age 11 years). The control group consisted of 63 healthy children and adolescents (23 males, 40 females), aged between 3 and 25 years (mean age 12.1 years). Patients underwent a dual-energy x-ray absorptiometry (DEXA) scan of the lumbar spine (L1-L4) and the z scores were calculated for each patient; the t score was considered for patients 18 years of age or older.

RESULTS

Abnormal BMD was found in 56 patients (58.3%), with values documenting osteopenia in 42 (75%) and osteoporosis in 14 (25%). A significant difference emerged between epileptic patients and the control group in BMD, z score, and body mass index (BMI) (p = <0.001). Lack of autonomous gait, severe mental retardation, long duration of antiepileptic treatment, topiramate adjunctive therapy, and less physical activity significantly correlated with abnormal BMD.

DISCUSSION

This study detected abnormal BMD in more than half of a large pediatric population with epilepsy with or without cerebral palsy and/or mental retardation. The clinical significance of these findings has yet to be clarified.

Effects of antiepileptic drug therapy on vitamin D status and biochemical markers of bone turnover in children with epilepsy

Reports of decreased serum 25-hydroxyvitamin D (25-OHD) and altered bone metabolism associated with antiepileptic drug (AED) treatment are inconsistent and predominantly restricted to adults. In this cross-sectional observational study, the aim was to evaluate the influence of AED treatment on vitamin D status and markers of bone turnover in children with epilepsy. In 38 children taking AEDs and 44 healthy control subjects, blood samples were collected to determine the levels of serum 25-OHD, intact parathyroid hormone (iPTH), calcium (Ca), phosphate (P), bone alkaline phosphatase (BAP), osteocalcin (OC) and C terminal telopeptide of type I collagen (ICTP). More than 75% of the patients were vitamin D deficient (serum 25-OHD<20 ng/mL) and 21% of the patients had an insufficient vitamin D status (serum 25-OHD=20-30 ng/mL). In the patients, the serum levels of OC (p = 0.002) and BAP (p < 0.001) were significantly increased, but ICTP (p = 0.002) concentrations were significantly decreased compared with the control group. When patients where divided into two groups according to their medication (mono- or polytherapy), significantly lower 25-OHD (p = 0.038) and ICTP (p = 0.005) levels and elevated BAP (p = 0.023) concentrations were found in patients under polytherapy. An association between 25-OHD and the measured bone markers could not be determined. Our results indicate that the prevalence of vitamin D deficiency in epilepsy patients under AED treatment is high, especially under polytherapy, and alteration markers of bone formation and resorption suggests an accelerated skeletal turnover. The routine monitoring of serum 25-OHD and vitamin D supplementation on an individual basis should be considered.

Nutrition support for neurologically impaired children: a clinical report of the North American Society for Pediatric Gastroenterology, Hepatology, and Nutrition

Undernutrition, growth failure, overweight, micronutrient deficiencies, and osteopenia are nutritional comorbidities that affect the neurologically impaired child. Monitoring neurologically impaired children for nutritional comorbidities is an integral part of their care. Early involvement by a multidisciplinary team of physicians, nurses, dieticians, occupational and speech therapists, psychologists, and social workers is essential to prevent the adverse outcomes associated with feeding difficulties and poor nutritional status. Careful evaluation and monitoring of severely disabled children for nutritional problems are warranted because of the increased risk of nutrition-related morbidity and mortality.

Effects of anticonvulsant therapy on vitamin D status in children: prospective monitoring study

Reports of hypovitaminosis D associated with anticonvulsant drugs in pediatric patients are conflicting. The effects of carbamazepine or sodium valproate on vitamin D status were evaluated prospectively in 51 ambulatory epileptic children who were followed during the first year of the study and in 25 and 6 children during the second and third year, respectively. Serum 25-hydroxyvitamin D, parathyroid hormone, calcium, and phosphorus levels were determined before and every 3 months during anticonvulsant therapy. Our subjects were grouped into four classes (0, 1, 2, and 3 consisted of the patients before and during the first, second, and third years of the treatment, respectively). The control group consisted of 80 healthy children. Comparisons between controls and patients of class 0 for the means for each season of all variables showed no significant differences. A decreasing trend in serum 25-hydroxyvitamin D (P < .03) and an increasing trend in serum parathyroid hormone (P < .04) levels were noticed in all seasons from class 0 to class 3. Twenty-five patients (49%) acquired hypovitaminosis D during the study period. The effects of seasonality on serum 25-hydroxyvitamin D, parathyroid hormone, and calcium were noticed in our patients grouped in classes 0, 2 and 3, as well as in controls. Evidence is provided that carbamazepine or sodium valproate can cause hypovitaminosis D in children.

A survey of vitamin D level in people with learning disability in long-stay hospital wards in Hong Kong

Serum vitamin D level was measured in 122 patients with learning disabilities in long-term care wards. Such people are at risk of developing vitamin D deficiency. Low vitamin D is often attributed to lack of sunshine, poor dietary intake and the deleterious effect of anticonvulsant therapy. The results of this study confirmed that a low level of vitamin D (14.38 +/- 7.9 nmol/l) prevails, regardless of anticonvulsant usage. Sunshine exposure was virtually non-existent for most patients. Research has shown that when sunlight exposure is limited, osteomalacia in the British Asian community is determined by dietary factors. Our subjects had three types of diet: standard, soft and tube feeding. For both males and females, the tube feeding group had a significantly higher mean level of vitamin D than the other groups. Regular sunshine exposure is recommended for people requiring long-term infirmary care; alternatively, dietary supplement of vitamin D should be considered.

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.

Loss of Seizure Control Due to Anticonvulsant-Induced Hypocalcemia

OBJECTIVE:

To report a case of loss of seizure control due to hypocalcemia resulting from long-term treatment with phenytoin and phenobarbital.

CASE SUMMARY:

A 32-year-old mentally retarded man presented with a 12-month history of loss of seizure control, after being seizure-free for 5 years on a fixed regimen of phenobarbital and phenytoin. He had been institutionalized at the age of 10 years and had received anticonvulsant drugs since he was diagnosed with tonic-clonic epilepsy 20 years ago. On investigation, serum concentrations of the anticonvulsant drugs were within the therapeutic range, indicating adequate medication dosages. Serum biochemistry was consistent with vitamin D deficiency: hypocalcemia, reduced 25-hydroxyvitamin D, increased alkaline phosphatase, and increased parathormone. Seizure control was regained after serum calcium had been normalized with administration of vitamin D and calcium.

DISCUSSION:

Antiepileptic drugs (AEDs) cause vitamin D deficiency through induction of hepatic microsomal enzymes that metabolize vitamin D. Institutionalized subjects are more vulnerable because of the added factors of multidrug therapy, poor diet, reduced exposure to sunlight, and physical inactivity. The resulting hypocalcemia can cause reactive seizures, thus offsetting the anticonvulsant action of the drugs. An objective causality assessment revealed that the adverse reactions of both phenobarbital and phenytoin were probable.

CONCLUSIONS:

Hypocalcemic seizures are uncommon and underdiagnosed complications of long-term therapy with AEDs. Loss of seizure control in a patient stabilized on AEDs is an indication to check the patient's calcium status. Proper treatment of this complication is vitamin D and calcium supplementation. Prophylactic supplementation with vitamin D is necessary in institutionalized patients treated with AEDs.

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.

Long-term valproate and lamotrigine treatment may be a marker for reduced growth and bone mass in children with epilepsy

PURPOSE

To determine whether long-term treatment with valproate (VPA) and/or lamotrigine (LTG) in children with epilepsy is associated with altered growth and/or bone metabolism.

METHODS

Twenty-seven boys and 26 girls, aged 3 to 17 years (9.2 +/- 3.9, mean +/- SD), with epilepsy treated with VPA and/or LTG for > or =2 years were evaluated for growth, nutrient intakes, physical activity, bone mineral density (BMD), and blood biochemical indices of mineral and bone metabolism.

RESULTS

Twenty-three (43.4%) of the children had a body height below the 10th percentile. Z-scores for BMD below -1.5 occurred in 24.4% of the children. When patients were divided into two groups according to daily activity score, a significantly lower Z-score for total body BMD (p = 0.007), percentile for body height (p = 0.05), and plasma parathyroid hormone (PTH; p = 0.04), osteocalcin (p = 0.04) and 25-hydroxyvitamin D (25OHD) (p = 0.01) were found in the inactive compared with the active group. Z-score for total body BMD was correlated with daily activity score (r = 0.43, p = 0.008). Plasma intact osteocalcin and intact PTH values correlated significantly (r = 0.36, p = 0.02). Plasma 1,25-dihydroxyvitamin D was within normal range for all subjects. When patients were divided into LTG-alone, VPA-alone, and LTG-plus-VPA treatment groups, significantly lower (p < 0.05) plasma osteocalcin and percentile for body height were found in the VPA-plus-LTG treatment group.

CONCLUSIONS

Long-term VPA and LTG therapy, particularly when combined, is associated with short stature, low BMD, and reduced bone formation. These alterations may be mediated primarily through reduced physical activity rather than through a direct link to the VPA and/or LTG therapy.

Evaluation of bone mineral metabolism in children receiving carbamazepine and valproic acid

Dual energy X-ray absorptiometry (DXA) was used to assess lumbar spine (L2-4) and femoral neck bone mineral density (BMD) in 36 children taking either carbamazepine or valproic acid for longer than one year, for generalized idiopathic epilepsy. Patients were matched with controls. Biochemical parameters of bone mineral metabolism were also measured. BMD values at both the femur neck and lumbar spine in both the carbamazepine and valproic acid groups were not significantly different from that of the control group. Serum levels of calcium were subnormal and alkaline phosphatase levels were high in the carbamazepine group. Urinary calcium levels were significantly lower in both groups than in the control group (p< or =0.05) and also significantly lower in the valproic acid group than in the carbamazepine group (p< or = 0.05). There were no other significant biochemical changes in either group. In conclusion, the results suggest that valproic acid and carbamazepine monotherapies have minimal effects on bone mineral metabolism, but routine monitoring of risk and consideration of prophylactic vitamin D supplementation is important.

Vitamin D levels in noninstitutionalized children with cerebral palsy

Calcitriol (1,25-dihydroxy vitamin D) is an important hormone in calcium and phosphate metabolism. Levels of calcitriol and its precursor, 25-hydroxy vitamin D (calcidiol), were measured in a heterogeneous group of 125 noninstitutionalized children and adolescents with spastic cerebral palsy. Levels of each were correlated with: (1) clinical factors including mobility, prior fracture, and use of anticonvulsants; (2) nutrition and growth parameters including skinfolds, body mass index, and use of vitamin supplements; and (3) other serum analyses including osteocalcin as a marker of bone formation, calcium, and alkaline phosphatase. Levels of calcidiol and calcitriol did not correlate with any of the various clinical, nutritional, or growth parameters examined. The prevalence of low (< 10 ng/mL) levels of calcidiol was significant (19%), and dependent on the season of the year in which the level was measured. In contrast, less than 2% of the patients were found to have a low (< 20 pg/mL) level of calcitriol and the mean was comparable to normal pediatric subjects. Levels of calcitriol are maintained in noninstitutionalized children with cerebral palsy despite anticonvulsants, poor nutrition, and calcidiol levels that vary greatly with the seasons.

Bone mineralization in the affected extremities of children with spastic hemiplegia

To assess the impact of neurologic involvement on bone mineralization, dual-energy X-ray absorptiometry was used to quantitate bone mineral content (BMC), bone mineral density (BMD), fat and lean muscle mass in the limbs of 19 children with spastic hemiplegic cerebral palsy. The BMC in the affected limb was on average 26.5% lower (upper limbs) and 15.6% lower (lower limbs) than in the corresponding uninvolved limb. Lean muscle mass was reduced by 15% and BMD by 6% in the involved limbs and did not differ significantly between upper and lower limbs. The fat content of involved and uninvolved limbs did not differ. Children with poor hand function had greater reductions in BMC (39.3%), BMD (11.3%) and lean muscle mass (22.5%) than did children with better hand function. Thus, bone size and density decrease with increasing neurologic involvement, and weight bearing may slightly lessen the effect.

Antiepileptic drug toxicity: definition and mechanism of action

A detailed review of the adverse reactions of anticonvulsants is given, focusing on the definitions of drug toxicity, sources of information, patterns of drug utilization, pharmacokinetic variables and different mechanisms of action. The information available in the literature provides a wide spectrum of drug toxicity with no attempt at a practical definition of the reported events. This favors uncertainty among practising physicians, who are led to use the individual items with different attitudes. Suggestions are given for the evaluation, prevention and treatment of anticonvulsant drug toxicity.

High 1,25-dihydroxyvitamin D and low 25-hydroxyvitamin D concentrations in plasma in patients receiving antiepileptic drugs

Plasma 25-hydroxyvitamin D (25-OH D), 1,25-dihydroxyvitamin D (1,25-(OH)2 D) and parathyroid hormone (PTH) concentrations were determined in 30 outpatients receiving various antiepileptic drugs (AED). None of the patients exhibited high plasma PTH levels. The plasma 1,25-(OH)2 D levels were normal or high, although in a third of the patients the 25-OH D levels were reduced. There was a correlation between the 25-OH D and serum calcium levels. These findings suggest that the low plasma concentrations of 25-OH D, not 1,25-(OH)2 D, might play an important part in the occurrence of AED-induced disturbances of bone metabolism.

Effect of increasing doses of phenytoin on the plasma 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D concentrations

The circulating 25-hydroxyvitamin D [25(OH)D] and 1,25-dihydroxyvitamin D [1,25-(OH)2D] concentrations were studied in a patient receiving increasing doses of phenytoin. The plasma 1,25(OH)2D concentrations were independent of the dose of phenytoin administered, as well as of the drug plasma concentrations. The plasma 25(OH)D concentrations were, on the other hand, increased by low phenytoin concentration but rapidly declined when the dose of phenytoin was increased and/or as the length of time of exposure to the drug increased. A linear relationship (R = 0.9651, P less than 0.05) was found between the plasma 25(OH)D concentrations and the dose/plasma phenytoin concentration ratio, suggesting that chronic phenytoin administration may have a dose-related effect on the circulating 25(OH)D concentrations.