Serum vitamin D metabolites in epileptic patients treated with 2 different anti-convulsants

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.

How Antiepileptics May Change the Serum Level of Vitamin D, Calcium, and Phosphorus in Children with Epilepsy

Objective

Studies have shown vitamin (Vit) D deficiency and bone disease in long-term use of antiepileptics, especially in young individuals. This study aimed to determine the relationship between antiepileptic drugs and the level of Vit D, calcium (Ca), and phosphorus (P) in children with epilepsy at the Shohada Hospital from 2016 to 2017.

Materials & Methods

In this case-control study, 60 consecutive children with epilepsy at the Shohada Hospital from 2016 to 2017 under treatment with anticonvulsions for more than six months were enrolled as the case group. The level of Vit D, Ca, and P was determined in the case group and compared with 60 children without seizure as the control group.

Results

The mean Ca and P were alike across the groups (P > 0.05). The mean Vit D3 level was 31.3 and 40 in the case and control groups, respectively, with significant difference (P=0.0001). The mean Ca and P were alike across the types of drug in the case group (P > 0.05); however, the mean Vit D3 level was lower in the case versus control group with significant difference (P=0.040).

Conclusion

Totally, according to the obtained results, it may be concluded that treatment with antiepileptic drugs, especially stimulant type, is related to the lower Vit D3 level, but not to the Ca and P levels.

Epilepsy and vitamin D

Several disorders, both systemic and those of the nervous system, have been linked with vitamin D deficiency. Neurological disorders with a vitamin D link include but are not limited to multiple sclerosis, Alzheimer and Parkinson disease, as well as cerebrovascular disorders. Epilepsy which is the second leading neurological disorder received much less attention. We review evidence supporting a link between vitamin D and epilepsy including those coming from ecological as well as interventional and animal studies. We also assess the literature on the interaction between antiepileptic drugs and vitamin D. Converging evidence indicates a role for vitamin D deficiency in the pathophysiology of epilepsy.

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.

Effect of carbamazepine therapy on vitamin D and parathormone in epileptic children

Evidence suggests that carbamazepine affects bone metabolism by altering vitamin D status. We prospectively compared 25-hydroxyvitamin D, parathormone, calcium, phosphorus, and alkaline phosphatase levels at initiation and 6 months of carbamazepine therapy in children, and correlated them with carbamazepine levels. We included 47 children newly diagnosed with partial epilepsy, initiated on carbamazepine therapy. Of these, 32 were studied for 6 months. Children were managed according to standard protocol. Various parameters were measured at initiation and at 6 months. Carbamazepine levels were estimated after 6 months. Mean age was 6.72 ± 2.22 years S.D. Mean 25-hydroxyvitamin D was 14.45 ± 9.77 ng/mL S.D. and 11.31 ± 9.15 ng/mL S.D. at baseline and 6 months (P = 0.023), respectively (21.7% decline). Mean parathormone increased from 34.24 ± 21.38 pg/mL S.D. to 45.01 ± 24.46 pg/mL S.D. (P = 0.001). Change in vitamin D correlated negatively with change in parathormone (r = -0.404, P = 0.022). Serum alkaline phosphatase increased from 283.50 ± 100.10 IU/L S.D. to 364.25 ± 126.98 IU/L S.D. (P < 0.001). Changes in vitamin D and parathormone did not correlate significantly with carbamazepine level. Carbamazepine therapy decreased levels of vitamin D. Hence vitamin D monitoring and supplementation may help prevent alterations in bone metabolism.

Metabolic consequences of antiepileptic drugs

PURPOSE OF REVIEW

Chemical properties of the widely used older generation antiepileptic drugs (AEDs) suggest that they might be responsible for a number of medical comorbidities.

RECENT FINDINGS

AEDs which induce the cytochrome P450 system adversely affect bone, lipid, and gonadal steroid metabolism. Specifically, phenytoin causes loss of bone mass in women, and both phenytoin and carbamazepine produce increases in serum lipids and C-reactive protein, as well as decreases in bioactive testosterone in men. Patients treated with inducing AEDs are at increased risk of fracture. Some contradictory data raise the question of whether bone mass is truly related to enzyme induction, and analogously, of whether reductions in testosterone truly account for male sexual dysfunction. Data showing elevations of surrogate cardiovascular and cerebrovascular risk endpoints with epilepsy patients, mostly inducing AED treated, are consistent and concerning, however. Another older AED, valproate, is associated with the occurrence of polycystic ovary syndrome when used in young adulthood or adolescence.

SUMMARY

Older generation AEDs are associated with a panoply of metabolic abnormalities. Although more research is needed to see whether individual drugs are directly tied to specific clinical outcomes (e.g. risk of infarction), extant data are sufficiently concerning to suggest that these drugs may produce significant adverse health consequences. Newer generation AEDs may be preferable.

Vitamin D Levels and Bone Turnover in Epilepsy Patients Taking Carbamazepine or Oxcarbazepine

PURPOSE

Evidence suggests that enzyme-inducing antiepileptic drugs (AEDs) may decrease serum 25-hydroxyvitamin D (25-OHD) levels and increase bone turnover. We sought to determine whether these are affected by treatment with carbamazepine (CBZ) or oxcarbazepine (OXC).

METHODS

We measured serum levels of 25-OHD, parathyroid hormone (PTH), osteocalcin (OCLN), bone alkaline phosphatase (BAP), and urinary N-telopeptides of type I collagen cross-links (NTX) in normal controls (n=24) and in epilepsy patients taking CBZ (n=21) or OXC (n=24) in monotherapy. CBZ patients were subsequently switched overnight to OXC monotherapy, and after 6 weeks, the tests were repeated.

RESULTS

25-OHD levels were lower in each drug-treated group (OXC, 19.4+/-2.3 pg/ml; CBZ, 20.4+/-2.4) than in the controls (27.5+/-2.8) (ANOVA, p=0.052). This difference was significant for the OXC group (p<0.05). PTH, BAP, and NTX did not differ significantly among groups. OCLN levels were somewhat elevated in the OXC group (2.79+/-0.47 ng/ml) and more clearly and significantly elevated in the CBZ group (3.63+/-0.36) compared with controls (2.38+/- 0.41) (p=0.053). Because the data were very similar between OXC and CBZ groups, they were combined to increase statistical power. The combined drug-treatment group had significantly higher BAP (p=0.02) and lower 25-OHD (p=0.015) than did controls. The latter remained significant even after accounting for the confounding effects of age on 25-OHD levels (p<0.05). No significant differences were found after CBZ patients were switched to OXC.

CONCLUSIONS

Epilepsy patients taking OXC or CBZ have significantly lower 25-OHD than do normal controls, with a pattern of changes in other bone biomarkers suggestive of secondary hyperparathyroidism. It may be prudent for patients taking CBZ or OXC to be prescribed 25-OHD replacement.

Induction of endogenous pathways by antiepileptics and clinical implications

The aim of this study was to review modifications of the endogenous pathways (e.g. enzyme elevations, normal body constituent depletion or higher formation/excretion of endogenous metabolites) which could be ascribed to enzyme induction by antiepileptic drugs (AEDs). Information on older (e.g. phenobarbital, phenytoin and carbamazepine) and newer drugs (where information is available) is discussed together with clinical implications. The enzymes involved in the endogenous pathways and induced by the AEDs will not be limited to the hepatic microsomal enzymes; extrahepatic enzymes and/or enzymes present in other subcellular fractions will also be discussed, if pertinent. The induction of endogenous pathways by AEDs has been taken into account in the past, but much less emphasis has been given compared with the extensive literature on induction by AEDs of the metabolism of concomitantly administered drugs, either of the same or of different classes. Not all of the endogenous pathways examined and induced by AEDs appear to result in serious clinical consequences (e.g. induction of hepatic ALP, increased excretion of d-glucaric acid or of 6 beta-hydroxycortisol). In some cases, induction of some pathways (e.g. increase of high-density lipoprotein cholesterol or of conjugated bilirubin) might even be a beneficial side-effect, however enzyme induction is considered rather a detrimental aspect for an AED, as induction is generally a broad and a non-specific phenomenon. The new AEDs have generally less induction potential than the older agents. Yet some (felbamate, topiramate, oxcarbazepine and lamotrigine) have the potential for inducing enzymes, whereas others (levetiracetam, gabapentin and vigabatrin) appear to be completely devoid of enzyme inducing characteristics, at least as far as the enzymes investigated are concerned.

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.

Epilepsy and bone health in adults

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.

The Association Between Antiepileptic Drugs and Bone Disease

A growing body of literature indicates an association between antiepileptic drugs (AEDs) and bone disease, including histologic, radiographic, and biochemical evidence. The AEDs most commonly reported to cause decreased bone mineral density and disorders of bone metabolism are inducers of the cytochrome P450 enzyme system (phenobarbital, phenytoin, carbamazepine, primidone). More recent studies also suggest that valproate, an enzyme inhibitor, causes abnormalities in bone health. Multiple mechanisms have been postulated to support the association; however, no single mechanism explains all the findings. Identifying bone disease in persons with epilepsy receiving AEDs is important, as multiple treatment options are available.

Strategies for optimizing antiepileptic drug therapy in elderly people

The elderly take more antiepileptic drugs (AEDs) than all other adults. This extensive use directly correlates with an increased prevalence of epilepsy in a growing population of older people, as well as other neuropsychiatric conditions such as neuropathic pain and behavioral disorders associated with dementia and for which AEDs are administered. The agents account for nearly 10% of all adverse drug reactions in the elderly and are the fourth leading cause of adverse drug reactions in nursing home residents. Numerous factors associated with advanced age contribute to the high frequency of untoward drug effects in this population; however, strategies are available to ensure optimal outcomes.

Adverse effects of antiepileptic drugs on bone structure: epidemiology, mechanisms and therapeutic implications

Antiepileptic drugs (AEDs) were first associated with disorders of bone in both adults and children in the late 1960s. The most severe manifestations of these disorders are osteopenia/osteoporosis, osteomalacia and fractures. Bone disease has been described in several groups of patients receiving AEDs. Groups identified as being more vulnerable to AED-associated bone disease include institutionalised patients, postmenopausal women, older men and children. Radiological and histological evidence of bone disease is found in patients taking AEDs. Numerous biochemical abnormalities of bone metabolism have also been described. The severity of bone and biochemical abnormalities is thought to correlate with the duration of AED exposure and the number of AEDs used. In monotherapy, the AEDs most commonly associated with altered bone metabolism are phenytoin, primidone and phenobarbital (phenobarbitone). To date there have been no reports of altered bone metabolism in individuals receiving the newer anticonvulsants (specifically lamotrigine, topiramate, vigabatrin and gabapentin). The mechanisms of AED-associated bone disease are not clearly elucidated; however, several theories have been proposed to explain the link. No definitive guidelines for evaluation or treatment have yet been determined.

Carbamazepine and valproic acid: effects on the serum lipids and liver functions in children

We aimed to determine the effects of carbamazepine, which induces liver microsomal enzymes, and valproic acid on the serum lipids and liver function test results in epileptic children. Thirty-eight epileptic children (18 males, 20 females, mean age 8.6 +/- 3.9 years) were evaluated for serum lipids and liver function test results at the onset and the second and sixth months of antiepileptic therapy. The results of the children receiving carbamazepine (n = 31) and valproic acid (n = 7) were compared. In addition, the values obtained at different periods of treatment were compared within each group. The differences in the serum lipid levels and liver function test results of the children in the carbamazepine group and the valproic acid group were not statistically significant throughout the study. However, the total cholesterol, low-density lipoprotein, total cholesterol/high-density lipoprotein, and gamma glutamyl transferase levels were significantly increased in the carbamazepine group during treatment (P < 0.05) but not in the valproic acid group. Carbamazepine treatment alters the serum lipid profile of the children in such a way that it facilitates the development of atherosclerosis. Valproic acid does not alter the levels of the serum lipids.

Alcohol withdrawal and carbamazepine

The use of pharmacologic intervention in the management of alcohol withdrawal syndrome is briefly presented. The use of carbamazepine, a tricyclic anticonvulsant with clinical efficacy in depressive illness, in alcohol withdrawal treatment is reviewed. A comparative analysis between carbamazepine and major drugs used in alcohol withdrawal syndrome is made. This includes the evaluation of both clinical advantages and disadvantages in addition to identification of drug adverse reaction and interaction with alcohol. The mechanism of action of carbamazepine is also examined. Carbamazepine appears to possess a useful pharmacotherapeutic potential in the management of acute alcohol withdrawal syndrome, and its use in long-term treatment is suggested.

Anticonvulsant drug therapy in human pregnancy: effects on serum concentrations of vitamin D metabolites in maternal and cord blood

Serum concentrations of the main vitamin D metabolites and of calcium, phosphate, and alkaline phosphatase were determined in each of the three trimesters of pregnancy and in simultaneously obtained maternal and cord blood at delivery in 22 epileptic women treated with diphenylhydantoin or carbamazepine alone or with a combination with one other drug. The results were compared with similarly obtained data from 22 normal pregnancies. Women in both groups received supplements of 400 IU vitamin D3 per day. All the women had 25-hydroxyvitamin D levels within the normal range for healthy adults (greater than 12 ng/ml) throughout pregnancy. The epileptic women had, however, significantly (p less than 0.05) lower median 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D levels and higher median 25,26-dihydroxyvitamin D values than the reference group. The 24,25-dihydroxyvitamin D concentrations did not differ significantly, but the median ratio of 24,25-dihydroxyvitamin D to 25-hydroxyvitamin D was higher in the epileptic women at the end of pregnancy (p = 0.05). The respective differences in cord serum concentrations reflected those of the mothers at delivery. Serum calcium tended to be lower during epileptic pregnancy, but none were hypocalcemic. The alkaline phosphatase and phosphate values did not consistently differ from those of the reference women. The median alkaline phosphatase level of cord serum was slightly higher in the epileptic group, but the calcium and phosphate levels were similar to the reference values. The various biochemical parameters of the carbamazepine-treated women tended to be intermediate between those of the healthy and diphenylhydantoin-treated groups. Antiepileptic drug therapy appears to affect vitamin D metabolism and calcium homeostasis during pregnancy. The derangements may not be of major clinical significance, however, in vitamin D-supplemented and normally functioning women on long-term low-dose therapy.

Side effects of carbamazepine, valproate and clonazepam during long-term treatment of epilepsy

Side effects of carbamazepine (CBZ), valproate (VPA) and clonazepam (CZP) are rare during long-term use but rather common and usually transient during the early phases of treatment. The usual side effects of CBZ are drowsiness, dizziness, and diplopia, which are dose dependent in long-term use, but CBZ does not seem to cause cognitive disturbances, as do phenobarbital and phenytoin. Other reactions to CBZ may include leukopenia, hyponatremia, disturbances of vitamin D metabolism and fortunately rarely, agranulocytosis and hepatitis. Use of VPA can lead to gastrointestinal discomfort, weight gain, hair loss, tremor and sedation, but these side effects are rather uncommon, mild, and transient during VPA monotherapy. Potentially hazardous reactions such as hepatitis and pancreatitis have occurred in a few patients on VPA, generally with multidrug therapy. Some of the side effects are dose related. They infrequently lead to withdrawal of VPA. Side effects limited to initiation of CZP therapy include drowsiness, ataxia, and behavioral changes; they are usually transient but can lead to dose reduction or even withdrawal of the drug. Except for development of tolerance, CZP seems to be practically free of long-term side effects.

Does carbamazepine cause disturbances in calcium metabolism in epileptic patients?

Calcium metabolism was examined in 30 adult epileptic outpatients on carbamazepine monotherapy. The patients had a normal bone mass, evaluated both on the forearm (100 +/- 13 of normal) and on the total skeleton (102 +/- 15), and normal serum concentrations of 25OHD. The serum calcium was decreased (P less than 0.001) and the serum alkaline phosphatase increased (P less than 0.001). The clinical significance of our study is that monotherapy with carbamazepine does not have the side effects on bone metabolism known as "anticonvulsant osteomalacia". Our results further question the connection between liver enzyme induction and anticonvulsant osteomalacia, since carbamazepine possesses the same potency of liver enzyme induction as phenytoin. Further studies on epileptic outpatients will be necessary in order to elucidate the connection between treatment with anticonvulsant drugs and anticonvulsant osteomalacia.