Homocysteine, folate, vitamin B-12 and vitamin B-6 in patients receiving antiepileptic drug monotherapy

We hypothesized that elevated plasma homocysteine concentrations (hyperhomocysteinemia) exist in patients receiving antiepileptic drugs (AED), and a long-term administration of AED may result in an increased risk of occlusive vascular disease in these patients. A total of 62 patients who received AED monotherapy (phenytoin, lamotrigine, carbamazepine or valproate) participated in this study. Blood concentrations of homocysteine, folate, vitamin B-12 and pyridoxal-5'-phosphate (PLP, a coenzyme form of vitamin B-6) were measured, and thermolabile genotypes of 5, 10-methylenetetrahydrofolate reductase (MTHFR) were also determined. Of 62 patients, only seven (11.4%) had hyperhomocysteinemia. Of 20 patients who received phenytoin, three (15.0%) had hyperhomocysteinemia, whereas 85% of these had plasma folate concentrations below the normal range. However, erythrocyte folate concentrations were abnormally low in only 25% of the patients who received phenytoin. Valproate administration increased serum vitamin B-12 concentrations. Over 55% of the entire patients had PLP concentrations below the normal range, although the reason is unknown. Only three patients had the homozygous thermolabile genotype of MTHFR; therefore, meaningful statistical analysis was not possible in this study. However, one patient with homozygous genotype who received phenytoin therapy had hyperhomocysteinemia with poor folate nutritional status, and the other two had normal homocysteine concentrations with normal folate status. Our data suggest that hyperhomocysteinemia is not a serious clinical concern in epileptic patients when folate nutriture is adequate.     

Assessment of copper status in epileptic patients treated with anticonvulsant drugs by measuring the specific oxidase activity of ceruloplasmin

Significant increases in serum levels and decreases in hair copper levels have been previously described in epileptic patients treated with anticonvulsant drugs. A condition not directly related to copper nutriture, such as chronic treatment with these drugs, could increase the serum concentrations of copper and ceruloplasmin and would mask a possible copper deficiency produced by drug-increased biliary copper excretion. Serum immunoreactive ceruloplasmin concentration and its oxidase activity were determined in 90 adult epileptic patients treated with phenobarbital (n=60), phenytoin (n=70), carbamazepine (n=33) and valproic acid (n=8). The levels of ceruloplasmin and oxidase activity were significantly higher (P<0.001) than in an age and gender-matched control group (n=49). The significant correlations (P<0.01) between ceruloplasmin and the urinary excretion of D-glucaric acid, serum gamma-glutamyltransferase (GGT) and drug score in the patients group, would suggest that phenobarbital-type enzyme-inducing agents may increase the hepatic synthesis of ceruloplasmin. In 11 patients with a beta-globulin migrating GGT isoform (GGT3), a sensitive marker of cholestasis, the levels of ceruloplasmin, oxidase activity and total GGT activity were significantly higher (P<0.05) than in the group of 79 patients without the GGT3 isoform; consequently, in some cases a drug-induced cholestasis may also contribute to the increase of serum copper and ceruloplasmin. The values obtained for the specific oxidase activity of ceruloplasmin (activity per unit mass of enzyme protein) suggest that in the most of the cases, chronic administration of phenobarbital, phenytoin, carbamazepine or valproic acid, does not produce marginal or moderate copper deficiency.     

Serum lipids, lipoproteins and apolipoproteins A and B in epileptic patients treated with valproic acid, carbamazepine or phenobarbital

Serum lipids, lipoproteins and apolipoproteins A and B were measured in 101 epileptic patients receiving chronic treatment with valproic acid, carbamazepine or phenobarbital and in 75 age- and sex-matched control subjects. In relation to controls, subjects treated with valproic acid showed significantly lower values of total and LDL-cholesterol levels; subjects treated with carbamazepine showed significantly higher values of HDL-cholesterol and apolipoprotein A concentrations and subjects treated with phenobarbital showed significantly higher values of total cholesterol, HDL-cholesterol, apolipoprotein A and apolipoprotein B levels. The total cholesterol/HDL-cholesterol ratio was significantly lower in patients receiving valproic acid or carbamazepine but not in the phenobarbital-treated group. Changes in serum lipids profile did not correlate with drug plasma concentrations nor the duration of the treatment.     

Homocysteine levels in epileptic children receiving antiepileptic drugs

The aim of this study is to investigate the homocysteine, folic acid, and vitamin B(12) levels in epileptic children receiving antiepileptic drugs. A total of 25 children with idiopathic epilepsy (8 valproate, 11 carbamazepine, and 6 oxcarbazepine) and 10 healthy children were included in the study. The mean homocysteine, folic acid, and vitamin B(12) levels in the study group were 7.57 +/- 3.78 micromol/L (normal = 5-15 micromol/L), 10.19 +/- 4.05 ng/mL (normal = 3.0-17 ng/mL), and 428.20 +/- 256.12 pg/mL (normal = 193-983 pg/mL), respectively. The differences between the mean plasma homocysteine, folic acid, and vitamin B(12) levels of the study and control groups were not significant (P = .522; P = .855; P = .798, respectively). However, plasma homocysteine levels were higher than the normal cutoff point accepted for childhood in 4 (16%) of the study patients. Out of these 4 children, 3 were from the carbamazepine group and 1 was from the valproate group. Although the number of the study patients is limited, the authors recommend assessment of plasma homocysteine, serum vitamin B(12), and folic acid levels in children receiving enzyme-inducing antiepileptic drugs.     

Utility of Free Level Monitoring of Antiepileptic Drugs

Criteria that were developed for monitoring free (unbound) rather than total (free plus bound) concentrations of antiepileptic drugs include extensive and variable binding to plasma proteins. Phenytoin and valproic acid belong to this category. It is shown that free drug concentration is independent of total drug concentration, whereas total drug concentration depends on free concentration and free fraction. Because antiepileptic drugs are predominantly bound to albumin, free fraction will increase in the presence of hypoalbuminemia (hepatic and renal disease, burns, and pregnancy). Free fraction also increases because of saturable binding (valproic acid) and competitive binding (valproic acid displacing phenytoin). There is suggestive evidence that side effects may be more closely related to the free, rather than to the total, plasma concentration of phenytoin. The clinical evidence that side effects or therapeutic effects are better correlated to the free, rather than the total, concentration of valproic acid or carbamazepine is not yet convincing. Knowledge of the free concentration improves our understanding of therapeutic and toxic effects of low total plasma concentrations. Further clinical trials are necessary for definitive assessment of the clinical relevance for free drug monitoring of valproic acid, carbamazepine, and phenytoin in the management of epileptic patients.     

Anticonvulsive drugs and blood levels of lactate, pyruvate, and glucose in children with seizures

Lactate, pyruvate, and glucose were determined in groups of 10 patients, each receiving single drug therapy for their seizure disorder with either phenytoin, valproic acid, carbamazepine, or phenobarbital, and in patients not taking medication. All drug levels were in their therapeutic ranges. The characteristics of the groups were similar, except for the phenytoin group being significantly older. No significant differences were found in glucose or pyruvate concentrations. However, patients on valproic acid had reduced lactate (p less than 0.05) and L/P ratios (p less than 0.05). The reduction in lactate in patients on valproate therapy may mask inborn errors of metabolism that normally result in an increase in blood lactate levels.     

Evolving antiepileptic drug treatment in juvenile myoclonic epilepsy

BACKGROUND: In the face of availability of newer antiepileptic drugs (AEDs) such as lamotrigine and topiramate, there is need to reassess the role of older AEDs in the treatment of juvenile myoclonic epilepsy (JME). OBJECTIVES: To explore whether lamotrigine and topiramate monotherapy or polytherapy can be effective options in the treatment of JME, and to determine whether older AEDs, such as phenytoin and carbamazepine, have a role in the treatment of JME. DESIGN: A retrospective cohort study. SETTING: A large academic teaching hospital. PATIENTS: Seventy-two consecutive JME patients treated with valproic acid, lamotrigine, topiramate, phenytoin, or carbamazepine between April 1, 1991, and March 31, 2001. METHODS: We compared the efficacy of valproic acid, lamotrigine, and topiramate monotherapy or polytherapy in the control of different seizure types of JME, and compared their efficacy and tolerability with the efficacy and tolerability of phenytoin and carbamazepine. RESULTS: Seizure outcome did not differ when patients receiving valproic acid monotherapy (n = 36) were compared with those receiving lamotrigine monotherapy (n = 14), and when patients receiving valproic acid polytherapy (n = 22) were compared with those receiving lamotrigine polytherapy (n = 21) or topiramate polytherapy (n = 15) (P>.05 for all). The combined data of myoclonic seizure control by all 3 AEDs were poorer when compared with the combined data of generalized tonic-clonic seizure control by all 3 AEDs (P =.03), but not when compared with the combined data of absence seizure control by all 3 AEDs (P =.43). Valproic acid, lamotrigine, and topiramate, when compared with phenytoin or carbamazepine, demonstrated significantly better control of myoclonic seizures (P<.01 for all), but not of generalized tonic-clonic seizures (P>.11 for all). CONCLUSIONS: Lamotrigine and topiramate are effective alternative options to valproic acid in the treatment of JME. Lamotrigine is an effective option as monotherapy and polytherapy. Topiramate is an effective option as polytherapy, but more data are needed to determine if it is an effective option as monotherapy. More effective therapy is needed to improve myoclonic seizure control. Older AEDs, such as phenytoin and carbamazepine, may not be indicated in JME patients.     

Salivary free concentrations of anti-epileptic drugs: an evaluation in a routine clinical setting

OBJECTIVE: This study was aimed at correlating the salivary and serum free concentrations of anti-epileptic drugs (carbamazepine, phenytoin and sodium valproate) in a population of neurological patients in a routine clinical setting. METHOD: Twenty-seven paired serum/saliva specimens from 22 patients: 10 for carbamazepine, 8 for phenytoin and 9 for sodium valproate were obtained to study these correlations. Salivary and serum free concentrations of anti-epileptic drugs, anti-epileptic drug dosing history, and associated information were collected prospectively. The salivary and serum free concentrations of the anti-epileptic drugs were simultaneously quantified using fluorescence polarization immunoassay (TDx analyzer). RESULTS: For both carbamazepine and phenytoin there was a strong correlation between the salivary and serum free concentrations, 0.99 and 0.98, respectively. The mean ratio of salivary to serum free carbamazepine concentration was 1.02 +/- 0.11 and 0.82 +/- 0.15 for phenytoin. A poor correlation between salivary and serum free concentration was observed for sodium valproate (0.70) with a mean ratio of salivary to serum free concentration of 0.48 +/- 0.27. CONCLUSION: Monitoring of free salivary concentrations of anti-epileptic drugs, particularly phenytoin and carbamazepine proved to be a realistic alternative in this routine clinical setting.     

Lack of pharmacokinetic interaction of levetiracetam on carbamazepine, valproic acid, topiramate, and lamotrigine in children with epilepsy

PURPOSE: To determine whether levetiracetam (LEV) affects plasma concentrations of carbamazepine, valproic acid, topiramate, and lamotrigine in children with epilepsy. METHODS: The potential for interaction of LEV with other antiepileptic drugs (AEDs) was assessed using plasma drug levels obtained in a randomized placebo-controlled phase III trial of adjunctive LEV in children receiving one or two concomitant AEDs. Multiple plasma AED levels at baseline and during adjunctive treatment with LEV or placebo were compared by repeated measures analysis of covariance and mean concentration ratios (treatment/baseline) were estimated with their 90% confidence intervals (CI). RESULTS: The study population included 187 children receiving any concomitant AED alone or in combination. The geometric mean concentrations at baseline and during LEV treatment were carbamazepine 8.4 microg/ml versus 8.1 microg/ml (coefficient of variation, CV = 30%; n = 35); valproic acid 83.8 versus 82.5 microg/ml (CV = 38%; n = 23); topiramate 7.3 versus 7.2 microg/ml (CV = 82%; n = 28); lamotrigine 8.2 versus 7.7 microg/ml (CV = 62%; n = 22). For each AED, the mean concentration ratios (LEV/baseline) and their 90% CIs showed that AED concentrations were unaffected by concomitant LEV administration. No differences were observed between LEV and placebo. CONCLUSIONS: LEV does not affect plasma concentrations of carbamazepine, valproic acid, topiramate, or lamotrigine in children with epilepsy.     

Serum lipid changes during anticonvulsive treatment serum lipids in epileptic children

Serum lipid profile changes were investigated in 53 children receiving phenobarbital (n = 14), carbamazepine (n = 21), and valproic acid (n = 18) for their newly diagnosed seizure disorder. The patients were followed prospectively. Serum total cholesterol, high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, and triglyceride concentrations increased after 3 months of treatment with carbamazepine and remained high after one year. Serum total cholesterol levels increased after 3 months of treatment with phenobarbital and remained high after one year. Serum lipid concentrations did not change during valproic acid therapy. Serum lipid profiles should be carefully monitored in children receiving enzyme inducing antiepileptic drugs.     

Adverse effects of antiepileptic drugs on bone mineral density

The aim of this study is to determine the frequency of changes in biochemical markers of bone metabolism in children who are receiving valproic acid, carbamazepine, and oxcarbazepine. Thirty healthy children and 68 children with idiopathic epilepsy treated with either carbamazepine (n = 23), valproic acid (n = 31), or oxcarbazepine (n = 14) for more than 1 year were enrolled into the study. Blood samples were obtained in order to determine biochemical parameters (calcium, phosphorus, alkaline phosphates, parathormone, and 25-hydroxyvitamin D). Bone mineral density was measured with the dual-energy x-ray absorptiometry method. There were no significant differences in the serum concentrations of calcium, phosphorus, aspartate aminotransferase, alanine aminotransferase, and albumin levels between the four groups. However, serum alkaline phosphatase concentrations were higher in the patient group as compared with the control subjects. In patients receiving antiepileptic drugs, bone mineral density values were significantly lower than the healthy control group. In conclusion, long-term antiepileptic drug treatment either with valproic acid, carbamazepine, or with oxcarbazepine which has unknown effects on skeletal mineralization, induces a state of decreased bone mineral density.     

Thyroglobulin and Thyroid Hormones in Patients on Long-Term Treatment with Phenytoin, Carbamazepine, and Valproic Acid

Serum concentrations of total triiodothyronine (T3) and thyroxine (T4) as well as serum thyroid-stimulating hormone (TSH) and thyroglobulin (Tg) were measured in 24 patients with epilepsy taking anticonvulsants (either phenytoin, carbamazepine, or valproic acid as single treatment) and in a control group of 28 patients with scoliosis but without thyroid disease. The T4 as well as the TSH concentrations were depressed in patients on phenytoin or carbamazepine treatment. The T3 concentration was increased in the patients on carbamazepine or valproic acid treatment, whereas the Tg levels were unaffected by all three drugs. Thus, a slight depression of the TSH concentration within the normal range does not influence the Tg release. The lack of change in the Tg concentration also speaks against a direct effect of the antiepileptic drugs on the thyroid gland.     

Clinically Significant Carbamazepine Drug Interactions: An Overview

Summary: Knowledge of the principles of drug action and distribution contributes to an understanding of the occurrence of drug interactions. The pharmacologic action of most drugs is postulated to occur by the formation of a drug-receptor complex at the site of action that is capable of altering the physiologic response of the target system. The therapeutic response observed depends on the sum of the numerous factors that can affect the disposition pattern of a drug. In an individual, the response to a given drug dose remains relatively constant, but in a large population, a fixed dose can produce a range of plasma concentrations and therefore varied clinical responses. For most drugs, there is a linear relationship between the total dose and the plasma concentration achieved at steady state. Saturation, or zero-order, kinetics accounts for nonlinear increases in drug concentration with dosage increase. Drug-drug interactions with carbamazepine include several types. (1) Autoinduction of carbamazepine metabolism increases the carbamazepine clearance rate, decreases the half-life, and decreases serum concentrations; the clinician must reevaluate a patient's serum levels at 4 to 6 weeks after initiation of therapy. (2) Carbamazepine induces the metabolism of other antiepileptic drugs, enhancing the clearance of phenytoin, primidone, valproic acid, clonazepam, and ethosuximide. (3) Other drugs added to the epileptic patient's drug regimen may induce the metabolism of carbamazepine, causing increased serum concentrations. (4) Inhibition of carbamazepine metabolism by other drugs can also occur; symptoms of drug intoxication rapidly follow. Interactions occur between carbamazepine and macrolide antibiotics, cimetidine, propoxyphene, and isoniazid. Drug-drug interactions are preventable. It is the responsibility of every physician to be alert to the potential for their occurrence whenever a change in the epileptic patient's drug regimen is made.     

Serum elevation of high density lipoprotein (HDL) cholesterol in epileptic patients taking carbamazepine or phenytoin

Serum lipids and the cholesterol concentration in the high density lipoprotein (HDL) fraction were measured in epileptic patients taking either carbamazepine or phenytoin as single drug treatment. There was a significant increase in HDL-cholesterol levels in patients taking both phenytoin and carbamazepine. Serum total-cholesterol concentrations in patients taking both drugs did not differ significantly from those of controls. The ratio of HDL-cholesterol/total cholesterol was increased in both drugs and the increase reached significance in patients taking phenytoin. There was a significant increase in serum triglycerides in females taking carbamazepine.     

The influence of seizure type on the efficacy of plasma concentrations of phenytoin, phenobarbital, and carbamazepine

Plasma concentrations of phenytoin, phenobarbital, or carbamazepine were monitored prospectively during successful single-drug therapy in 78 patients who had various types of epileptic seizures. Mean plasma concentrations necessary for complete control of tonic-clonic seizures alone were as follows: phenytoin, 14 micrograms/mL (n = 28); phenobarbital, 18 micrograms/mL (n = 10); and carbamazepine, 5.5 micrograms/mL (n = 2). Epilepsy with simple or complex partial seizures alone or together with tonic-clonic seizures was completely controlled at the following plasma concentrations: phenytoin, 23 micrograms/mL (n = 25); phenobarbital, 37 micrograms/mL (n = 5); and carbamazepine, 7 micrograms/mL (n = 7). Higher plasma concentrations of phenytoin, phenobarbital, and carbamazepine are necessary for control in epilepsy with simple or complex partial seizures compared with epilepsy with tonic-clonic seizures alone. The efficacy of plasma concentrations of phenytoin, phenobarbital, and carbamazepine varies with the type of seizure.     

Refractory idiopathic absence status epilepticus: A probable paradoxical effect of phenytoin and carbamazepine

PURPOSE: To compare the frequency of seizures and status epilepticus and their response to first-line drugs in patients with idiopathic generalized epilepsies receiving carbamazepine or phenytoin to those receiving other drugs or no treatment. METHODS: We performed a retrospective chart review of all cases of idiopathic generalized epilepsies treated by the authors between 1985 and 1994. We compared seizure frequency and mean intravenous benzodiazepine dose required to control absence status epilepticus, intraindividually in subjects on carbamazepine or phenytoin before and after discontinuation of these compounds, and interindividually to subjects without treatment or receiving other drugs. RESULTS: Bouts of absence or tonic-clonic status epilepticus and seizures in subjects treated with phenytoin or carbamazepine at therapeutic concentrations were considerably more frequent and proved intractable to treatment with valproic acid or benzodiazepines, compared with a cohort of subjects also with idiopathic generalized epilepsies, but naive to, or receiving subtherapeutic or therapeutic doses of other agents. CONCLUSIONS: Our observations strongly suggest that therapeutic concentrations of phenytoin and carbamazepine exacerbate idiopathic generalized epilepsies. Subjects in whom absence is one of the seizure types seem at a particularly high risk for responding paradoxically. These findings underscore the value of accurate classification of seizures and particularly the syndromic approach to diagnosis and point to the potential for iatrogenic complications with indiscriminate use of antiseizure drugs.     

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.     

AD患者血清Hcy叶酸及维生素B_(12)与认知功能减退的关系研究

目的研究维生素B_(12)和叶酸水平以及同型半胱氨酸是否对阿尔茨海默症(AD)患者存在潜在影响。方法运用美国国立神经病学、语言障碍和卒中-阿尔茨海默病和相关疾病学会(NINCDS-ADRDA)标准严格筛选AD患者95例。从体检中心选取年龄、性别及受教育程度匹配的无脑血管病、无认知障碍的健康对照组76例。采用化学发光微粒子免疫分析法检测171例年龄≥50岁的老年痴呆患者血清维生素B_(12)和叶酸水平。采用肝素抗凝的血浆进行循环酶法Hcy测定。探讨血清低水平维生素B_(12)和叶酸以及高水平同型半胱氨酸是否是老年痴呆发生的危险因素。认知功能的评价采用目前通用的神经心理测试:中文版简易精神状态检查表(MMSE)。采用Logistic回归分析评估血清维生素B_(12)、叶酸以及同型半胱氨酸与老年痴呆患病风险的关系。结果 171例中153例叶酸正常,其中对照组79例(51.63%),实验组74例(43.27%);124例维生素B_(12)正常,其中对照组60例(48.39%),实验组64例(51.61%);101例同型半胱氨酸正常,其中对照组51例(50.50%),实验组50例(49.50%)。作各协变量调整后,AD患者血清维生素B_(12)及叶酸水平以及同型半胱氨酸与CMMES评分无相关性(P0.05)。但低血清维生素B_(12)水平以及低叶酸水平与AD患病风险相关。结论血清维生素B_(12)和叶酸水平以及同型半胱氨酸水平与AD患者认知功能之间无明显关联。低水平维生素B_(12)以及低水平叶酸可能通过某种机制增加AD患病风险,低水平同型半胱氨酸可能通过某种机制降低AD患病风险。     

Homocysteine,vitamin B6, and vascular disease in AD patients

BACKGROUND: Cerebrovascular disease is a cause of dementia and is associated with elevated plasma levels of homocysteine. Patients with AD tend to have unexplained elevations of homocysteine concentrations vs healthy control subjects. Vitamin B(6) status, a potential determinant of plasma homocysteine, has not been characterized in patients with AD. OBJECTIVE: To investigate plasma homocysteine, vitamin B(6) status, and the occurrence of vascular disease in patients with AD. METHODS: Forty-three patients with AD and 37 control subjects without AD were studied for homocysteine, B vitamin status (folate, vitamin B(12), pyridoxal-5'-phosphate [PLP]), kidney function (creatinine), and thyroid function (thyroid-stimulating hormone, thyroxin). In addition, the presence of vascular disease was assessed by reviewing both medical histories and brain imaging data provided by CT and MRI. RESULTS: The OR for elevated plasma homocysteine (>12 micromol/L) was only 2.2 (not significant) for subjects with AD. In contrast, the OR was 10.0 (p = 0.03) for subjects with vascular disease (n = 26). The OR for low plasma PLP (<25 nmol/L) was 12.3 (p = 0.01) for patients with AD. No significant relationship was observed between vascular disease and PLP level or between plasma homocysteine and PLP concentrations. CONCLUSIONS: Elevated plasma homocysteine in patients with AD appears related to vascular disease and not AD pathology. In addition, low vitamin B(6) status is prevalent in patients with AD. It remains to be determined if elevated plasma homocysteine or low vitamin B(6) status directly influences AD pathogenesis or progression.