The effects on lipid and apolipoprotein serum levels of long-term carbamazepine, valproic acid and phenobarbital therapy in children with epilepsy

The aim of the present study was to assess the effect of long-term carbamazepine (CBZ), valproic acid (VPA) and phenobarbital (PB) treatment on serum lipids and apolipoproteins in epileptic children. Serum levels of total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), very low-density lipoprotein cholesterol (VLDL-C) and triglycerides (TGs) were measured and the LDL-C/HDL-C and TC/HDL-C ratios were calculated in 320 children and adolescents (129 receiving CBZ, 127 receiving VPA and 64 receiving PB) suffering from various types of epilepsy. Additionally, in a subgroup of 181 children (68 CBZ; 78 VPA; 35 PB) apolipoprotein A-I (apoA-I), apolipoprotein B (apoB), HDL2-C and HDL3-C were measured and apoA-I/apoB and HDL2-C/HDL3-C ratios were calculated. Results of the measurements were compared with those of 169 age-and sex-matched healthy controls. None of the variables considered was significantly correlated with time elapsed since start of treatment or with drug concentration in serum. TC and LDL-C serum levels were high in children receiving CBZ or PB and low in those treated with VPA. Serum LDL-C level exceeded 130 mg/dl in 27.9% of CBZ-group, 31.8% of the subjects receiving PB, but only in 7% of those receiving VPA and in 11.8% of control group subjects. CBZ-treated children also showed high HDL-C and HDL3-C values. In the group receiving VPA, HDL2-C, HDL2-C/HDL3-C ratio and apo B were significantly lower than in the control group. Mean apoA-I levels were low in all treated groups: by contrast, in neither group did TGs, VLDL-C levels and TC/HDL-C or LDL-C/HDL-C ratios differ significantly from the corresponding control group. Our results suggest that the effects of long-term AED therapy on lipid profile and, particularly, on apolipoprotein serum levels increase risk of atherosclerosis-related disease. Moreover, these results confirm our previously reported increased risk in CBZ and PB-treated patients.     

Effects of antiepileptic drugs on delivery and early childhood--comparison among mono-therapies of valproic acid, phenytoin, carbamazepine and phenobarbital

The effects of antiepileptic drugs (AED) on infants during pregnancy and delivery were studied in a total of 82 epileptic mothers on various monotherapies; 29 cases receiving valproic acid (VPA), 20 receiving phenytoin (PHT), 18 on carbamazepine (CBZ) and 15 on phenobarbital (PB). While AED serum concentrations were low in most cases of VPA, PHT and PB except for one case of VPA which exceeded therapeutic limits, concentrations were within therapeutic levels in many cases of CBZ. Conclusion: When compared with normal controls, abnormal deliveries such as caesarian section were seen more frequently in epileptic mothers under AED treatment. In addition, infants in PB cases were shown to have significantly lower mean birth length, weight and head circumference, suggesting that PB may retard fetal growth. The incidence of malformation in cases of VPA, PHT, CBZ and PB, was 10.3%, 5.0%, 0% and 6.7%, respectively. There were five types of malformation: in VPA cases, spina bifida, Siamese twins and ventricular septal defect tended to be severe, while in PHT and PB cases, cor biloculare and hypospadias respectively were observed. In cases of VPA, serum levels in the umbilical cord were found to be 150% higher than those in the mother.     

Clinical Side Effects of Phenobarbital, Primidone, Phenytoin, Carbamazepine, and Valproate During Monotherapy in Children

The rate of onset of side effects was examined in 392 pediatric outpatients who received long-term monotherapy with phenobarbital (PB), primidone (PRM), phenytoin (PHT), carbamazepine (CBZ), or valproate (VPA) for epilepsy or febrile convulsions. The severity of side effects (based on need to alter treatment), the nature of each drug's most common side effects, and the doses and plasma levels of occurrence were recorded. Our results show that usually accepted therapeutic ranges are well tolerated. Indeed, although some form of side effect occurred in 50% of patients, treatment had to be changed in only 18% and the drug had to be stopped in only 7%. In decreasing order, the rates for side effects were PHT (71%) greater than PB (64%) greater than CBZ (43%) greater than VPA (43%) greater than PRM (29%). Serious side effects requiring withdrawal of treatment occurred at the following rates: PHT (10%) greater than VPA (8%) greater than PRM (8%) greater than PB (4%) greater than CBZ (3%). Among our patients, the best tolerated antiepileptic drug (AED) was CBZ, and the least tolerated was PHT. Behavioral disorders were most common with PB, neurologic disorders with PHT, digestive tract disorders with VPA, and gingival hyperplasia and hirsutism with PHT. Behavioral disorders involving excitement seen with PB and PRM occurred most commonly at low plasma levels. Behavioral disorders involving depression seen with PB and VPA, those involving excitement seen with PHT and VPA, and digestive disorders seen with VPA occurred particularly when plasma levels were high.     

Comparison of AccuLevel and TDx: Evaluation of On-Site Monitoring of Antiepileptic Drugs

Therapeutic drug monitoring, an important aid in antiepileptic drug (AED) therapy, has a lag time before results are obtained from clinical laboratories. The AccuLevel test is an enzyme immunochromatographic method for quantitative measurement of AEDs including phenobarbital (PB), phenytoin (PHT), and carbamazepine (CBZ), with results available within 20 min. A comparison between AccuLevel and TDx, (fluorescence polarization immunoassay) was conducted in 233 paired blood samples from patients with AED therapy, including 12 Eskimo children receiving treatment in Greenland. Forty-five blood samples were analyzed for PB, 80 for PHT, and 108 for CBZ. Linear regression analysis showed good agreement between the two methods (r = 0.951, 0.958, and 0.945, respectively). The test is easy to perform, but care must be taken to follow the correct procedure, or inaccuracies will result. That happened in some of our results. A reduction in lag time, using on-site drug monitoring, was demonstrated. The AccuLevel is a rapid, accurate, and convenient method for use in AED monitoring.     

儿童癫痫及抗癫痫治疗对血脂水平影响的研究

对１１４例儿童癫痫患者的血脂水平进行监测。结果发现癫痫本身对血脂水平无影响，抗癫痫药物治疗后总胆固醇和甘油三产高，且随治疗时间的延长差异更为明显，高密度脂蛋白无变化。丙戊酸钠对血脂无影响，而苯舀英钠，苯巴比舀，卡马西平可使ＴＣ，ＴＧ明显升高。     

Comparison of antiepileptic drug levels in sudden unexpected deaths in epilepsy with deaths from other causes

PURPOSE: (a) To compare postmortem antiepileptic drug (AED) levels in patients with sudden unexpected death in epilepsy (SUDEP) with those in a control group of subjects with epilepsy. If SUDEP patients more frequently had undetectable or subtherapeutic AED levels, this would suggest that compliance with AED treatment is poorer in this group and that poor compliance is a risk factor for SUDEP. (b) To determine whether a particular AED was detected more commonly in the SUDEP group, suggesting that this AED is associated with a higher risk of SUDEP. METHODS: A retrospective study of coronial cases was performed. Postmortem AED levels in 44 SUDEP cases and 44 control cases were compared. The control group consisted of epileptics who died of causes other than epilepsy, including natural disease (e.g., ischemic heart disease, accidents, and suicide). The AEDs measured included carbamazepine (CBZ), phenytoin, (PHT), valproate (VPA), phenobarbitone (PB), lamotrigine (LTG), clonazepam (CZP), and clobazam (CLB). The number of SUDEP and control cases in which CBZ only was detected were compared, as were the number in which PHT only was detected. RESULTS: Compared with the controls, the SUDEP group showed no difference in the number with no detectable AEDs (13 vs. 11), the number with subtherapeutic AEDs (10 vs. 13), and the number with therapeutic levels (21 in both groups). CBZ only was detected in 11 SUDEPs and 11 controls, and PHT only in five SUDEPs and 10 controls. CONCLUSIONS: Our study suggests the SUDEP group were no less compliant with AED treatment than the control group. This study does not support the hypothesis that poor compliance with AED treatment is a risk factor for SUDEP. There was no evidence that PHT or CBZ is associated with a higher risk of SUDEP.     

Effects of Discontinuation of Phenytoin, Carbamazepine, and Valproate on Concomitant Antiepileptic Medication

We report a prospective, controlled study of the effects of the reduction and discontinuation of phenytoin (PHT) (22 patients), carbamazepine (CBZ) (23 patients), and valproate (VPA) (25 patients) with concomitant antiepileptic drugs (AEDs). The principal changes in the serum concentrations of concomitant AEDs were (a) phenobarbital (PB) concentrations decreased by a mean of 30% on discontinuation of PHT; (b) total CBZ concentrations increased by a mean of 48% and free CBZ concentrations increased by a mean of 30% on discontinuation of PHT, with no change in CBZ-10, 11-epoxide (CBZ-E) concentrations; (c) VPA concentrations increased by a mean of 19% on discontinuation of PHT; (d) VPA concentrations increased by a mean of 42% on discontinuation of CBZ; (e) ethosuximide (ESM) concentrations increased by a mean of 48% on discontinuation of CBZ; (f) PHT concentrations decreased by a mean of 26% on discontinuation of CBZ; (g) PHT free fraction decreased from a mean of 0.11 to 0.07 on discontinuation of VPA; and (h) the mean concentrations of total and free CBZ increased by a mean of 10 and 16%, respectively, on VPA discontinuation, with a concomitant mean 24% decrease in total CBZ-E and a 22% decrease in free CBZ-E. Apart from the decrease in PB concentrations on PHT discontinuation, all significant changes had occurred by 1 week after the end of AED discontinuation. The implication for clinical practice is that a serum AED concentration at this time reflects the new steady state. Free concentrations did not add any clinically useful information to that gained from analysis of total serum concentrations.     

Interactions of Phenobarbital and Phenytoin with Carbamazepine and Its Metabolites' Concentrations, Concentration Ratios, and Level/Dose Ratios in Epileptic Children

Summary: The effects of phenytoin (PHT) or phenobarbital (PB) comedication on the concentrations, concentration ratios, and level/dose ratios of carbamazepine (CBZ) and its metabolites were investigated. The hetero-induction effects of CBZ metabolism by PHT or PB were clearly demonstrated. Serum CBZ level/dose ratios in patients with CBZ polytherapy were decreased while CBZ- l0,11-epoxide (CBZ-E) and trans -l0,11-dihydroxy-10, 1-dihydro-CBZ (CBZ-H) concentrations were increased as compared with those of patients receiving CBZ alone. The concentration ratios of CBZ-H/CBZ and CBZ-E/ CBZ were also greater in patients receiving CBZ +PHT or CBZ+PB than in patients receiving CBZ alone. In addition, positive correlations between serum PHT concentration and CBZ-H/CBZ or CBZ-E/CBZ concentration ratios were observed. There were no significant differences in CBZ-H/CBZ-E concentration ratios, the free fractions of CBZ and its metabolites, and CBZ-E or CBZ-H 1eveYdose ratios among the three groups of patients. Because this approach investigates the in vivo relation between the substrates and products of the enzymes involved in CBZ biotransformation, more detailed information about the drug interactions was obtained. The results suggest that the PHT has a potent induction effect on CBZ epoxidase, whereas PB is a moderate inducer.     

Thyroid Function with Antiepileptic Drugs

Serum thyroid hormone balance was assessed in 108 patients receiving chronic antiepileptic drug (AED) therapy. Forty-five patients were receiving carbamazepine (CBZ), 26 phenytoin (PHT), 16 CBZ-PHT, 11 valproate (VPA), and 10 CBZ-VPA. Serum thyroxine (T4) and free thyroxine (FT4) concentrations were low in patient groups receiving CBZ and/or PHT. Serum T4 concentrations were below the normal range in 24 (53.3%) CBZ patients, 11 (42.3%) PHT patients, 12 (75%) CBZ-PHT patients, and in all 10 patients (100%) receiving CBZ-VPA. Furthermore, serum levels of FT4 were below the normal range in 13 (28.9%) CBZ patients, 6 PHT (23.1%) patients, 5 (31.3%) CBZ-PHT patients, and 5 (50%) CBZ-VPA patients. Despite the decreased serum T4 and FT4 levels in these patients, serum basal and stimulated thyrotropin (TSH) concentrations were normal, except for the slightly increased basal TSH in the CBZ-VPA group. In the VPA group, the findings were different from those in other patients: T4 serum levels were unchanged and FT4, T3, and basal TSH levels increased, but stimulated TSH levels did not differ from those of the control group. The decrease in serum thyroid hormone levels during CBZ and/or PHT medication probably is caused by an accelerated hepatic plasma clearance of these hormones due to induction of hepatic microsomal enzyme systems by these AEDs. VPA, an AED with no liver enzyme-inducing properties, does not cause similar changes. The feedback mechanism is not activated, possibly because of a hypothalamic interference by CBZ and PHT.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of long-term antiepileptic drug monotherapy on vascular risk factors and atherosclerosis

Purpose: Long‐term therapy with antiepileptic drugs (AEDs) has been associated with metabolic consequences that lead to an increase in risk of atherosclerosis in patients with epilepsy. We compared the long‐term effects of monotherapy using different categories of AEDs on markers of vascular risk and the atherosclerotic process. Methods: One hundred sixty adult patients who were receiving AED monotherapy, including two enzyme‐inducers (carbamazepine, CBZ; and phenytoin, PHT), an enzyme‐inhibitor (valproic acid, VPA), and a noninducer (lamotrigine, LTG) for more than 2 years, and 60 controls were enrolled in this study. All study participants received measurement of common carotid artery (CCA) intima media thickness (IMT) by B‐mode ultrasonography to assess the extent of atherosclerosis. Other measurements included body mass index, and serum lipid profile or levels of total homocysteine (tHcy), folate, uric acid, fasting blood sugar, high sensitivity C‐reactive protein (hs‐CRP), or thiobarbituric acid reactive substances (TBARS). Key Findings: Long‐term monotherapy with older‐generation AEDs, including CBZ, PHT, and VPA, caused significantly increased CCA IMT in patients with epilepsy. After adjustment for the confounding effects of age and gender, the CCA IMT was found to be positively correlated with the duration of AED therapy. Patients with epilepsy who were taking enzyme‐inducing AED monotherapy (CBZ, PHT) manifested disturbances of cholesterol, tHcy or folate metabolism, and elevation of the inflammation marker, hs‐CRP. On the other hand, patients on enzyme‐inhibiting AED monotherapy (VPA) exhibited an increase in the levels of uric acid and tHcy, and elevation of the oxidative marker, TBARS. However, no significant alterations in the markers of vascular risk or CCA IMT were observed in patients who received long‐term LTG monotherapy. Significance: Patients with epilepsy who were receiving long‐term monotherapy with CBZ, PHT, or VPA exhibited altered circulatory markers of vascular risk that may contribute to the acceleration of the atherosclerotic process, which is significantly associated the duration of AED monotherapy. This information offers a guide for the choice of drug in patients with epilepsy who require long‐term AED therapy, particularly in aged and high‐risk individuals.     

Antiepileptic Drugs and Peripheral Nerve Function: A Multicenter Screening Investigation of 141 Patients with Chronic Treatment

Summary: One hundred forty-one adult patients treated for no less than 6 months with standard daily doses of the commonest antiepileptic drugs (AEDs) were recruited in five Italian centers and submitted to intensive clinical and electrophysiologic investigation to assess the effects of AEDs on peripheral nerves. Eighty percent of the patients were receiving monotherapy. Carbamazepine (CBZ) was the most common AED (51 cases), followed by phenytoin (PHT) (46), phenobarbital (PB) (42), and valproate (VPA) (25). Fifty-three percent of the patients had one or more symptoms of polyneuropathy (paresthesias being the most common complaint). The neurologic examination was abnormal in 32%. Electrophysiologic findings in two or more separate nerves were abnormal in 77 patients (54.6%); of these, 27 (19.1%) had abnormal neurologic findings and 21 (14.9%) also had symptoms of polyneuropathy. Sensory functions were most frequently impaired. Sural nerve biopsy was performed in 4 patients receiving monotherapy with CBZ, PHT, PB, and VPA. Except in patients receiving VPA (in whom no morphologic abnormalities were detected), mild predominantly axonal damage with secondary myelin changes was noted. A correlation was noted between polyneuropathy, age of the patient and, to a lesser extent, receipt of two or more AEDs.     

Comparison the cognitive effect of anti-epileptic drugs in seizure-free children with epilepsy before and after drug withdrawal

We studied the cognitive effects of antiepileptic drugs (AED), by investigating epileptic children who were seizure-free for at least 2 years and who had undergone fixed monotherapy. Seventy consecutive epileptic children (25 with carbamazepine (CBZ), 22 with phenobarbital (PB), and 23 with valproate (VPA)) were examined by Wechsler Intelligence Scale for Children-Revised (WISC-R) and auditory event-related potentials (P(300)) at three sessions: before AED reduction, then 1 and 7 months after complete withdrawal of treatment. There were no significant differences in IQ and subtests scores of WISC-R in any group at any of the three sessions. P(300) latencies were significantly increased in the children receiving PB but not in children receiving CBZ or VPA. P(300) amplitudes were increased but not significantly different among the three groups. These findings suggest that PB may affect cognitive function on children, but the changes of P(300) latencies may improve after discontinuation.     

Pharmacokinetic behaviour of carbamazepine and its main metabolite-10, 11 epoxide of carbamazepine in monotherapy or in combination with other anti-epileptic drugs

A combination of anti-epileptic drugs is used for the necessary control of seizures. This results in a modulation of the metabolism in the epileptic patient and a concentration of the drugs and their metabolites in serum and in the brain, the target organ. Carbamazepine-10,11 epoxide (CBZE) is the main active metabolite of carbamazepine (CBZ). We have studied their interrelationship in concentrations in the plasma of 68 patients receiving CBZ, either as monotherapy or in combination with phenytoin (PHT) and phenobarbital (PB). The rate of CBZ metabolism was modulated in drug co-administration, which, depending on the grade of the induction of cytochrome p-450, decreases or increases the concentration of CBZE. A graph plotting the relationship between CBZ and CBZE concentrations in patients stabilized on a regime of CBZ alone is linear. The ratio of concentrations of CBZE/CBZ in serum is 0.12 when CBZ is administered as monotherapy, rising to 0.14 (CBZ + PB), 0.18 (CBZ + PHT) and 0.25 (CBZ + PHT + PB) when administered with the other drugs mentioned. From this it can be hypothesized that the additive of induction activities of PHT and PB operates on the mixed function oxidase system.     

Pregabalin drug interaction studies: lack of effect on the pharmacokinetics of carbamazepine, phenytoin, lamotrigine, and valproate in patients with partial epilepsy

PURPOSE: Pregabalin (PGB) is an alpha2-delta ligand with demonstrated efficacy in epilepsy, neuropathic pain, and anxiety disorders. PGB is highly efficacious as adjunctive therapy in patients with refractory partial seizures. METHODS: Given its efficacy as adjunctive therapy, the potential for interaction of PGB with other antiepileptic drugs (AEDs) was assessed in patients with partial epilepsy in open-label, multiple-dose studies. Patients received PGB, 600 mg/day (200 mg q8h) for 7 days, in combination with their individualized maintenance monotherapy with valproate (VPA), phenytoin (PHT), lamotrigine (LTG), or carbamazepine (CBZ). RESULTS: Trough steady-state concentrations of CBZ (and its epoxide metabolite), PHT, LTG, and VPA were unaffected by concomitant PGB administration. Likewise, PGB steady-state pharmacokinetic parameter values were similar among patients receiving CBZ, PHT, LTG, or VPA and, in general, were similar to those observed historically in healthy subjects receiving PGB alone. The PGB-AED combinations were generally well tolerated. PGB may be added to VPA, LTG, PHT, or CBZ therapy without concern for pharmacokinetic drug-drug interactions.     

抗癫痫药体外诱导鼠星形胶质细胞多药耐受基因P-糖蛋白的表达

目的：了解常用抗癫痫药（AED）对大鼠大脑上 星形胶质细胞多药耐受基因（MDR1）的诱导作用,探讨难治性癫痫的耐药机制。方法：给予不同浓度的苯巴比妥钠（PB）、苯妥英钠（PHT）、卡马西平（CBZ）和丙戊酸钠（VPA）持续作用于培养的新生鼠大脑皮质星形胶质细胞,分别在给药后10、20和30d,用免疫细胞化学法检测MDR1的标志物P－糖蛋白（Pgp)的表达率。结果,无药物作用的正常星形胶质细胞Pgp的表达率在各时点均小于5％,低浓度组各药在各时点Pgp的表达率与对照组比较差异无显著意义,有效血药浓度组仅PB20mg/L,PB40mg/L和PHT20mg/L在30d时Pgp表达增强;给药后10d,高浓度组各药Pgp表达率无明显增高;20d时PB、PHT和VPA组Pgp表达增强;30d时4种AED均有Pgp表达增强。结论AED可以诱导MDR1表达增强,且与剂量和时间相关。AED诱导的MDR1表达增强可能参与了难治性癫痫的形成。     

Adverse effects of carbamazepine,phenytoin, valproate and lamotrigine monotherapy in epileptic adult Chinese patients

Objective

Antiepileptic drugs (AEDs) have been widely used in patients with epilepsy but the adverse effects in adult Chinese patients have not been investigated. This study evaluated the adverse effects of four commonly prescribed AED monotherapies with carbamazepine (CBZ), phenytoin (PHT), valproate (VPA), and lamotrigine (LTG) in adult Chinese patients with epilepsy.

Methods

The prospective open-label clinical trial was conducted at the Chongqing Epilepsy Center. The study enrolled 505 adults with newly diagnosed epilepsy, including generalized tonic–clonic (n = 110), partial and partial secondarily generalized (n = 395) seizures. Patients were evaluated by two clinicians at the Center and were prescribed one type of AED monotherapy with CBZ, PHT, VPA or LTG for a 24-month period. An adverse effect profile, as well as efficacy of monotherapy, was obtained through a face-to-face interview with the patient at each visit. A physical examination and routine laboratory tests were performed during a clinical screening.

Results

A total of 62.6% (316/505) patients successfully completed the AED monotherapy study: 64.3% of those receiving CBZ, 55.9%—PHT, 61.5%—VPA, and 66.2%—LTG. However, 34.7% of the patients discontinued the AED monotherapy because of unsatisfactory seizure control. Overall, 18% of patients experienced adverse effects: for CBZ (25/168; 14.9%), PHT (18/59; 30.5%), VPA (32/192; 16.7%) and LTG (16/86; 18.6%). The most common drug-related adverse events included gastrointestinal disturbances, loss of appetite and nausea, weight gain and fatigue/tiredness. Tremor and nystagmus occurred in some patients receiving PHT and VPA. Two CBZ, one PHT and four LTG patients (n = 7) discontinued the study due to rash.

Conclusion

Adult Chinese patients with epilepsy accepted and tolerated monotherapy with CBZ, PHT, VPA, and LTG. No fatal adverse events occurred. Unsatisfactory seizure control was a primary reason for withdrawal from the AED monotherapy study.     

Comparison between premortem and postmortem serum concentrations of phenobarbital, phenytoin, carbamazepine and its 10,11-epoxide metabolite in institutionalized patients with epilepsy

The last premortem serum concentrations of phenobarbital (PB), phenytoin (PHT), carbamazepine (CBZ) and its CBZ-10,11-epoxide metabolite (CE) were compared with the corresponding postmortem serum concentrations in 16 adult patients of an epilepsy centre. Based on complete postmortem examinations, 12 individuals showed a known cause of death (KCD) and four patients succumbed from sudden unexplained death (SUD). The last premortem and the postmortem serum levels of PB (r = 0.991), PHT (r = 0.986), CBZ (r = 0.985) and CE (r = 0.936) were highly correlated. However, the regression analysis indicated that, except for CE, the premortem concentrations were significantly higher than the postmortem concentrations, i.e. 65% for PB, 34% for PHT, and 16% for CBZ. Varying time lapses (4-62 h) between death and serum sampling during autopsy did not significantly influence the ratio of premortem to postmortem serum levels for PB, PHT, CBZ, and CE (p > 0.1). Furthermore we found no significant differences between the premortem and the postmortem serum concentration ratios CE/CBZ. Considering the above variables, the data of SUD and KCD patients were comparable. Postmortem decrease in anticonvulsant serum concentrations, especially for PB and PHT, should be considered in order to avoid misinterpretation in respect to so-called 'subtherapeutic' serum levels and noncompliance in context with SUD or fatal intoxication.     

Reduction in Internal Carotid Arterial Blood Flow Velocity in Children During Antiepileptic Drug Therapy with Clinical Dosages

Summary: We studied the effect of antiepileptic drugs (AEDs) on internal carotid artery (ICA) blood flow velocity, as an index of total cerebral blood flow (CBF). The subjects were 45 newly diagnosed children with febrile convulsion or epilepsy who were seizure-free for a period long enough not to affect the results. They had no neurologic deficit, received fixed monotherapy, and were examined by a noninvasive Doppler ultrasound method, in comparisonwith 13 age-matched normal volunteers with no AED. In 30 patients, the measurements were performed before and after AED administration [10 with phenobarbital (PB), 10 with carbamazepine (CBZ), and 10 with valproate (VPA)], and performed before and after AED discontinuation in the remaining 15 patients (all with PB). Normal volunteers underwent the two consecutive examinations with a mean interval equal to that of the entire patient group, and there was no difference in velocity values between the measurements. In patients receiving CBZ or VPA, a significant reduction was noted in blood flow velocity after drug administration. Although velocity values in the patients receiving PB did not change after drug administration, they were significantly increased after complete discontinuation. In the present study, a slight but significant reduction in CBF caused by AED administration at therapeutic doses in children was suggested.     

Drug Interaction Profile of Topiramate

Summary: In separate studies, potential pharmacokinetic interactions of topiramate (TPM) with phenytoin (PHT), carbamazepine (CBZ), and valproate (VPA) were evaluated. TPM was added to the baseline antiepileptic drug (AED) at a dosage of up to 800 mg/day, after which the baseline drug was discontinued, when possible. Addition of TPM produced no change in plasma levels of CBZ or CBZ epoxide (CBZ-E). Modest increases in PHT plasma levels in six of 12 patients treated with PHT and TPM, and a small mean decrease in VPA levels noted in patients receiving VPA with TPM, were considered unlikely to require adjustments in the dosage of the concomitant AED when TPM is added or discontinued. When patients were changed from concomitant therapy with PHT or CBZ to TPM monotherapy, TPM clearance was reduced by approximately 50%, suggesting that an adjustment in TPM dose may be required when PHT or CBZ is discontinued from TPM-treated patients. A slight increase in plasma TPM levels during monotherapy compared to concomitant therapy with VPA was considered clinically insignificant and not likely to require TPM dosage adjustment. In another study, oral clearance of digoxin was slightly increased when TPM was added, resulting in a small decrease in peak plasma levels of digoxin. In vitro studies conducted to date on a number of specific cy-tochrome P450 isoforms show an effect of TPM only on the CYP2C_meph isoform. The risk for clinically meaningful changes in plasma levels of traditional AEDs when TPM is added to or discontinued from concomitant regimens appears to be minimal. However, adjustments in TPM dosages are likely to be needed when potent enzyme inducers, such as PHT or CBZ, are added or discontinued. TPM has a relatively low propensity for clinically significant drug interactions, and its pharmacokinetic and drug interaction profiles represent a clear advance over those of the traditional AEDs.