The impact on family scale: psychometric analysis of long and short forms in parents of children with epilepsy

Epilepsy in a child or adolescent can have severe psychosocial impact on the whole family and burdens them, especially the parents. As the familial background is essential for the child's coping and the progression of the epilepsy, parental burden should be considered within a comprehensive treatment approach. This study validated the applicability of the Impact on Family Scale (IOFS), a well-established instrument that assesses the strains of families with chronically ill or disabled children, in parents of children with epilepsy. In a sample of 219 parents, the psychometric properties of the original IOFS version (33 items) and two short forms (15 and 11 items, respectively) were examined. Both short forms revealed good reliability (Cronbach's alpha, test-retest reliability), and construct validity was verified by correlations with epilepsy- and burden-related variables. However, exploratory and confirmatory factor analyses indicated superior characteristics of the short form with 11 items (IOFS-11). In conclusion, the IOFS-11 as well as the IOFS-15 proved to be practicable, reliable, and valid tools to assess the impact of childhood epilepsy on family life in research and clinical practice.

Levetiracetam in children with refractory epilepsy: A multicenter open label study in Germany

PURPOSE

To evaluate the efficacy and tolerability of Levetiracetam (LEV) in a large pediatric cohort with drug-resistant epilepsy from a prospective multicenter observational study.

METHODS

We report the results of a multicenter observational survey of a cohort of 285 pediatric patients (mean: 9.9 years, range: 0; 6-17; 11) with refractory generalized and focal epilepsy who received Levetiracetam as an add-on open label treatment trial. The average duration of epilepsy was 6.0 years and the patients were treated with a mean of 7.0 antiepileptic drugs (AED) before LEV was introduced.

RESULTS

No serious persistent adverse events were reported. Reversible colitis and an apnoea syndrome in a child with phosphorylase-A-kinase-deficiency were noted. Mild to moderate side effects were reported in 128 patients (44.9%), consisting most frequently of somnolence (23.9%), general behavioral changes (15.4%), aggression (10.5%) and sleep disturbances (3.2%). In 209 patients, efficacy was analyzed over a treatment period of at least 12 weeks compared to a baseline of 2 weeks. Thirteen patients (6.2%) became seizure free, 39 (18.7%) responded with a seizure reduction of more than 50% following introduction of LEV. No response to LEV was reported in 65.1% (n=136). A decrease of initial treatment effect was seen in 37 patients (17.8%) while in 6.7% the seizure frequency doubled to the baseline (n=14). In seven patients (3.3%), the effect of LEV on seizure frequency could not be evaluated. A positive psychotropic effect was observed in 18 patients (8.6%). Mental retardation was associated with poor response and associated with more side effects and earlier discontinuation of LEV therapy.

CONCLUSION

LEV is a well-tolerated new AED that may effectively improve seizure control as an add-on drug in resistant epilepsy in childhood with good tolerability. However, neurologically handicapped children appear at increased risk for reversible neurocognitive side effects and have a poorer treatment response.

Clinical pharmacokinetics of oxcarbazepine

Oxcarbazepine is an antiepileptic drug with a chemical structure similar to carbamazepine, but with different metabolism. Oxcarbazepine is rapidly reduced to 10,11-dihydro-10-hydroxy-carbazepine (monohydroxy derivative, MHD), the clinically relevant metabolite of oxcarbazepine. MHD has (S)-(+)- and the (R)-(-)-enantiomer, but the pharmacokinetics of the racemate are usually reported. The bioavailability of the oral formulation of oxcarbazepine is high (>95%). It is rapidly absorbed after oral administration, reaching peak concentrations within about 1-3 hours after a single dose, whereas the peak of MHD occurs within 4-12 hours. At steady state, the peak of MHD occurs about 2-4 hours after drug intake. The plasma protein binding of MHD is about 40%. Cerebrospinal fluid concentrations of MHD are in the same range as unbound plasma concentrations of MHD. Oxcarbazepine can be transferred significantly through the placenta in humans. Oxcarbazepine and MHD exhibit linear pharmaco-kinetics and no autoinduction occurs. Elimination half-lives in healthy volunteers are 1-5 hours for oxcarbazepine and 7-20 hours for MHD. Longer and shorter elimination half-lives have been reported in elderly volunteers and children, respectively. Mild to moderate hepatic impairment does not appear to affect MHD pharmacokinetics. Renal impairment affects the pharmacokinetics of oxcarbazepine and MHD. The interaction potential of oxcarbazepine is relatively low. However, enzyme-inducing antiepileptic drugs such as phenytoin, phenobarbital or carbamazepine can reduce slightly the concentrations of MHD. Verapamil may moderately decrease MHD concentrations, but this effect is probably without clinical relevance. The influence of oxcarbazepine on other antiepileptic drugs is not clinically relevant in most cases. However, oxcarbazepine appears to increase concentrations of phenytoin and to decrease trough concentrations of lamotrigine and topiramate. Oxcarbazepine lowers concentrations of ethinylestra-diol and levonorgestrel, and women treated with oxcarbazepine should consider additional contraceptive measures. Due to the absent or lower enzyme-inducing effect of oxcarbazepine, switching from carbamazepine to oxcarbazepine can result in increased serum concentrations of comedication, sometimes associated with adverse effects. The effect of oxcarbazepine appears to be related to dose and to serum concentrations of MHD. In general, daily fluctuations of MHD concentration are relatively slight, smaller than would be expected from the elimination half-life of MHD. However, relatively high fluctuations can be observed in individual patients. Therapeutic monitoring may help to decide whether adverse effects are dependent on MHD concentrations. A mean therapeutic range of 15-35 mg/L for MHD seems to be appropriate. However, more systematic studies exploring the concentration-effect relationship are required.

Oxcarbazepine-induced hyponatremia and the regulation of serum sodium after replacing carbamazepine with oxcarbazepine in children

While severe hyponatremia is reported to be more frequent in adults treated with oxcarbazepine (OXC) than with carbamazepine (CBZ), there is not sufficient data about the incidence of hyponatremia in childhood during treatment with OXC. We evaluated changes in serum electrolyte balance in 75 children with epilepsy before and during treatment with OXC and after replacing carbamazepine (CBZ) therapy with OXC therapy. All patients had normal sodium serum levels at the onset of OXC. During treatment with OXC we found hyponatremia (Na +< 135 mmol/l) without clinical symptoms in 26.6 % of the children (n = 20), sodium levels below 125 mmol/l were observed in 2 children (2.6 %). Clinically relevant hyponatremia occurred in one girl only (1.3 %). In a subgroup of 27 children, in whom CBZ was directly replaced with OXC, hyponatremia without symptoms was found in one child under CBZ (3.7 %) and in six children under OXC (22.2 %). Dosage of OXC, serum levels of the active metabolite of OXC, antiepileptic comedication or patients' age and gender were of no predictive value for the development of hyponatremia. Electrolytes should be measured before establishing OXC and if clinically relevant side effects occur.

Seizure-inducing paradoxical reaction to antiepileptic drugs

We report on an 18-month-old girl with a seizure frequency of five/day, receiving an antiepileptic polytherapy consisting of primidone, clonazepam and phenytoin. Following discontinuation of clonazepam and primidone, the patient has been seizure-free under monotherapy for 2 years and shows marked developmental progress. Possible mechanisms of this paradoxical effect of antiepileptic drugs and the implications for antiepileptic therapy are discussed.

Carbamazepine-induced combined phonic and motor tic in a boy with Down's syndrome

We report the occurrence of a tic in a boy with Down's syndrome. The movement disorder was induced by carbamazepine (CBZ) and resolved completely after discontinuation of CBZ. The development of tics seems to be a rare, idiosyncratic side effect of CBZ in children.

Gabapentin in childhood epilepsy: a prospective evaluation of efficacy and safety

PURPOSE

To evaluate the efficacy and safety of gabapentin (GBP) in partial epilepsy in children.

METHODS

We performed a prospective open label add-on study in 52 children and adolescents (age 1.8-17.5 years, mean 11.1 years) with refractory partial seizures. Gabapentin was added to one other baseline drug and the efficacy was rated according to seizure type and frequency.

RESULTS

The GBP dose ranged from 26 to 78 mg/kg per day (mean 52 mg/kg per day) and was well tolerated in most patients. The seizure frequency remained unchanged in 34 patients (65%). We saw a provocation of seizures in three children (6%). Initially 15 patients (29%) benefited from GBP: five (10%) with a seizure reduction of 50-74%, seven (13%) with a reduction of 75-99% and three (6%) became seizure free. All but three experienced a development of tolerance within the next weeks to months.

CONCLUSIONS

Although gabapentin seems also to be safe in children, the efficacy in refractory partial seizures was disappointing.

Hyponatremia induced by oxcarbazepine in children

We report the case of a 12-year-old girl with severe clinically relevant hyponatremia (118 mmol/l) and hypochloremia (81 mmol/l) during treatment with oxcarbazepine (OCBZ). The adverse effects were rapidly reversible after discontinuation of OCBZ and did not occur when exposed to carbamazepine. We reviewed the charts of 48 patients who received OCBZ as in-patients in our epilepsy centre and found hyponatremia in nine and hypochloremia in four. The mean sodium level of all patients was 139 mmol/l (range 118-150 mmol/l). We did not see any correlation between sodium or chloride levels and dose of OCBZ or blood serum level of the active metabolite 10-OH-carbazepine. We emphasize that children are at risk of developing electrolyte disturbances during treatment with OCBZ and thus the level of at least sodium should be monitored in those patients.

Comparison of phenytoin and carbamazepine serum concentrations measured by high-performance liquid chromatography, the standard TDx assay, the enzyme multiplied immunoassay technique, and a new patient-side immunoassay cartridge system

Steady-state concentrations of phenytoin (PHT) and carbamazepine (CBZ) were measured by a novel patient-side immunoassay system with a single-use cartridge (Biotrack 516). The Biotrack determinations were performed in whole blood and extrapolated to serum on the basis of the hemoglobin content. The results were compared with serum concentrations measured by high-performance liquid chromatography (HPLC) or the standard TDx and enzyme multiplied immunoassay (EMIT) techniques. A total of 222 samples from epileptic patients on PHT and 322 samples from patients on CBZ were analyzed. In the case of PHT there was a highly linear correlation [r = 0.985, y = 1.113x-0.589; x = HPLC, y = Biotrack] between HPLC and the Biotrack system in the concentration range of 2.5-30 micrograms/ml. In the case of CBZ, the correlation between HPLC and the Biotrack system in the concentration range of 2.0-20 micrograms/ml was somewhat lower [r = 0.931, y = 1.29x-0.136; x = HPLC, y = Biotrack]. Comparable results were also found for the correlation of the Biotrack system with the TDx assay or with the EMIT assay, respectively. Comedication had no influence, or only a minor influence (valproic acid), on the concentration of PHT and CBZ measured by the Biotrack system. Furthermore, the concentration of the metabolite carbamazepine-10, 11-epoxide had no influence on the concentration of CBZ measured by the Biotrack system. Since the automated cartridge system is simple, can be used rapidly, and is performed with only a few drops of blood, this technique offers some advantages for routine clinical use, especially under outpatient conditions.

Pharmacokinetics of sulthiame in epileptic patients

Sulthiame is an antiepileptic drug that was introduced approximately 30 years ago for the treatment of epilepsy. Currently it is rarely used, but recent studies show its efficacy, especially in the treatment of focal epilepsies in children. Because there are hardly any pharmacokinetic studies of sulthiame in humans, we studied the dose-level relationship, the elimination half-life, and the daily fluctuations in the concentration of sulthiame among children and adults with epilepsy. The evaluation of the sulthiame serum concentrations of 86 patients gave, considering age and comedication, a relatively high correlation (r = 0.82) between the sulthiame dose/body weight and the sulthiame serum concentration. Children on a comparable sulthiame dose per body weight have lower sulthiame concentrations than adults. In our study sulthiame was, with few exceptions, administered in combination with other antiepileptic drugs. The sulthiame serum concentrations were lower in comedication with carbamazepine than with valproic acid. The evaluation of the individual sulthiame dose-level relationship of 8 patients showed in most cases a close and linear relationship. After withdrawal of sulthiame in 11 patients, short elimination half-lives (8.65 +/- 3.10 h) were estimated. This was in accordance with the large daily fluctuations in the sulthiame concentrations (swing: 103.9 +/- 59.3%) of the nine patients examined. The shorter half-lives and higher daily fluctuations in children indicate a higher clearance of sulthiame among children.