Antiepileptic drugs--best practice guidelines for therapeutic drug monitoring: a position paper by the subcommission on therapeutic drug monitoring, ILAE Commission on Therapeutic Strategies

Population pharmacokinetics of oxcarbazepine and its monohydroxy derivative in epileptic children

AIMS

Oxcarbazepine is an antiepileptic drug with an activity mostly due to its monohydroxy derivative metabolite (MHD). A parent-metabolite population pharmacokinetic model in children was developed to evaluate the consistency between the recommended paediatric doses and the reference range for trough concentration (C_trough ) of MHD (3-35 mg l^-1 ).

METHODS

A total of 279 plasma samples were obtained from 31 epileptic children (age 2-12 years) after a single dose of oxcarbazepine. Concentration-time data were analysed with Monolix 4.3.2. The probability to obtain C_trough between 3-35 mg l^-1 was determined by Monte Carlo simulations for doses ranging from 10 to 90 mg kg^-1  day^-1 .

RESULTS

A parent-metabolite model with two compartments for oxcarbazepine and one compartment for MHD best described the data. Typical values for oxcarbazepine clearance, central and peripheral distribution volume and distribution clearance were 140 l h^-1  70 kg^-1 , 337 l 70 kg^-1 , 60.7 l and 62.5 l h^-1 , respectively. Typical values for MHD clearance and distribution volume were 4.11 l h^-1  70 kg^-1 and 54.8 l 70 kg^-1 respectively. Clearances and distribution volumes of oxcarbazepine and MHD were related to body weight via empirical allometric models. Enzyme-inducing antiepileptic drugs (EIAEDs) increased MHD clearance by 29.3%. Fifty-kg children without EIAEDs may need 20-30 mg kg^-1  day^-1 instead of the recommended target maintenance dose (30-45 mg kg^-1  day^-1 ) to obtain C_trough within the reference range. By contrast, 10-kg children with EIAEDs would need 90 mg kg^-1  day^-1 instead of the maximum recommended dose of 60 mg kg^-1  day^-1 .

CONCLUSION

This population pharmacokinetic model of oxcarbazepine supports current dose recommendations, except for 10-kg children with concomitant EIAEDs and 50-kg children without EIAEDs.

A Systematic Appraisal of Neurosurgical Seizure Prophylaxis: Guidance for Critical Care Management

Clinical decisions are often made in the presence of some uncertainty. Health care should be based on a combination of scientific evidence, clinical experience, economics, patient value judgments, and preferences. Seizures are not uncommon following brain injury, surgical trauma, hemorrhage, altered brain metabolism, hypoxia, or ischemic events. The impact of seizures in the immediate aftermath of injury may be a prolonged intensive care stay or compounding of the primary injury. The aim of brain injury management is to limit the consequences of the secondary damage. The original intention of seizure prophylaxis was to limit the incidence of early-onset seizures. However, clinical trials have been equivocal on this point, and there is concern about the adverse effects of antiepileptic drug therapy. This review of the literature raises concerns regarding the arbitrary division of seizures into early onset (7 d) and late onset (8 d and beyond). In many cases it would appear that seizures present within 24 hours of the injury or after 7 days, which would be outside of the scope of current seizure prophylaxis guidance. There also does not appear to be a pathophysiological reason to divide brain injury-related seizures into these timeframes. Therefore, a solution to the conundrum is to reevaluate current practice. Prophylaxis could be offered to those receiving intensive care for the primary brain injury, where the impact of seizure would be detrimental to the management of the brain injury, or other clinical judgments where prophylaxis is prudent. Neurosurgical seizure management can then focus attention on which agent has the best adverse effect profile and the duration of therapy. The evidence seems to support levetiracetam as the most appropriate agent. Although previous reviews have identified an increase cost associated with the use of levetiracetam, current cost comparisons with phenytoin demonstrate a marginal price differential. The aim of this review is to assimilate the applicable literature regarding seizure prophylaxis. The final guidance is a forum upon which further clinical research could evaluate a new seizure prophylaxis paradigm.

Going down the tubes! Impact on seizure control of antiepileptic medication given via percutaneous feeding tubes

BACKGROUND

Long-term feeding by percutaneous endoscopic gastrostomy tube (PEG) is uncommon but can present significant issues when both nutrition and medication have to be fed down the same tube. This is especially important in people with epilepsy where the dose and bioavailability of antiepileptic drugs are critical to maintain adequate seizure control. This group with long-term PEG tubes is particularly vulnerable and dependent on their carers to provide high standard of care. Indeed, approximately half of the people with long-term feeding tubes suffer from severe intellectual disability which requires careful coordination of all members of the multidisciplinary team. It is all the more important when consideration is given that around 50% of people with severe ID have seizures, mostly treatment resistant.

METHOD

A detailed literature review was conducted with the focus on the numerous factors that can affect medication delivery and absorption with the potential to destabilize seizure control in people with PEG. Issues concerning the site of drug absorption, excipients and dilution, interaction between antiepileptic drugs and the nutritional feed, bioavailability, and problems with the PEG tube are considered.

RESULTS

There is limited research in this area and the studies are often based on small numbers, healthy volunteers or in vitro findings.

CONCLUSION

In the absence of sound research data, seizure control in each patient with a PEG needs to be considered on an individual basis. Establishing a baseline by measuring the serum levels prior to the tube insertion may be helpful, followed by checking the levels after PEG insertion.

Simultaneous Determination of Carbamazepine and Carbamazepine-10,11-epoxide in Different Biological Matrices by LC-MS/MS

An uncomplicated, sensitive liquid chromatography linked to mass spectrometry (LC/MS) for evaluation of carbamazepine and carbamazepine-10,11-epoxide (its metabolite) in human plasma, human saliva, rat plasma, and rabbit plasma was developed. Analyses were conducted on a Zorbax SB-C18, 100 mm × 3 mm ID, 3.5 μm column, at a column temperature of 40 ºC. The mobile phase was comprised of 0.1% formic acid in water and methanol in a 35 : 65 (v/v) ratio, with a flow rate of 0.4 mL/min. Lacosamide was utilized as internal standard. Under these chromatographic conditions, the retention times of lacosamide, carbamazepine-10,11-epoxide, and carbamazepine were 1.4 min, 1.6 min, and 2.2 min, respectively. The quantification of the analytes was performed using multiple reaction monitoring, with the use of a triple quadrupole mass spectrometer with electrospray positive ionization. The monitored ions were m/z 194 derived from m/z 237 for carbamazepine, m/z 180 derived from m/z 253 for carbamazepine-10,11-epoxide, and m/z 108 derived from m/z 251 for lacosamide. The samples were prepared by protein precipitation from 0.2 mL of plasma/saliva using 0.6 mL of internal standard solution in methanol. Calibration curves were constructed over the ranges 1.1–17.6 µg/mL and 0.23–5.47 µg/mL for carbamazepine and carbamazepine-epoxide, respectively. The coefficients of determination obtained by using a weighted (1/x) linear regression were greater than 0.994. The reported LC-MS/MS method was applied to preclinical pharmacokinetic studies and therapeutic drug monitoring.

Clonazepam-associated Bradycardia in a Disabled Elderly Woman with Multiple Complications

We herein report an 87-year-old woman who was taking clonazepam at 1.5 mg/day. She was hospitalized with an old cerebral infarction complicated with symptomatic epilepsy, dementia, dyslipidemia, and chronic cholecystitis. Electrocardiogram revealed severe bradycardia at 31 beats/min. The bradycardia disappeared on day 3 after clonazepam withdrawal, although the serum clonazepam level had been within normal limits. She was diagnosed with clonazepam-associated bradycardia, which was likely related to the potential calcium channel-blocking properties of clonazepam. Because of age-related pharmacokinetic and pharmacodynamic changes, the adverse effects of clonazepam should be considered, especially in disabled elderly individuals with multiple comorbidities.

Lamotrigine serum levels: Ceiling effect in people with epilepsy in remission?

BACKGROUND

Antiepileptic drug titration in epilepsy remains mostly empirical. Since in practice seizure remission may be obtained with low doses, we aimed to determine whether patients in remission have lower lamotrigine levels than those with ongoing seizures.

METHODS

Retrospective comparison of the distribution of lamotrigine levels among unselected patients in remission and with ongoing seizures. Remission was defined as 3 times the longuest interseizure interval and at least one year. Only trough levels were analyzed.

RESULTS

Between 2009 and 2014, we identified 93 adults, among whom 10 were in remission. Patients in remission had significantly (p=0.008) lower serum levels (median 2.3mg/L, range: 0.7-8.2) than those with ongoing seizures (median 5.4mg/L, range: 1.1-18.2). We did not find any patient in remission with levels higher than 8.2mg/L. Distribution of dosages also differed among the groups, but less significantly (median: 175 vs 300mg, p=0.03).

CONCLUSION

An association between lamotrigine serum levels and seizure response can be observed. This suggests the existence of a ceiling level, above which remission is unlikely and should prompt antiepileptic medication switch rather than further up-titration of lamotrigine in drug-naïve patients with epilepsy.

Association Between Pregnancy and Perinatal Outcomes Among Women With Epilepsy

Importance

To date, few attempts have been made to examine associations between exposure to maternal epilepsy with or without antiepileptic drug (AED) therapy and pregnancy and perinatal outcomes.

Objectives

To investigate associations between epilepsy in pregnancy and risks of pregnancy and perinatal outcomes as well as whether use of AEDs influenced risks.

Design, Setting, and Participants

A population-based cohort study was conducted on all singleton births at 22 or more completed gestational weeks in Sweden from 1997 through 2011; of these, 1 424 279 were included in the sample. Information on AED exposure was available in the subset of offspring from July 1, 2005, to December 31, 2011. Data analysis was performed from October 1, 2016, to February 15, 2017.

Main Outcomes and Measures

Pregnancy, delivery, and perinatal outcomes. Multivariable Poisson log-linear regression was used to estimate adjusted risk ratios (aRRs) and 95% CIs, after adjusting for maternal age, country of origin, educational level, cohabitation with a partner, height, early pregnancy body mass index, smoking, year of delivery, maternal pregestational diabetes, hypertension, and psychiatric disorders.

Results

Of the 1 429 652 births included in the sample, 5373 births were in 3586 women with epilepsy; mean (SD) age at first delivery of the epilepsy cohort was 30.54 (5.18) years. Compared with pregnancies of women without epilepsy, women with epilepsy were at increased risks of adverse pregnancy and delivery outcomes, including preeclampsia (aRR 1.24; 95% CI, 1.07-1.43), infection (aRR, 1.85; 95% CI, 1.43-2.29), placental abruption (aRR, 1.68; 95% CI, 1.18-2.38), induction (aRR, 1.31; 95% CI, 1.21-1.40), elective cesarean section (aRR, 1.58; 95% CI, 1.45-1.71), and emergency cesarean section (aRR, 1.09; 95% CI, 1.00-1.20). Infants of mothers with epilepsy were at increased risks of stillbirth (aRR, 1.55; 95% CI, 1.05-2.30), having both medically indicated (aRR, 1.24; 95% CI, 1.08-1.43) and spontaneous (aRR, 1.34; 95% CI, 1.20-1.53) preterm birth, being small for gestational age at birth (aRR, 1.25; 95% CI, 1.13-1.30), and having neonatal infections (aRR, 1.42; 95% CI, 1.17-1.73), any congenital malformation (aRR, 1.48; 95% CI, 1.35-1.62), major malformations (aRR, 1.61; 95% CI, 1.43-1.81), asphyxia-related complications (aRR, 1.75; 95% CI, 1.26-2.42), Apgar score of 4 to 6 at 5 minutes (aRR, 1.34; 95% CI, 1.03-1.76), Apgar score of 0 to 3 at 5 minutes (aRR, 2.42; 95% CI, 1.62-3.61), neonatal hypoglycemia (aRR, 1.53; 95% CI, 1.34-1.75), and respiratory distress syndrome (aRR, 1.48; 95% CI, 1.30-1.68) compared with infants of unaffected women. In women with epilepsy, using AEDs during pregnancy did not increase the risks of pregnancy and perinatal complications, except for a higher rate of induction of labor (aRR, 1.30; 95% CI, 1.10-1.55).

Conclusions and Relevance

Epilepsy during pregnancy is associated with increased risks of adverse pregnancy and perinatal outcomes. However, AED use during pregnancy is generally not associated with adverse outcomes.

Seizures and Choice of Antiepileptic Drugs Following Subarachnoid Hemorrhage: A Review

Seizures are important complications following a subarachnoid hemorrhage (SAH). The evidence for the use of antiepileptic drugs (AEDs) in treatment and prevention of those seizures is conflicting. The purpose of this review is to provide an up-to-date evidence summary of the incidence and outcomes of seizures following an SAH as well as the use of different AEDs post-SAH in order to evaluate the need for seizure prophylaxis, the choice of AEDs, and their dosing considerations in SAH patients. A literature search of PubMed, Medline, Embase, and the Cochrane Library was performed. A total of 37 studies were reviewed, mostly observational. Definitions of seizures in temporal relation to initial hemorrhage were variable. Similarly, the rates of seizures varied in the literature, ranging from 0 to 31%. Given the reported adverse outcomes associated with AED usage, seizure prophylaxis is not warranted. Levetiracetam appears to be better tolerated than phenytoin in SAH patients, though further research is needed. Higher initial dosing of levetiracetam might be required due to its enhanced clearance in SAH patients. In conclusion, there is a lack of quality evidence to definitively recommend the use of one AED over another. Further prospective research comparing the use of different AEDs in patients with an SAH is needed.

Zebrafish as a Model for Epilepsy-Induced Cognitive Dysfunction: A Pharmacological, Biochemical and Behavioral Approach

Epilepsy is a neuronal disorder allied with distinct neurological and behavioral alterations characterized by recurrent spontaneous epileptic seizures. Impairment of the cognitive performances such as learning and memory is frequently observed in epileptic patients. Anti-epileptic drugs (AEDs) are efficient to the majority of patients. However, 30% of this population seems to be refractory to the drug treatment. These patients are not seizure-free and frequently they show impaired cognitive functions. Unfortunately, as a side effect, some AEDs could contribute to such impairment. The major problem associated with conducting studies on epilepsy-related cognitive function is the lack of easy, rapid, specific and sensitive in vivo testing models. However, by using a number of different techniques and parameters in the zebrafish, we can incorporate the unique feature of specific disorder to study the molecular and behavior basis of this disease. In the view of current literature, the goal of the study was to develop a zebrafish model of epilepsy induced cognitive dysfunction. In this study, the effect of AEDs on locomotor activity and seizure-like behavior was tested against the pentylenetetrazole (PTZ) induced seizures in zebrafish and epilepsy associated cognitive dysfunction was determined using T-maze test followed by neurotransmitter estimation and gene expression analysis. It was observed that all the AEDs significantly reversed PTZ induced seizure in zebrafish, but had a negative impact on cognitive functions of zebrafish. AEDs were found to modulate neurotransmitter levels, especially GABA, glutamate, and acetylcholine and gene expression in the drug treated zebrafish brains. Therefore, combination of behavioral, neurochemical and genenetic information, makes this model a useful tool for future research and discovery of newer and safer AEDs.

A study on the bioequivalence of lithium and valproate salivary and blood levels in the treatment of bipolar disorder

Lithium (Li) and valproate (VPA) are used in the treatment of bipolar disorder (BD), with narrow therapeutic window requiring periodic control of serum levels. This prevents intoxication, lack of efficacy due to low serum concentrations, and allows monitoring adherence. We aimed at evaluating the bioequivalence of salivary and blood levels of LI or VPA in a sample of adult BD patients. Secondarily, lithium bioequivalence was evaluated across different patients' lifespans. BD patients treated with either Li or VPA underwent contemporary standard serum and salivary measurements. Blood levels of both drugs were taken according to standard procedures. Li salivary levels were performed by an adapted potentiometric method on the AVL9180 electrolyte analyzer. VPA salivary levels were taken with an immune-assay method with turbidimetric inhibition. A total of 50 patients (38 on Li, 12 on VPA) were enrolled. Blood-saliva bioequivalence for VPA was not found due to a high variability in salivary measures. Li measures resulted in a high correlation (r=0.767, p<0.001), showing no partial correlation with age (r=0.147, p=0.380). Li salivary test is a reliable method of measuring Li availability and is equivalent to serum levels. Potential advantages of Li salivary testing are its non-invasive nature and the possibility of doing the test during the usual appointment with the psychiatrist.

Drug-Level Monitoring on Admission for Presurgical Epilepsy Evaluation

OBJECTIVE

Evaluation for surgical treatment is offered to patients who do not respond to antiepileptic drugs. Pseudo-pharmacoresistance (PPR) has been described in the context of impaired compliance, incorrect diagnosis of epilepsy or pharmacological interference resulting in too low blood levels. We were interested to determine the frequency and causes of PPR in patients admitted for presurgical evaluation.

METHODS

We reviewed 553 drug levels in 199 patients and analyzed the relative frequency of drugs below reference range (10 and 20% below the range).

RESULTS

Patients who had at least one serum level below the 10% cut-off amounted to 33% and 9% of patients had at least one serum level below the 20% cut-off. Only in 2 patients (1%), this was due to poor compliance. Low levels were equally frequent in mono- or polytherapy. Drugs that were most frequently found out of range were phenytoin, valproate, and topiramate. In monotherapy, lamotrigine was often prescribed in too low dosages.

CONCLUSION

Low drug levels are frequently observed in surgical candidates due to pharmacological interference or insufficient dosing. Poor compliance or incorrect diagnosis does not appear to be a significant concern in this patient group. Our data strengthen the need for regular drug monitoring even in advanced chronic epilepsy to avoid unnecessary health costs by too low and ineffective dosages.

A randomized, double-blind, placebo-controlled crossover study of the effects of levetiracetam on cognition, mood, and balance in healthy older adults

OBJECTIVE

The cognitive and mood effects of levetiracetam (LEV) in older adults are not known. This study compared the cognitive and mood effects of LEV to placebo in healthy older adults.

METHODS

Cognitive, mood, and balance variables were compared between LEV and placebo using a randomized, double-blind, placebo-controlled crossover study with two 5-week treatment periods. Healthy volunteers (n = 20) aged 65-80 (mean age 72.4) received either LEV or placebo in which the LEV target dose was 1,000 mg/day. Volunteers, aged 65-80, were without epilepsy to limit potentially confounding the impact of seizures and/or underlying neuropathology on outcomes. LEV was initiated at 250 mg twice a day for 2 weeks, then increased to 500 mg twice a day for 2 weeks, and then tapered to 250 mg twice a day for 1 week. This was randomized with placebo for the two treatment arms. Measures included standardized neuropsychological, mood, and balance tests yielding 32 variables. Balance was assessed using subjective report (e.g., A-B neurotoxicity scale) and objective data (e.g., Berg Balance Scale).

RESULTS

Average LEV serum concentration was 16.9 (standard deviation [SD} 7.7). Repeated-measures analysis of variance (ANOVA) found no differences between LEV and placebo phases for 29 (90.6%) of 32 variables including no change in balance. Performance on LEV was better than placebo on a visual memory (MCG Complex Figure Recall; p = 0.007) and two attention tests (Trail Making Test, Part A, p = 0.009; Stroop Interference, p = 0.004). There was a trend for greater irritability and fatigue (POMS Anger and Fatigue) during the LEV phase (p = 0.029, p = 0.035). Effect-size changes were generally small (Cohen d < 0.5).

SIGNIFICANCE

LEV was well tolerated in this elderly population in terms of cognition, mood, and balance. When anticonvulsant medication is indicated for older adults, LEV has pharmacokinetic advantages, and these data indicate no adverse impact on cognition or balance.

Sodium Channel Blockers in the Treatment of Epilepsy

Sodium channel blockers have been the mainstay of the pharmacological management of focal and generalised tonic-clonic seizures for more than 70 years. The focus of this paper will be on phenytoin, carbamazepine, lamotrigine, oxcarbazepine, rufinamide, lacosamide and eslicarbazepine acetate. All these antiepileptic drugs have similar efficacy and share similar dose-dependent, adverse effect profiles, although phenytoin, carbamazepine and oxcarbazepine are more likely to cause idiosyncratic reactions than the others. With the exception of lamotrigine, rufinamide and lacosamide, all are enzyme inducers and most are minor teratogens; although data on teratogenicity are sparse with lacosamide and eslicarbazepine acetate. There is increasing evidence that these drugs differ mechanistically, with the newer agents, lacosamide and eslicarbazepine acetate, having their major pharmacological effect on the slow inactivation state of the sodium channel, which may be associated with better tolerability at higher dosage, although hard evidence in support of this observation is currently not available. Rufinamide is licensed only for Lennox-Gastaut syndrome in children aged 4 years and above. There is a move away from using enzyme inducers, particularly phenytoin and carbamazepine, in everyday clinical practice. There seems little doubt, however, that some sodium channel blockers will have an enduring place in the management of epilepsy well into the 21st century.

Effect of ketogenic diet and other dietary therapies on anti-epileptic drug concentrations in patients with epilepsy

WHAT IS KNOWN AND OBJECTIVE

The ketogenic diet (KD) is an effective high-fat, adequate-protein, low-carbohydrate diet for patients with refractory epilepsy. The aim of this study was to investigate the potential effects of the KD and other dietary therapies on the concentrations of anticonvulsants in patients with epilepsy.

METHODS

Patients with epilepsy who were treated with the KD and other dietary therapies for more than 30 days with at least one measurement performed both before and during the diet were evaluated. The mean serum concentrations and the mean serum concentrations per weight per daily dose per bioavailability (F) of anti-epileptic drugs (AEDs) before and during the treatment were assessed. We also compared the rates of events out of reference ranges of the AEDs between before and during the KD and other dietary therapies. We compared the serum albumin, alanine transaminase and aspartate transaminase data of patients with valproic acid before and during the KD.

RESULTS AND DISCUSSION

One-hundred thirty-nine patients including 81 male patients were enrolled. The median age of the patients was 2.91 (0.15-15.46) years. The median duration of the dietary therapies was 153 (35-2307) days. After the dietary therapies, the serum concentrations of carbamazepine, lamotrigine, levetiracetam, topiramate and valproic acid decreased, whereas that of phenobarbital slightly increased. However, statistical significance was found only with valproic acid (67.07±25.89 μg/mL vs 51.00±20.19 μg/mL, P<.05). The serum concentrations per weight per daily dose per drug F significantly decreased for valproic acid (1.38±1.39×10^-2 vs 0.82±0.82×10^-2  μg d mL^-1  F^-1 ) and phenobarbital (6.66±7.20×10^-2 vs 4.75±4.07×10^-2  μg d mL^-1  F^-1 , P<.05). The rate of occurrence of events out of reference ranges significantly increased with valproic acid (36.08% vs 57.23%, P<.05).

WHAT IS NEW AND CONCLUSIONS

Most anti-epileptic drug serum concentrations remained stable during the KD and other related dietary therapies except those of valproic acid. Therefore, serum concentrations of valproic acid should be monitored when the KD and other dietary therapies are concomitantly administered.

Comparison of Levetiracetam Dosing Regimens in End-Stage Renal Disease Patients Undergoing Intermittent Hemodialysis

BACKGROUND

Levetiracetam (LEV) is primarily renally eliminated. In end-stage renal disease (ESRD) patients on hemodialysis (HD), pharmacokinetic studies recommend daily dosing with 50% supplemental doses after 4-hour HD sessions. However, poor medication adherence after HD could result in fluctuating plasma drug levels.

OBJECTIVE

To compare two LEV dosing regimens, daily versus twice-daily (BID), in ESRD patients undergoing HD.

METHODS

Consecutive ESRD patients (April 2013 to May 2014) receiving maintenance inpatient HD and prescribed LEV prior to admission to our academic tertiary hospital were prospectively analyzed. Demographics, initial lab values, adverse reactions, seizures, and LEV regimens were recorded. LEV levels were obtained pre-HD and post-HD along with levels after receiving post-HD doses. Recovery of plasma levels after HD was assessed by comparison of levels predialysis versus postdialysis and post-HD doses.

RESULTS

We identified 22 patients who met inclusion criteria; 14 BID and 8 daily dosing. Mean predialysis, postdialysis, and post-HD dose plasma levels were higher in patients receiving LEV BID compared with daily (43.1 ± 6.3, 19.4 ± 5.2, 34.9 ± 4.3 vs 21.1 ± 3.9, 6.9 ± 1.5, 11.9 ± 1.7 µg/mL; P < 0.05). BID post-HD levels were 41.9 ± 4.6% of predialysis levels versus 36.9 ± 7.3% with daily dosing ( P = 0.275). Post-HD dose levels were 81.4±4.3% of predialysis on LEV BID versus 65.7 ± 8.8% on LEV daily ( P = 0.045). No seizures were reported during hospital admission in either group.

CONCLUSIONS

Compared to LEV daily, BID dosing achieved significantly higher levels and a better recovery to predialysis levels. Although limited by small numbers, a similar relationship between postdialysis levels was not detected.

Pharmacological and neuroethological study of the acute and chronic effects of lamotrigine in the genetic audiogenic seizure hamster (GASH:Sal)

The present study aimed to investigate the behavioral and anticonvulsant effects of lamotrigine (LTG) on the genetic audiogenic seizure hamster (GASH:Sal), an animal model of audiogenic seizure that is in the validation process. To evaluate the efficiency of acute and chronic treatments with LTG, GASH:Sals were treated with LTG either acutely via intraperitoneal injection (5-20mg/kg) or chronically via oral administration (20-25mg/kg/day). Their behavior was assessed via neuroethological analysis, and the anticonvulsant effect of LTG was evaluated based on the appearance and the severity of seizures. The results showed that acute administration of LTG exerts an anticonvulsant effect at the lowest dose tested (5mg/kg) and that chronic oral LTG treatment exerts an anticonvulsant effect at a dose of 20-25mg/kg/day. Furthermore, LTG treatment induced a low rate of secondary adverse effects. This article is part of a Special Issue entitled "Genetic and Reflex Epilepsies, Audiogenic Seizures and Strains: From Experimental Models to the Clinic".

Phenobarbital in intensive care unit pediatric population: predictive performances of population pharmacokinetic model

An external evaluation of phenobarbital population pharmacokinetic model described by Marsot et al. was performed in pediatric intensive care unit. Model evaluation is an important issue for dose adjustment. This external evaluation should allow confirming the proposed dosage adaptation and extending these recommendations to the entire intensive care pediatric population. External evaluation of phenobarbital published population pharmacokinetic model of Marsot et al. was realized in a new retrospective dataset of 35 patients hospitalized in a pediatric intensive care unit. The published population pharmacokinetic model was implemented in nonmem 7.3. Predictive performance was assessed by quantifying bias and inaccuracy of model prediction. Normalized prediction distribution errors (NPDE) and visual predictive check (VPC) were also evaluated. A total of 35 infants were studied with a mean age of 33.5 weeks (range: 12 days-16 years) and a mean weight of 12.6 kg (range: 2.7-70.0 kg). The model predicted the observed phenobarbital concentrations with a reasonable bias and inaccuracy. The median prediction error was 3.03% (95% CI: -8.52 to 58.12%), and the median absolute prediction error was 26.20% (95% CI: 13.07-75.59%). No trends in NPDE and VPC were observed. The model previously proposed by Marsot et al. in neonates hospitalized in intensive care unit was externally validated for IV infusion administration. The model-based dosing regimen was extended in all pediatric intensive care unit to optimize treatment. Due to inter- and intravariability in pharmacokinetic model, this dosing regimen should be combined with therapeutic drug monitoring.

A novel LC-MS/MS method for the simultaneous quantification of topiramate and its main metabolites in human plasma

The aim of the present report was to develop and validate simple, sensitive and reliable LC-MS/MS method for quantification of topiramate (TPM) and its main metabolites: 2,3-desisopropylidene TPM, 4,5-desisopropylidene TPM, 10-OH TPM and 9-OH TPM in human plasma samples. The most abundant metabolite 2,3-desisopropylidene TPM was isolated from patients urine, characterized and afterwards used as an authentic standard for method development and validation. Sample preparation method employs 100μL of plasma sample and liquid-liquid extraction with a mixture of ethyl acetate and diethyl ether as extraction solvent. Chromatographic separation was achieved on a 1290 Infinity UHPLC coupled to 6460 Triple Quad Mass Spectrometer operated in negative MRM mode using Kinetex C18 column (50×2.1mm, 2.6μm) by gradient elution using water and methanol as a mobile phase and stable isotope labeled TPM as internal standard. The method showed to be selective, accurate, precise and linear over the concentration ranges of 0.10-20μg/mL for TPM, 0.01-2.0μg/mL for 2,3-desisopropylidene TPM, and 0.001-0.200μg/mL for 4,5-desisopropylidene TPM, 10-OH TPM and 9-OH TPM. The described method is the first fully validated method capable of simultaneous determination of TPM and its main metabolites in plasma over the selected analytical range. The suitability of the method was successfully demonstrated by the quantification of all analytes in plasma samples of patients with epilepsy and can be considered as reliable analytical tool for future investigations of the TPM metabolism.

Safety and efficacy of topiramate in neonates with hypoxic ischemic encephalopathy treated with hypothermia (NeoNATI): a feasibility study

PURPOSE

To investigate the feasibility of a study based on treatment with topiramate (TPM) added to moderate hypothermia in newborns with hypoxic ischemic encephalopathy (HIE).

MATERIALS AND METHODS

Multicenter randomized controlled trial. Term newborns with precocious metabolic, clinical and electroencephalographic (EEG) signs of HIE were selected according to their amplified integrated EEG pattern and randomized to receive either TPM (10 mg/kg once a day for the first three days of life) plus moderate hypothermia or hypothermia alone. Safety was assessed by monitoring cardiorespiratory parameters and blood samples collected to check renal, liver, metabolic balance and TPM pharmacokinetics. Efficacy was evaluated by the combined frequency of mortality and severe neurological disability as primary outcome. Incidence of magnetic resonance injury, epilepsy, blindness, hearing loss, neurodevelopment at 18-24 months of life was assessed as secondary outcomes.

RESULTS

Forty-four asphyxiated newborns were enrolled in the study. Twenty one newborns (10 with moderate and 11 with severe HIE) were allocated to hypothermia plus TPM and 23 (12 moderate and 11 severe HIE) to hypothermia. No statistically or clinically significant differences were observed for safety, primary or secondary outcomes. However, a reduction in the prevalence of epilepsy was observed in newborns co-treated with TPM.

CONCLUSIONS

Results of this pilot trial suggest that administration of TPM in newborns with HIE is safe but does not reduce the combined frequency of mortality and severe neurological disability. The role of TPM co-treatment in preventing subsequent epilepsy deserves further studies.

Influence of age and co-medication on the steady-state pharmacokinetics of valproic acid in Tunisian patients with epilepsy

AIM

Valproic acid (VPA) is a widely prescribed broad-spectrum antiepileptic drug. However, the use of VPA is complicated in clinical practice by its remarkably wide variability of pharmacokinetics. The objective of this study was to investigate the effects of demographic factors and associated therapies on steady-state plasma VPA concentrations in patients with epilepsy.

METHODS

This retrospective cohort study was carried out using the routine therapeutic drug monitoring (TDM) database. Stepwise logistic regression analysis was used to compare serum VPA levels in 78 epilepsy patients treated with VPA in association with at least one other drug that could have interacted with CYP2C9, CYP2C19 or UGT enzymes.

RESULTS

The frequency of subtherapeutic serum VPA levels was significantly increased with younger age (P<0.02), the number of co-medications (P<0.007) and use of enzyme-inducing co-medications (P<0.02). No significant correlations between VPA dose and trough plasma concentrations were found, as the latter did not increase in proportion to the dose.

CONCLUSION

Routine monitoring of VPA serum levels would be extremely useful in epilepsy patients in the pediatric age group and in those who require associated enzyme-inducing medications.

Valproate Protein Binding Is Highly Variable in ICU Patients and Not Predicted by Total Serum Concentrations: A Case Series and Literature Review

STUDY OBJECTIVE

The free fraction of valproate (the pharmacologically active moiety, normally 5-10%) may vary significantly in critically ill patients, but this topic is understudied, with only four prior intensive care unit (ICU) case reports. The objective of this study was to evaluate the range of valproate plasma protein binding in ICU patients.

DESIGN

Observational study of consecutive ICU patients.

SETTING

Neurocritical and medical critical care services in a nonuniversity academic medical center.

PATIENTS

Consecutive ICU patients treated with valproate with serum albumin less than 4 g/dl.

MEASUREMENTS AND MAIN RESULTS

Simultaneous total and free trough serum valproate concentrations were measured as were serum creatinine, blood urea nitrogen, albumin, platelets, and transaminase values. The reference concentration range was 50-125 mg/L (total) and 5-17 mg/L (free). Valproate concentrations were categorized as within reference range, low, or high, and as concordant if both concentrations were in the same category. Data are reported as median (interquartile range). Fifteen patients (nine men) were evaluated. The median age was 63 (34-70) years. The valproate dose was 3 g/day (35 mg/kg/day). No patient had a valproate free fraction of 5-10%; the median was 48%, and the range was 15-89%. Total and free concentrations showed poor correlation (0.43) and were concordant in only two patients (both in the reference range). Free valproate concentration was poorly predicted by an equation correcting for albumin (r = 0.45). Suspected adverse drug events occurred in 10 patients: hyperammonemia in 7 of 12 tested (58%), elevated transaminases in 2 of 15 (13%), and thrombocytopenia in 5 of 15 (33%).

CONCLUSIONS

Protein binding of valproate was highly inconsistent in this cohort of ICU patients, and total valproate concentrations did not predict free concentrations, even when correcting for albumin. Additional research to define best practice for dosing and monitoring valproate and the relationship between free valproate concentrations and clinical or adverse effects in ICU patients is needed.

A simple and cost-effective HPLC-UV method for the detection of levetiracetam in plasma/serum of patients with epilepsy

A simple, fast and cost-effective method was developed and validated for the determination of levetiracetam (LEV) in plasma/serum of patients using high performance liquid chromatography (HPLC) with ultraviolet detection. The stability of LEV plasma/serum samples over time and in different blood collection tubes was evaluated. Serum/plasma samples were deproteinized by methanol spiked with the internal standard, gabapentin. HPLC was carried out on a Venusil XBP C₁₈ , 250 × 4.6 mm, 5 μm column, at a flow rate of 1.0 mL/min and with mobile phase consisting of 50 mm potassium dihydrogen phosphate-acetonitrile at a pH of 5.5. The UV detector was set at 205 nm and 10 μL was injected. Total runtime was 15 min. Calibration curves were linear (correlation coefficient = 0.999) over a concentration range of 1-60 μg/mL. Relative standard deviation values for both the inter-day and intra-day precision and accuracy were <5% for the concentration range. The influence of different collection tubes and the effect of time on the stability of LEV was investigated. These factors may cause inaccuracies owing to drug-protein binding and interference in the matrix. This method is simple, fast, cost-effective, reliable and accurate with minimal sample preparation for daily routine use in therapeutic drug monitoring.

Development and validation of a reversed-phase HPLC method for licarbazepine monitoring in serum of patients under oxcarbazepine treatment

Licarbazepine is the pharmacologically active metabolite of oxcarbazepine, a drug indicated for the treatment of partial seizures and bipolar disorders. Several HPLC methods have been developed thus far but there is lack of control for interferences from antipsychotic drugs. The aim of the present study was to develop a simple, low-cost and reliable HPLC-UV method for the determination of licarbazepine in human serum in the presence of co-administered antiepileptic, antipsychotic and commonly prescribed drugs. Sample preparation consisted of a single protein precipitation step with methanol. Separation lasted ~9 min on a reversed-phase C₁₈ column using a mobile phase composed of 50 mm sodium-dihydrogen-phosphate-monohydrate/acetonitrile (70:30, v/v) delivered isocratically at 0.9 mL/min and 30°C. Wavelength was 210 nm and calibration curve was linear with r² 0.998 over the range 0.2-50.0 μg/mL. Coefficient of variation was <5.03% and bias <-4.92%. Recovery ranged from 99.49 to 104.52% and the limit of detection was 0.0182 μg/mL. No interferences from the matrix or from antiepileptic, antipsychotic and commonly prescribed drugs were observed. The method was applied to serum samples of patients under oxcarbazepine treatment and proved to be a useful tool for the therapeutic drug monitoring of licarbazepine during monotherapy or adjunctive treatment of seizures or affective disorders.

Antiepileptic Drug Removal by Continuous Renal Replacement Therapy: A Review of the Literature

Continuous renal replacement therapy (CRRT) is used for managing acute kidney injury in critically ill patients. Removal of antiepileptic drugs (AEDs) by CRRT could be significant and may complicate patients' intensive care unit stay. The objective of the current review was to summarize the available evidence for AED removal by CRRT. An electronic literature search of PubMed (1946 to May 2016), Medline (1946 to May 2016), and Embase (1974 to May 2016) databases for studies discussing AED removal by CRRT was conducted. A total of 31 case reports discussing 32 patients were found. AEDs reported were levetiracetam (n = 3), valproic acid (n = 9), carbamazepine (n = 10), phenytoin (n = 3), phenobarbital (n = 4), lacosamide (n = 1), gabapentin (n = 1), and topiramate (n = 1). Two-thirds of the reports were about using CRRT in drug overdose and one-third was about AED removal by CRRT during therapy. Based on the current limited evidence and pharmacokinetic characteristics of AEDs, renally eliminated AEDs and/or AEDs with limited protein binding such as levetiracetam are more likely to be removed by CRRT than AEDs that are mainly metabolized and extensively protein bound such as carbamazepine. In conclusion, there is not enough evidence to provide robust dosing recommendations for AEDs in patients undergoing CRRT. Further studies are needed.

Effective withdrawal of antiepileptic drugs in premonitoring admission to capture seizures during limited video-EEG monitoring

Objective

Withdrawal of antiepileptic drugs (AEDs) is commonly applied to capture seizures in video‐EEG (vEEG) monitoring for patients with infrequent but intractable seizures. Because of the half‐life of AEDs, AED withdrawal during only vEEG tends to be inadequate to provoke seizures within the vEEG admission. We hypothesize that prewithdrawal of long‐half‐life AEDs in premonitoring admission (PMA) is safe and effective to capture seizures in the limited time of vEEG. We determined the effect of half‐life on the interval between AED withdrawal and seizure occurrence.

Methods

We collected 87 patients with three criteria: (1) seizure occurrence ≤3 per month; (2) AEDs ≥2; (3) AED withdrawal during their admission, among 126 consecutive patients who underwent vEEG in the Department of Neurosurgery, Hiroshima University Hospital between 2011 and 2014. We divided patients into two groups on the basis of half‐life of AED: Group A (23 patients) with phenobarbital (PB) and/or zonisamide (ZNS); Group B (64 patients) with other AEDs. In Group A, PB and ZNS were withdrawn during 4‐day PMA before vEEG started. Further AED withdrawal was performed during vEEG, depending on the seizure occurrence.

Results

The number of AEDs on admission was significantly higher in Group A (2–6, 3.5 ± 0.9; range, mean ±SD) than in Group B (2–5, 2.8 ± 0.8) (p < 0.01). All 23 Group A patients and 13 (20%) Group B patients underwent AED withdrawal during PMA. Seizures occurred during PMA in two patients in both Group A (9%) and Group B (15%). The first seizure occurred significantly longer after the start of withdrawal in Group A (6.1 ± 2.0 days) than in Group B (2.8 ± 1.3 days) (p < 0.01). Seizures were equally captured between both groups: 96% in Group A and 92% in Group B during vEEG.

Significance

For epilepsy patients who are treated with PB and/or ZNS, we recommend the planning of AED withdrawal during PMA before the start of vEEG to succeed in capturing seizures during the limited time of vEEG monitoring.

Correlation between prescribed daily dose, seizure freedom and defined daily dose in antiepileptic drug treatment

Background Although defined daily doses (DDD) for antiepileptic drugs (AED) have been assigned only in combination therapy, based on the literature, most patients take them in monotherapy. Furthermore, discrepancies between DDD and prescribed daily dose (PDD) were observed. Objective First, to determine PDDs of AEDs and to reveal PDD/DDD ratio among seizure free versus not seizure free patients in everyday clinical practice. Second, to test the applicability of 75% cut-off of DDD to achieve seizure freedom. Furthermore, to find out what factors might influence PDD. Setting Outpatient data files at a Hungarian university hospital were studied. Methods A retrospective, 20-year cross-sectional database was compiled from 1282 epileptic outpatients' files. Main outcome measure Seizure freedom and PDD were used as outcome measures. Results The mean DDD% of all prescribed AEDs increased steadily from monotherapy, through bitherapy towards polytherapy (p < 0.0001). Most seizure free patients took AEDs in doses in the range of ≤75% of DDDs in monotherapy and bitherapy. Older AEDs (carbamazepine and valproate) were given in a significantly higher mean dose in bitherapy in the seizure free group. Among the newer types, only levetiracetam and lamotrigine had a significantly higher DDD% in mono-, bi-, and polytherapy. Confirmed by logistic regression analysis, gender, age, type of epilepsy, and number of AEDs had a significant impact on the value of 75% DDD. Conclusion No significant unfavourable impact of the lower ratio of PDD/DDD on the outcome of achieving seizure freedom has been confirmed. As a measure of seizure freedom, 75% of DDD may be used, although individual therapy must be emphasised. Precisely quantified DDD would provide a more accurate calculation of other derived values.

An Analytical Study to Correlate Serum Levels of Levetiracetam with Clinical Course in Patients with Epilepsy

Introduction:

With the advancement of therapeutics, newer antiepileptic drugs (AEDs) like Levetiracetam (LEV), with good therapeutic efficacy and tolerability are available. But unfortunately, therapeutic drug monitoring is not routinely done in India for these drugs.

Objectives:

The objective of this study is to determine the range of serum levels of LEV in patients at stabilized doses and correlate them with their clinical course.

Materials and Methods:

Patients with epilepsy and started on LEV were enrolled from the Neurology Department after the Ethics Committee approval. Serum levels of LEV were estimated using high-performance liquid chromatography and correlated with patient demographics, dosage, dosage forms, concomitant AEDs, compliance of the patient, therapeutic effect, adverse drug reactions (ADRs), and suspected toxicity.

Results:

Serum levels of LEV ranged from 0.4 to 102.2 μg/ml at different time points and demonstrated a negligible positive correlation with age of the patients (r = 0.12) but negligible negative correlation with bodyweight (r = −0.19). No conclusive relationship could be established for dose, gender, dosage forms, clinical efficacy (seizure frequency), ADRs, and toxicity. Compliance was verified in all the patients. Levels were found to reduce with the use of concomitant enzyme inducer drugs (56.78%) whereas increase with valproic acid (7.8%).

Conclusion:

These findings emphasize the need for monitoring the serum levels of newer AEDs like LEV considering the various parameters studied here, so as to maintain the therapeutic efficacy by preventing under or over dosage and to generate a broader database of serum levels of LEV in the Indian population to help appropriate prescribing with more confidence.

Tolerability and Safety of Commonly Used Antiepileptic Drugs in Adolescents and Adults: A Clinician's Overview

This paper discusses the issues surrounding the tolerability and safety of the commonly used antiepileptic drugs (AEDs) in adolescents and adults. The content includes dose-related adverse effects, idiosyncratic reactions, behavioural and psychiatric comorbidities, chronic problems, enzyme induction and teratogenesis. Twenty-one AEDs are discussed in chronological order of their introduction into the UK, starting with phenobarbital and ending with brivaracetam. Wherever possible, advice is given on anticipating, recognising and managing these issues and thereby improving the lives of people with epilepsy, most of whom will need to take one or more of these agents for life. Avoidance of side effects will increase the possibility of achieving and maintaining long-term seizure freedom. Alternatively, adverse events from AEDs will substantially reduce quality of life and often result in higher healthcare costs.

Progress report on new antiepileptic drugs: A summary of the Thirteenth Eilat Conference on New Antiepileptic Drugs and Devices (EILAT XIII)

The Thirteenth Eilat Conference on New Antiepileptic Drugs and Devices (EILAT XIII) took place in Madrid, Spain, on June 26-29, 2016, and was attended by >200 delegates from 31 countries. The present Progress Report provides an update on experimental and clinical results for drugs presented at the Conference. Compounds for which summary data are presented include an AED approved in 2016 (brivaracetam), 12 drugs in phase I-III clinical development (adenosine, allopregnanolone, bumetanide, cannabidiol, cannabidivarin, 2-deoxy-d-glucose, everolimus, fenfluramine, huperzine A, minocycline, SAGE-217, and valnoctamide) and 6 compounds or classes of compounds for which only preclinical data are available (bumetanide derivatives, sec-butylpropylacetamide, FV-082, 1OP-2198, NAX 810-2, and SAGE-689). Overall, the results presented at the Conference show that considerable efforts are ongoing into discovery and development of AEDs with potentially improved therapeutic profiles compared with existing agents. Many of the drugs discussed in this report show innovative mechanisms of action and many have shown promising results in patients with pharmacoresistant epilepsies, including previously neglected rare and severe epilepsy syndromes.

Influence of Ivabradine on the Anticonvulsant Action of Four Classical Antiepileptic Drugs Against Maximal Electroshock-Induced Seizures in Mice

Although the role of hyperpolarization-activated cyclic nucleotide-gated (HCN) channels in neuronal excitability and synaptic transmission is still unclear, it is postulated that the HCN channels may be involved in seizure activity. The aim of this study was to assess the effects of ivabradine (an HCN channel inhibitor) on the protective action of four classical antiepileptic drugs (carbamazepine, phenobarbital, phenytoin and valproate) against maximal electroshock-induced seizures in mice. Tonic seizures (maximal electroconvulsions) were evoked in adult male albino Swiss mice by an electric current (sine-wave, 25 mA, 0.2 s stimulus duration) delivered via auricular electrodes. Acute adverse-effect profiles of the combinations of ivabradine with classical antiepileptic drugs were measured in mice along with total brain antiepileptic drug concentrations. Results indicate that ivabradine (10 mg/kg, i.p.) significantly enhanced the anticonvulsant activity of valproate and considerably reduced that of phenytoin in the mouse maximal electroshock-induced seizure model. Ivabradine (10 mg/kg) had no impact on the anticonvulsant potency of carbamazepine and phenobarbital in the maximal electroshock-induced seizure test in mice. Ivabradine (10 mg/kg) significantly diminished total brain concentration of phenytoin and had no effect on total brain valproate concentration in mice. In conclusion, the enhanced anticonvulsant action of valproate by ivabradine in the mouse maximal electroshock-induced seizure model was pharmacodynamic in nature. A special attention is required when combining ivabradine with phenytoin due to a pharmacokinetic interaction and reduction of the anticonvulsant action of phenytoin in mice. The combinations of ivabradine with carbamazepine and phenobarbital were neutral from a preclinical viewpoint.

Pharmacokinetic variability, efficacy and tolerability of eslicarbazepine acetate-A national approach to the evaluation of therapeutic drug monitoring data and clinical outcome

BACKGROUND

Eslicarbazepine acetate (ESL) is a new antiepileptic drug (AED), still insufficiently studied regarding pharmacokinetic variability, efficacy and tolerability. The purpose of this study was to evaluate therapeutic drug monitoring (TDM) data in Norway and relate pharmacokinetic variability to clinical efficacy and tolerability in a long-term clinical setting in patients with refractory epilepsy.

METHODS

This retrospective observational study included TDM-data from the main laboratories and population data from the Norwegian Prescription Database in Norway, in addition to clinical data from medical records of adult patients using ESL for up to three years, whenever possible.

RESULTS

TDM-data from 168 patients were utilized for assessment of pharmacokinetic variability, consisting of 71% of the total number of patients in Norway using ESL, 2011-14. Median daily dose of ESL was 800mg (range 400-1600mg), and median serum concentration of ESL was 53μmol/L (range 13-132μmol/L). Inter-patient variability of ESL was extensive, with 25-fold variability in concentration/dose ratios. Additional clinical data were available from 104 adult patients out of the 168, all with drug resistant focal epilepsy. After 1, 2 and 3 years follow-up, the retention rate of ESL was 83%, 72% and 64%, respectively. ESL was generally well tolerated as add-on treatment, but sedation, cognitive impairment and hyponatremia were reported. Hyponatremia (sodium <137mmol/L) was present in 36% of the patients, and lead to discontinuation in three.

CONCLUSION

Pharmacokinetic variability of ESL was extensive and the demonstration of usefulness of TDM requires further studies. In patients with drug resistant focal Epilepsy, the high retention rate indicated good efficacy and tolerability. Hyponatremia was observed in one third of the patients. The present results point to a need for individualization of treatment and TDM may be useful.