Changes in the use of antiseizure medications in children and adolescents in Norway, 2009-2018

Pharmacokinetic Variability of Rufinamide and Stiripentol in Children with Refractory Epilepsy: A Retrospective Study of Therapeutic Drug Monitoring from the National Epilepsy Centers in Denmark and Norway

BACKGROUND

Rufinamide and stiripentol, orphan drugs used in Lennox-Gastaut and Dravet syndromes, respectively, are antiseizure medications (ASMs), often administered to children; however, pharmacokinetic studies are lacking. The authors compared the pharmacokinetic variability of these drugs with respect to the dose, serum concentrations, comedication, age, and duration of treatment.

METHODS

Children and adolescents (<18 years) whose serum concentrations were measured were retrospectively identified from the therapeutic drug monitoring (TDM) databases at 2 national epilepsy centers in Norway and Denmark (2012-2021).

RESULTS

Data from 165 patients (56% boys/44% girls) treated with rufinamide and 52 patients (50% boys/50% girls) treated with stiripentol were included. For rufinamide, the median age was 10 (range 2-17) years, dose 23 (3-73) mg/d, and serum concentration 34 (3-227) µmol/L [8.1 mg/L (0.71-54.0 mg/L)]. For stiripentol, the median age was 8.5 (range 1-17) years, dose 37 (18-76) mg/d, and serum concentration 33 (4-113) µmol/L [7.7 mg/L (0.93-26.3 mg/L)]. The concomitant use of 1-9 other ASMs during the data collection was noted. Pharmacokinetic variability, calculated as the concentration/(dose/kg) ratio, ranged from 0.26 to 11.31 (µmol/L)/(mg/kg) for rufinamide and 0.17-1.52 (µmol/L)/(mg/kg) for stiripentol. The intraindividual coefficients of variation ranged widely, from 5% to 110% for rufinamide and 11%-117% for stiripentol. The treatment period was at least 5 years in 50% of patients. No statistically significant effects of age, sex, or ASM comedication were observed, possibly due to the small sample size and heterogeneous groups with variable seizure situations, comorbidities, and changes in comedication and physiology.

CONCLUSIONS

This study demonstrates considerable pharmacokinetic variability in and between patients for both drugs and similar use in terms of age, burden of comedication and retention rates. TDM may be useful in the clinical setting to monitor and optimize treatment in this vulnerable patient group.

Pharmacokinetic Variability of Sulthiame: The Impact of Age, Drug-Drug Interactions, and Biochemical Markers of Toxicity in Patients with Epilepsy

PURPOSE

Sulthiame is an antiseizure medication increasingly used for epilepsy. The aim of this study was to investigate the pharmacokinetic variability of sulthiame in children and adults with epilepsy with respect to age, comedication, dose, serum concentration, and biochemical markers of toxicity in a clinical setting.

METHOD

Retrospective quantitative data from the therapeutic drug monitoring (TDM) database at the Section for Clinical Pharmacology, the National Center for Epilepsy, Norway (2015-2021), were used.

RESULTS

TDM data from 326 patients (127 female/199 male) were included [mean age, 11.4 (range 2-44) years; mean weight, 41 (range 14-109) kg]. Interindividual pharmacokinetic variability in the concentration/(dose/body weight) (C/(D/kg)) ratio was 16-fold; intraindividual variability was up to 8-fold (coefficient of variation = 10%-78%). Young children (younger than 6 years) had a significantly lower C/(D/kg) ratio than older age groups ( P < 0.05). Various comedications did not significantly affect the C/(D/kg) ratio, possibly owing to the small sample size. However, CYP2C19-mediated inhibition by sulthiame was indicated because patients using clobazam and sulthiame (n = 28) had a 3.5-fold higher N-desmethylclobazam C/(D/kg) ratio than those using neutral comedication (n = 45; P < 0.001). Patients with pH values below the adjusted normal range (7.32-7.42; n = 15) had a 33% higher sulthiame concentration than those with normal pH values (n = 22; P < 0.05). Blood gas measurements, especially pH, may serve as markers of toxicity and can be used in combination with clinical data when toxicity is suspected.

CONCLUSIONS

This study revealed the extensive intraindividual and interindividual pharmacokinetic variability of sulthiame, with age as a contributing factor. Sulthiame has clinically relevant interactions with clobazam. The use of TDM and pH as a biochemical marker may contribute to individualized and safe sulthiame treatment.

Hepatotoxicity of newer antiseizure medications in children: an overview and disproportionality analysis of VigiBase

BACKGROUND

We aimed to characterize newer antiseizure medications (ASMs)-induced hepatotoxicity in children and identify signals of disproportionate reporting of hepatotoxicity-related adverse drug events (ADEs).

RESEARCH DESIGN AND METHODS

Case reports reported to VigiBase were accessed using Empirica™ Signal software. To summarize characteristics of the retrieved cases, descriptive statistics were used. A disproportionality analysis was conducted using the Multi-item Gamma Poisson Shrinker algorithm, which calculates Empirical Bayesian Geometric Mean value and its lower and upper 95% confidence limits (EB05 and EB95, respectively). EB05 > 2, N > 0 was considered a signal.

RESULTS

Based on 870 analyzed cases, a higher proportion of cases was reported in girls than in boys and in patients aged 2-11 years than in other age groups. Most cases were serious. In 25 cases, hepatotoxicity resulted in death. A high proportion of patients (n = 275, 31.61%) experienced hypersensitivity reactions, mostly due to lamotrigine. The disproportionality analysis yielded 17 signals concerning felbamate, lamotrigine, levetiracetam, oxcarbazepine, stiripentol, and topiramate. Four signals were for severe liver injury and concerned felbamate, lamotrigine, levetiracetam, and topiramate. Gender-biased reporting frequency was detected for four ASM-ADE combinations.

CONCLUSION

Our results should serve to raise clinicians' awareness about the potential association between several newer ASMs and drug-induced liver injury in children.

If the Patient Does Not Take the Medication, It Will Not Work

COGNITIVE AND BEHAVIORAL COMORBIDITIES

AN UNWANTED EFFECT OF ANTIEPILEPTIC DRUGS IN CHILDREN: Adriana Ulate-Campos, Iván Sánchez Fernández Seminars in Pediatric Neurology Volume 24, Issue 4, November 2017, Pages 320-330 Epilepsy is one of the most common neurological disorders and, despite optimally chosen and dosed antiepileptic drugs (AEDs), approximately 20%-30% of patients will continue to have seizures. Behavior and cognition are negatively impacted by seizures, but AEDs are also a major contributor to behavioral and cognitive deficits. However, the cognitive and behavioral effect of AEDs in children is insufficiently emphasized in the literature. This review summarizes the cognitive and behavioral effects of AEDs in the pediatric population with the objective of helping pediatricians and pediatric neurologists to select the AEDs with the best profile for their individual patient's needs.

Rufinamide, a Triazole-Derived Antiepileptic Drug, Stimulates Ca2+-Activated K+ Currents While Inhibiting Voltage-Gated Na+ Currents

Rufinamide (RFM) is a clinically utilized antiepileptic drug that, as a triazole derivative, has a unique structure. The extent to which this drug affects membrane ionic currents remains incompletely understood. With the aid of patch clamp technology, we investigated the effects of RFM on the amplitude, gating, and hysteresis of ionic currents from pituitary GH₃ lactotrophs. RFM increased the amplitude of Ca²⁺-activated K⁺ currents (I_K(Ca)) in pituitary GH₃ lactotrophs, and the increase was attenuated by the further addition of iberiotoxin or paxilline. The addition of RFM to the cytosolic surface of the detached patch of membrane resulted in the enhanced activity of large-conductance Ca²⁺-activated K⁺ channels (BK_Ca channels), and paxilline reversed this activity. RFM increased the strength of the hysteresis exhibited by the BK_Ca channels and induced by an inverted isosceles-triangular ramp pulse. The peak and late voltage-gated Na⁺ current (I_Na) evoked by rapid step depolarizations were differentially suppressed by RFM. The molecular docking approach suggested that RFM bound to the intracellular domain of K_Ca1.1 channels with amino acid residues, thereby functionally affecting BK_Ca channels' activity. This study is the first to present evidence that, in addition to inhibiting the I_Na, RFM effectively modifies the I_K(Ca), which suggests that it has an impact on neuronal function and excitability.

Cardiac morbidity and mortality associated with the use of lamotrigine

OBJECTIVE

The US Food and Drug Administration recently issued a warning against the use of the antiseizure medication lamotrigine in people at risk of cardiac rhythm and conduction abnormalities. This study assessed the risk of cardiac morbidity and mortality in new users of lamotrigine.

METHODS

In a Danish population-based cohort study, we followed cohort members aged ≥15 years for the first 2 years after they initiated lamotrigine therapy. The main outcomes were cardiac conduction disorders in people without pre-existing cardiac morbidity and all-cause mortality in people with pre-existing cardiac morbidity. Cox proportional hazards models provided hazard ratios (HRs) and corresponding 95% confidence intervals (CIs) for comparison of the risk in current versus past users of lamotrigine.

RESULTS

There were 91 949 (36 618 males [39.8%]) new users of lamotrigine (median age = 45.7 years, interquartile range = 32.0-60.2 years). Among users without pre-existing cardiac disease (n = 86 769), 194 (.23%) developed a cardiac conduction disorder. Comparison of the risk in current and past lamotrigine treatment periods yielded an adjusted HR of new onset cardiac conduction disorder of 1.03 (95% CI = .76-1.40). Among users with pre-existing cardiac disease (n = 5180), 1150 (22.2%) died. Comparison of the risk in current and past lamotrigine treatment periods yielded an adjusted HR for all cause-mortality of 1.05 (95% CI = .93-1.19).

SIGNIFICANCE

In this large population-based study, lamotrigine use was associated neither with a risk of cardiac conduction disorders in people without pre-existing cardiac morbidity nor with all-cause mortality in people with pre-existing cardiac morbidity.