Efficacy of lamotrigine and vigabatrin in drug-resistant epilepsies of childhood

Meta-analyses of newer antiepileptic drugs as adjunct for treatment of focal epilepsy in children

AIM

This study conducted a systematic review evaluating the effectiveness of newer antiepileptic drugs (AEDs) (namely, lamotrigine, levetiracetam, topiramate, vigabatrin, zonisamide, oxcarbazepine, perampanel, gabapentin, and stiripentol) as add-on for treatment of focal epilepsy in children.

METHODS

Articles were retrieved from EMBASE, Medline and Cochrane Library from inception to January 2016. Treatment outcomes were analysed based on responder, seizure-free, withdrawal and adverse event rates. Quality of each study was also assessed.

RESULTS

Twelve articles fulfilled the inclusion criteria. Heterogeneity and quality of the included studies were considered acceptable. Overall, newer AEDs as adjunct therapy in children with inadequate control of focal seizure showed a trend of better seizure outcomes. The pooled ORs for responder, seizure-free and withdrawal rates were 2.15 (95%CI:1.72, 2.69), 1.99 (95%CI:0.72, 5.48) and 0.69 (95%CI:1.13, 2.39) respectively. Adverse events of newer AEDs were comparatively higher than placebo (OR:1.64, 95%CI:1.13, 2.39).

CONCLUSION

In our updated review, newer AEDs as adjunct therapy for focal epilepsy in children have trends of better effectiveness compared to placebo. Newer AEDs are associated with statistically more children with >50% seizure reduction, and a trend of better seizure freedom. Their tolerability would also be considered acceptable with the observed low withdrawal rate. However, the relative lack of well-conducted RCTs evaluating their effectiveness against other active AED treatment in children would not facilitate evidence-based practice. This highlights the knowledge gap and the need for more well-conducted RCTs against active treatments to ascertain the long term effectiveness and the role of newer AEDs in managing epilepsy in children.

Effect of vigabatrin on seizure control and safety profile in different subgroups of children with epilepsy

OBJECTIVE

To evaluate the efficacy and safety of vigabatrin in pediatric epilepsy.

METHODS

We retrospectively reviewed patients with epilepsy treated with vigabatrin over a 2-year period at a pediatric tertiary center. We assessed the relationship between seizure frequency, etiology, vigabatrin dose, adverse events, medication discontinuation reasons, and electroencephalography (EEG) characteristics.

RESULTS

One hundred three patients followed at Boston Children's Hospital were treated with vigabatrin and had complete medical records. Within the follow-up interval, 69 (67%) of 103 patients had discontinued vigabatrin therapy. Two patients (1.9%) died during therapy for unknown reasons. Median age at vigabatrin initiation was 8 months (interquartile range [IQR] 5-15). Median starting dose was 48.1 mg/kg per day (IQR 29.8-52.3) with a median target of 100 mg/kg (IQR 81.9-107.9). Median treatment duration was 12.1 months (n = 89, IQR 5.0-22.9) overall, and 13.3 months (IQR 5.2-23.2) for patients who discontinued vigabatrin. The most common reasons for discontinuation were controlled seizures in 31 (43.7%) of 71 and unsatisfactory therapeutic effect in 23 (32.4%) of 71. Median percent seizure reduction from baseline to first follow-up was 83.3% (IQR 27.4-99.8) and 96.7% (IQR 43.3-100) to last follow-up. Twenty-four (38.7%) of 62 patients with a follow-up posttreatment remained seizure-free. Four patients who had initially achieved seizure freedom relapsed. Patients with structural/metabolic etiology had greater median percent seizure reduction at first follow-up than patients with genetic etiology (98.7% vs. 61.4%, respectively, p = 0.001). Hypsarrhythmia resolved after therapy in 18 of 20 (90%, 95% confidence interval [CI] 70-97) patients with pretreatment hypsarrhythmia, and 2 patients presented with hypsarrhythmia posttreatment. Risk of having hypsarrhythmia was reduced by 32% (95% CI 14.9-49.1) posttreatment.

SIGNIFICANCE

Vigabatrin is efficacious in all seizure types and resolved hypsarrhythmia in most patients. In this series with a median treatment duration of 12.1 months, vigabatrin had a good safety profile with a low rate of discontinuation due to nonophthalmologic and ophthalmologic adverse effects.

Behavioral adverse effects of antiepileptic drugs in epilepsy

Patient tolerability is a significant limiting factor in the treatment of epilepsy and adverse effect profiles often determine drug retention rates. A full appreciation of the behavioral effects of a wide range of antiepileptic drugs (AEDs) is therefore essential to make informed treatment decisions. In this timely review, we highlight key alterations in mood, emotional experience, and other behavioral/psychiatric features, which can exert a crucial impact on patients' quality of life and well-being. With a view to prescribing both in general and in relation to more specific clinical characteristics, the evidence reviewed indicates that the incidence and characteristics of behavioral effects may be related to age, epilepsy type, the presence of learning disability, and previous psychiatric history. Medication parameters including dosage, titration rate, efficacy in controlling seizures, and concurrent AEDs can also contribute to the occurrence of behavioral effects. However, there are a number of limitations in drawing conclusions from the available literature. These include variation in study design, treatment group, and assessment tools that lead to difficulties comparing findings across studies, and problems with the consistency of available information relating to the study methodology. Future longitudinal studies assessing the impact of tolerance or developmental change on behavioral effects and specific studies comparing the effects of commonly prescribed agents across subgroups of patients with epilepsy will make an informative contribution to the available literature. A valuable outcome of further research may be the development of specific instruments that are sensitive to the behavioral effects associated with particular AEDs.

Systemic adrenocorticotropic hormone administration down-regulates the expression of corticotropin-releasing hormone (CRH) and CRH-binding protein in infant rat hippocampus

Systemic adrenocorticotropic hormone (ACTH) administration is a first-line therapy for the treatment of infantile spasms, an age-specific seizure disorder of infancy. It is proposed that exogenous ACTH acts via negative feedback to suppress the synthesis of corticotropin-releasing hormone (CRH), a possible endogenous convulsant in infant brain tissue. The aim of this study was to determine whether systemic ACTH treatment in infant rats down-regulates the hippocampal CRH system, including CRH, CRH-binding protein (CRH-BP), and CRH receptors (CRH-R1 and CRH-R2). Daily i.p. injection of ACTH for 7 consecutive days (postnatal days 3-9) elevated serum corticosterone levels 20-fold measured on postnatal day 10, indicating systemic absorption and circulation of the ACTH. Semiquantitative reverse transcriptase-PCR demonstrated that both CRH and CRH-BP mRNA obtained from the hippocampi of ACTH-injected infant rats was significantly depressed relative to saline-injected animals. Comparable reductions in both CRH and CRH-BP synthesis were further demonstrated with radioimmunoassay. In contrast, neither CRH-R1 nor CRH-R2 mRNA was altered by ACTH treatment, relative to saline-injected rats. This latter finding was confirmed electrophysiologically by measuring the enhancement of hippocampal population spikes by exogenous CRH, also showing no differences between ACTH- and saline-injected rats. The results of this study support the proposal that systemic ACTH treatment down-regulates CRH expression in infant brain, perhaps contributing to the therapeutic efficacy observed during treatment of infantile spasms.

Characteristics of patients initiated on the new antiepileptic drugs: a PADS study

Whereas randomized controlled trials remain a standard for evaluating and comparing efficacy and safety of the new antiepileptic drugs (AEDs), postmarketing drug research offers a useful means of comparing efficacy and safety of new AEDs. However, differences in baseline characteristics of patients in different drug groups create the potential for bias in drug comparison studies. In this study, baseline demographic characteristics of 1,386 patients initiating lamotrigine (LTG), tiagabine (TGB), or topiramate (TPM) were compared to identify patient characteristics that may influence AED use in epilepsy patients. Data were collected at 14 epilepsy centers and included medications, seizure types and syndromes, and prior adverse events. There were 402 patients in the LTG group, 725 TPM, and 259 TGB. The groups differed both in their number of concurrent AEDs (p<0.001) and in their number of prior AEDs (p<0.01). There was no difference in proportion with partial versus generalized epilepsy syndromes. The groups differed in the proportions of patients with complex partial seizures (p=0.049), primary generalized tonic-clonic seizures (p=0.01), and myoclonic seizures (p=0.03). Baseline behavioral adverse event rate was lowest in patients initiating TPM (p<0.01); LTG patients had the lowest rate of prior AED-related rash (p=0.02). There was no relationship between AED assignment and patient age, age of epilepsy onset, epilepsy duration, institutionalization status, gender, or psychiatric history. Numerous epidemiological differences were identified among patients placed on the new AEDs, including current and prior AED profiles, seizure types, and prior adverse event history. Accounting for these differences is of crucial importance because they may bias conclusions of nonrandomized post-marketing trials comparing the drugs.