Profile of once-daily zonisamide as monotherapy for treatment of partial seizures in adults

A new population pharmacokinetic model for dosing optimization of zonisamide in patients with refractory epilepsy

Zonisamide exhibits significant pharmacokinetic variability, demanding for the development of population pharmacokinetic (PopPK) models to identify key factors influencing drug disposition. This study aimed to develop and validate a PopPK model to optimize zonisamide posology in patients with refractory epilepsy. A total of 114 plasma concentrations of zonisamide, obtained from 64 patients, were used for PopPK model development, employing the nonlinear mixed-effects modelling approach. The final model was evaluated by visually inspecting the goodness-of-fit plots and the visual predictive check plot and by the bootstrap resampling method. A one-compartment model with first-order elimination was the one that best described the pharmacokinetic profile of zonisamide. Between-patient variability (BPV) was included on clearance (CL/F), volume of distribution (Vd/F) and absorption rate constant (ka). The residual error (RE) was modeled as proportional. The final model estimates for CL/F, Vd/F and ka were 0.761 L/h, 48.10 L and 0.671 h⁻¹, respectively. The BPV associated with CL/F, Vd/F, and ka was 43.93%, 52.06%, and 91.27%, respectively, while the proportional RE was 7.18%. The concomitant administration of enzyme-inducing antiseizure drugs (EIASDs), included in the model as inducer drug load (INDDL), significantly accounted for BPV associated with CL/F and led to increased CL/F in patients receiving EIASDs compared to the others. Consequently, patients receiving EIASDs require higher daily doses of zonisamide to achieve therapeutic plasma concentrations compared to those not treated with EIASDs. Model validation, using bootstrap and visual predictive checks, confirmed its stability and robustness, making it a valuable tool for individualized zonisamide dosing in adults with refractory epilepsy.

Global trends in research of glutamate in epilepsy during past two decades: A bibliometric analysis

Epilepsy affects more than 70 million people in the world. It is characterized by recurrent spontaneous seizures, and it is related to many neurological, cognitive, and psychosocial consequences. Glutamate neurotransmitter dysfunction has essential functions in the pathophysiology of epilepsy. In this work, bibliometric analysis was conducted to explore the trends, frontiers, and hotspots of the global scientific output of glutamate in epilepsy research in the past 20 years. The Science Citation Index Expanded of the Web of Science Core Collection (WoSCC) was searched to obtain information on publications and records published between 2002 and 2021. VOSviewer and CiteSpace were used to conduct bibliometric and visual analyses on the overall distribution of annual output, major countries, active institutions, journals, authors, commonly cited literature, and keywords. The impact and quality of the papers were assessed using the global citation score (GCS). Four thousand eight hundred ninety-one publications were retrieved in total. During the past two decades, the number of publications (Np) associated with glutamate in epilepsy has risen yearly. The United States has published the most papers; its H-index and number of citations are also the highest. The League of European Research Universities (LERU) was the most productive institution. In 2016, the total score of the paper written by Zhang Y was 854, ranking first. The keywords that appear most frequently are “epilepsy,” “glutamate,” “temporal lobe epilepsy (TLE),” “hippocampus,” and “seizures.” This study showed that although the publications related to epileptic glutamate fluctuated slightly, the Np increased overall. The United States is a great creator and influential country in this field. The first three authors are Eid, T., Aronica, E., and Smolders, I. “spectrum,” “animal model,” “inflammation,” “mutation,” “dysfunction,” and “prefrontal cortex” are increasing research hotspots. By recognizing the most critical indicators (researchers, countries, research institutes, and journals of glutamate release in epilepsy research), the research hotspot of glutamate in epilepsy could help countries, scholars, and policymakers in this field enhance their understanding of the role of glutamate in epilepsy and make decisions.

Reactive metabolites of the anticonvulsant drugs and approaches to minimize the adverse drug reaction

Several generations of antiepileptic drugs (AEDs) are available in the market for the treatment of seizures, but these are amalgamated with acute to chronic side effects. The most common side effects of AEDs are dose-related, but some are idiosyncratic adverse drug reactions (ADRs) that transpire due to the formation of reactive metabolite (RM) after the bioactivation process. Because of the adverse reactions patients usually discontinue the medication in between the treatment. The AEDs such as valproic acid, lamotrigine, phenytoin etc., can be categorized under such types because they form the RM which may prevail with life-threatening adverse effects or immune-mediated reactions. Hepatotoxicity, teratogenicity, cutaneous hypersensitivity, dizziness, addiction, serum sickness reaction, renal calculi, metabolic acidosis are associated with the metabolites of drugs such as arene oxide, N-desmethyldiazepam, 2-(1-hydroxyethyl)-2-methylsuccinimide, 2-(sulphamoy1acetyl)-phenol, E-2-en-VPA and 4-en-VPA and carbamazepine-10,11-epoxide, etc. The major toxicities are associated with the moieties that are either capable of forming RM or the functional groups may itself be too reactive prior to the metabolism. These functional groups or fragment structures are typically known as structural alerts or toxicophores. Therefore, minimizing the bioactivation potential of lead structures in the early phases of drug discovery by a modification to low-risk drug molecules is a priority for the pharmaceutical companies. Additionally, excellent potency and pharmacokinetic (PK) behaviour help in ensuring that appropriate (low dose) candidate drugs progress into the development phase. The current review discusses about RMs in the anticonvulsant drugs along with their mechanism vis-a-vis research efforts that have been taken to minimize the toxic effects of AEDs therapy.

Effects of zonisamide monotherapy on bone health in drug-naive epileptic patients

OBJECTIVE

Alteration of bone strength is an adverse effect of antiepileptic drug treatment. We investigated the effects of zonisamide (ZNS) monotherapy on bone mineral density (BMD) and biomarkers of bone metabolism after 13 months of treatment in drug-naive epileptic patients.

METHODS

Fifty-nine patients with new onset drug-naive epilepsy were enrolled (29 women, 30 men; mean age = 31.5 ± 11.5 years). The BMD and T scores were measured at the lumbar spine and femoral neck by using dual-energy X-ray absorptiometry. Biomarkers specific for bone metabolism (bone-specific alkaline phosphatase, parathyroid hormone, osteocalcin, insulinlike growth factor-1, C-telopeptide, and vitamin D3 levels) were measured before and after long-term ZNS monotherapy. Analysis of covariance (ANCOVA) was used to estimate BMD and biomarkers of bone metabolism before and after ZNS therapy. Age, sex, treatment duration, and ZNS dosage were included as covariates for adjustment in the ANCOVA model. Furthermore, subgroup analyses were performed for each sex, and the effect size was calculated.

RESULTS

After 13 months of ZNS treatment, the BMD and T scores at the lumbar spine (L1-L4 level) and femoral neck were not significantly different. Moreover, the biochemical markers showed no significant differences after ZNS monotherapy. Women showed significantly decreased baseline BMD at the femoral neck compared to men (P = .026), although the mean age and body mass index were not significantly different between the sexes. No significant changes in BMD or biomarkers of bone metabolism were seen in either sex after 13 months of ZNS treatment.

SIGNIFICANCE

The results suggest that long-term ZNS monotherapy does not affect bone health in drug-naive patients with epilepsy negatively.

Perampanel: Does it have broad-spectrum potential?

This article reviews the profile of perampanel, a novel noncompetitive α-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate (AMPA) receptor antagonist, and its role as a potential broad-spectrum antiepileptic drug in the treatment of epilepsy. For this narrative review, data were collected using specified search criteria. Articles reporting the evidence for perampanel's efficacy from preclinical models, phase 3 clinical studies, observational studies, and descriptive evidence were included. AMPA receptors play a key role in mediating the action of glutamate at the excitatory synapse. Preclinical research showed the AMPA receptor blockade to constitute a promising target for antiepileptic drug therapy. In animal models, perampanel proved to be protective against seizures and reduce seizure severity and duration. Four phase-3 randomized controlled trials (3 in patients with focal seizures and one in primary generalized tonic-clonic seizures in idiopathic generalized epilepsy) have been completed. In focal (partial) onset seizures, perampanel (4, 8, and 12 mg) significantly reduced seizure frequency per 28 days (23.3%-28.8% vs 12.8%; P < .01) and responder rates (≥50% reduction in seizures) (28.5%-35.3% vs 19.3%; P < .05) compared with placebo. In primary generalized tonic-clonic seizures, perampanel 8 mg resulted in greater reduction in seizure frequency per 28 days (-76.5% vs -38.4%; P < .0001) and responder rate (64.2% vs 39.5%; P = .0019) than placebo. The efficacy, safety, and tolerability of perampanel have been reproduced in real-world clinical practice, and the agent has been shown to be effective in other epilepsy syndromes. Perampanel is a potentially broad-spectrum antiepileptic drug with a novel mechanism of action that may be a useful addition for patients with epilepsy with various seizure types. The availability of novel antiepileptic drugs for epilepsy treatment enables more individualized treatment for these patients.

Oxcarbazepine oral suspension in young pediatric patients with partial seizures and/or generalized tonic-clonic seizures in routine clinical practice in China: a prospective observational study

BACKGROUND

This study aimed to assess efficacy and safety of oxcarbazepine (OXC) oral suspension in pediatric patients aged 2-5 years with partial seizures (PS) and/or generalized tonic-clonic seizures (GTCS) in real-world clinical practice in China.

METHODS

This 26-week, prospective, single-arm, multicenter, observational study recruited pediatric patients aged 2-5 years with PS or GTCS suitable for OXC oral suspension treatment based on physicians' judgments from 11 medical centers in China. Enrolled subjects started OXC oral suspension treatment as monotherapy or in combination with other antiepileptic drugs. Primary efficacy outcome was the percentage of pediatric subjects achieving ≥ 50% seizure frequency reduction at the end of the 26-week treatment. Secondary efficacy-related parameters and safety parameters such as adverse events (AEs) and serious AEs (SAEs) were also monitored during the 26-week treatment period.

RESULTS

Six hundred and six pediatric patients were enrolled and 531 (87.6%) completed the study. After 26 weeks of treatment, 93.3% subjects achieved ≥ 50% seizure frequency reduction, and 81.8% achieved 100% seizure frequency reduction compared to baseline. Among different seizure types, OXC was effective in all subjects with simple PS and in > 90% of subject with other type of seizure present in the study. AEs were observed in 49 (8.1%) subjects. Only three subjects experienced SAE. Rash (n = 18, 2.97%) was the most common AE. Only 17 subjects discontinued due to AEs.

CONCLUSION

This study, reporting the real-world data, further confirms the efficacy and good safety profile of OXC oral suspension in Chinese pediatric patients aged 2-5 years with PS and/or GTCS.

Zonisamide as a treatment for partial epileptic seizures: a systematic review

Although the majority of people with epilepsy have a good prognosis and their seizures can be well controlled with pharmacotherapy, up to one-third of patients can develop drug-resistant epilepsy, especially those patients with partial seizures. This unmet need has driven considerable efforts over the last few decades aimed at developing and testing newer antiepileptic agents to improve seizure control. One of the most promising antiepileptic drugs of the new generation is zonisamide, a benzisoxazole derivative chemically unrelated to other anticonvulsant agents. In this article, the authors present the results of a systematic literature review summarizing the current evidence on the efficacy and tolerability of zonisamide for the treatment of partial seizures. Of particular interest within this updated review are the recent data on the use of zonisamide as monotherapy, as they might open new therapeutic avenues.