Impact of perampanel on pharmacokinetics of concomitant antiepileptics in patients with partial-onset seizures: pooled analysis of clinical trials

Perampanel in post-stroke epilepsy: Clinical practice data from the PERampanel as Only Concomitant antiseizure medication (PEROC) study

INTRODUCTION

Post-stroke epilepsy (PSE) is one of the most common causes of acquired epilepsy. Nevertheless, there is limited evidence regarding the clinical profile of antiseizure medications (ASMs) in PSE. This study aims to evaluate the 12-month effectiveness and tolerability of perampanel (PER) used as only add-on treatment in patients with PSE in a real-world setting.

METHODS

We performed a subgroup analysis of PSE patients included in a previous retrospective, longitudinal, multicentre observational study on adults. Treatment discontinuation, seizure frequency and adverse events were collected at 3, 6 and 12 months. Sub-analyses by early (≤1 previous ASM) or late PER add-on were also conducted.

RESULTS

Our analysis included 56 individuals with PSE, characterized by varying initial treatment modalities and timeframes relative to disease onset. We found notable retention rates (92.8%, 83.7%, and 69% at 3, 6, and 12 months), with treatment withdrawal mainly due to poor tolerability. One year after PER introduction, seizure frequency significantly reduced, with a responder rate (≥50% reduction) of 83.9% and a seizure-free rate of 51.6%. Adverse events occurred in 25 (46.3%) patients, mainly dizziness, irritability, and behavioural disorders. No major statistical differences were found between early (30 patients, 53.6%) and late add-on groups, except for a higher 6-month responder rate in the early add-on group.

CONCLUSION

Adjunctive PER was effective and well-tolerated in patients with PSE in a real-world setting. Perampanel demonstrated good efficacy and safety as both early and late add-on treatment, making it a compelling option for this unique patient population.

Interactions between antiepileptic drugs and direct oral anticoagulants for primary and secondary stroke prevention

INTRODUCTION

Direct oral anticoagulants (DOAC) are the guideline-recommended therapy for prevention of stroke in atrial fibrillation (AF) and venous thromboembolism. Since approximately 10% of patients using antiepileptic drugs (AED) also receive DOAC, aim of this review is to summarize data about drug-drug interactions (DDI) of DOAC with AED by using data from PubMed until December 2023.

AREAS COVERED

Of 49 AED, only 16 have been investigated regarding DDI with DOAC by case reports or observational studies. No increased risk for stroke was reported only for topiramate, zonisamide, pregabalin, and gabapentin, whereas for the remaining 12 AED conflicting results regarding the risk for stroke and bleeding were found. Further 16 AED have the potential for pharmacodynamic or pharmacokinetic DDI, but no data regarding DOAC are available. For the remaining 17 AED it is unknown if they have DDI with DOAC.

EXPERT OPINION

Knowledge about pharmacokinetic and pharmacodynamic DDI of AED and DOAC is limited and frequently restricted to in vitro and in vivo findings. Since no data about DDI with DOAC are available for 67% of AED and an increasing number of patients have a combined medication of DOAC and AED, there is an urgent need for research on this topic.

The latest advances in the pharmacological management of focal epilepsies in children: a narrative review

INTRODUCTION

Focal epilepsy constitutes the most common epilepsy in children, and medical treatment represents the first-line therapy in this condition. The main goal of medical treatment for children and adolescents with epilepsy is the achievement of seizure freedom or, in drug-resistant epilepsies, a significant seizure reduction, both minimizing antiseizure medications (ASM)-related adverse events, thus improving the patient's quality of life. However, up to 20-40% of pediatric epilepsies are refractory to drug treatments. New ASMs came to light in the pediatric landscape, improving the drug profile compared to that of the preexisting ones. Clinicians should consider several factors during the drug choice process, including patient and medication-specific characteristics.

AREAS COVERED

This narrative review aims to summarize the latest evidence on the effectiveness and tolerability of the newest ASMs administered as monotherapy or adjunctive therapy in pediatric epilepsies with focal onset seizures, providing a practical appraisal based on the existing evidence.

EXPERT OPINION

The latest ASMs have the potential to be effective in the pharmacological management of focal onset seizures in children, and treatment choice should consider several drug- and epilepsy-related factors. Future treatments should be increasingly personalized and targeted on patient-specific pathways. Future research should focus on discovering new chemical compounds and repurposing medications used for other indications.

Efficacy and safety of perampanel as the first add-on therapy for children with epilepsy: A real-world multicenter prospective observational study

OBJECTIVE

Perampanel (PER) is a new anti-seizure medication (ASM) with a novel mechanism of action. This study aimed to determine the efficacy and safety of PER when added to monotherapy in children and adolescents (age, 4-18 years) with epilepsy.

METHOD

A multicenter prospective observational study was performed on children and adolescents (age, 4-18 years) with epilepsy who did not respond to ASM monotherapy between July 2021 and October 2022. PER was used as the first add-on therapy for the enrolled patients. Seizure-free rate, response rate, inefficacy rate, and drug retention rate were the main observation indicators during the 6 months of treatment. The patients were grouped based on treatment efficacy, and factors affecting efficacy were statistically analyzed. Adverse reactions were also recorded.

RESULTS

In this study, 93 patients with epilepsy were enrolled; among them, 9 patients were lost to follow-up (attrition rate, 9.7 %), and 84 were included in the analysis. Five patients with unknown efficacy discontinued taking PER early due to intolerable adverse reactions, and 79 patients (48 males, 31 females; mean age, 11.0 ± 3.9 years) finally remained. Genetic epilepsy and structural epilepsy were found in 22 patients and 36 patients, respectively. The mean duration of epilepsy history at the time of PER initiation was 4.0 ± 3.8 years, and the mean maintenance dosage of add-on PER was 4.5 ± 1.8 mg/day (equivalent to 0.14 ± 0.07 mg/kg/day). Among the 79 patients, 28 patients were diagnosed with epilepsy syndrome, including 13 patients having self-limited epilepsy with centrotemporal spikes, among whom 9 patients were seizure-free after adding PER during the 6-month follow-up (seizure-free rate, 69.2 %). For these 79 patients, the seizure-free, response, and retention rates at the end of follow-up were 45.6 %, 74.7 %, and 82.1 %, respectively. Among the 84 patients included in the analyses, adverse reactions occurred in 20 patients, mainly dizziness (8 patients), somnolence (6 patients), and irritability (4 patients), and 4 patients developed two adverse reactions simultaneously. Univariate analyses revealed statistically significant differences in efficacy between groups with structural and non-structural epilepsy and between groups with different baseline concomitant ASMs, suggesting that these factors affected the efficacy of PER as the first add-on therapy.

CONCLUSION

The overall response rate of PER as the first add-on therapy for children and adolescents with epilepsy who were followed up for 6 months was 74.7 %, indicating a relatively favorable safety and tolerability profile. The group of the baseline concomitant ASM administered and the etiological classification of epilepsy as either structural or non-structural were the factors influencing the efficacy of PER as the first add-on therapy.

The Cognitive and Behavioural Effects of Perampanel in Children with Neurodevelopmental Disorders: A Systematic Review

In children and adolescents with epilepsy, neurodevelopmental comorbidities can impair the quality of life more than seizures. The aim of this review was to evaluate the cognitive and behavioural effects of perampanel (PER) in the paediatric population. We performed a systematic search of the literature, selecting studies published in English including children and adolescents with epilepsy treated with PER. Cognitive and behavioural outcomes were assessed through validated neuropsychological standardised scales. Eighteen studies involving 3563 paediatric patients were included. Perampanel did not impair general cognitive functions and visuospatial skills, whereas a slight improvement in verbal memory and a decline in attentional power were detected. In adolescents with refractory epilepsies, high doses and/or rapid titration of PER and an underlying psychiatric disorder were risk factors for developing or worsening psychiatric outcomes such as anger, aggressiveness, and irritability. Data on children and adolescents treated with new antiseizure medications are scant, and neuropsychiatric effects are tricky to be detected during developmental age. According to the currently available evidence, PER showed an overall favourable risk-benefit profile. Pharmacodynamics, co-administration of other antiseizure medications, and family and personal history of neuropsychiatric disorders should be considered before PER treatment.

Mining and analysis of adverse drug reactions associated with perampanel based on FAERS database

INTRODUCTION

Perampanel (PER) is a non-competitive AMPA glutamate receptor antagonist used as an anti-seizure medication. Large post-marketing databases are still lacking for safety analysis of the new generation of anti-seizure medications. Based on the FDA's adverse event reporting system (FAERS) database, this study aimed to investigate, assess, and offer evidence for the safety of PER to support clinical decision-making.

METHODS

Perampanel-related adverse reaction signals were mined using the reporting odds ratio (ROR), medicines and healthcare products regulatory agency (MHRA), and Bayesian confidence propagation neural network (BCPNN). The rate and occurrence of reported adverse responses were examined.

RESULTS

With the three methodologies used in combination, 83 signals mostly related to psychosis and different nervous system disorders were detected. Among them, suicide behavior, respiratory depression, hepatotoxicity, cognitive impairment, and other possible novel signals warranted consideration. Further examination of the age and gender differences in the detected signals revealed that elderly patients should be closely monitored for any change in consciousness and the occurrence of movement disorders; male patients should be observed for negative mental reactions like a personal attack and homicidal ideation; and female patients should be watched for the occurrence of negative reactions in memory, weight, vision, liver function, and other specific areas.

CONCLUSIONS

This study found that PER had the risk of causing suicide behavior, respiratory depression, hepatotoxicity, and cognitive impairment among other adverse effects. When used clinically, PER should be closely monitored for the occurrence of adverse effects on mental health and behavior. However, these results should be interpreted with caution.

Perampanel in Brain Tumor-Related Epilepsy: A Systematic Review

Brain tumor-related epilepsy (BTRE) is a common comorbidity in patients with brain neoplasms and it may be either the first symptom or develop after the tumor diagnosis. Increasing evidence suggests that brain tumors and BTRE share common pathophysiological mechanisms. Glutamatergic mechanisms can play a central role in promoting both primary brain tumor growth and epileptogenesis. Perampanel (PER), which acts as a selective antagonist of glutamate α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid (AMPA) receptors, may play a role both in the reduction in tumor growth and the control of epileptiform activity. This systematic review aimed to summarize the pre-clinical and clinical evidence about the antitumor properties, antiseizure effects and tolerability of PER in BTRE. Eight pre-clinical and eight clinical studies were identified. The currently available evidence suggests that PER can be an effective and generally well-tolerated therapeutic option in patients with BTRE. In vitro studies demonstrated promising antitumor activity of PER, while no role in slowing tumor progression has been demonstrated in rat models; clinical data on the potential antitumor activity of PER are scarce. Additional studies are needed to explore further the effects of PER on tumor progression and fully characterize its potentialities in patients with BTRE.

Optimal Use of Perampanel in Elderly Asian Patients with Epilepsy: Expert Opinion

Managing epilepsy in the elderly remains complicated largely due to factors related to aging. In this population, management practices are increasingly shifting towards the use of newer-generation anti-seizure medications (ASMs) as they are generally associated with better tolerability and safety profiles than older ones. Perampanel is a new ASM with broad-spectrum efficacy and a favorable safety profile. However, because of the lack of information and experience in its use, the prescription of perampanel has not been optimized in the elderly in the real-world setting in Asia. A group of epilepsy experts across the region convened at a series of virtual meetings to share their experience and discuss recommendations on perampanel use in elderly patients, including dose optimization, considerations with treatment initiation, and strategies to manage adverse events and maximize tolerability. This article summarizes key clinical and real-world evidence for perampanel in the elderly and consolidates the experts’ opinions on optimizing perampanel use in elderly Asian patients with epilepsy, providing practical guidance for clinicians to address challenges related to treatment initiation and tolerance.

Intravenous Perampanel as an Interchangeable Alternative to Oral Perampanel: A Randomized, Crossover, Phase I Pharmacokinetic and Safety Study

Intravenous (IV) drug administration enables treatment of epilepsy when oral administration is temporarily not feasible. Perampanel is a once‐daily antiseizure medication currently available as oral formulations. Study 050 (NCT03376997) was an open‐label, randomized, single‐dose, crossover study to evaluate the interchangeability of oral and IV perampanel in healthy subjects (N = 48). Bioequivalence of single 12‐mg doses of IV (30‐, 60‐, or 90‐minute infusion) and oral perampanel, ≥6 weeks apart, was assessed. Analyses indicated bioequivalence of area under the plasma concentration–time curve extrapolated to infinity for 30‐ and 60‐minute IV infusions and oral perampanel doses (geometric mean ratio [90% confidence interval], 0.93 [0.84–1.02] and 1.03 [0.97–1.09], respectively); however, IV maximum observed drug concentration (C_max) values were 1.35‐ to 1.61‐fold higher than C_max. Simulated plasma concentration–time profiles using pooled pharmacokinetic data further supported oral and IV perampanel interchangeability in two scenarios: 12‐mg per day IV dosing during a temporary 7‐day switch from oral steady‐state maintenance therapy, and treatment initiation with 2‐mg perampanel. Thirty‐four (70.8%) subjects experienced treatment‐related adverse events. The IV perampanel safety profile was similar to that of oral perampanel without new safety concerns. Perampanel IV infusions may be a suitable temporary alternative to oral perampanel for treatment maintenance and/or initiation.

Not your usual drug-drug interactions: Monoclonal antibody-based therapeutics may interact with antiseizure medications

Therapeutic monoclonal antibodies (mAbs) have emerged as the fastest growing drug class. As such, mAbs are increasingly being co-prescribed with other drugs, including antiseizure medications (ASMs). Although mAbs do not share direct targets or mechanisms of disposition with small-molecule drugs (SMDs), combining therapeutics of both types can increase the risk of adverse effects and treatment failure. The primary goal of this literature review was identifying mAb-ASM combinations requiring the attention of professionals who are treating patients with epilepsy. Systematic PubMed and Embase searches (1980-2021) were performed for terms relating to mAbs, ASMs, drug interactions, and their combinations. Additional information was obtained from documents from the US Food and Drug Administration (FDA) and the European Medicines Agency (EMA). Evidence was critically appraised - key issues calling for clinicians' consideration and important knowledge gaps were identified, and practice recommendations were developed by a group of pharmacists and epileptologists. The majority of interactions were attributed to the indirect effects of cytokine-modulating antibodies on drug metabolism. Conversely, strong inhibitors or inducers of drug-metabolizing enzymes or drug transporters could potentially interact with the cytotoxic payload of antibody-drug conjugates, and ASMs could alter mAb biodistribution. In addition, mAbs could potentiate adverse ASM effects. Unfortunately, few studies involved ASMs, requiring the formulation of class-based recommendations. Based on the current literature, most mAb-ASM interactions do not warrant special precautions. However, specific combinations should preferably be avoided, whereas others require monitoring and potentially adjustment of the ASM doses. Reduced drug efficacy or adverse effects could manifest days to weeks after mAb treatment onset or discontinuation, complicating the implication of drug interactions in potentially deleterious outcomes. Prescribers who treat patients with epilepsy should be familiar with mAb pharmacology to better anticipate potential mAb-ASM interactions and avoid toxicity, loss of seizure control, or impaired efficacy of mAb treatment.

Pharmacokinetic Drug-Drug Interactions among Antiepileptic Drugs, Including CBD, Drugs Used to Treat COVID-19 and Nutrients

Anti-epileptic drugs (AEDs) are an important group of drugs of several generations, ranging from the oldest phenobarbital (1912) to the most recent cenobamate (2019). Cannabidiol (CBD) is increasingly used to treat epilepsy. The outbreak of the SARS-CoV-2 pandemic in 2019 created new challenges in the effective treatment of epilepsy in COVID-19 patients. The purpose of this review is to present data from the last few years on drug–drug interactions among of AEDs, as well as AEDs with other drugs, nutrients and food. Literature data was collected mainly in PubMed, as well as google base. The most important pharmacokinetic parameters of the chosen 29 AEDs, mechanism of action and clinical application, as well as their biotransformation, are presented. We pay a special attention to the new potential interactions of the applied first-generation AEDs (carbamazepine, oxcarbazepine, phenytoin, phenobarbital and primidone), on decreased concentration of some medications (atazanavir and remdesivir), or their compositions (darunavir/cobicistat and lopinavir/ritonavir) used in the treatment of COVID-19 patients. CBD interactions with AEDs are clearly defined. In addition, nutrients, as well as diet, cause changes in pharmacokinetics of some AEDs. The understanding of the pharmacokinetic interactions of the AEDs seems to be important in effective management of epilepsy.

Perampanel dosage in plasma samples: development and validation of a novel HPLC method with combined UV-Fluorescence detection

Therapeutic drug monitoring (TDM) is a recognized method to improve the quality of use of antiepileptic drugs, such as perampanel (PRP). It is the first compound in the class of selective non-competitive antagonists of AMPA receptors approved in 2012 in Europe and United States for adjunctive therapy of partial seizures. Although several studies have recently underlined that a general reference range for PRP plasmatic concentration might be difficult to propose, TDM of this drug is important in specific clinical situations, as hepatic or renal impairment or co-administration with enzyme-inducing antiepileptics. Several methods have been described in literature for the determination of PRP in different biological matrices, which include the use of liquid chromatography methods coupled with ultraviolet, fluorescence, mass or tandem-mass spectrometry detection. Here we describe the development and validation of a novel method for the measurement of PRP in plasma samples, based on a HPLC-UV/FL double detection approach and using ketoprofen as internal standard. PRP concentration in a small subset of plasma samples of treated patients was evaluated using both our approach and a commercially available CE-IVD LC-MS/MS method. The results obtained were compared, and confirmed the possibility to use our method as an alternative to LC-MS/MS in clinical routine.

Effect and tolerability of perampanel in patients with drug-resistant epilepsy

OBJECTIVE

Perampanel is one of the most recently approved antiseizure medications. The aim of the present study was to assess clinical efficacy and tolerability, in combination with pharmacokinetic variability, of perampanel treatment in patients at a tertiary referral center for epilepsy.

METHODS

We performed a retrospective observational study of patients given perampanel as adjunctive treatment in the period January 2013 - February 2019 at the National Center for Epilepsy at Oslo University Hospital, Norway.

RESULTS

Clinical data were available for 175 mainly adult patients with drug-resistant epilepsy with mean treatment duration of 16.1 months. We found that 23% (40 patients) were responders (i.e., achieving more than 50% reduction in seizure frequency), four of whom became seizure free, 29% (51 patients) experienced a modest effect, whereas for 29% (50 patients) perampanel had no seizure-reducing effect. A paradoxical effect, with seizure aggravation, was reported in 9% (15 patients). The responder rate was significantly higher in those with slow vs. fast dosage titration. Logistic regression analysis showed better efficacy among those with generalized vs. those with focal epilepsy. Adverse effects were reported by 135 patients (77%), ranging from mild (34%), to moderate (41%) and severe (2%). In 55 patients (41%), these adverse effects resulted in discontinuation of treatment with perampanel. The most frequent adverse effects were psychiatric symptoms (34%), dizziness (31%), and sleepiness (26%). Of the 31 patients for whom serum concentration measurements were available, the mean daily perampanel dose was 6.3 mg (SD 3.0), with a mean serum concentration at steady state of 1.03 μmol/L (range: 0.15-3.59 μmol/L). There were pronounced differences between patients, as demonstrated by a 12-fold variability in the range of concentration/dose (C/D)-ratios (0.06 to 0.69 μmol/L/mg), where enzyme inducers contributed.

CONCLUSION

Our results demonstrate that perampanel had a modest seizure-reducing effect in this very treatment-resistant patient group. Predictors of treatment success were generalized epilepsy and slow dosage titration. In patients without a history of psychiatric problems, clinicians could consider increasing dose of perampanel beyond 6 mg daily, taking co-medication and serum concentrations into account.

Perampanel-induced, new-onset food aversion in a 29-year-old female with medically refractory frontal lobe epilepsy

BACKGROUND

Perampanel is a selective, noncompetitive amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid glutamate receptor antagonist indicated for management of partial-onset and primary generalized seizures in epilepsy patients aged ≥12 years.

PATIENT HISTORY

A 29-year-old, white female with significant history of medically refractory frontal lobe epilepsy, status post right frontal and temporal resections, was initiated on perampanel as an add-on therapy to phenytoin extended-release (330 mg/d) and clonazepam (2.5 mg/d). She previously failed several antiepileptic drugs because of inefficacy and/or intolerance. Perampanel was initiated at 2 mg/d and the dose was increased by 2 mg/d increments every 2 to 3 weeks. Following the first dose, nausea and drowsiness were reported but resolved the following day. Three days after titration to 6 mg/d, the patient developed complete food aversion and became more irritable and anxious while no seizure frequency improvement was noted. No change of sense of taste was reported. After reduction to 4 mg/d, adverse effects improved but did not completely resolve until 2 months following perampanel discontinuation.

REVIEW OF LITERATURE

A PubMed search revealed no published literature or case reports of perampanel-induced food aversion or anorexia in a presence or absence of phenytoin and clonazepam.

CONCLUSION

In this report, a temporal relationship was observed between perampanel dose-increase and the development of food aversion. Return to baseline appetite and eating habits following perampanel discontinuation strongly suggest perampanel involvement. At this time, the exact mechanism(s) behind food aversion associated with perampanel is/are unknown.

Pharmacokinetic and pharmacodynamic considerations for the clinical efficacy of perampanel in focal onset seizures

INTRODUCTION

Medical therapy is the mainstay of management of epilepsy. Despite the increasing number of available antiepileptic drugs (AEDs), approximately one-third of epileptic patients do not have adequate control of seizures. There is still a need for the development of new AEDs with enhanced effectiveness and tolerability. Areas covered: The present manuscript is based on an Internet and PubMed search (January 2005 to August 2018). It is focused on pharmacokinetic and clinical data of perampanel (PER) for the treatment of epilepsy. Expert opinion: PER has a novel mechanism of action, which opens up new options for a rational combination therapy. Phase III trials have demonstrated the efficacy and safety of PER as adjunctive therapy for the treatment of partial-onset seizures (POS) and primary generalized tonic-clonic seizures in patients aged ≥12 years. PER is also approved by FDA as monotherapy for the treatment of POS. A clinical trial is ongoing to verify the efficacy and safety of PER monotherapy in untreated patients with POS. In the future, head-to-head comparisons are needed to determine the exact position of PER relative to other AEDs. Moreover, further studies are needed to evaluate the efficacy and safety of PER in patients aged <12 years.

ABBREVIATIONS

4βOHC: 4β-hydroxycholesterol; AUC: area under the curve; CBZ: Carbamazepine; CLCr: creatinine clearance; Cmax: maximum plasma concentration; CYP: cytochrome P; EIAED: enzyme-inducing antiepileptic drug; EMA: European Medicines Agency; FDA: Food and Drug Administration; GI: gastrointestinal; OXC: oxcarbazepine; PER: perampanel; PGTC: primary generalized tonic-clonic; PHT: phenytoin; POS: partial-onset seizures; QD: once-daily; TEAE: treatment-emergent adverse event; Tmax: median time to reach peak concentration; UGT: uridine diphosphoglucose-glucuronosyltransferase; VPA: valproic acid.

Pharmacokinetic Interactions of Clinical Interest Between Direct Oral Anticoagulants and Antiepileptic Drugs

Direct oral anticoagulants (DOACs), namely apixaban, dabigatran, edoxaban, and rivaroxaban are being increasingly prescribed among the general population, as they are considered to be associated to lower bleeding risk than classical anticoagulants, and do not require coagulation monitoring. Likewise, DOACs are increasingly concomitantly prescribed in patients with epilepsy taking, therefore, antiepileptic drugs (AEDs), above all among the elderly. As a result, potential interactions may cause an increased risk of DOAC-related bleeding or a reduced antithrombotic efficacy. The objective of the present review is to describe the pharmacokinetic interactions between AEDs and DOACs of clinical relevance. We observed that there are only few clinical reports in which such interactions have been described in patients. More data are available on the pharmacokinetics of both drugs classes which allow speculating on their potential interactions. Older AEDs, acting on cytochrome P450 isoenzymes, and especially on CYP3A4, such as phenobarbital, phenytoin, and carbamazepine are more likely to significantly reduce the anticoagulant effect of DOACs (especially rivaroxaban, apixaban, and edoxaban). Newer AEDs not affecting significantly CYP or P-gp, such as lamotrigine, or pregabalin are not likely to affect DOACs efficacy. Zonisamide and lacosamide, which do not affect significantly CYP activity in vitro, might have a quite safe profile, even though their effects on P-gp are not well-known, yet. Levetiracetam exerts only a potential effect on P-gp activity, and thus it might be safe, as well. In conclusion, there are only few case reports and limited evidence on interactions between DOACs and AEDs in patients. However, the overall evidence suggests that the interaction between these drug classes might be of high clinical relevance and therefore further studies in larger patients' cohorts are warranted for the future in order to better clarify their pharmacokinetic and define the most appropriate clinical behavior.

Pharmacokinetic Considerations with the Use of Antiepileptic Drugs in Patients with HIV and Organ Transplants

PURPOSE OF REVIEW

Antiepileptic drugs are frequently administered to patients with HIV infection or in recipients of organ transplants. The potentially serious drug-drug interactions between the "classic" antiepileptic drugs, antiretrovirals, and immunosuppressants have been extensively studied. Evidence-based information on the second and third generation of antiepileptic drugs is almost non-existent. The purpose of this review is to analyze the pharmacokinetic profile of these newer agents to assess their potential for drug interactions with antiretrovirals and immunosuppressants.

RECENT FINDINGS

As a group, the newer generations of antiepileptic drugs have shown a more favorable drug interaction potential compared to the "classic" ones. A group of moderate enzyme-inducing drugs includes eslicarbazepine acetate, oxcarbazepine, rufinamide, and topiramate. These drugs are not as potent inducers as the "classic" drugs but may potentially decrease the serum concentrations of some antiretrovirals and immunosuppressants. Antiepileptic drugs with no or minimal enzyme-inducing properties include brivaracetam, gabapentin, lacosamide, lamotrigine, levetiracetam, perampanel, pregabalin, and vigabatrin. The newer generations of antiepileptic drugs have expanded the therapeutic options in patients with HIV infection or organ transplants.

Reference ranges for antiepileptic drugs revisited: a practical approach to establish national guidelines

BACKGROUND AND OBJECTIVE

Laboratories sometimes use different reference ranges for the same antiepileptic drug (AED), particularly for new and poorly investigated drugs. This may contribute to misunderstandings, concerns or inappropriate dose changes, which in turn may affect therapeutic effect, drug safety or treatment adherence. Therefore, the Norwegian Association of Clinical Pharmacology wished to update and harmonize the reference ranges for AEDs and establish national guidelines for Norway.

METHODS

A working group collected information on the reference ranges used by Norwegian laboratories for all commonly used AEDs. These reference ranges were compared to recent recommendations by the International League Against Epilepsy, current literature, applicable clinical studies, reference ranges used by leading Northern European epilepsy centers outside of Norway, and routine data derived from Norwegian laboratory databases.

RESULTS

Reference ranges varied between laboratories for four of 23 available AEDs (lamotrigine, valproate, eslicarbazepine and oxcarbazepine). For four AEDs (brivaracetam, perampanel, stiripentol and sulthiame), reference ranges had not previously been established. In total, 13 reference ranges were either harmonized, updated or newly established. No changes were applied to the remaining 10 AEDs.

CONCLUSION

Updated and harmonized reference ranges are now available for 22 of the 23 AEDs available in Norway. The exception is vigabatrin (reference range not applicable). Revision of reference ranges is an important part of pharmacovigilance of AEDs and must be a continuous process based on current literature and clinical experience.

Spotlight on perampanel in the management of seizures: design, development and an update on place in therapy

Purpose

Perampanel is a first-in-class antiepileptic medication approved for the treatment of partial (focal) seizures, and as adjunctive treatment for primarily generalized tonic–clonic seizures. The pharmacology, efficacy data, adverse-effect profile, pharmacokinetics and place in therapy are reviewed.

Summary

Perampanel is indicated for use in patients with epilepsy who are 12 years of age or older. It is the first medication designed specifically to be a non-competitive antagonist at post-synaptic α-amino-3-hydroxyl-5-methyl-4-isoxazole-propionate receptors. Efficacy in refractory seizures has been established, and ongoing efficacy demonstrated by post-marketing data. The drug is completely absorbed, and exhibits a half-life that allows for once-daily administration in doses up to 12 mg/day. Drug interactions are minimal, but increased doses may be necessary when given with strong inducers of cytochrome P450 enzymes, including when perampanel is co-administered with other antiepileptics that exhibit this property. The most common adverse effects noted in both clinical trials and post-marketing are dizziness and somnolence. Psychiatric and behavioral adverse events have been documented in both adult and pediatric patients, including those with no corresponding diagnostic history.

Conclusion

Perampanel is a novel adjunctive antiepileptic medication that is an effective option for adolescents and adults with partial seizures, and primarily generalized tonic–clonic seizures uncontrolled with other medications.

Impact of perampanel on pharmacokinetics of concomitant antiepileptics in patients with partial-onset seizures: pooled analysis of clinical trials

Aims

To evaluate the impact of perampanel and demographics on clearance of concomitant antiepileptic drugs (AEDs), in patients with refractory partial‐onset seizures.

Methods

Pooled data from three Phase III clinical studies with adjunctive perampanel were used. Blood samples for evaluation of 11 concomitant AEDs were taken during baseline (before perampanel initiation), and at weeks 10, 14, and 19 during the maintenance phase of perampanel treatment (2–12 mg/day, once daily at bedtime). Models estimating apparent clearance of each concomitant AED were fitted to the data, and the effects of perampanel and demographic variables on clearance were determined. Final models were assessed with goodness of fit plots including population predictions and individual predictions against observations.

Results

No significant impact of perampanel on clearance was found for clonazepam (n = 81), levetiracetam (n = 330), phenobarbital (n = 54), phenytoin (n = 90), topiramate (n = 226) or zonisamide (n = 93). Statistically significant, but small and not clinically relevant increases in model‐predicted clearance were detected for carbamazepine (+4.3% with 12 mg perampanel; n = 379), clobazam (+3.4% males, +7.7% females, 12 mg; n = 114), lamotrigine (+9.3%, 12 mg; n = 356), and valproic acid (+5.0%, 12 mg; n = 349). Oxcarbazepine clearance was reduced (26%; n = 200), but the clinical relevance is unclear as levels of the active metabolite (the monohydroxy derivative of oxcarbazepine) were not measured.

Conclusions

Population PK data show that perampanel (2–12 mg/day, once daily at bedtime) has no relevant impact on the clearance of the most commonly used concomitant AEDs.