Pharmacoresistant epilepsy: Definition and explanation

Therapeutic efficacy of voltage-gated sodium channel inhibitors in epilepsy

Epilepsy is a neurological disease characterized by excessive and abnormal hyper-synchrony of electrical discharges of the brain and a predisposition to generate epileptic seizures resulting in a broad spectrum of neurobiological insults, imposing psychological, cognitive, social and also economic burdens to the sufferer. Voltage-gated sodium channels (VGSCs) are essential for the generation and propagation of action potentials throughout the central nervous system. Dysfunction of these channels has been implicated in the pathogenesis of epilepsy. VGSC inhibitors have been demonstrated to act as anticonvulsants to suppress the abnormal neuronal firing underlying epileptic seizures, and are used for the management and treatment of both genetic-idiopathic and acquired epilepsies. We discuss the forms of idiopathic and acquired epilepsies caused by VGSC mutations and the therapeutic efficacy of VGSC blockers in idiopathic, acquired and pharmacoresistant forms of epilepsy in this review. We conclude that there is a need for better alternative therapies that can be used alone or in combination with VGSC inhibitors in the management of epilepsies. The current anti-seizure medications (ASMs) especially for pharmacoresistant epilepsies and some other types of epilepsy have not yielded expected therapeutic efficacy partly because they do not show subtype-selectivity in blocking sodium channels while also bringing side effects. Therefore, there is a need to develop novel drug cocktails with enhanced selectivity for specific VGSC isoforms, to achieve better treatment of pharmacoresistant epilepsies and other types of epileptic seizures.

The Effect of High-Dose Methyl Vitamin B12 Therapy on Epileptogenesis in Rats: An In Vivo Study

Introduction Epileptogenesis has been considered one of the most prevalent diseases affecting significant numbers of individuals worldwide. Since vitamin B12 has been reported to possess antiepileptic effects, this supports that vitamin B12 deficiency is correlated to seizure occurrence. Hence, this study aimed to evaluate the neuroprotective effects of vitamin B12 injection on pentylenetetrazole (PTZ)-induced rats. Methods The study was performed using 40 adult female Sprague-Dawley rats (~250 g). A 45 mg/kg PTZ was intraperitoneally injected into rat models to induce seizure effects. Different groups of rat models received methyl vitamin B12 therapy at different dosages, a low dosage of 45 µg/kg and a high dosage of 85 µg/kg, at different pre-treatment periods, one day and two weeks prior to PTZ injection. A control group, which received only PTZ injection, served as a reference. The seizure latency, seizure intensity, and differences in the quality of seizures and their characteristics, from simple twitches to complete seizures, were observed after 30 minutes of PTZ injection. Results In general, the latency to convulsion significantly increased when vitamin B12 pre-treatment was employed. The longest latency time (LT) of 520.63±73.83 seconds was observed when a high dosage of vitamin B12 at 85 µg/kg was injected one day prior to PTZ inoculation, which was significantly higher than that of the control group at 176.88±62.67 seconds (P<0.001). Moreover, the duration of convulsion significantly decreased in which the lowest duration time (DT) of 7.00±4.68 seconds was observed when a high dosage of vitamin B12 at 85 µg/kg was injected two weeks prior to PTZ inoculation, which was significantly lower than that of the control group at 257.75±41.93 seconds (P<0.001). Lastly, the percentage of the population with PTZ-induced convulsion generally decreased after vitamin B12 pre-treatment in which majority showed more of simple less aggressive twitches rather than tonic-clonic seizures. Conclusion The results showed that vitamin B12 pre-treatment alleviates the seizure occurrence among PTZ-kindled rat models. These findings then suggest that vitamin B12 is a potential strategy and treatment for epilepsy and other related epileptogenesis activities.

Anti-high mobility group box protein 1 monoclonal antibody downregulating P-glycoprotein as novel epilepsy therapeutics

Epilepsy, a neurological illness, is characterized by recurrent uncontrolled seizures. There are many treatments of options that can be used as the therapy of epilepsy. However, anti-seizure medications as the primary treatment choice for epilepsy show many possible adverse effects and even pharmacoresistance to the therapy. High Mobility Group Box 1 (HMGB1) as an initiator and amplifier of the neuroinflammation is responsible for the onset and progression of epilepsy by overexpressing P-glycoprotein on the blood brain barrier. HMGB1 proteins then activate TLR4 in neurons and astrocytes, in which proinflammatory cytokines are produced. Anti-HMGB1 mAb works by blocking the HMGB1, reducing inflammatory activity in the brain that may affect epileptogenesis. Through the process, anti-HMGB1 mAb reduces the TLR4 activity and other receptors that may involve in promote signal of epilepsy such as RAGE. Several studies have shown that anti-HMGB1 has the potential to inhibit the increase in serum HMGB1 in plasma and brain tissue. Further research is needed to identify the mechanism of the inhibiting of overexpression of P-glycoprotein through anti-HMGB1 mAb.

Probabilistic mapping of thalamic nuclei and thalamocortical functional connectivity in idiopathic generalised epilepsy

It is well established that abnormal thalamocortical systems play an important role in the generation and maintenance of primary generalised seizures. However, it is currently unknown which thalamic nuclei and how nuclear‐specific thalamocortical functional connectivity are differentially impacted in patients with medically refractory and non‐refractory idiopathic generalised epilepsy (IGE). In the present study, we performed structural and resting‐state functional magnetic resonance imaging (MRI) in patients with refractory and non‐refractory IGE, segmented the thalamus into constituent nuclear regions using a probabilistic MRI segmentation method and determined thalamocortical functional connectivity using seed‐to‐voxel connectivity analyses. We report significant volume reduction of the left and right anterior thalamic nuclei only in patients with refractory IGE. Compared to healthy controls, patients with refractory and non‐refractory IGE had significant alterations of functional connectivity between the centromedian nucleus and cortex, but only patients with refractory IGE had altered cortical connectivity with the ventral lateral nuclear group. Patients with refractory IGE had significantly increased functional connectivity between the left and right ventral lateral posterior nuclei and cortical regions compared to patients with non‐refractory IGE. Cortical effects were predominantly located in the frontal lobe. Atrophy of the anterior thalamic nuclei and resting‐state functional hyperconnectivity between ventral lateral nuclei and cerebral cortex may be imaging markers of pharmacoresistance in patients with IGE. These structural and functional abnormalities fit well with the known importance of thalamocortical systems in the generation and maintenance of primary generalised seizures, and the increasing recognition of the importance of limbic pathways in IGE.

Gephyrin and CYP2C9 Genetic Polymorphisms in Patients with Pharmacoresistant Epilepsy

Purpose

Gephyrin (GPHN) is an essential protein in the regulation of inhibitory postsynaptic density and polymorphism in the corresponding gene may have a role in the development of pharmacoresistant epilepsy (PRE). For the first time, we aimed to evaluate the association of rs928553T/C variants with PRE susceptibility. Moreover, we have analyzed the genetic polymorphism affecting CYP2C9 “rs12782374G/A” in the same population to detect the effect of SNP on the drug-metabolizing ability of patients with PRE.

Patients and Methods

This case-control study enrolled 100 patients (group A) and 100 healthy, age and sex-matched controls, unrelated to patients (group B). TaqMan™ assays using real-time PCR were run for genotyping of rs928553T/C and rs12782374G/A in all participants.

Results

GPHN T>C polymorphism revealed significant risk association with occurrence of PRE using dominant, recessive and codominant models as follows: TT vs (TC+CC): OR 0.23, 95%CI: 0.13–0.43, P<0.001. In addition, (TT+TC vs CC): OR 0.38, 95%CI: 0.18–0.77, P<0.001. Also, T vs C (OR 0.34, 95%CI: 0.22–0.51, P=<0.001). Similarly, CYP2C9 G>A polymorphism showed a significant increased risk of PRE (GG vs (GA+AA): OR 0.11, 95%CI: 0.05–0.23, P<0.001). Furthermore, (GG+GA vs AA): OR 0.18, 95%CI: 0.084–0.39, P<0.001. Also, G vs A (OR 0.24, 95%CI: 0.15–0.366, P=<0.001).

Conclusion

Mutation of both GPHN (rs928553) and CYP2C9 (rs1278237) genes may be implicated as a genetic mediators of resistance in patients with PRE.

Summarizing current refractory disease definitions in rheumatoid arthritis and polyarticular juvenile idiopathic arthritis: systematic review

OBJECTIVES

To identify how refractory disease (or relevant terminology variations) in RA and polyarticular JIA (polyJIA) is defined and establish the key components of such definitions.

METHODS

Searches were undertaken of English-language articles within six medical databases, including manual searching, from January 1998 to March 2020 (PROSPERO: CRD42019127142). Articles were included if they incorporated a definition of refractory disease, or non-response, in RA/polyJIA, with clear components to the description. Qualitative content analysis was undertaken to describe refractory disease in RA/polyJIA and classify each component within each definition.

RESULTS

Of 6251 studies screened, 646 met the inclusion criteria; 581 of these applied non-response criteria while 65 provided refractory disease definitions/descriptions. From the non-response studies, 39 different components included various disease activity measures, emphasizing persistent disease activity and symptoms, despite treatment with one or more biologic DMARD (bDMARD). From papers with clear definitions for refractory disease, 41 components were identified and categorized into three key themes: resistance to multiple drugs with different mechanisms of action, typically two or more bDMARDs; persistence of symptoms and disease activity; and other contributing factors. The most common term used was 'refractory' (80%), while only 16.9% reported explicitly how their definition was generated (e.g. clinical experience or statistical methods).

CONCLUSION

Refractory disease is defined as resistance to multiple drugs with different mechanisms of action by persistence of physical symptoms and high disease activity, including contributing factors. A clear unifying definition needs implementing, as the plethora of different definitions makes study comparisons and appropriate identification of patients difficult.

Possible interplay between the theories of pharmacoresistant epilepsy

Epilepsy is one of the oldest known neurological disorders and is characterized by recurrent seizure activity. It has a high incidence rate, affecting a broad demographic in both developed and developing countries. Comorbid conditions are frequent in patients with epilepsy and have detrimental effects on their quality of life. Current management options for epilepsy include the use of anti-epileptic drugs, surgery, or a ketogenic diet. However, more than 30% of patients diagnosed with epilepsy exhibit drug resistance to anti-epileptic drugs. Further, surgery and ketogenic diets do little to alleviate the symptoms of patients with pharmacoresistant epilepsy. Thus, there is an urgent need to understand the underlying mechanisms of pharmacoresistant epilepsy to design newer and more effective anti-epileptic drugs. Several theories of pharmacoresistant epilepsy have been suggested over the years, the most common being the gene variant hypothesis, network hypothesis, multidrug transporter hypothesis, and target hypothesis. In our review, we discuss the main theories of pharmacoresistant epilepsy and highlight a possible interconnection between their mechanisms that could lead to the development of novel therapies for pharmacoresistant epilepsy.

Development and validation of an innovative UPLC method to quantify lacosamide, oxcarbazepine, and lamotrigine in the serum of children with epilepsy in China

This study has developed and validated a novel UPLC method to quantify lacosamide (LCM), oxcarbazepine (OXC), and lamotrigine (LTG) in children with epilepsy in Xinjiang, China. Phenytoin sodium was used as the internal standard. The mobile phase contained ammonium dihydrogen phosphate solution (10 mmol/L, pH = 4.0) and methanol (55:45, v/v). The flow rate, injection volume, column temperature, and detection wavelength were 0.2 mL/min, 2 μL, 30°C, and 240 nm, respectively. The method was linear within 0.5-40, 2.5-80, and 2.5-40 μg/mL for LCM, 10-hydroxycarbazepine (MHD), and LTG, respectively (r²  ≥ 0.998). The intra- and inter-day precision as measured by the relative standard deviation values was between 1.36 and 4.50, 0.54 and 1.91, and 0.58 and 1.56%. Recovery ranged from 96.58 to 106.22%. All serum samples could be maintained for up to 3 h at ambient temperature, 24 h at 4°C, 30 days at -30°C, and after successive freeze-thaw cycles (24 h per cycle) in the absence of significant degradation.

A Potent Lignan from Prunes Alleviates Inflammation and Oxidative Stress in Lithium/Pilocarpine-Induced Epileptic Seizures in Rats

Prunus domestica L. is an edible plant that is included in the family Rosaceae and proven to possess potent anti-inflammatory and anxiolytic activity. Pinoresinol-4-O-β-d-glucopyranoside (PGu) was isolated from Prunus domestica methanol extract and its structure was determined using 1-D and 2-D NMR (one- and two-dimensional nuclear magnetic resonance). PGu was evaluated for its anticonvulsant activity using lithium/pilocarpine-induced epileptic seizures in rats. PGu displayed a notable antioxidant and anti-inflammatory activity in vitro. It ameliorates the seizures triggered by pilocarpine in a dose-dependent manner, manifested by retarding seizure onset, reducing the number of rats developing seizures, and enhancing the survival of animals after seizure exposure. PGu reduced MDA (malondialdehyde) level by 24.2% in addition to increasing catalase activity by 44.4% at 50 mg/kg b.w compared to pilocarpine-treated animals. This was confirmed by histopathological examination in which pretreatment with PGu (50 mg/kg b.w.) attenuated neurodegeneration and seizures with no histopathological alteration in neurons of the cerebral cortex. In the immunohistochemical examination, it significantly declined the elevated Cyclooxygenase-2 (COX-2) by 40% and decreased Inducible nitric oxide synthase (iNOS) expression by 18% as expressed by the optical density. PGu revealed a pronounced fitting within the active site of 5-LOX (lipoxygenase-5) with a free binding energy (∆G) equals to −65.05 kcal/mol. PGu could perfectly serve as a potent lead drug for the relief of epileptic seizures, which appeals to many patients owing to its natural origin.

Anticonvulsive and behavior modulating effects of sophoretin and rutoside

INTRODUCTION

Seizures are the hallmarks of most types of epilepsies. Behavioral and cognitive impairments coincide with interictal periods even though it is not clear whether these impairments spring out of the seizure itself or accompanying sociopsychological burden of the disease.

MATERIALS AND METHODS

In this study, we investigated behavioral and cognitive consequences of a single GABA receptor-related seizure in mice, and examined the potential anticonvulsive and behavior-modulating properties of sophoretin (quercetin) and rutoside (rutin).

RESULTS

The study demonstrated that sophoretin and rutoside, common flavonoids of the human diet, delay the seizure onset and reduce the seizure stage. Moreover, they exerted an antidepressant-like effect, which was independent of the seizure. Neither treatments nor seizure altered recognition and spatial memory performances of the mice.

CONCLUSIONS

Behavioral or cognitive disturbances that are evident in epileptic patients did not appear following a single seizure. In addition, we suggest that both sophoretin and rutoside successfully alleviate the seizure severity without interfering in the behavioral stability and cognitive performance. Hence, these flavonoids may be of use as adjuncts to the current treatment options.

Comparison of oxcarbazepine efficacy and MHD concentrations relative to age and BMI: Associations among ABCB1, ABCC2, UGT2B7, and SCN2A polymorphisms

Genetic polymorphisms are related to the concentration and efficacy of oxcarbazepine (OXC). 10-Hydroxycarbazepine (MHD) is the major pharmacologically active metabolite of OXC, and it exerts an antiepileptic effect. This study aimed to explore the connection between the MHD concentration and genes such as ATP-binding cassette B1 (ABCB1), ATP-binding cassette C2 (ABCC2), UDP-glucuronosyltransferase-2B7 and sodium voltage-gated channel alpha subunit 2 (SCN2A), which participate in the antiepileptic function of OXC.Total 218 Chinese epileptic patients, were stratified into different groups according to their age, body mass index (BMI) and OXC efficacy. The genotypes of 7 single nucleotide polymorphisms in all subjects were determined by polymerase chain reaction-improved multiple ligase detection reaction assay. The MHD plasma concentration was detected by high-performance liquid chromatography and then standardized through dosage and body weight.In general, the ABCC2 rs2273697 mutant (P = .026) required a significantly higher standardized MHD concentration. For age groups, carriers of the ABCC2 rs2273697 mutant showed a significantly higher standardized MHD concentration than noncarriers in the juvenile group (P = .033). In terms of BMI, a significantly higher standardized MHD concentration was found in the ABCB1 rs2032582 mutant of the normal weight group (P = .026). The SCN2A rs17183814 mutant required a significantly higher OXC maintenance (P = .014) in the low-weight group, while lower OXC maintenance dose (P = .044) and higher standardized MHD concentration (P = .007) in the overweight group.The ABCC2 rs2273697 polymorphism was significantly associated with MHD plasma concentration in the whole patient cohort and in patients stratified by different ages, this finding provides potential theoretical guidance for the rational and safe clinical use of OXC.

Development of the 1,2,4-triazole-based anticonvulsant drug candidates acting on the voltage-gated sodium channels. Insights from in-vivo, in-vitro, and in-silico studies

The treatment of epilepsy remains difficult mostly since almost 30% of patients suffer from pharmacoresistant forms of the disease. Therefore, there is an urgent need to search for new antiepileptic drug candidates. Previously, it has been shown that 4-alkyl-5-substituted-1,2,4-triazole-3-thione derivativatives possessed strong anticonvulsant activity in a maximal electroshock-induced seizure model of epilepsy. In this work, we examined the effect of the chemical structure of the 1,2,4-triazole-3-thione-based molecules on the anticonvulsant activity and the binding to voltage-gated sodium channels (VGSCs) and GABA_A receptors. Docking simulations allowed us to determine the mode of interactions between the investigated compounds and binding cavity of the human VGSC. Selected compounds were also investigated in a panel of ADME-Tox assays, including parallel artificial membrane permeability assay (PAMPA), single cell gel electrophoresis (SCGE) and cytotoxicity evaluation in HepG2 cells. The obtained results indicated that unbranched alkyl chains, from butyl to hexyl, attached to 1,2,4-triazole core are essential both for good anticonvulsant activity and strong interactions with VGSCs. The combined in-vivo, in-vitro and in-silico studies emphasize 4-alkyl-5-substituted-1,2,4-triazole-3-thiones as promising agents in the development of new anticonvulsants.

Synthesis and anticonvulsant activity of phenoxyacetyl derivatives of amines, including aminoalkanols and amino acids

A series of 17 new phenoxyacetamides has been prepared via multistep chemical synthesis as a continuation of the research carried out by our group on di- and tri-substituted phenoxyalkyl and phenoxyacetyl derivatives of amines. The obtained compounds vary in an amide component, for example aminoalkanol or (un)modified amino acid moieties were introduced. The structures of selected products were confirmed by means of crystallographic methods. All 17 compounds were the subject of preliminary screening for potential anticonvulsant activity (MES, 6 Hz and/or scMET tests) and neurotoxicity (rotarod) in mice after intraperitoneal administration, while several active compounds were subsequently examined in additional models (e.g. MES and rotarod - rats, p.o. or i.p., hippocampal kindling - rats, i.p.). Finally, safety studies (cytotoxicity and cell proliferation assays on astrocytes, metabolic stability assessment, mutagenicity evaluation) were performed for several active compounds, including the most promising one (R-(-)-2-(2,6-dimethylphenoxy)-N-(1-hydroxypropan-2-yl)acetamide, MES ED₅₀ = 12.00 mg per kg b.w., rats, p.o.).

Development and full validation of an innovative HPLC-diode array detection technique to simultaneously quantify lacosamide, levetiracetam and zonisamide in human plasma

AIM

To implement pharmacokinetic drug monitoring and individualize the posology of new antiepileptic drugs, the first HPLC-diode array detection method was developed and validated to simultaneously quantify lacosamide, levetiracetam and zonisamide in human plasma.

MATERIALS & METHODS

Preceded by a reproducible liquid-liquid extraction, chromatographic separation was achieved by using a C18 column of 5 cm length and a mobile phase of water/acetonitrile. Full validation was performed according to international guidelines.

RESULTS

The method was linear within 0.5-30, 2.5-40.0 and 0.5-50.0 μg ml-1 for lacosamide, levetiracetam and zonisamide, respectively (r2 ≥ 0.998), accurate (-12.411-8.303%), precise (≤8.875%).

CONCLUSION

This innovative HPLC-diode array detection method was successfully employed in clinical practice and is expected to empower epileptic patients with a personalized pharmacotherapy service. [Formula: see text].

Polymorphic Variants of SCN1A and EPHX1 Influence Plasma Carbamazepine Concentration, Metabolism and Pharmacoresistance in a Population of Kosovar Albanian Epileptic Patients

Aim

The present study aimed to evaluate the effects of gene variants in key genes influencing pharmacokinetic and pharmacodynamic of carbamazepine (CBZ) on the response in patients with epilepsy.

Materials & Methods

Five SNPs in two candidate genes influencing CBZ transport and metabolism, namely ABCB1 or EPHX1, and CBZ response SCN1A (sodium channel) were genotyped in 145 epileptic patients treated with CBZ as monotherapy and 100 age and sex matched healthy controls. Plasma concentrations of CBZ, carbamazepine-10,11-epoxide (CBZE) and carbamazepine-10,11-trans dihydrodiol (CBZD) were determined by HPLC-UV-DAD and adjusted for CBZ dosage/kg of body weight.

Results

The presence of the SCN1A IVS5-91G>A variant allele is associated with increased epilepsy susceptibility. Furthermore, carriers of the SCN1A IVS5-91G>A variant or of EPHX1 c.337T>C variant presented significantly lower levels of plasma CBZ compared to carriers of the common alleles (0.71±0.28 vs 1.11±0.69 μg/mL per mg/Kg for SCN1A IVS5-91 AA vs GG and 0.76±0.16 vs 0.94±0.49 μg/mL per mg/Kg for EPHX1 c.337 CC vs TT; P<0.05 for both). Carriers of the EPHX1 c.416A>G showed a reduced microsomal epoxide hydrolase activity as reflected by a significantly decreased ratio of CBZD to CBZ (0.13±0.08 to 0.26±0.17, p<0.05) also of CBZD to CBZE (1.74±1.06 to 3.08±2.90; P<0.05) and CDR_CBZD (0.13±0.08 vs 0.24±0.19 μg/mL per mg/Kg; P<0.05). ABCB1 3455C>T SNP and SCN1A 3148A>G variants were not associated with significant changes in CBZ pharmacokinetic. Patients resistant to CBZ treatment showed increased dosage of CBZ (657±285 vs 489±231 mg/day; P<0.001) but also increased plasma levels of CBZ (9.84±4.37 vs 7.41±3.43 μg/mL; P<0.001) compared to patients responsive to CBZ treatment. CBZ resistance was not related to any of the SNPs investigated.

Conclusions

The SCN1A IVS5-91G>A SNP is associated with susceptibility to epilepsy. SNPs in EPHX1 gene are influencing CBZ metabolism and disposition. CBZ plasma levels are not an indicator of resistance to the therapy.

Drug utilisation study in patients receiving antiepileptic drugs in Colombia

INTRODUCTION

This study examines the indications according to which antiepileptic drugs are prescribed and used in a population of patients enrolled in the Colombian national health system (SGSSS).

METHODS

Retrospective cross-sectional study. From the pool of individuals in 34 Colombian cities who used antiepileptic drugs between 18 July, 2013 and 31 August, 2014 during a period of no less than 12 months, we obtained a random sample stratified by city. Socio-demographic, pharmacological and comorbidity variables were analysed. Continuous and categorical variables were compared, and logistic regression models were used.

RESULTS

Our patient total was 373 patients, with 197 women (52.1%) and a mean age of 41.9 ± 21.7 years; 65.4% of the patients were treated with monotherapy. The most frequently used drugs were valproic acid (53.1%) and carbamazepine (33.2%). Epilepsy was the most frequent indication (n=178; 47.7%); however, 52.3% of the patients were prescribed antiepileptics for different indications, especially neuropathic pain (26.8%), affective disorders (14.2%) and migraine prophylaxis (12.3%). A total of 81 patients with epilepsy (46.6%) displayed good seizure control while another 25 (14.4%) had drug-resistant epilepsy. In the multivariate analysis, medication adherence was associated with a lower risk of treatment failure in patients with epilepsy (OR: 0.27; 95%CI, 0.11-0.67).

CONCLUSIONS

In Colombia, antiepileptic drugs are being used for indications other than those originally intended. Monotherapy is the most commonly used treatment approach, together with the use of classic antiepileptic drugs.

Direct nose-to-brain delivery of lamotrigine following intranasal administration to mice

Pharmacoresistance is considered one of the major causes underlying the failure of the anticonvulsant therapy, demanding the development of alternative and more effective therapeutic approaches. Due to the particular anatomical features of the nasal cavity, intranasal administration has been explored as a means of preferential drug delivery to the brain. The purpose of the present study was to assess the pharmacokinetics of lamotrigine administered by the intranasal route to mice, and to investigate whether a direct transport of the drug from nose to brain could be involved. The high bioavailability achieved for intranasally administered lamotrigine (116.5%) underscored the fact that a substantial fraction of the drug has been absorbed to the systemic circulation. Nonetheless, the heterogeneous biodistribution of lamotrigine in different brain regions, with higher concentration levels attained in the olfactory bulb comparatively to the frontal cortex and the remaining portion of the brain, strongly suggest that lamotrigine was directly transferred to the brain via the olfactory neuronal pathway, circumventing the blood-brain barrier. Therefore, it seems that intranasal route can be assumed as a suitable and valuable drug delivery strategy for the chronic treatment of epilepsy, also providing a promising alternative approach for a prospective management of pharmacoresistance.