Topiramate: a review of its use in the treatment of epilepsy

UGT1A polymorphism rs4148324 associated with topiramate plasma concentration to dose ratio in children with epilepsy

PURPOSE

The objective of this study is to evaluate the association between genetic polymorphisms and the concentration to dose ratio of topiramate in children with epilepsy.

METHODS

A cohort of 163 pediatric patients with epilepsy receiving topiramate therapy were enrolled. The ultra-performance liquid chromatography-tandem mass spectrometry method was employed to measure the trough plasma concentration of topiramate at steady-state. These concentrations were normalized by dividing them by the ratio of total daily dose to body weight, yielding the concentration to dose ratio (CDR) of topiramate. MassArray system identified 30 single nucleotide polymorphisms associated with the pharmacokinetics and pharmacodynamics of topiramate. The CDR values were logarithmic transformed (lnCDR) for normal distribution. The association between the identified genetic polymorphisms and lnCDR was assessed using the PLINK software, employing linear regression analysis with adjustments by epilepsy types, estimated glomerular filtration rate, alanine aminotransferase, valproic acid, phenobarbital, and oxcarbazepine.

RESULTS

Variant rs4148324 (UGT1A1/3/4/5/6/7/8/9/10, BETA = 0.182, P = 0.010) was significantly associated with lnCDR of topiramate. Patients carrying the G allele exhibited higher normalized topiramate plasma concentrations. No other significant associations were found.

CONCLUSIONS

In pediatric patients receiving topiramate therapy, rs4148324 was associated with normalized topiramate plasma concentration. Further studies are warranted to validate and confirm the findings.

Topiramate dosage optimization for effective antiseizure management via population pharmacokinetic modeling

OBJECTIVE

Despite the suggested topiramate serum level of 5-20 mg/L, numerous institutions have observed substantial drug response at lower levels. We aim to investigate the correlation between topiramate serum levels, drug responsiveness, and adverse events to establish a more accurate and tailored therapeutic range.

METHODS

We retrospectively analyzed clinical data collected between January 2017 and January 2022 at Seoul National University Hospital. Drug responses to topiramate were categorized as "insufficient" or "sufficient" by reduction in seizure frequency ≥ 50%. A population pharmacokinetic model estimated serum levels from spot measurements. ROC curve analysis determined the optimal cutoff values.

RESULTS

A total of 389 epilepsy patients were reviewed having a mean dose of 178.4 ± 117.9 mg/day and the serum level, 3.9 ± 2.8 mg/L. Only 5.6% samples exhibited insufficient response, with a mean serum level of 3.6 ± 2.5 mg/L while 94.4% demonstrated sufficient response, with a mean 4.0 ± 2.8 mg/L, having no statistical significance. Among the 69 reported adverse events, logistic regression analysis identified a significant association between ataxia and serum concentration (p = 0.04), with an optimal cutoff value of 6.5 mg/L.

INTERPRETATION

This study proposed an optimal therapeutic concentration for topiramate based on patients' responsiveness to the drug and the incidence of adverse effects. We recommended serum levels below 6.5 mg/L to mitigate the risk of ataxia-related side effects while dose elevation was found unnecessary for suboptimal responders, as the drug's effectiveness plateaus at minimal doses.

Population pharmacokinetics of topiramate in Chinese children with epilepsy

OBJECTIVE

Topiramate, a broad-spectrum antiepileptic drug, exhibits substantial inter-individual variability in both its pharmacokinetics and therapeutic response. The aim of this study was to investigate the influence of patient characteristics and genetic variants on topiramate clearance using population pharmacokinetic (PPK) models in a cohort of Chinese pediatric patients with epilepsy.

METHOD

The PPK model was constructed using a nonlinear mixed-effects modeling approach, utilizing a dataset comprising 236 plasma concentrations of topiramate obtained from 181 pediatric patients with epilepsy. A one-compartment model combined with a proportional residual model was employed to characterize the pharmacokinetics of topiramate. Covariate analysis was performed using forward addition and backward elimination to assess the influence of covariates on the model parameters. The model was thoroughly evaluated through goodness-of-fit analysis, bootstrap, visual predictive checks, and normalized prediction distribution errors. Monte Carlo simulations were utilized to devise topiramate dosing strategies.

RESULT

In the final PPK models of topiramate, body weight, co-administration with oxcarbazepine, and a combined genotype of GKIR1-UGT (GRIK1 rs2832407, UGT2B7 rs7439366, and UGT1A1 rs4148324) were identified as significant covariates affecting the clearance (CL). The clearance was estimated using the formulas CL (L/h) = 0.44 × (BW⁄11.7)0.82 × eOXC for the model without genetic variants and CL (L/h) = 0.49 × (BW⁄11.7)0.81 × eOXC × eGRIK1-UGT for the model incorporating genetic variants. The volume of distribution (Vd) was estimated using the formulas Vd (L) = 6.6 × (BW⁄11.7). The precision of all estimated parameters was acceptable. Furthermore, the model demonstrated good predictability, exhibiting stability and effectiveness in describing the pharmacokinetics of topiramate.

CONCLUSION

The clearance of topiramate in pediatric patients with epilepsy may be subject to the influence of factors such as body weight, co-administration with oxcarbazepine, and genetic polymorphism. In this study, PPK models were developed to better understand and account for these factors, thereby improving the precision and individualization of topiramate therapy in children with epilepsy.

Current and emerging pharmacotherapy for the treatment of Lennox-Gastaut syndrome

INTRODUCTION

Lennox-Gastaut syndrome (LGS) is a severe childhood-onset epileptic encephalopathy, characterized by multiple seizure types, generalized slow spike-and-wave complexes in the EEG, and cognitive impairment. Seizures in LGS are typically resistant to treatment with antiseizure medications (ASMs). Tonic/atonic ('drop') seizures are of particular concern, due to their liability to cause physical injury.

AREAS COVERED

We summarize evidence for current and emerging ASMs for the treatment of seizures in LGS. The review focuses on findings from randomized, double-blind, placebo-controlled trials (RDBCTs). For ASMs for which no double-blind trials were identified, lower quality evidence was considered. Novel pharmacological agents currently undergoing investigation for the treatment of LGS are also briefly discussed.

EXPERT OPINION

Evidence from RDBCTs supports the use of cannabidiol, clobazam, felbamate, fenfluramine, lamotrigine, rufinamide, and topiramate as adjunct treatments for drop seizures. Percentage decreases in drop seizure frequency ranged from 68.3% with high-dose clobazam to 14.8% with topiramate. Valproate continues to be considered the first-line treatment, despite the absence of RDBCTs specifically in LGS. Most individuals with LGS will require treatment with multiple ASMs. Treatment decisions should be individualized and take into account adverse effects, comorbidities, general quality of life, and drug interactions, as well as individual efficacy.

Role of Non-Covalent Interactions in Carbonic Anhydrase I-Topiramate Complex Based on QM/MM Approach

Carbonic anhydrase (CA) I with a Topiramate (TPM) complex was investigated on the basis of a Quantum Mechanics/Molecular Mechanics (QM/MM) approach. The QM part was treated using Density Functional Theory (DFT) while the MM was simulated using Amberff14SB and GAFF force fields. In addition, the TIP3P model was applied to reproduce the polar environment influence on the studied complex. Next, three snapshots (after 5 ps, 10 ps, and 15 ps of the simulation time) were taken from the obtained trajectory to provide an insight into the non-covalent interactions present between the ligand and binding pocket of the protein. Our special attention was devoted to the binding site rearrangement, which is known in the literature concerning the complex. This part of the computations was performed using ωB97X functional with Grimme D3 dispersion corrections as well as a Becke-Johnson damping function (D3-BJ). Two basis sets were applied: def2-SVP (for larger models) and def2-TZVPD (for smaller models), respectively. In order to detect and describe non-covalent interactions between amino acids of the binding pocket and the ligand, Independent Gradient Model based on Hirshfeld partitioning (IGMH), Interaction Region Indicator (IRI), Quantum Theory of Atoms in Molecules (QTAIM) and Natural Bond Orbitals (NBO) methods were employed. Finally, Symmetry-Adapted Perturbation Theory (SAPT) was applied for energy decomposition between the ligand and protein. It was found that during the simulation time, the ligand position in the binding site was preserved. Nonetheless, amino acids interacting with TPM were exchanging during the simulation, thus showing the binding site reorganization. The energy partitioning revealed that dispersion and electrostatics are decisive factors that are responsible for the complex stability.

The potential of intravenous topiramate for the treatment of status epilepticus

There is considerable clinical evidence that topiramate (TPM) has a high potential in the treatment of refractory and super-refractory status epilepticus (RSE, SRSE). Because TPM is only approved for oral administration, it is applied as suspension via a nasogastric tube for SE treatment. However, this route of administration is impractical in an emergency setting and leads to variable absorption with unpredictable plasma levels and time to peak concentration. Thus, the development of an intravenous (i.v.) solution for TPM is highly desirable. Here we present data on two parenteral formulations of TPM that are currently being developed. One of these solutions is using sulfobutylether-β-cyclodextrin (SBE-β-CD; Captisol®) as an excipient. A 1% solution of TPM in 10% Captisol® has been reported to be well tolerated in safety studies in healthy volunteers and patients with epilepsy or migraine, but efficacy data are not available. The other solution uses the FDA- and EMA-approved excipient amino sugar meglumine. Meglumine is much more effective to dissolve TPM in water than Captisol®. A 1% solution of TPM can be achieved with 0.5-1% of meglumine. While the use of Captisol®-containing solutions is restricted in children and patients with renal impairment, such restrictions do not apply to meglumine. Recently, first-in-human data were reported for a meglumine-based solution of TPM, indicating safety and efficacy when used as a replacement for oral administration in a woman with epilepsy. Based on the multiple mechanisms of action of TPM that directly target the molecular neuronal alterations that are thought to underlie the loss of efficacy of benzodiazepines and other anti-seizure medications during prolonged SE and its rapid brain penetration after i.v. administration, we suggest that parenteral (i.v.) TPM is ideally suited for the treatment of RSE and SRSE. This paper was presented at the 8th London-Innsbruck Colloquium on Status Epilepticus and Acute Seizures held in September 2022.

Cognitive reawakening and improved quality of life achieved after discontinuing 16 years of anti-seizure treatment with topiramate

A 42-year-old female patient with epilepsy and a co-morbid migraine suffered from the severe cognitive side effects of topiramate (TPM) for more than 16 years with detrimental consequences for her daily functioning, career, and social interaction. Even a prodromal stage of dementia was suggested, giving rise to fears of developing a neurodegenerative disease. Recently, cognitive monitoring of attention and executive function before and after withdrawal of TPM revealed a significant recovery from the severe negative cognitive side effects of the long-standing and inefficacious antiseizure medication (ASM). Whereas the side effects were reversible after cessation, their consequences for the patient`s biography were permanent. A considerable increase in quality of life, however, was observed without TPM and family members were impressed by the improvements. This case illustrates the potentially severe consequences of negative cognitive side effects which affect daily functioning, career and social life, thus underscoring the importance of being knowledgeable of the potential cognitive risks when prescribing an ASM. Because cognitive side effects may not depend solely on ASM choice and drug load, but also on individual idiosyncratic intolerances, and patients might stay on their treatment for many years, cognitive monitoring is highly recommended.

Sodium Valproate Combined With Topiramate vs. Sodium Valproate Alone for Refractory Epilepsy: A Systematic Review and Meta-Analysis

Background: Among antiepileptic drugs (AEDs), sodium valproate alone or in the combination of topiramate (TPM) for treating refractory epilepsy was controversial. This meta-analysis aimed to systematically evaluate the clinical effects of these two regimens in this population. Methods: Relevant studies up to August 2021 were identified through systematic searches of CNKI, Wanfang, PubMed, and Embase databases. We assessed the effectiveness and the frequency of absence seizures, atonic seizures, and tonic-clonic seizures. The included literature's risk of bias was evaluated using the Cochrane Collaboration's Risk of Bias tool. Sensitivity analysis was conducted to confirm the results' stability. STATA 15.0 was utilized for all pooled analyses in the included studies. Results: Totally 10 articles were determined for our meta-analysis, involving 976 patients with epilepsy in total (combined group, n = 488; monotherapy group, n = 488). The results of this meta-analysis indicated that the total effective rate of sodium valproate combined with TPM was higher than that of sodium valproate alone (random-effect model: OR = 3.52; 95% CI 1.47 to 8.47; p < 0.001; I ² = 73.8%). The frequency of absence seizures in the combined group was lower (fixed-effect model: WMD = -6.02; 95% CI -6.50 to -5.54; I ² = 0.0%) than that in the monotherapy group, with a statistical difference (p < 0.05). The combined group had lower frequency of atonic seizures (WMD = -4.56, 95% CI -6.02 to -3.10; I ² = 82.6%) and lower frequency of tonic-clonic seizures (WMD = -3.32; 95% CI -4.75 to -1.89; I ² = 96.4%). In addition, the distinct difference of adverse events was non-existent between two groups. Conclusions: Sodium valproate combined with TPM was more effective than sodium valproate alone for epilepsy therapy. This meta-analysis provides feasibility data for a larger-scale study on AED therapy of refractory epilepsy and may contribute to better therapy strategies for epilepsy clinically.

Pharmacogenetics of Addiction Therapy

Drug addiction is a serious relapsing disease that has high costs to society and to the individual addicts. Treatment of these addictions is still in its nascency, with only a few examples of successful therapies. Therapeutic response depends upon genetic, biological, social, and environmental components. A role for genetic makeup in the response to treatment has been shown for several addiction pharmacotherapies with response to treatment based on individual genetic makeup. In this chapter, we will discuss the role of genetics in pharmacotherapies, specifically for cocaine, alcohol, and opioid dependences. The continued elucidation of the role of genetics should aid in the development of new treatments and increase the efficacy of existing treatments.

Evaluation of a Rapid Topiramate Titration Scheme for the Early Detection of Cognitive Side Effects

BACKGROUND

Topiramate (TPM) is effective for treating epilepsy, but executive dysfunction is a common side effect that could significantly affect everyday life. Additionally, previous studies have suggested that patients might be unaware of these changes.

OBJECTIVE

To evaluate a rapid TPM titration scheme for the early detection of adverse cognitive side effects.

METHODS

In this retrospective study, we assessed changes in objective cognitive performance (EpiTrack^®) after rapidly titrating TPM (50 mg per day during an inpatient stay) in 49 epilepsy patients and compared those results with an outpatient control group that underwent the recommended standard titration (n = 23 with 25-50 mg per week).

RESULTS

Using Bayesian statistics, analyses revealed decisive evidence of a negative effect on cognitive performance when TPM was introduced (BF 31480000000) independent of the titration speed (BF 0.739). When using a fast titration rate, deficits in executive function increased from a baseline of 53.1 to 73.5% at follow-up, and 55.1% experienced a statistically significant intraindividual decline. When using the standard titration scheme, impairments increased from 52.2 to 65.2%, with an intraindividual deterioration found in 52.2% of the patients.

CONCLUSION

Physicians might be able to detect adverse cognitive side effects sooner in epilepsy patients if TPM is administered using a faster titration rate while applying repeated cognitive assessments within days. This approach might help prevent any unnoticed intolerance and eventual negative consequences for the patient. Therefore, we recommend monitoring early on for adverse changes instead of withholding a potentially effective treatment option because of anticipated side effects.

Acute Angle-Closure Crisis Secondary to Topiramate-Induced Ciliochoroidal Effusion With Underlying Plateau Iris Configuration

Objective:

The development of ciliochoroidal effusions and secondary acute angle-closure crisis (AACC) is an uncommon side effect of topiramate, a common antiepileptic now FDA-approved for migraine prophylaxis. The mechanisms that underlie the development of ciliochoroidal effusions after topiramate use remain unclear.

Materials and Methods:

Ultrasound biomicroscopy (UBM) was also performed in all participants after stopping topiramate.

Results:

Six patient cases are presented with medication-induced AACC following the initiation or escalation of topiramate. Ciliochoroidal effusions were confirmed by gray-scale sonography in all patients at presentation. The images revealed either plateau iris configuration or atypical plateau iris configuration. Plateau iris configuration is defined by presence of an anteriorly rotated ciliary body processes and an absent posterior sulcus. Atypical plateau iris configuration refers to when the iris inserts directly into the ciliary body face. This case series, of medication-induced angle-closure crisis, suggests that plateau iris configuration is a shared anatomical feature in the development of topiramate-induced ciliochoroidal effusions.

Usefulness of extended-release topiramate in patients with epilepsy: A two-year retention study

WHAT IS KNOWN AND OBJECTIVE

Extended-release topiramate (TPM-XR) was recently approved for the treatment of epilepsy, but there is only limited real-world information on the clinical usefulness of TPM-XR in epilepsy patients. We investigated the usefulness of TPM-XR in clinical practice by analysing the retention of TPM-XR in adult epilepsy patients.

METHODS

We performed a single-centre retrospective study covering two years. Epilepsy patients taking TPM-XR were included in the study and classified into one of three groups: the monotherapy group, in which patients took only TPM-XR; the adjunctive therapy group, in which patients took TPM-XR concomitant with other AEDs; and the switching AED regimen group, in which patient's AED was switched from immediate-release TPM (TPM-IR) to TPM-XR. We evaluated the retention rates of TPM-XR and analysed the differences in retention rate among the three patient groups.

RESULTS AND DISCUSSION

We included 164 epilepsy patients who received TPM-XR for the treatment of epilepsy. The overall retention rate of TPM-XR was generally favourable: 79.1% after one year and 77.7% after two years. The switching AED regimen group had a better retention rate than the other two groups (p = 0.04), with a one-year retention rate of 90.6% and a two-year retention rate of 88.1%.

WHAT IS NEW AND CONCLUSION

The favourable retention rate of TPM-XR shows that TPM-XR can be an effective treatment option for epilepsy patients, as either a monotherapy or as an adjunctive therapy. Additionally, switching AED regimen to TPM-XR from TPM-IR can be considered in selected epilepsy patients with poor adherence to TPM-IR.

A Comprehensive Review of Tic Disorders in Children

Tics are characterized by sudden, rapid, recurrent, nonrhythmic movement or vocalization, and are the most common movement disorders in children. Their onset is usually in childhood and tics often will diminish within one year. However, some of the tics can persist and cause various problems such as social embarrassment, physical discomfort, or emotional impairments, which could interfere with daily activities and school performance. Furthermore, tic disorders are frequently associated with comorbid neuropsychiatric symptoms, which can become more problematic than tic symptoms. Unfortunately, misunderstanding and misconceptions of tic disorders still exist among the general population. Understanding tic disorders and their comorbidities is important to deliver appropriate care to patients with tics. Several studies have been conducted to elucidate the clinical course, epidemiology, and pathophysiology of tics, but they are still not well understood. This article aims to provide an overview about tics and tic disorders, and recent findings on tic disorders including history, definition, diagnosis, epidemiology, etiology, diagnostic approach, comorbidities, treatment and management, and differential diagnosis.

Molecular Correlates of Topiramate and GRIK1 rs2832407 Genotype in Pluripotent Stem Cell-Derived Neural Cultures

BACKGROUND

There is growing evidence that the anticonvulsant topiramate is efficacious in reducing alcohol consumption. Further, an intronic single nucleotide polymorphism (rs2832407, C A) in the GRIK1 gene, which encodes the GluK1 subunit of the excitatory kainate receptor, predicted topiramate's effectiveness in reducing heavy drinking in a clinical trial. The molecular correlates of GRIK1 genotype that may relate to topiramate's ability to reduce drinking remain unknown.

METHODS

We differentiated induced pluripotent stem cells (iPSCs) characterized by GRIK1 rs2832407 genotype from 8 A/A and 8 C/C donors into forebrain-lineage neural cultures. Our differentiation protocol yielded mixed neural cultures enriched for glutamatergic neurons. Basal mRNA expression of the GRIK1 locus was examined via quantitative polymerase chain reaction (qPCR). The effects of acute topiramate exposure on excitatory spontaneous synaptic activity were examined via whole-cell patch-clamp electrophysiology. Results were compared and contrasted between iPSC donor genotypes.

RESULTS

Although characterization of the GRIK1 locus revealed no effect of rs2832407 genotype on GRIK1 isoform mRNA expression, a significant difference was observed on GRIK1 antisense-2 expression, which was greater in C/C neural cultures. Differential effects of acute exposure to 5 μM topiramate were observed on spontaneous synaptic activity in A/A versus C/C neurons, with a smaller reduction in excitatory event frequency observed in C/C donor neurons.

CONCLUSIONS

This work highlights the use of iPSC technologies to study pharmacogenetic treatment effects in psychiatric disorders and furthers our understanding of the molecular effects of topiramate exposure in human neural cells.

Topiramate Blood Levels During Polytherapy for Epilepsy in Children

BACKGROUND

The therapeutic range of topiramate (TPM) blood level is not set because the efficacy and safety are not considered to be related to the level. However, the therapeutic target without side effects is necessary, so the optimal range of TPM blood level was analyzed in this study.

STUDY QUESTION

This study was conducted to evaluate the efficacy of TPM over 2 years and the utility of measuring blood levels of TPM during the follow-up of epileptic patients.

STUDY DESIGN

Thirty patients (18 males, 12 females; age range, 6 months-15 years) were treated with TPM for epilepsy. The initial dosage of TPM was 1-3 mg·kg·d. If the effect proved insufficient after 2 weeks, the dosage was increased to 4-9 mg·kg·d.

MEASURES AND OUTCOMES

Blood levels of TPM were measured by liquid chromatography-tandem mass spectrometry at 1, 6, 12, and 24 months after levels reached steady state. The efficacy of TPM was evaluated by the reduction in epileptic seizure rate (RR) at the time of blood sampling. Statistical analysis was performed using the Mann-Whitney U test.

RESULTS

A positive correlation was seen between blood levels and maintenance dosages, but no correlation was observed between blood levels and RR. Any significant difference was not identified in TPM levels between the effective group (RR ≥50%) and the ineffective group (RR <50%; P = 0.159). In the subgroup of patients who did not use valproic acid, a significant difference in TPM levels was apparent between the effective and ineffective groups (P = 0.029). The optimal range of TPM was advocated 3.5-5.0 μg/mL. The optimal range was set, so that ranges did not overlap between the effective and ineffective groups. No patients experienced any side effects.

CONCLUSIONS

Measuring blood levels of TPM based on the classification of concomitant drugs and adjusting the dosage to reach the optimal range were recommended.

Differential effects of antiepileptic drugs on human bone cells

Antiepileptic drugs (AED) have been associated to in vivo deleterious consequences in bone tissue. The present work aimed to characterize the cellular and molecular effects of five different AED on human osteoclastogenesis and osteblastogenesis. It was observed that the different drugs had the ability to differentially modulate both processes, in a way dependent on the identity and dose of the AED. Shortly, valproic acid stimulated either osteoclastogenesis and osteoblastogenesis, whereas carbamazepine, gabapentin, and lamotrigine revealed an opposite behavior; topiramate elicited a decrease of osteoclast development and an increase in osteoblast differentiation. This is the first report describing the direct effects of different AED on human primary bone cells, which is a very important issue, because these drugs are usually consumed in long-term therapeutics, with acknowledged in vivo effects in bone tissue.

Pharmacotherapy for Seizures in Neonates with Hypoxic Ischemic Encephalopathy

Seizures are common in neonates with moderate and severe hypoxic ischemic encephalopathy (HIE) and are associated with worse outcomes, independent of HIE severity. In contrast to adults and older children, no new drugs have been licensed for treatment of neonatal seizures over the last 50 years, because of a lack of controlled clinical trials. Hence, many antiseizure medications licensed in older children and adults are used off-label for neonatal seizure, which is associated with potential risks of adverse effects during a period when the brain is particularly vulnerable. Phenobarbital is worldwide the first-line drug and is considered standard of care, although there is a limited evidence base for its efficacy. Second-line agents include phenytoin, benzodiazepines, levetiracetam, and lidocaine. These drugs are discussed in more detail along with two emerging drugs (bumetanide and topiramate). More safety, pharmacokinetic, and efficacy data are needed from well-designed clinical trials to develop safe and effective antiseizure regimes for the treatment of neonatal seizures in HIE.

Population Pharmacokinetics of Topiramate in Japanese Pediatric and Adult Patients With Epilepsy Using Routinely Monitored Data

BACKGROUND

Topiramate is a second-generation antiepileptic drug used as monotherapy and adjunctive therapy in adults and children with partial seizures. A population pharmacokinetic (PPK) analysis was performed to improve the topiramate dosage adjustment for individualized treatment.

METHODS

Patients whose steady-state serum concentration of topiramate was routinely monitored at Kyoto University Hospital from April 2012 to March 2013 were included in the model-building data. A nonlinear mixed effects modeling program was used to evaluate the influence of covariates on topiramate pharmacokinetics. The obtained PPK model was evaluated by internal model validations, including goodness-of-fit plots and prediction-corrected visual predictive checks, and was externally confirmed using the validation data from January 2015 to December 2015.

RESULTS

A total of 177 steady-state serum concentrations from 93 patients were used for the model-building analysis. The patients' age ranged from 2 to 68 years, and body weight ranged from 8.6 to 105 kg. The median serum concentration of topiramate was 1.7 mcg/mL, and half of the patients received carbamazepine coadministration. Based on a one-compartment model with first order absorption and elimination, the apparent volume of distribution was 105 L/70 kg, and the apparent clearance was allometrically related to the body weight as 2.25 L·h·70 kg without carbamazepine or phenytoin. Combination treatment with carbamazepine or phenytoin increased the apparent clearance to 3.51 L·h·70 kg. Goodness-of-fit plots, prediction-corrected visual predictive check, and external validation using the validation data from 43 patients confirmed an appropriateness of the final model. Simulations based on the final model showed that dosage adjustments allometrically scaling to body weight can equalize the serum concentrations in children of various ages and adults.

CONCLUSIONS

The PPK model, using the power scaling of body weight, effectively elucidated the topiramate serum concentration profile ranging from pediatric to adult patients. Dosage adjustments based on body weight and concomitant antiepileptic drug help obtain the dosage of topiramate necessary to reach an effective concentration in each individual.

Bilateral acute angle closure glaucoma and myopic shift by topiramate-induced ciliochoroidal effusion: case report and literature review

PURPOSE

To report two cases of ciliochoroidal effusion after the usage of topiramate.

CASES

Two middle-aged women experienced sudden onset of acute glaucoma and acquired myopia after taking topiramate. Ultrasound biomicroscopy demonstrated bilateral ciliochoroidal effusion and angle closure. The A-scan ultrasonography revealed shallow anterior chamber and thick lens. After the treatment and drug withdrawal, intraocular pressure, refractive status and angle anatomy returned to normal and there was resolution of ciliochoroidal effusion. During the clinical course, the anterior chamber depth (ACD) increased from 2.02 to 3.30 mm (1.28 mm of changes) OD and from 1.94 to 3.36 mm (1.42 mm of changes) OS. The lens thickness (LT) became thinner from 4.53 to 4.31 mm (0.22 mm of changes) OD and from 4.59 to 4.30 mm (0.29 mm of changes) OS in the first case. In the second case, the ACD increased from 2.33 to 3.07 mm (0.74 mm of changes) OD and from 2.30 to 3.05 mm (0.75 mm of changes) OS. The LT became thinner from 4.42 to 4.27 mm (0.15 mm of changes) OD and from 4.38 to 4.26 mm (0.12 mm of changes) OS. The forward displacement of the lens-iris diaphragm contributed more to the shallowness of the anterior chamber than the thickening of the lens itself (only accounting for 20%).

CONCLUSION

Topiramate-induced bilateral acute angle closure glaucoma and myopic shift was due to ciliochoroidal effusion which resulted in thicker lens and shallow anterior chamber. The later was mainly due to anterior displacement of the lens-iris diaphragm.

The Impact of Anti-Epileptic Drugs on Growth and Bone Metabolism

Epilepsy is a common neurological disorder worldwide and anti-epileptic drugs (AEDs) are always the first choice for treatment. However, more than 50% of patients with epilepsy who take AEDs have reported bone abnormalities. Cytochrome P450 (CYP450) isoenzymes are induced by AEDs, especially the classical AEDs, such as benzodiazepines (BZDs), carbamazepine (CBZ), phenytoin (PT), phenobarbital (PB), and valproic acid (VPA). The induction of CYP450 isoenzymes may cause vitamin D deficiency, hypocalcemia, increased fracture risks, and altered bone turnover, leading to impaired bone mineral density (BMD). Newer AEDs, such as levetiracetam (LEV), oxcarbazepine (OXC), lamotrigine (LTG), topiramate (TPM), gabapentin (GP), and vigabatrin (VB) have broader spectra, and are safer and better tolerated than the classical AEDs. The effects of AEDs on bone health are controversial. This review focuses on the impact of AEDs on growth and bone metabolism and emphasizes the need for caution and timely withdrawal of these medications to avoid serious disabilities.

Topiramate Extended Release: A Review in Epilepsy

Once-daily oral topiramate extended release (USL255; hereafter referred to as topiramate XR) [QUDEXY(®) XR] is approved in the USA for use as initial monotherapy and adjunctive therapy in patients aged ≥2 years with partial-onset seizures (POS) or primary generalized tonic-clonic seizures and as adjunctive therapy in patients aged ≥2 years with seizures associated with Lennox-Gastaut syndrome. Compared with twice-daily topiramate immediate release at the same total daily dose, topiramate XR provided bioequivalent exposure, an extended absorption rate (permitting convenient once-daily dosing) and more constant therapeutic plasma concentrations (potentially minimizing topiramate-associated adverse events). Switching between the two formulations did not affect the maintenance of topiramate concentrations. Moreover, the contents of a topiramate XR capsule may be sprinkled on to soft food for patients who have difficulty swallowing. In a multinational phase III study in adults with refractory POS, adjunctive topiramate XR was associated with significantly greater improvements from baseline in weekly median seizure frequency and the proportion of patients achieving a ≥50 % reduction in seizure frequency compared with placebo. These benefits were sustained during a 55-week open-label extension study. Adjunctive topiramate XR was generally well tolerated in these studies, with the majority of treatment-emergent adverse events being mild or moderate in intensity. In conclusion, current evidence suggests once-daily topiramate XR extends the treatment options currently available for patients aged ≥2 years with epilepsy, with its dosing regimen potentially delivering tolerability and adherence advantages over AEDs that require more frequent administration.

Evaluation of Ocular Side Effects in the Patients on Topiramate Therapy for Control of Migrainous Headache

INTRODUCTION

Topiramate, a sulfa-derivative monosaccharide, is an antiepileptic drug which is administered in the control of migraine. It is reported to cause various ocular side effects such as visual field defect and myopic shift. To investigate the alterations in refractive error, properties of the cornea and changes in the anterior chamber in patients that receive Topiramate for migraine control.

MATERIALS AND METHODS

This is a hospital-based, non-interventional, observational study that is conducted at Imam Hossein Hospital, affiliated to Shahid Beheshti University of Medical Sciences, Department of Neurology, in collaboration with the department of Ophthalmology. Thirty three consecutive patients with the diagnosis of migraine that were candidate for Topiramate therapy were recruited. Patients with history of ocular trauma or surgery, keratoconus, glaucoma, congenital ocular malformations and any history of unexplained visual loss were excluded. After thorough ophthalmic examination, all the patients underwent central corneal thickness (CCT) measurement, and Pentacam imaging (Scheimpflug camera) at the baseline. Various parameters were extracted and used for analysis. Anterior chamber volume (ACV), anterior chamber depth (ACD), and anterior chamber angle (ACA) measurement was performed. These measurements were repeated on day 30(th) and 90(th) after the initiation of Topiramate therapy. According to the normality tests, parameters with normal distribution were analysed using the repeated measures test and the remaining parameters (with non-normal distribution) were analysed using the non-parametric k-sample test. A p-value< 0.05 was considered statistically significant, according to Bonferroni post hoc correction.

RESULTS

There were 66 eyes of 33 patients under the diagnosis of migrainous headache, that Topiramate was initiated for headache control, included in the study. The mean value of refractive error had a statistically significant myopic change, from -0.23 diopters (D) at the baseline to -0.61 D at the 90(th) day of follow-up period (p-value < 0.001). Mean CCT was 531.43 μm at the baseline and increased to 534.72 μm at the 30(th) day, and 537.51 μm at the 90(th) day after the administration of Topiramate (p-value=0.001). Mean value of other parameters, ACV, ACD, and ACA, did not reveal statistically significant change.

CONCLUSION

Myopic shift and gradually increasing CCT in the patients after Topiramate administration should be considered before any refractive surgery. We found no gradual change in the anterior chamber and angle parameters in our patients in the 90 days of follow up. More studies with a longer duration of follow-up are needed to elucidate dose-dependent ocular manifestations.

International Veterinary Epilepsy Task Force consensus proposal: medical treatment of canine epilepsy in Europe

In Europe, the number of antiepileptic drugs (AEDs) licensed for dogs has grown considerably over the last years. Nevertheless, the same questions remain, which include, 1) when to start treatment, 2) which drug is best used initially, 3) which adjunctive AED can be advised if treatment with the initial drug is unsatisfactory, and 4) when treatment changes should be considered. In this consensus proposal, an overview is given on the aim of AED treatment, when to start long-term treatment in canine epilepsy and which veterinary AEDs are currently in use for dogs. The consensus proposal for drug treatment protocols, 1) is based on current published evidence-based literature, 2) considers the current legal framework of the cascade regulation for the prescription of veterinary drugs in Europe, and 3) reflects the authors' experience. With this paper it is aimed to provide a consensus for the management of canine idiopathic epilepsy. Furthermore, for the management of structural epilepsy AEDs are inevitable in addition to treating the underlying cause, if possible.

Sulfonamides and their isosters as carbonic anhydrase inhibitors

Molecules containing the sulfonamide group (R-SO2NH2) as well as its structurally related isosters, sulfamido (R-NH-SO2NH2) and sulfamato (R-O-SO2NH2), constitute the most important class of inhibitors acting on the metalloenzyme carbonic anhydrase (EC 4.2.1.1). Despite their presence in the literature, in general the reports lack of a clear and organic overview linking the main structural features of the clinically used inhibitors with the therapeutic aspects. The current review is intended to highlight the structural basis of the interactions of sulfonamide-like groups within the active site of the carbonic anhydrases and will summarize the clinical use of the most interesting molecules for the treatment of relevant pathologies, such as glaucoma, obesity, cancer and CNS-affecting diseases.

Topiramate-associated urinary incontinence: a case verified by rechallenge

Topiramate is an anticonvulsant that has been widely used in psychiatric conditions. The most common treatment-related adverse effects of topiramate were diarrhea, nausea, loss of appetite, fatigue, paresthesia, cognitive impairment, and metabolic acidosis. The following is a case report intended to draw attention to a rarely reported adverse effect of topiramate. A male patient treated with topiramate developed urinary incontinence that was considered drug associated because of the temporal relationship between its appearance and the commencement of topiramate, its resolution upon topiramate discontinuation, and its recurrence with topiramate rechallenge. Urinary incontinence, although not life threatening, can be a distressing problem with a profound impact on quality of life. This case reminds that physicians prescribing topiramate should be aware of this possible adverse effect and communicate it to patients and their caregivers.

Pharmacokinetic interactions between topiramate and pioglitazone and metformin

OBJECTIVE

To investigate potential drug-drug interactions between topiramate and metformin and pioglitazone at steady state.

METHODS

Two open-label studies were performed in healthy adult men and women. In Study 1, eligible participants were given metformin alone for 3 days (500 mg twice daily [BID]) followed by concomitant metformin and topiramate (titrated to 100mg BID) from days 4 to 10. In Study 2, eligible participants were randomly assigned to treatment with pioglitazone 30 mg once daily (QD) alone for 8 days followed by concomitant pioglitazone and topiramate (titrated to 96 mg BID) from days 9 to 22 (Group 1) or to topiramate (titrated to 96 mg BID) alone for 11 days followed by concomitant pioglitazone 30 mg QD and topiramate 96 mg BID from days 12 to 22 (Group 2). An analysis of variance was used to evaluate differences in pharmacokinetics with and without concomitant treatment; 90% confidence intervals (CI) for the ratio of the geometric least squares mean (LSM) estimates for maximum plasma concentration (Cmax), area under concentration-time curve for dosing interval (AUC12 or AUC24), and oral clearance (CL/F) with and without concomitant treatment were used to assess a drug interaction.

RESULTS

A comparison to historical data suggested a modest increase in topiramate oral clearance when given concomitantly with metformin. Coadministration with topiramate reduced metformin oral clearance at steady state, resulting in a modest increase in systemic metformin exposure. Geometric LSM ratios and 90% CI for metformin CL/F and AUC12 were 80% (75%, 85%) and 125% (117%, 134%), respectively. Pioglitazone had no effect on topiramate pharmacokinetics at steady state. Concomitant topiramate resulted in decreased systemic exposure to pioglitazone and its active metabolites, with geometric LSM ratios and 90% CI for AUC24 of 85.0% (75.7%, 95.6%) for pioglitazone, 40.5% (36.8%, 44.6%) for M-III, and 83.8% (76.1%, 91.2%) for M-IV, respectively. This effect appeared more pronounced in women than in men. Coadministration of topiramate with metformin or pioglitazone was generally well tolerated by healthy participants in these studies.

CONCLUSIONS

A modest increase in metformin exposure and decrease in topiramate exposure was observed at steady state following coadministration of metformin 500 mg BID and topiramate 100mg BID. The clinical significance of the observed interaction is unclear but is not likely to require a dose adjustment of either agent. Pioglitazone 30 mg QD did not affect the pharmacokinetics of topiramate at steady state, while coadministration of topiramate 96 mg BID with pioglitazone decreased steady-state systemic exposure to pioglitazone, M-III, and M-IV. While the clinical consequence of this interaction is unknown, careful attention should be given to the routine monitoring for adequate glycemic control of patients receiving this concomitant therapy. Concomitant administration of topiramate with metformin or pioglitazone was generally well tolerated and no new safety concerns were observed.

Sleep-related eating disorder: a descriptive study in Chilean patients

OBJECTIVES

We aimed to describe a group of adults diagnosed with sleep-related eating disorder (SRED) at the Sleep Medicine Center of the Pontificia Universidad Catolica de Chile.

METHODS

We performed a descriptive study of 34 consecutive patients who met the criteria of the International Classification of Sleep Disorders for SRED evaluated during a 3-year period who did not have an eating disorder according to the criteria of the Diagnostic and Statistical Manual of Mental Disorders, fourth edition. All patients had a structured clinical interview performed by a sleep specialist and completed the Beck Depression Inventory (BDI). Polysomnography (PSG) was performed when clinically indicated for ruling out other sleep-related disorders (18 patients; 52.9%). Patients' demographic and clinical data, comorbidities, and treatment response also were analyzed.

RESULTS

Most patients were women (n=23; 67.6%). The average age at the time of diagnosis was 39±13.8 (17-67 years) and the latency since symptom onset was 8.3±8.8 years. Most patients had several episodes per night (average, 2.6±1.6; 1-8) and all except one patient had partial or total amnesia of these events (n=33; 97%). Comorbidities were frequent and included insomnia (n=20; 58.8%), restless legs syndrome (RLS) (n=16; 47%), sleep-disordered breathing (SDB) (n=9; 26%), psychiatric disorders (n=13; 38.2%), and overweight or obesity (n=14; 41.1%). Most patients were hypnotic users (n=21; 61.7%) and reported weight-centered anxiety (n=23; 67.6%). Twenty patients (58.8%) were treated with topiramate, 17 of whom had adequate symptomatic responses.

CONCLUSION

Our SRED patients showed female preponderance, amnesia during the episodes, association with other sleep disorders, use of hypnotics, weight-centered anxiety, and positive response to topiramate. The presence of anxiety focused on weight in most patients may be an important element in the emergence of this behavior during sleep.

Population pharmacokinetics of topiramate in adult patients with epilepsy using nonlinear mixed effects modelling

The objective of the study was to develop population pharmacokinetic model of topiramate (TPM) using nonlinear mixed effects modelling approach. Data were collected from 78 adult epileptic patients on mono- or co-therapy of TPM and other antiepileptic drugs, such as carbamazepine (CBZ), valproic acid, lamotrigine, levetiracetam, phenobarbital and pregabalin. Steady-state TPM concentrations were determined in blood samples by high performance liquid chromatography with fluorescence detection. A one-compartment model with first order absorption and elimination was used to fit the concentration-time TPM data. Volume of distribution of TPM was estimated at 0.575 l/kg. The influence of demographic, biochemical parameters and therapy characteristics of the patients on oral clearance (CL/F) was evaluated. Daily carbamazepine dose (DCBZ) and renal function estimated by Modification of diet in renal disease (MDRD) formula significantly (p<0.001) influenced CL/F and were included in the final model: CL/F · (l/h)=1.53(l/h) · [1+0.476 · DCBZ(mg/day)/1000(mg/day)] · EXP[0.00476 · [MDRD(ml/ min)-95.72(ml/min)]]. Increase of CL/F with DCBZ and MDRD was best described by linear and exponential models. Mean TPM CL/F during CBZ co-therapy was 2.46 l/h, which is higher for 60.8% than in patients not co-treated with CBZ. Evaluation by bootstrapping showed that the final model was stable. The predictive performance was evaluated by adequate plots and indicated satisfactory precision. This model allows individualisation of TPM dosing in routine patient care, especially useful for patients on different CBZ dosing regimen.

Topiramate as an adjunctive treatment in patients with refractory status epilepticus: an observational cohort study

BACKGROUND

Refractory status epilepticus (RSE) is the most severe manifestation of status epilepticus (SE), often requiring intensive care and therapeutic coma. It is associated with prolonged intensive care unit (ICU) and hospital stays, as well as increased morbidity and mortality. Treatment involves both intravenous anaesthetics and antiepileptic drugs (AEDs) that can be administrated intravenously, by nasogastric tube or by percutaneous endoscopic gastrostomy. Experience with some of the newer AEDs for the treatment of RSE is restricted and higher-class evidence regarding tolerability and efficacy is lacking. Topiramate is a potent broad-spectrum AED with several modes of action, including blockade of the ionotropic glutamatergic AMPA receptor, which is likely to be an important mechanism for the treatment of SE. While there is no commercially available intravenous formulation, topiramate can be administered enterally, which may make it suitable for the treatment of RSE.

OBJECTIVE

The objective of this study was to evaluate the tolerability, safety profile and efficacy of adjunctive and enterally administered topiramate in patients with RSE.

METHODS

A medical chart review was performed of all consecutive patients treated for RSE between August 2004 and December 2011 at the ICU of the University Hospital Basel (Basel, Switzerland).

RESULTS

113 (43%) of all consecutive 268 patients with SE developed RSE. Of those, 35 (31%) were treated with topiramate. Median age was 60.5 years. Topiramate was used as an add-on treatment after 1-6 (median 4) prior administered AEDs had failed. It was introduced after a median of 2 (range 2-23) days for a duration of 1-24 (median 3) days. The response rate after topiramate administration as the third AED was 86% (6/7 patients), and remained stable at 67% after administration as the fourth, fifth, sixth or seventh AED when the groups of successfully and probably successfully treated patients were pooled. Overall, RSE was terminated in 71% of patients within 72 hours after first administration of topiramate, in 9% of patients, within 24 hours (none in the 800 mg/day group; 9% in the 400-799 mg/day group; and 11% in the <400 mg/day group). Mortality was 31% and was not strictly dependent on failure to terminate RSE, but also on the underlying aetiology of RSE. There were no serious or fatal adverse events directly attributable to topiramate. Adverse effects included slight hyperchloremic acidosis and hyperammonemia (all associated with co-medication with valproic acid).

CONCLUSION

Treatment with enterally administered topiramate was feasible, well tolerated and had a good safety profile in patients with RSE in this observational, single-centre, cohort study. Refractory SE was terminated in the majority of patients within 3 days after initiation of topiramate. Prospective studies are warranted to further evaluate topiramate for the treatment of RSE.

Antiepileptic drugs and pregnancy outcomes

The treatment of epilepsy in women of reproductive age remains a clinical challenge. While most women with epilepsy (WWE) require anticonvulsant drugs for adequate control of their seizures, the teratogenicity associated with some antiepileptic drugs (AEDs) is a risk that needs to be carefully addressed. Antiepileptic medications are also used to treat an ever broadening range of medical conditions such as bipolar disorder, migraine prophylaxis, cancer, and neuropathic pain. Despite the fact that the majority of pregnancies of WWE who are receiving pharmacological treatment are normal, studies have demonstrated that the risk of having a pregnancy complicated by a major congenital malformation is doubled when comparing the risk of untreated pregnancies. Furthermore, when AEDs are used in polytherapy regimens, the risk is tripled, especially when valproic acid (VPA) is included. However, it should be noted that the risks are specific for each anticonvulsant drug. Some investigations have suggested that the risk of teratogenicity is increased in a dose-dependent manner. More recent studies have reported that in utero exposure to AEDs can have detrimental effects on the cognitive functions and language skills in later stages of life. In fact, the FDA just issued a safety announcement on the impact of VPA on cognition (Safety Announcement 6-30-2011). The purpose of this document is to review the most commonly used compounds in the treatment of WWE, and to provide information on the latest experimental and human epidemiological studies of the effects of AEDs in the exposed embryos.

Impaired verbal fluency under topiramate--evidence for synergistic negative effects of epilepsy, topiramate, and polytherapy

BACKGROUND AND PURPOSE

Treatment with topiramate (TPM) is known to negatively affect executive functions and verbal fluency in particular. However, judgments of cognitive side effects under TPM rarely consider clinical conditions and possible effects of epilepsy, treatment, and drug load.

METHODS

This retrospective cross-sectional study in large cohorts of patients with epilepsy evaluated the impact of TPM mono- and polytherapy on verbal fluency. To isolate TPM-induced effects from those of epilepsy and antiepileptic medication in general, verbal fluency under TPM (N = 421) was compared to the performance of a matched sample of patients with an antiepileptic medication other than TPM (N = 351), untreated patients (N = 108), and healthy controls (N = 100).

RESULTS

Impaired verbal fluency performance was seen in 77% of the patients treated with TPM. Compared to healthy controls, verbal fluency in untreated patients was reduced by 22%, under monotherapy without TPM by 31% and under TPM monotherapy by 45%. With and without TPM, verbal fluency performance linearly decreased with each additional drug in polytherapy. On each level, performance under TPM was 21-28% worse than in the respective condition without TPM. Unimpaired performance under TPM was primarily associated with lower dose, higher education, and a later onset of epilepsy.

CONCLUSIONS

The majority of patients under TPM shows reduced verbal fluency. However, when taking the cumulative negative effects of epilepsy, and the concomitant drug regimen into account, TPM is associated with a 21-28% poorer performance as compared with other drugs. Additionally, the data indicate an impact of dose and reserve capacity on the occurrence of impairments.

Topiramate and the vision: a systematic review

BACKGROUND AND PURPOSE

Topiramate (TPM) is a sulfa-derivative monosaccharide that is used mainly for treating epilepsy and preventing migraine. Within the gamut of side effects attributable to this drug, ophthalmologic manifestations are of crucial importance. In this study, for the first time, the aim was to provide a systematic literature review regarding this issue.

METHODS

For the time period 1996-2011, a PubMed search was made for the studies concerning the adverse/beneficial effects of TPM on vision. Overall, 404 citations out of a total of 2756 TPM-related studies were examined for relevance.

RESULTS

A total of 74 relevant studies were reviewed, 65 of which comprise small observational studies describing the ophthalmic side effects of TPM in 84 patients. Of these patients, 66 were affected by ciliochoroidal effusion syndrome as the cardinal ocular side effect of TPM (17 cases of myopic shift and 49 cases of angle closure glaucoma). A comprehensive statistical analysis is provided on these 66 subjects. Other rare side effects of TPM on the vision were also reviewed, including massive choroidal effusion, ocular inflammatory reactions, visual field defects, probable effects on retina, cornea, and sclera, and neuroophthalmologic complications. In addition, a framework is provided to classify these results.

DISCUSSION

Due to the expanding spectrum of indications for the administration of TPM, neurologists and psychiatrists should be aware of its diverse ocular side effects. In conclusion, ocular complications following this drug should be taken seriously and be subjected to ophthalmic counseling.

Antiepileptic drug interactions - principles and clinical implications

Antiepileptic drugs (AEDs) are widely used as long-term adjunctive therapy or as monotherapy in epilepsy and other indications and consist of a group of drugs that are highly susceptible to drug interactions. The purpose of the present review is to focus upon clinically relevant interactions where AEDs are involved and especially on pharmacokinetic interactions. The older AEDs are susceptible to cause induction (carbamazepine, phenobarbital, phenytoin, primidone) or inhibition (valproic acid), resulting in a decrease or increase, respectively, in the serum concentration of other AEDs, as well as other drug classes (anticoagulants, oral contraceptives, antidepressants, antipsychotics, antimicrobal drugs, antineoplastic drugs, and immunosupressants). Conversely, the serum concentrations of AEDs may be increased by enzyme inhibitors among antidepressants and antipsychotics, antimicrobal drugs (as macrolides or isoniazid) and decreased by other mechanisms as induction, reduced absorption or excretion (as oral contraceptives, cimetidine, probenicid and antacides). Pharmacokinetic interactions involving newer AEDs include the enzyme inhibitors felbamate, rufinamide, and stiripentol and the inducers oxcarbazepine and topiramate. Lamotrigine is affected by these drugs, older AEDs and other drug classes as oral contraceptives. Individual AED interactions may be divided into three levels depending on the clinical consequences of alterations in serum concentrations. This approach may point to interactions of specific importance, although it should be implemented with caution, as it is not meant to oversimplify fact matters. Level 1 involves serious clinical consequences, and the combination should be avoided. Level 2 usually implies cautiousness and possible dosage adjustments, as the combination may not be possible to avoid. Level 3 refers to interactions where dosage adjustments are usually not necessary. Updated knowledge regarding drug interactions is important to predict the potential for harmful or lacking effects involving AEDs.