Topiramate for the treatment of epilepsy and other nervous system disorders

Obtaining long-term recovery: advances in optimizing treatment outcomes in patients with binge-eating disorder

INTRODUCTION

Binge-eating disorder (BED) is a complex and disabling eating disorder (ED) associated with considerable burden and impairments in quality of life and physical/mental health. It has been recognized as a formal ED category since 2013, however BED is still underdetected and undertreated.

AREAS COVERED

This review summarizes the advances in the understanding of the pathophysiology of BED as well as the evidence on the efficacy of the existing treatments. The authors searched Scopus, PubMed, ClinicalTrials.Gov, and ANZCTR with terms including 'assessment' OR 'treatment' OR 'diagnosis' OR 'mechanisms' AND 'binge eating' OR 'binge-eating disorder' for manuscripts published between January 2013 and April 2023.

EXPERT OPINION

Most of the trials on treatments of BED have been in people of high weight with weight loss as an outcome. Nevertheless, less is known about the treatment of this condition in people with body mass index (BMI) within the normal range where weight stabilization may be a more appropriate goal. Moreover, there is a need for an enhanced appreciation of the role of combination treatment to improve overall outcomes. Also, there are important opportunities for future research in understanding the mechanisms of action and effectiveness of BED treatments.

Decreased cerebrospinal fluid kynurenic acid in epileptic spasms: A biomarker of response to corticosteroids

Background

Epileptic (previously infantile) spasms is the most common epileptic encephalopathy occurring during infancy and is frequently associated with abnormal neurodevelopmental outcomes. Epileptic spasms have a diverse range of known (genetic, structural) and unknown aetiologies. High dose corticosteroid treatment for 4 weeks often induces remission of spasms, although the mechanism of action of corticosteroid is unclear. Animal models of epileptic spasms have shown decreased brain kynurenic acid, which is increased after treatment with the ketogenic diet. We quantified kynurenine pathway metabolites in the cerebrospinal fluid (CSF) of infants with epileptic spasms and explored clinical correlations.

Methods

A panel of nine metabolites in the kynurenine pathway (tryptophan, kynurenine, kynurenic acid, 3-hydroxykynurenine, xanthurenic acid, anthranilic acid, 3-hydroxyanthranilic acid, quinolinic acid, and picolinic acid) were measured using liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS). CSF collected from paediatric patients less than 3 years of age with epileptic spasms (n=34, 19 males, mean age 0.85, median 0.6, range 0.3–3 yrs) were compared with other epilepsy syndromes (n=26, 9 males, mean age 1.44, median 1.45, range 0.3–3 yrs), other non-inflammatory neurological diseases (OND) (n=29, 18 males, mean age 1.47, median 1.6, range 0.1–2.9 yrs) and inflammatory neurological controls (n=12, 4 males, mean age 1.80, median 1.80, range 0.8–2.5 yrs).

Findings

There was a statistically significant decrease of CSF kynurenic acid in patients with epileptic spasms compared to OND (p<0.0001). In addition, the kynurenic acid/kynurenine (KYNA/KYN) ratio was lower in the epileptic spasms subgroup compared to OND (p<0.0001). Epileptic spasms patients who were steroid responders or partial steroid responders had lower KYNA/KYN ratio compared to patients who were refractory to steroids (p<0.005, p<0.05 respectively).

Interpretation

This study demonstrates decreased CSF kynurenic acid and KYNA/KYN in epileptic spasms, which may also represent a biomarker for steroid responsiveness. Given the anti-inflammatory and neuroprotective properties of kynurenic acid, further therapeutics able to increase kynurenic acid should be explored.

Funding

Financial support for the study was granted by Dale NHMRC Investigator grant APP1193648, Petre Foundation, Cerebral Palsy Alliance and Department of Biochemistry at the Children's Hospital at Westmead. Prof Guillemin is funded by NHMRC Investigator grant APP1176660 and Macquarie University.

Investigational drugs for the treatment of binge eating disorder (BED): an update

Introduction: Binge eating disorder (BED) is the most common eating disorder and is frequently associated with psychiatric and medical comorbidities and functional impairment. Although psychological treatments have been the cornerstones of BED treatment, pharmacologic interventions also play an important part of the multimodal management of this condition.Areas covered: This review examines investigational, approved and other pharmacological agents for the treatment of BED. We searched PubMed and clinicaltrials.gov to identify pharmacological interventions for the management of this condition.Expert opinion: BED pharmacological studies have incorporated new drug targets based on our enhanced understanding of the pathophysiology of BED. Neurobiological dysregulation in the reward center and impulse control circuitry and related disturbances in dopamine neurotransmission are among the neurobiological explanations that have been suggested for BED. These mechanisms serve as a pharmacodynamic foundation for the development of new compounds such as lisdexamfetamine (LDX) and dasotraline. Despite these advances, pharmacological trials in BED have numerous challenges that must be overcome. For most compounds studied, larger and more definitive trials is a high priority.

Insights into the binding mode of sulphamates and sulphamides to hCA II: crystallographic studies and binding free energy calculations

Sulphamate and sulphamide derivatives have been largely investigated as carbonic anhydrase inhibitors (CAIs) by means of different experimental techniques. However, the structural determinants responsible for their different binding mode to the enzyme active site were not clearly defined so far. In this paper, we report the X-ray crystal structure of hCA II in complex with a sulphamate inhibitor incorporating a nitroimidazole moiety. The comparison with the structure of hCA II in complex with its sulphamide analogue revealed that the two inhibitors adopt a completely different binding mode within the hCA II active site. Starting from these results, we performed a theoretical study on sulphamate and sulphamide derivatives, demonstrating that electrostatic interactions with residues within the enzyme active site play a key role in determining their binding conformation. These findings open new perspectives in the design of effective CAIs using the sulphamate and sulphamide zinc binding groups as lead compounds.

Topiramate: Effects on cognition in patients with epilepsy, migraine headache and obesity

This paper reviews the clinical implications of topiramate (TPM)-induced cognitive deficits in patients with epilepsy, migraine headache, obesity, and in normal populations, followed by reviews of the literature describing the reversal of such deficits upon medication discontinuation. It also discusses animal investigations of TPM's role of neuroprotection in brain injury. TPM's most intolerable adverse effects (AEs) are on verbal fluency and reaction time, resulting in high discontinuation rates in patients taking it for epilepsy and migraine headache. However, because TPM is so effective in the treatment of epilepsy and migraine headache, its use is expected to continue. There appears to be greater tolerance of TPM's cognitive AEs when it is used in the treatment of obesity, perhaps because of the lower doses required. Research attempting to predict the populations most vulnerable to the cognitive effects caused by TPM is ongoing. Studies suggest that one such population may include patients with a past psychiatric history. Slow titration and administration of the lowest possible doses may decrease risk of cognitive deficits.

Weight-reducing side effects of the antiepileptic agents topiramate and zonisamide

Drug-induced weight alteration can be a serious side effect that applies to several therapeutic agents and must be referred to in the respective approved labeling texts. The side effect may become health threatening in case of significant weight change in either direction. Several antiepileptic drugs (AEDs) are associated with weight gain such as gabapentin, pregabalin, valproic acid, and vigabatrin and to some extent carbamazepine. Others are weight neutral such as lamotrigine, levetiracetam, and phenytoin or associated with slight weight loss as, e.g., felbamate. The focus of this chapter is on the two AEDs causing strong weight loss: topiramate and zonisamide. For both drugs, several molecular mechanisms of actions are published. We provide a review of these potential mechanisms, some of which are based on in vivo studies in animal models for obesity, and of clinical studies exploring these two drugs as single entities or in combinations with other agents.

Topiramate versus carbamazepine for the treatment of classical trigeminal neuralgia: a meta-analysis

BACKGROUND

Carbamazepine is currently the drug of first choice in the treatment of trigeminal neuralgia. However, it is reported as efficacious in only 70-80% of patients, and can be associated with adverse effects such as drowsiness, confusion, nausea, ataxia, nystagmus and hypersensitivity, which may necessitate discontinuation of medication. Therefore, alternative drugs such as oxcarbazepine, baclofen and topiramate are also used to treat the disease.

OBJECTIVES

The aim of this study was to compare the effectiveness and safety of topiramate with carbamazepine in the treatment of classical trigeminal neuralgia.

METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) [Issue 3 of 12, March 2011], MEDLINE, EMBASE, the Chinese Biomedical Database (CBM), the Chinese National Knowledge Infrastructure (CNKI) and the Chinese Science and Technique Journals Database (VIP) for the period January 1998 to March 2011, and we also manually searched all relevant journals. We included all confirmed randomized controlled trials treating trigeminal neuralgia with topiramate and carbamazepine. We evaluated the risk of bias of the included trials according to the Cochrane Handbook for Systematic Reviews of Interventions, Version 5.1. The Cochrane Collaboration's software RevMan 5.1 was used for the meta-analysis.

RESULTS

A total of six randomized controlled trials with poor methodological quality were included. All trials were conducted in China. Altogether, they included 354 patients with trigeminal neuralgia. The results of the meta-analysis showed that topiramate was more effective than carbamazepine after a treatment duration of 2 months (relative risk [RR] = 1.20, 95% CI 1.04, 1.39, p = 0.01). However, no difference was found in the effectiveness rate after a treatment duration of 1 month (RR = 1.00, 95% CI 0.87, 1.14, p = 0.94), in the remission rate after a treatment duration of 1 month (RR = 1.06, 95% CI 0.83, 1.36, p = 0.63), in the remission rate after a treatment duration of 2 months (RR = 1.31, 95% CI 0.96, 1.80, p = 0.09) or in adverse events when comparing topiramate with carbamazepine.

CONCLUSIONS

Present trials comparing topiramate with carbamazepine are all poor in methodological quality. A meta-analysis of these studies showed that the overall effectiveness and tolerability of topiramate did not seem to differ from carbamazepine in the treatment of classical trigeminal neuralgia. However, the meta-analysis yielded a favourable effect of topiramate compared with carbamazepine after a treatment duration of 2 months. RESULTS were limited due to the poor methodological quality and the geographic localization of the randomized controlled trials identified. Therefore, large, international, well conducted, randomized controlled trials are needed to further assess the relative efficacy and tolerability of topiramate and carbamazepine in this indication.

The antiepileptic drug topiramate is a substrate for human P-glycoprotein but not multidrug resistance proteins

PURPOSE

Resistance to antiepileptic drugs (AEDs) is the major problem in the treatment of epilepsy. One of the candidate mechanisms of pharmacoresistance is the limitation of AED access to the seizure focus by overexpression of efflux transporters, including P-glycoprotein (Pgp) and multidrug resistance proteins (MRPs).In this respect, it is important to know which AEDs are substrates for such drug transporters in humans.

METHODS

In the present study, we used polarized kidney cell lines (LLC, MDCK) transfected with human drug transporters (Pgp, MRP1, MRP2 or MRP5) to evaluate whether the AED topiramate is a substrate for any of these transporters. Known Pgp and MRP substrates were used for comparison.

RESULTS

Basolateral-to-apical transport of topiramate, which could be counteracted with the Pgp inhibitor, tariquidar, was determined in Pgp overexpressing LLC cells, whereas topiramate was not transported by any of the MRPs. A comparison with previous experiments in the same transport assay showed that topiramate exhibited the most pronounced Pgp-mediated efflux transport among the AEDS that have been studied as yet.

CONCLUSIONS

Thus, these data indicate that brain levels of topiramate may be affected by overexpression of Pgp as determined in patients with intractable epilepsy.

Efficacy of topiramate in adult patients with symptomatic epilepsy: an open-label, long-term, retrospective observation

BACKGROUND

Topiramate is a newer generation antiepileptic drug with a wide range of antiepileptic efficacy as monotherapy or as adjunctive therapy, and which has shown positive activity in intractable epilepsy and newly diagnosed epilepsy. Topiramate has also been shown to exert good seizure control with a low incidence of adverse effects in brain tumour-associated epilepsy. However, there have been few reports on the efficacy of topiramate in the treatment of symptomatic epilepsy of varying aetiologies.

OBJECTIVE

The aim of the present study was to evaluate the efficacy of topiramate in the treatment of adult patients with symptomatic epilepsy of various aetiologies.

METHODS

This was an open-label, long-term, retrospective observation. 227 patients with symptomatic epilepsy (110 male, 117 female) were enrolled into this study. The underlying aetiologies included low-grade brain tumour, head trauma, cerebrovascular diseases, infection, diabetes mellitus, hydrocephalus and parasitosis. Topiramate was titrated up to a target dosage of 200 mg/day and maintained for at least 1 year. Response to topiramate was defined as > or = 50% reduction in seizure frequency compared with baseline. Seizure free was defined as no seizure occurring during 1 year of topiramate therapy.

RESULTS

157 (69.2%) patients were responders and 124 (54.6%) patients were seizure free with topiramate administration. Responders by subgroup included 40 patients (74.0%) with low-grade brain tumour, 32 (55.2%) with trauma, 30 (90.9%) with cerebrovascular disease, 21 (55.3%) with infection, 18 (81.8%) with diabetes, 12 (85.7%) with parasitosis and 4 (50.0%) with hydrocephalus. The percentage of seizure-free patients by subgroup was 61.0% with brain tumours, 31.0% with trauma, 78.8% with cerebrovascular disease, 44.7% with infection, 59.0% with diabetes, 85.7% with parasitosis and 50.0% with hydrocephalus. The incidence of adverse effects was 36.1%. The most commonly reported adverse effects were weight loss, memory impairments, paraesthesia, headache and dizziness; most were mild to moderate in severity and transient. Sixty-eight (30.0%) patients withdrew from topiramate treatment in this study: topiramate was discontinued in 56 patients because of lack of efficacy and in 12 patients because of adverse effects. At the end of the study, 109 patients received topiramate monotherapy, including 52 newly diagnosed patients and 57 subjects who transferred to topiramate monotherapy successfully; another 118 patients received add-on topiramate therapy. The percentage of patients responding to topiramate was 85.3% in the monotherapy group and 54.2% in the topiramate add-on therapy group; the percentage of seizure-free patients was 68.8% in the topiramate monotherapy group and 41.5% in the topiramate add-on therapy group.

CONCLUSION

When administered either as a single drug or as an add-on drug, topiramate is effective and well tolerated in adult patients with symptomatic epilepsy of various aetiologies.

Psychiatric issues in chronic pain

Chronic pain requires comprehensive care. While interdisciplinary approaches are recommended, the role of psychiatrists is often misunderstood. Psychiatrists should be involved with the care of patients with chronic pain as early as possible to maximize outcome. Psychiatrists offer an expertise that specifically addresses important deficiencies in the care of patients with chronic pain: 1) the lack of a detailed formulation, 2) the lumping of all psychopathology, and 3) the failure to effectively use psychopharmacologic treatments. This review provides a framework for formulating the diagnoses and treatments of patients with chronic pain.

Patient-reported cognitive side effects of antiepileptic drugs: predictors and comparison of all commonly used antiepileptic drugs

Subjective cognitive side effects (CSEs) are common in patients taking antiepileptic drugs (AEDs). The objective of this study was to predict which patients are at risk for CSEs, and compare the CSE profiles of all commonly used AEDs. In this nonrandomized retrospective study, medical records of 1694 adult outpatients with epilepsy seen at our center over a 5-year period who had taken one or more AEDs were examined. Non-AED predictors of CSEs were investigated, and rates of AED-related CSEs were compared in 1189 patients (546 on monotherapy) newly started on an AED at our center. The average rate of AED-related intolerable CSEs (leading to dosage change or discontinuation) was 12.8%. On multivariate analysis, no significant non-AED predictors of CSEs were found. Significantly more intolerable CSEs were attributed to topiramate (21.5% of 130 patients) than to most other AEDs, including carbamazepine (9.9%), gabapentin (7.3%), levetiracetam (10.4%), lamotrigine (8.9%), oxcarbazepine (11.6%), and valproate (8.3%). CSE rates with zonisamide (14.9%) were significantly higher than those for gabapentin and lamotrigine. After exclusion of CSEs during the first 8 weeks of therapy, rates of CSEs were lower, but relative differences remained unchanged. In monotherapy, significantly more intolerable CSEs occurred with topiramate (11.1% of 18 patients) than with carbamazepine or valproate, and both phenytoin and zonisamide were associated with more CSEs than valproate. From this study, it can be concluded that intolerable patient-reported CSEs are most common with topiramate, followed by zonisamide, phenytoin, and oxcarbazepine. They are least likely to be reported with gabapentin, valproate, lamotrigine, carbamazepine, and levetiracetam.

Efficacy of topiramate in bulimia nervosa and binge-eating disorder: a systematic review

OBJECTIVE

The objective of this review was to establish the efficacy of topiramate as treatment for eating disorders associated with obesity.

METHODS

We reviewed all five published controlled clinical trials that tested the efficacy of topiramate in treating bulimia nervosa (BN) or binge-eating disorder (BED). Two trials involving 128 patients studied topiramate efficacy in BN, and three trials (528 patients) studied patients with BED. Data on the number of participants, weeks of follow-up, dropouts, binge frequency and weight were extracted.

RESULTS

Short-term treatment with topiramate is more effective than treatment with placebo in decreasing binge episodes per week (overall result: topiramate group: -5.0+/-0.6; placebo group: -3.3+/-1.2), binge days per week (topiramate group: -3.5+/-0.6; placebo group: -2.3+/-0.7) and corporal weight (topiramate group: -4.6+/-2.3; placebo group: -0.5+/-0.6) in both BN and BED. The high number of withdrawals and the small sample sizes in four of the five controlled clinical trials limit the generalizability of this result.

CONCLUSION

Topiramate is effective in the short-term treatment of eating disorders associated with obesity. Additional studies are needed to prove its efficacy in the long term and to determine the optimal effective dose.

Tolerability and Safety of Topiramate in Chinese Patients with Epilepsy

OBJECTIVES

This study focused on (i) evaluating the long-term tolerability and safety of topiramate in Chinese patients with epilepsy, and (ii) comparing the tolerability and safety of topiramate monotherapy versus polytherapy in the same population.

METHODS

This was a prospective, open-label, long-term (36 months) clinical trial. 320 patients (275 adults and 45 children) with epilepsy were recruited into the study; of these, 156 patients had generalised seizures, 151 patients had partial seizures and 13 patients had unclassifiable seizures. All patients received topiramate approximately 200 mg/day either as monotherapy or as adjunctive therapy. At each visit, a physical examination and routine laboratory analysis were performed, and the adverse event (AE) profile was obtained by face-to-face interview.

RESULTS

268 patients received topiramate <or=100 mg/day and 52 patients received topiramate 100-200 mg/day. Topiramate-associated AEs occurred in 98 patients (30.6%). The most common AEs were weight loss in 18 patients (8.4%), paraesthesias in 17 (7.2%), poor memory in ten (3.8%), and dizziness in six (2.8%). Most AEs were mild to moderate and transitory; discontinuation of topiramate was observed in 13 patients (4.1%) as a result of AEs such as impaired memory (seven patients [54%]), paraesthesias (four patients [31%]), and weight loss and cutaneous reaction (each one patient [7.5% each]). The rate of AEs was significantly higher with use of topiramate as monotherapy than as adjunctive therapy (68 patients vs 30 patients [47.8% vs 16.4%], respectively).

CONCLUSION

Topiramate is well tolerated in Chinese patients with epilepsy in clinical practice. Compared with its use as adjunctive therapy, topiramate monotherapy is associated with a significantly higher frequency of adverse events.