Topiramate as an add-on antiepileptic drug in treating refractory canine idiopathic epilepsy

Comparison of neuroprotective effects of a topiramate-loaded biocomposite based on mesoporous silica nanoparticles with pure topiramate against methylphenidate-induced neurodegeneration

BACKGROUND

Methylphenidate (MPH) abuse has been criticized for its role in neurodegeneration. Also, a high risk of seizure was reported in the first month of MPH treatment. Topiramate, a broad-spectrum Antiepileptic Drug (AED), has been used as a neuroprotective agent in both aforementioned complications. Nanotechnology is introduced to increase desirable neurological treatment with minimum side effects. We aimed to investigate the potential neuroprotective activity of topiramate loaded on nanoparticles.

METHODS AND RESULTS

MTT assay was performed to evaluate the cellular cytotoxicity of Mesoporous Silica Nanoparticles (MSN). Male rats were randomly divided into eight groups. Rats received an intraperitoneal (i.p) MPH (10 mg/kg) injection and a daily oral dose of topiramate (TPM, 30 mg/kg), MSN with Zn core (10 and 30 mg/kg), and MSN with Cu core (10 and 30 mg/kg) for three weeks. On day 21, a seizure was induced by a single injection of pentylenetetrazole (PTZ) to evaluate the protective effects of TPM-loaded nanoparticles on seizure latency and duration following MPH-induced neurotoxicity. Moreover, the hippocampal content of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β), malondialdehyde (MDA), and the anti-oxidant enzymes (SOD, GPx, and GR) activities were assessed. Also, BAX and Bcl-2 as two main apoptotic markers were evaluated.

RESULTS

MPH neurotoxicity was observed as a raised duration and reduced latency in PTZ-induced seizure. However, TPM-loaded MSN with Zn species (NE) treatment reduced the duration and improved the latency time. Also, NE and, somewhat, TPM-loaded MSN with Cu species (NM) administration reduced inflammatory cytokines, MDA, and Bax levels and increased activities in the rat hippocampus.

CONCLUSION

TPM-loaded nanoparticles could be used as neuroprotective agents against MPH-induced neurodegeneration by improving seizure parameters and reducing inflammatory, oxidant, and apoptotic factors.

Pathophysiology of drug-resistant canine epilepsy

Drug resistance continues to be a major clinical problem in the therapeutic management of canine epilepsies with substantial implications for quality of life and survival times. Experimental and clinical data from human medicine provided evidence for relevant contributions of intrinsic severity of the disease as well as alterations in pharmacokinetics and -dynamics to failure to respond to antiseizure medications. In addition, several modulatory factors have been identified that can be associated with the level of therapeutic responses. Among others, the list of potential modulatory factors comprises genetic and epigenetic factors, inflammatory mediators, and metabolites. Regarding data from dogs, there are obvious gaps in knowledge when it comes to our understanding of the clinical patterns and the mechanisms of drug-resistant canine epilepsy. So far, seizure density and the occurrence of cluster seizures have been linked with a poor response to antiseizure medications. Moreover, evidence exists that the genetic background and alterations in epigenetic mechanisms might influence the efficacy of antiseizure medications in dogs with epilepsy. Further molecular, cellular, and network alterations that may affect intrinsic severity, pharmacokinetics, and -dynamics have been reported. However, the association with drug responsiveness has not yet been studied in detail. In summary, there is an urgent need to strengthen clinical and experimental research efforts exploring the mechanisms of resistance as well as their association with different etiologies, epilepsy types, and clinical courses.

The pharmacokinetics of single oral dose extended-release topiramate and adverse effects after multi-dose administration in healthy cats

Current treatment options for feline epilepsy are limited to medications that require administration of multiple doses per day or administration of a capsule or large tablet. Expanding the current treatment options could improve patient and owner compliance and optimize seizure control. Topiramate has been used sparingly in veterinary medicine, and limited pharmacokinetic studies have focused on immediate release formulations in dogs. If effective and safe, topiramate extended-release (XR) could broaden the current treatment options for feline epilepsy. The aims of this two-phase study were to establish single-dose pharmacokinetics for topiramate XR in cats, identify a dosing regimen that maintains steady-state plasma drug concentrations within a reference range extrapolated from human medicine (5-20 μg/mL), and evaluate the safety of topiramate XR in cats following multidose administration. Topiramate XR administered orally at 10 mg/kg once daily for 30 days was sufficient to achieve the desired concentrations in all cats. While no clinically apparent adverse effects were observed, four out of eight cats developed subclinical anemia, calling into question the safety of topiramate XR with chronic administration. Further studies are necessary to better understand the potential adverse effects and overall efficacy of topiramate XR for the treatment of feline epilepsy.

Presumptive renal tubular acidosis secondary to topiramate administration in a cat

OBJECTIVE

To describe renal tubular acidosis (RTA) and secondary acquired hyperaldosteronism in a cat as an adverse effect of topiramate therapy.

CASE SUMMARY

An 8-year-old neutered female cat on chronic oral topiramate therapy at a recommended dose (11.9 mg/kg q 8 h) for seizure control was presented with severe metabolic acidosis and hypokalemia. Plasma electrolyte and acid-base analysis identified a severe metabolic acidosis (pH 7.153, reference interval: 7.31-7.46), hypokalemia (2.08 mmol/L [2.08 mEq/L], reference interval: 3.5-4.8 mmol/L [3.5-4.8 mEq/L]), and ionized hypercalcemia (1.85 mmol/L [1.85 mEq/L], reference range: 1.1-1.4 mmol/L [1.1-1.4 mEq/L]). Urinalysis revealed a urine specific gravity of 1.021 and a pH of 7.0. Diagnostic workup suggested distal RTA as a cause of the cat's acid-base and electrolyte disturbances. Aldosterone concentration was moderately increased, suggestive of secondary hyperaldosteronism. The metabolic abnormalities resolved with supportive care and discontinuation of topiramate.

NEW OR UNIQUE INFORMATION PROVIDED

Topiramate is suggested to have led to the development severe RTA in a cat.

In vitro and in vivo experimental models employed in the discovery and development of antiepileptic drugs for pharmacoresistant epilepsy

Epilepsy is one of the most common chronic, recurrent and progressive neurological diseases. In spite of the large number of antiepileptic drugs currently available for the suppression of seizures, about one-third of patients develop drug-resistant epilepsy, even when they are administered the most appropriate treatment available. Thus, nonclinical models can be valuable tools for the elucidation of the mechanisms underlying the development of pharmacoresistance and also for the development of new therapeutic agents that may be promising therapeutic approaches for this unmet medical need. Up today, several epilepsy and seizure models have been developed, exhibiting similar physiopathological features of human drug-resistant epilepsy; moreover, pharmacological response to antiepileptic drugs clinically available tends to be similar in animal models and humans. Therefore, they should be more intensively used in the preclinical discovery and development of new candidates to antiepileptic drugs. Although useful, in vitro models cannot completely replicate the complexity of a living being and their potential for a systematic use in antiepileptic drug screening is limited. The whole-animal models are the most commonly employed and they can be classified as per se drug-resistant due to an inherent poor drug response or be based on the selection of subgroups of epileptic animals that respond or not to a specific antiepileptic drug. Although more expensive and time-consuming, the latter are chronic models of epilepsy that better exhibit the disease-associated alterations found in human epilepsy. Several antiepileptic drugs in development or already marketed have been already tested and shown to be effective in these models of drug-resistant epilepsy, constituting a new hope for the treatment of drug-resistant epilepsy. This review will provide epilepsy researchers with detailed information on the in vitro and in vivo nonclinical models of interest in drug-resistant epilepsy, which may enable a refined selection of most relevant models for understanding the mechanisms of the disease and developing novel antiepileptic drugs.

Antiepileptic drugs' tolerability and safety--a systematic review and meta-analysis of adverse effects in dogs

Background

The safety profile of anti-epileptic drugs (AEDs) is an important consideration for the regulatory bodies, owners and prescribing clinicians. Information on their adverse effects still remains limited. A systematic review including a meta-analytic approach was designed to evaluate existing evidence for the safety profile of AEDs in canine patients. Electronic searches of PubMed, CAB Direct and Google scholar were carried out without date or language restrictions. Conference proceedings were also searched. Peer-reviewed full-length studies reporting adverse effects of AEDs in epileptic and healthy non-epileptic dogs were included. Studies were allocated to three groups based on their design. Individual studies were evaluated based on the quality of evidence (study design, study group sizes, subject enrolment quality and overall risk of bias) and the outcome measures reported (proportion of specific adverse effects for each AED, prevalence and 95 % confidence interval of the affected population in each study and comparative odds ratio of adverse effects for AEDs).

Results

Ninety studies, including six conference proceedings, reporting clinical outcomes of AEDs’ adverse effects were identified. Few studies were designed as blinded randomised controlled clinical trials. Many studies included low canine populations with unclear criteria of subject enrolment and short treatment periods. Direct comparisons suggested that imepitoin and levetiracetam might have a better safety profile than phenobarbital, whilst the latter might have a better safety profile than potassium bromide. However, none of these comparisons showed a statistically significant difference. Comparisons between other AEDs were not possible as a considerable amount of studies lacked power calculations or adequate data to allow further statistical analysis. Individual AED assessments indicated that levetiracetam might be one of the safest AEDs, followed by imepitoin and then phenobarbital and potassium bromide; these findings were all supported by a strong level of evidence. The safety profile in other AEDs was variable, but weak evidence was found to permit firm conclusions or to compare their safety to other AEDs.

Conclusions

This systematic review provides objective evaluation of the most commonly used AEDs’ adverse effects. Adverse effects usually appeared mild in all AEDs and subsided once doses and/or serum levels were monitored or after the AED was withdrawn. Although phenobarbital might be less safe than imepitoin and levetiracetam, there was insufficient evidence to classify it as an AED with a high risk of major adverse effects. It is important for clinicians to evaluate both AEDs’ effectiveness and safety on an individual basis before the selection of the appropriate monotherapy or adjunctive AED therapy.

Crowdsourcing reproducible seizure forecasting in human and canine epilepsy

See Mormann and Andrzejak (doi:10.1093/brain/aww091) for a scientific commentary on this article.  

Seizures are thought to arise from an identifiable pre-ictal state. Brinkmann et al. report the results of an online, open-access seizure forecasting competition using intracranial EEG recordings from canines with naturally occurring epilepsy and human patients undergoing presurgical monitoring. The winning algorithms forecast seizures at rates significantly greater than chance.

See Mormann and Andrzejak (doi:10.1093/brain/aww091) for a scientific commentary on this article.  

Accurate forecasting of epileptic seizures has the potential to transform clinical epilepsy care. However, progress toward reliable seizure forecasting has been hampered by lack of open access to long duration recordings with an adequate number of seizures for investigators to rigorously compare algorithms and results. A seizure forecasting competition was conducted on kaggle.com using open access chronic ambulatory intracranial electroencephalography from five canines with naturally occurring epilepsy and two humans undergoing prolonged wide bandwidth intracranial electroencephalographic monitoring. Data were provided to participants as 10-min interictal and preictal clips, with approximately half of the 60 GB data bundle labelled (interictal/preictal) for algorithm training and half unlabelled for evaluation. The contestants developed custom algorithms and uploaded their classifications (interictal/preictal) for the unknown testing data, and a randomly selected 40% of data segments were scored and results broadcasted on a public leader board. The contest ran from August to November 2014, and 654 participants submitted 17 856 classifications of the unlabelled test data. The top performing entry scored 0.84 area under the classification curve. Following the contest, additional held-out unlabelled data clips were provided to the top 10 participants and they submitted classifications for the new unseen data. The resulting area under the classification curves were well above chance forecasting, but did show a mean 6.54 ± 2.45% (min, max: 0.30, 20.2) decline in performance. The kaggle.com model using open access data and algorithms generated reproducible research that advanced seizure forecasting. The overall performance from multiple contestants on unseen data was better than a random predictor, and demonstrates the feasibility of seizure forecasting in canine and human epilepsy.

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.

Short-term use of antiepileptic drugs is neurotoxic to the immature brain

Previous studies have shown that the long-term use of antiepileptic drugs can cause nervous system damage. However, short-term antiepileptic drug treatment is frequently given to infants, especially neonates, to control seizure. Whether the short-term use of antiepileptic drugs is neurotoxic remains unclear. In the present study, immature rats, 3–21 days of age, were intraperitoneally injected with phenobarbital and/or topiramate for 3 consecutive days. Hematoxylin-eosin and immunohistochemical staining revealed that phenobarbital and topiramate, individually or in combination, were cytotoxic to hippocampal CA1 neurons and inhibited the expression of GluR1 and NR2B, excitatory glutamate receptor subunits. Furthermore, the combination of the two drugs caused greater damage than either drug alone. The results demonstrate that the short-term use of antiepileptic drugs damages neurons in the immature brain and that the combined use of antiepileptic drugs exacerbates damage. Our findings suggest that clinicians should consider the potential neurotoxic risk associated with the combined use of antiepileptic drugs in the treatment of seizure.

Treatment in canine epilepsy--a systematic review

Background

Various antiepileptic drugs (AEDs) are used for the management of canine idiopathic epilepsy (IE). Information on their clinical efficacy remains limited. A systematic review was designed to evaluate existing evidence for the effectiveness of AEDs for presumptive canine IE. Electronic searches of PubMed and CAB Direct were carried out without date or language restrictions. Conference proceedings were also searched. Peer-reviewed full-length studies describing objectively the efficacy of AEDs in dogs with IE were included. Studies were allocated in two groups, i.e. blinded randomized clinical trials (bRCTs), non-blinded randomized clinical trials (nbRCTs) and non-randomized clinical trials (NRCTs) (group A) and uncontrolled clinical trials (UCTs) and case series (group B). Individual studies were evaluated based on the quality of evidence (study design, study group sizes, subject enrolment quality and overall risk of bias) and the outcome measures reported (in particular the proportion of dogs with ≥50% reduction in seizure frequency).

Results

Twenty-six studies, including two conference proceedings, reporting clinical outcomes of AEDs used for management of IE were identified. Heterogeneity of study designs and outcome measures made meta-analysis inappropriate. Only four bRCTs were identified in group A and were considered to offer higher quality of evidence among the studies. A good level of evidence supported the efficacy of oral phenobarbital and imepitoin and fair level of evidence supported the efficacy of oral potassium bromide and levetiracetam. For the remaining AEDs, favorable results were reported regarding their efficacy, but there was insufficient evidence to support their use due to lack of bRCTs.

Conclusions

Oral phenobarbital and imepitoin in particular, as well as potassium bromide and levetiracetam are likely to be effective for the treatment of IE. However, variations in baseline characteristics of the dogs involved, significant differences between study designs and several potential sources of bias preclude definitive recommendations. There is a need for greater numbers of adequately sized bRCTs evaluating the efficacy of AEDs for IE.