The pharmacokinetics of levetiracetam in healthy dogs concurrently receiving phenobarbital

A review of the pharmacology and clinical applications of levetiracetam in dogs and cats

OBJECTIVE

To review and summarize the pharmacology of the antiepileptic drug (AED), levetiracetam (LEV), and to discuss its clinical utility in dogs and cats.

DATA SOURCES

Veterinary and human peer-reviewed medical literature and the authors' clinical experience.

SUMMARY

LEV is an AED with mechanisms of action distinct from those of other AEDs. In people and small animals, LEV exhibits linear kinetics, excellent oral bioavailability, and minimal drug-drug interactions. Serious side effects are rarely reported in any species. LEV use is gaining favor for treating epilepsy in small animals and may have wider clinical applications in patients with portosystemic shunts, neuroglycopenia, and traumatic brain injury. In people, LEV may improve cognitive function in patients with dementia.

CONCLUSION

LEV is a well-tolerated AED with well-documented efficacy in human patients. Although its use is becoming more common in veterinary medicine, its role as a first-line monotherapy in small animal epileptics remains to be determined. This review of the human and animal literature regarding LEV describes its role in epileptic people and animals as well as in other disease states and provides recommendations for clinical usage.

Response to Levetiracetam Treatment and Long-Term Follow-Up in Dogs With Reactive Seizures Due to Probable Exogenous Toxicity

Limited information is available on the long-term follow-up and seizure recurrence in dogs with reactive seizures due to suspected exogenous toxicity. The purpose of this study was to report the long-term follow-up of 13 dogs referred to a single referral hospital, diagnosed with reactive seizures and treated with a standardized levetiracetam protocol. All dogs received a loading levetiracetam dose of 60 mg/kg/IV once, followed by a maintenance dose of 20 mg/kg every 8 h as part of an open-label clinical study. Levetiracetam was withdrawn after a 6-months seizure-free period by reducing levetiracetam to 20 mg/kg every 12 h for a 4-week seizure-free period, followed by levetiracetam 20 mg/kg every 24 h for a 4-week seizure-free period, before levetiracetam treatment was stopped. No adverse effects of the treatment were reported. No dogs experienced any seizures after discharge or after levetiracetam withdrawal. Median follow-up time from time of discharge was of 78 months (=6 years 6 months). The result of this study supports the use of levetiracetam for treatment of reactive seizures due to exogenous substance intoxication. Moreover, our results do not support the need for long-term antiepileptic treatment in cases of reactive seizures due to exogenous intoxication.

Postattenuation neurologic signs after surgical attenuation of congenital portosystemic shunts in dogs: A review

The development of postattenuation neurologic signs (PANS) is a poorly understood and potentially devastating complication after surgical attenuation of congenital portosystemic shunts in dogs. Postattenuation neurologic signs include seizures but also more subtle neurologic signs such as depression, behavioral changes, tremors, and twitching. They most commonly occur within 7 days postoperatively and are typically unrelated to hyperammonemia, hypoglycemia, or electrolyte disturbances. This narrative review summarizes the findings of 50 publications from 1988-2020 that report occurrence of PANS. While most published reports included only dogs affected by postattenuation seizures (PAS), others included dogs with any form of PANS. Overall, PANS (including PAS) affected 1.6%-27.3% of dogs, whereas incidence of PAS ranged from 0%-18.2%. The etiology of PANS remains unknown; however, several theories have been proposed. Risk factors include preoperative hepatic encephalopathy, increasing age, and possibly certain breeds and extrahepatic shunt morphology. There is increasing evidence that prophylactic antiepileptic drugs do not prevent PANS. Treatment is centered around controlling neurologic signs with antiepileptic drugs and providing supportive intensive care. The 30-day survival rate in studies that included a minimum of four dogs affected by PANS was 0%-100% (median, 50.0%) and 0%-75.0% (median, 37.5%) for those with PAS. Mortality associated with PANS was typically related to occurrence of generalized seizure activity. Prognostic factors positively associated with short-term survival included having a history of preoperative seizures and development of focal seizures only. If affected dogs survived to discharge, survival for several years was possible, and the majority of neurologic signs manifested as part of the phenomenon of PANS appeared to resolve.

Population pharmacokinetics of extended-release levetiracetam in epileptic dogs when administered alone, with phenobarbital or zonisamide

BACKGROUND

Extended-release levetiracetam (LEV-XR) has gained acceptance as an antiepileptic drug in dogs. No studies have evaluated its disposition in dogs with epilepsy.

HYPOTHESIS/OBJECTIVES

To evaluate the pharmacokinetics of LEV-XR in epileptic dogs when administered alone or with phenobarbital or zonisamide.

ANIMALS

Eighteen client-owned dogs on steady-state maintenance treatment with LEV-XR (Group L, n = 6), LEV-XR and phenobarbital (Group LP, n = 6), or LEV-XR and zonisamide (Group LZ, n = 6).

METHODS

Pharmacokinetic study. Blood samples were collected at 0, 2, 4, 8, and 12 hours after LEV-XR was administered with food. Plasma LEV concentrations were determined by high-pressure liquid chromatography. A population pharmacokinetic approach and nonlinear mixed effects modeling were used to analyze the data.

RESULTS

Treatment group accounted for most of the interindividual variation. The LP group had lower CMAX (13.38 μg/mL) compared to the L group (33.01 μg/mL) and LZ group (34.13 μg/mL), lower AUC (134.86 versus 352.95 and 452.76 hours·μg/mL, respectively), and higher CL/F (0.17 versus 0.08 and 0.07 L/kg/hr, respectively). The half-life that defined the terminal slope of the plasma concentration versus time curve (~5 hours) was similar to values previously reported for healthy dogs.

CONCLUSIONS AND CLINICAL IMPORTANCE

Considerable variation exists in the pharmacokinetics of LEV-XR in dogs with epilepsy being treated with a common dose regimen. Concurrent administration of phenobarbital contributed significantly to the variation. Other factors evaluated, including co-administration of zonisamide, were not shown to contribute to the variability. Drug monitoring may be beneficial to determine the most appropriate dose of LEV-XR in individual dogs.

Pharmacokinetics of rectal levetiracetam as add-on treatment in dogs affected by cluster seizures or status epilepticus

Background

Levetiracetam can be used for seizure control alone or in combination with other antiepileptic medications. A previous study achieved the minimum targeted serum drug concentration after rectal administration of levetiracetam in healthy dogs. The purpose of the present study was to determine the pharmacokinetics of rectal LEV in dogs presented for cluster seizures or status epilepticus and potentially in treatment with other anti-epileptic drugs. Furthermore, preliminary information on response to this treatment as add-on to the standard treatment protocol is reported.

Results

Eight client-owned dogs were enrolled. Plasma levetiracetam concentrations (measured at 0, 30, 60, 90, 120, 180, 240, 360, 720, and 1440 min after drug administration) reached the minimum target concentration (5 μg/ml) at 30 min in all but one patient. At T1 (30 min) the mean concentration was 28.2 ± 15.5 μg/ml. Plasma concentrations remained above the targeted minimum concentration in all patients until 240 min and in 7/8 until 360 min. Six out of eight patients experienced no seizures in the 24-h period after hospitalization and were classified as “responders”.

Conclusions

Minimum plasma levetiracetam concentration can be reached after rectal administration of 40 mg/kg in dogs affected by cluster seizures and status epilepticus and concurrently receiving other antiepileptic drugs. These preliminary results may encourage the evaluation of rectal levetiracetam as an additional treatment option for cluster seizures and status epilepticus in a larger number of dogs.

Electronic supplementary material

The online version of this article (10.1186/s12917-018-1522-0) contains supplementary material, which is available to authorized users.

A Review: Emergency Management of Dogs With Suspected Epileptic Seizures

Dogs with seizure disorders are commonly presented to the general practitioner for initial evaluation. The most common diagnosis provided is idiopathic epilepsy. As witnessing seizures is often traumatic for owners, it is important for the practitioner to understand seizure classification, know when to initiate antiepileptic drug therapy and be comfortable with client education regarding seizures. This review briefly discusses the most up-to-date classification of seizures, the necessity to obtain accurate histories and complete examinations, base-line diagnostics to perform, the importance of owner education, and when to start medications. This is not intended to discuss detailed differential lists, in-depth information on antiepileptic drug therapy, long-term management of epileptics or those refractory to their current treatment.

2015 ACVIM Small Animal Consensus Statement on Seizure Management in Dogs

This report represents a scientific and working clinical consensus statement on seizure management in dogs based on current literature and clinical expertise. The goal was to establish guidelines for a predetermined, concise, and logical sequential approach to chronic seizure management starting with seizure identification and diagnosis (not included in this report), reviewing decision‐making, treatment strategies, focusing on issues related to chronic antiepileptic drug treatment response and monitoring, and guidelines to enhance patient response and quality of life. Ultimately, we hope to provide a foundation for ongoing and future clinical epilepsy research in veterinary medicine.

A single-blinded phenobarbital-controlled trial of levetiracetam as mono-therapy in dogs with newly diagnosed epilepsy

Treatment of canine epilepsy is problematic. Few antiepileptic drugs have proven efficacy in dogs and undesirable adverse effects and pharmacoresistance are not uncommon. Consequently, the need for investigation of alternative treatment options is ongoing. The objective of this study was to investigate the efficacy and tolerability of levetiracetam as mono-therapy in dogs with idiopathic epilepsy. The study used a prospective single-blinded parallel group design. Twelve client-owned dogs were included and were randomised to treatment with levetiracetam (30 mg/kg/day or 60 mg/kg/day divided into three daily dosages) or phenobarbital (4 mg/kg/day divided twice daily). Control visits were at days 30, 60 and then every 3 months for up to 1 year. Two or more seizures within 3 months led to an increase in drug dosage (levetiracetam: 10 mg/kg/day, phenobarbital: 1 mg/kg/day). Five of six levetiracetam treated dogs and one of six phenobarbital treated dogs withdrew from the study within 2-5 months due to insufficient seizure control. In the levetiracetam treated dogs there was no significant difference in the monthly number of seizures before and after treatment, whereas in the phenobarbital treated dogs there were significantly (P = 0.013) fewer seizures after treatment. Five phenobarbital treated dogs were classified as true responders (≥50% reduction in seizures/month) whereas none of the levetiracetam treated dogs fulfilled this criterion. Adverse effects were reported in both groups but were more frequent in the phenobarbital group. In this study levetiracetam was well tolerated but was not effective at the given doses as mono-therapy in dogs with idiopathic epilepsy.

International veterinary epilepsy task force consensus proposal: outcome of therapeutic interventions in canine and feline epilepsy

Common criteria for the diagnosis of drug resistance and the assessment of outcome are needed urgently as a prerequisite for standardized evaluation and reporting of individual therapeutic responses in canine epilepsy. Thus, we provide a proposal for the definition of drug resistance and partial therapeutic success in canine patients with epilepsy. This consensus statement also suggests a list of factors and aspects of outcome, which should be considered in addition to the impact on seizures. Moreover, these expert recommendations discuss criteria which determine the validity and informative value of a therapeutic trial in an individual patient and also suggest the application of individual outcome criteria. Agreement on common guidelines does not only render a basis for future optimization of individual patient management, but is also a presupposition for the design and implementation of clinical studies with highly standardized inclusion and exclusion criteria. Respective standardization will improve the comparability of findings from different studies and renders an improved basis for multicenter studies. Therefore, this proposal provides an in-depth discussion of the implications of outcome criteria for clinical studies. In particular ethical aspects and the different options for study design and application of individual patient-centered outcome criteria are considered.

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.

Disposition of Extended Release Levetiracetam in Normal Healthy Dogs After Single Oral Dosing

Background

Levetiracetam is an anticonvulsant used for control of canine epilepsy. An extended release preparation should improve dosing convenience.

Objectives

To determine the disposition of extended release levetiracetam in normal dogs after single dosing.

Animals

Pharmacokinetic study: 16 healthy, adult dogs.

Methods

Using a partially randomized crossover study, levetiracetam (30 mg/kg) was administered intravenously (IV) and orally (PO) as extended release preparation with or without food. Blood was collected for 24 hours (IV) or 36 hours (PO). Serum levetiracetam was quantitated by immunoassay and data were subjected to noncompartmental analysis.

Results

Pharmacokinetic parameters for fasted versus fed animals, respectively, were (mean ± SEM): C_max = 26.6 ± 2.38 and 30.7 ± 2.88 μ/mL, T_max = 204.3 ± 18.9 and 393.8 ± 36.6 minutes, t_1/2 = 4.95 ± 0.55 and 4.48 ± 0.48 hours, MRT = 9.8 ± 0.72 and 10 ± 0.64 hours, MAT = 4.7 ± 0.38 and 5.6 ± 0.67 hours, and F = 1.04 ± 0.04 and 1.26 ± 0.07%. Significant differences were limited to T_max (longer) and F (greater) in fed compared to fasted animals. Serum levetiracetam concentration remained above 5 μ/mL for approximately 20 hours in both fasted and fed animals.

Conclusions and Clinical Importance

Extended release levetiracetam (30 mg/kg q12h), with or without food, should maintain concentrations above the recommended minimum human therapeutic concentration.

Effect of chronic administration of phenobarbital, or bromide, on pharmacokinetics of levetiracetam in dogs with epilepsy

BACKGROUND

Levetiracetam (LEV) is a common add-on antiepileptic drug (AED) in dogs with refractory seizures. Concurrent phenobarbital administration alters the disposition of LEV in healthy dogs.

HYPOTHESIS/OBJECTIVES

To evaluate the pharmacokinetics of LEV in dogs with epilepsy when administered concurrently with conventional AEDs.

ANIMALS

Eighteen client-owned dogs on maintenance treatment with LEV and phenobarbital (PB group, n = 6), LEV and bromide (BR group, n = 6) or LEV, phenobarbital and bromide (PB-BR group, n = 6).

METHODS

Prospective pharmacokinetic study. Blood samples were collected at 0, 1, 2, 4, and 6 hours after LEV administration. Plasma LEV concentrations were determined by high-pressure liquid chromatography. To account for dose differences among dogs, LEV concentrations were normalized to the mean study dose (26.4 mg/kg). Pharmacokinetic analysis was performed on adjusted concentrations, using a noncompartmental method, and area-under-the-curve (AUC) calculated to the last measured time point.

RESULTS

Compared to the PB and PB-BR groups, the BR group had significantly higher peak concentration (Cmax ) (73.4 ± 24.0 versus 37.5 ± 13.7 and 26.5 ± 8.96 μg/mL, respectively, P < .001) and AUC (329 ± 114 versus 140 ± 64.7 and 98.7 ± 42.2 h*μg/mL, respectively, P < .001), and significantly lower clearance (CL/F) (71.8 ± 22.1 versus 187 ± 81.9 and 269 ± 127 mL/h/kg, respectively, P = .028).

CONCLUSIONS AND CLINICAL IMPORTANCE

Concurrent administration of PB alone or in combination with bromide increases LEV clearance in epileptic dogs compared to concurrent administration of bromide alone. Dosage increases might be indicated when utilizing LEV as add-on treatment with phenobarbital in dogs.

Assessment into the usage of levetiracetam in a canine epilepsy clinic

Background

Retrospective studies can complement information derived from double-blinded randomized trials. There are multiple retrospective studies reporting good efficacy and tolerability of the anti-epileptic drug levetiracetam (LEV) in human patients with epilepsy; however, reports of LEV's tolerability and efficacy in dogs with epilepsy remain limited. The purpose of this retrospective study was to describe the use of LEV in a canine epilepsy clinic and determine the long-term efficacy and tolerability of LEV in veterinary clinical practice. The electronic database of a UK based referral hospital was searched for LEV usage in dogs with seizures. Information and data necessary for the evaluation were obtained from a combination of electronic and written hospital records, the referring veterinary surgeons’ records and telephone interviews with dog owners. Only dogs that were reportedly diagnosed with idiopathic epilepsy were included in the study.

Results

Fifty-two dogs were included in this retrospective study. Two treatment protocols were recognised; 29 dogs were treated continuously with LEV and 23 dogs received interval or pulse treatment for cluster seizures. LEV treatment resulted in 69% of dogs having a 50% or greater reduction of seizure frequency whilst 15% of all the dogs were completely free from seizures. Seizure frequency reduced significantly in the whole population. No dog was reported to experience life-threatening side effects. Mild side effects were experienced by 46% of dogs and a significantly higher number of these dogs were in the pulse treatment group. The most common side-effects reported were sedation and ataxia.

Conclusions

LEV appears to be effective and well tolerated for reduction of seizures.

Seizures and epilepsy in cats

Seizures are a common presenting complaint in cats, although causes and options for the treatment of seizures in this species have been historically poorly described in the veterinary literature. Seizure manifestation in cats may be different than what is typically seen in dogs, but the underlying causes of seizure activity are the same. These include primary epilepsies, structural epilepsies, and reactive seizures. Although primary epilepsy was once believed to be rare in cats, we now commonly appreciate this syndrome, albeit at a lower frequency than in dogs. Because of this, a complete diagnostic work-up is recommended for all cats presenting for initial evaluation of seizures. Symptomatic treatment of seizures in cats is similar to dogs, with only a few limitations related to species-specific antiepileptic drug toxicities. The goal of this review is to summarize the recent veterinary literature related to feline seizures, with a focus on seizure classification, clinical manifestation, diagnostic evaluation, and treatment options.

Antiepileptic drug therapy and monitoring

Over the past 2 decades, the number of antiepileptic drugs (AEDs) available to veterinarians has grown exponentially. Coupled with this increase is the ability to rapidly and accurately diagnose underlying brain disease with readily accessible magnetic resonance imaging. As a result, the veterinary community is attuned to the need for early treatment intervention. As more treatment choices become available, the unrelenting questions still arise are when should treatment begin, which initial drug therapy is best for our patients, when should treatment changes be considered, and finally, what are the advantages that newer drugs provide for our patients. The purpose of this chapter is to review decision-making strategies for AED therapy, provide an overview of the applicability of current AED available, and present information on the therapeutic advances in epilepsy.

Imepitoin as novel treatment option for canine idiopathic epilepsy: pharmacokinetics, distribution, and metabolism in dogs

Imepitoin is a novel anti-epileptic licensed in the European Union for the treatment of canine idiopathic epilepsy. The aim of this study was to characterize the pharmacokinetics of imepitoin in dogs and to evaluate the interaction with drug metabolizing enzymes. Upon administration of imepitoin tablets at a dose of 30 mg/kg to beagle dogs, high plasma levels were observed within 30 min following oral dosing, with maximal plasma concentrations of 14.9–17.2 μg/mL reached after 2–3 h. In a crossover study, co-administration of imepitoin tablets with food reduced the total AUC by 30%, but it did not result in significant changes in T_max and C_max, indicating lack of clinical relevance. No clinically relevant effects of sex and no accumulation or metabolic tolerance were observed upon twice daily dosing. Following single dose administration of 10–100 mg/kg, dose linearity was found. Administering [¹⁴C] imepitoin, high enteral absorption of 92% and primary fecal excretion were identified. Plasma protein binding was only 55%. At therapeutic plasma concentrations, imepitoin did not inhibit microsomal cytochrome P450 family liver enzymes in vitro. In rats, no relevant induction of liver enzymes was found. Therefore, protein binding or metabolism-derived drug–drug interactions are unlikely. Based on these data, imepitoin can be dosed twice daily, but the timing of tablet administration in relation to feeding should be kept consistent.

Levetiracetam rectal administration in healthy dogs

BACKGROUND

Levetiracetam is used to manage status epilepticus (SE) and cluster seizures (CS) in humans. The drug might be absorbed after rectal administration and could offer a practical adjunct to rectal administration of diazepam in managing SE and CS.

HYPOTHESIS

Levetiracetam is rapidly absorbed after rectal administration in dogs and maintains target serum concentrations for at least 9 hours.

ANIMALS

Six healthy privately owned dogs between 2 and 6 years of age and weighing 10-20 kg.

METHODS

Levetiracetam (40 mg/kg) was administered rectally and blood samples were obtained immediately before (time zero) and at 10, 20, 40, 60, 90, 180, 360, and 540 minutes after drug administration. Dogs were observed for signs of adverse effects over a 24-hour period after drug administration.

RESULTS

CLEV at 10 minutes was 15.3 ± 5.5 μg/mL (mean, SD) with concentrations in the target range (5-40 μg/mL) for all dogs throughout the sampling period. Cmax (36.0 ± 10.7 μg/mL) and Tmax (103 ± 31 minutes) values were calculated and 2 disparate groups were appreciated. Dogs with feces in the rectum at the time of drug administration had lower mean Cmax values (26.7 ± 3.4 μg/mL) compared with those without (45.2 ± 4.4 μg/mL). Mild sedation was observed between 60 and 90 minutes without other adverse effects noted.

CONCLUSIONS AND CLINICAL IMPORTANCE

This study supports the use of rectally administered levetiracetam in future studies of clinical effectiveness in the management of epileptic dogs.