Comparative efficacy of valnoctamide and sec-butylpropylacetamide (SPD) in terminating nerve agent-induced seizures in pediatric rats

Refractory and Super-Refractory Status Epilepticus in Nerve Agent-Poisoned Rats Following Application of Standard Clinical Treatment Guidelines

Nerve agents (NAs) induce a severe cholinergic crisis that can lead to status epilepticus (SE). Current guidelines for treatment of NA-induced SE only include prehospital benzodiazepines, which may not fully resolve this life-threatening condition. This study examined the efficacy of general clinical protocols for treatment of SE in the specific context of NA poisoning in adult male rats. Treatment with both intramuscular and intravenous benzodiazepines was entirely insufficient to control SE. Second line intervention with valproate (VPA) initially terminated SE in 35% of rats, but seizures always returned. Phenobarbital (PHB) was more effective, with SE terminating in 56% of rats and 19% of rats remaining seizure-free for at least 24 h. The majority of rats demonstrated refractory SE (RSE) and required treatment with a continuous third-line anesthetic. Both ketamine (KET) and propofol (PRO) led to high levels of mortality, and nearly all rats on these therapies had breakthrough seizure activity, demonstrating super-refractory SE (SRSE). For the small subset of rats in which SE was fully resolved, significant improvements over controls were observed in recovery metrics, behavioral assays, and brain pathology. Together these data suggest that NA-induced SE is particularly severe, but aggressive treatment in the intensive care setting can lead to positive functional outcomes for casualties.

Phenobarbital as alternate anticonvulsant for organophosphate-induced benzodiazepine-refractory status epilepticus and neuronal injury

Objective

Organophosphates (OPs) such as diisopropylfluorophosphate (DFP) and soman are lethal chemical agents that can produce seizures, refractory status epilepticus (SE), and brain damage. There are few optimal treatments for late or refractory SE. Phenobarbital is a second‐line drug for SE, usually after lorazepam, diazepam, or midazolam have failed to stop SE. Practically, 40 minutes or less is often necessary for first responders to arrive and assist in a chemical incident. However, it remains unclear whether administration of phenobarbital 40 minutes after OP intoxication is still effective. Here, we investigated the efficacy of phenobarbital treatment at 40 minutes postexposure to OP intoxication.

Methods

Acute refractory SE was induced in rats by DFP injection as per a standard paradigm. After 40 minutes, subjects were given phenobarbital intramuscularly (30‐100 mg/kg) and progression of seizure activity was monitored by video‐EEG recording. The extent of brain damage was assessed 3 days after DFP injections by neuropathology analysis of neurodegeneration and neuronal injury by unbiased stereology.

Results

Phenobarbital produced a dose‐dependent seizure protection. A substantial decrease in SE was evident at 30 and 60 mg/kg, and a complete seizure termination was noted at 100 mg/kg within 40 minutes after treatment. Neuropathology findings showed significant neuroprotection in 100 mg/kg cohorts in brain regions associated with SE. Although higher doses resulted in greater protection against refractory SE and neuronal damage, they did not positively correlate with improved survival rate. Moreover, phenobarbital caused serious adverse effects including anesthetic or comatose state and even death.

Significance

Phenobarbital appears as an alternate anticonvulsant for OP‐induced refractive SE in hospital settings. A careful risk‐benefit analysis is required because of negative outcomes on survival and cardio‐respiratory function. However, the need for sophisticated support and critical monitoring in hospital may preclude its use as medical countermeasure in mass casualty situations.

Synthesis of a novel amide derivative of valproic acid and 1,3,4-thiadiazole with antiepileptic activity

Valproates are commonly used to treat various forms of epilepsy. Problems accompanying their clinical application include drug resistance, adverse effects, acute and chronic toxicity. Safer anticonvulsants with improved efficacy can be obtained through the chemical modification of valproic acid structure. Thiadiazole-linked amide derivatives of valproates hold great promise because 1,3,4-thiadiazole can improve the drug’s bioavailability and reduce its toxicity. The aim of this work was to synthesize a novel amide derivative of valproic acid and 1,3,4-thiadiazole exerting antiepileptic activity. The chemical structure of the synthesized valproate was studied by IR, proton NMR and 13С-NMR-spectroscopy, mass spectroscopy and elemental analysis. The purity and individuality of the compound was confirmed by thin-layer and high-performance liquid chromatography. Its antiepileptic activity was assessed in the test with intraperitoneally injected 250 mg/kg isoniazid and subsequent Probit analysis. The synthesized N-(5-ethyl-1,3,4-thiadiazol-2-yl)-2-propyl pentane amide (valprazolamide) had the following characteristics. ESI+MS: m/z 256.1 [M + H]+; MRM transitions: m/z 256.1 — m/z 81.0 and m/z 130.1. The valproate exerted antiepileptic activity against isoniazid-induced seizures in mice. In the test with isoniazid, ED50 of intraperitoneally injected VPZ was 126.8 mg/kg (95% CI: 65.5–245.4). Its therapeutic index was 7.3.

Moving beyond sodium valproate: choosing the right anti-epileptic drug in children

Introduction: Sodium valproate is a widely used anti-epileptic drug with a broad spectrum of activity and mechanism of action. It has consequently been the first-line drug for most seizure types in children for the past fifty years. A wide range of side effects come along with these exceptional properties, including teratogenicity and neuro-cognitive impairments in offspring. Therefore, epilepsy treatment in children and adolescents should be reassessed in light of newer antiepileptic drugs as well as a more targeted-approach with older drugs. Areas covered: The authors review the main concerns of valproate use in terms of adverse effects on different systems and drug interactions. The current alternatives to valproate in absence, myoclonic, tonic-clonic and focal onset seizures in children/adolescents are also reviewed. Expert opinion: There are several issues that research should address in antiepileptic therapy and in clinical studies with children, given the peculiarity of this population. Future perspectives in epilepsy therapy should now lead towards an individualized treatment.