The etomidate analog ET-26 HCl retains superior myocardial performance: Comparisons with etomidate in vivo and in vitro

The preclinical pharmacological study of a novel intravenous anesthetic, ET-26 hydrochloride, in aged rats

Background

ET-26 hydrochloride (ET-26HCl) is a novel analogue of etomidate approved for clinical trials. However, all results from recent studies were accomplished in young adult animals. The objective of this study was to evaluate the efficacy and safety of ET-26HCl in aged rats.

Methods

Aged Sprague-Dawley rats were randomly divided into three groups (three males and three females in each group) were given dose of two-fold of median effective dose (ED₅₀) of ET-26HCl, etomidate and propofol: the measurements of loss of the righting reflex (LORR) and cardiovascular and respiratory function after injection at the two-fold dose of the median effective dose were used for evaluation of effectiveness and safety, and the modified adrenocorticotropic hormone-stimulation experiment was used to evaluate the inhibition effect of the drugs on the synthesis of adrenal cortical hormones.

Results

There was no significant difference in the onset time among propofol, etomidate and ET-26HCl. The duration of propofol (850.5 ± 77.4 s) was significantly longer than that caused by etomidate (489.8 ± 77.0 s, p = 0.007) and ET-26HCl (347.3 ± 49.0 s, p = 0.0004). No significant difference was observed in the time to stand and normal activity among drugs. A total of 66.7% of rats in the ET-26HCl group were evaluated to have mild hematuria. Then, etomidate and ET-26HCl had a milder blood pressure inhibition effect than propofol. Apnea was observed in all rats administered propofol and the duration for this side effect was 45.0 ± 9.0 s. For etomidate and ET-26HCl, no apnea was observed. No other clinical signs of side-effect were observed, and no rats died. No significant difference was observed in corticosterone concentrations between ET-26HCl and solvent group. However, rats administered etomidate had lower corticosterone concentrations than those administered ET-26HCl at 15, 30, and 60 min.

Conclusions

Our results indicate ET-26HCl in aged rats is an effective sedative-hypnotic with stable myocardial and respiratory performance and also have mild adrenocortical suppression. Thus, these findings increase the potential for the clinical use of ET-26HCl in the elderly population.

Novel anesthetics in pediatric practice: is it time?

PURPOSE OF REVIEW

Steadily mounting evidence of anesthesia-induced developmental neurotoxicity has been a challenge in pediatric anesthesiology. Considering that presently used anesthetics have, in different animal models, been shown to cause lasting behavioral impairments when administered at the peak of brain development, the nagging question, 'Is it time for the development of a new anesthetic' must be pondered.

RECENT FINDINGS

The emerging 'soft analogs' of intravenous anesthetics aim to overcome the shortcomings of currently available clinical drugs. Remimazolam, a novel ester-analog of midazolam, is a well tolerated intravenous drug with beneficial pharmacological properties. Two novel etomidate analogs currently in development are causing less adrenocortical suppression while maintaining equally favorable hemodynamic stability and rapid metabolism. Quaternary lidocaine derivatives are explored as more potent and longer lasting alternatives to currently available local anesthetics. Xenon, a noble gas with anesthetic properties, is being considered as an anesthetic-sparing adjuvant in pediatric population. Finally, alphaxalone is being reevaluated in a new drug formulation because of its favorable pharmacological properties.

SUMMARY

Although a number of exciting anesthetic drugs are under development, there is currently no clear evidence to suggest their lack of neurotoxic properties in young brain. Well designed preclinical studies are needed to evaluate their neurotoxic potential.

Safety Pharmacology Study of ET-26 Hydrochloride, a Potential Drug for Intravenous General Anesthesia, in Rats and Beagle Dogs

Background: ET-26 hydrochloride (ET-26HCl), a class 1 new drug, was developed to reserve the advantages of etomidate with a mild adrenocortical inhibition.

Purpose: this study was to evaluate the potential adverse effects on the cardiovascular system of beagle dogs and the respiratory and central nervous systems of rats.

Methods: three established methods, the whole-body plethysmography for respiratory function, the prototype telemetry transmitter for cardiovascular function, and the standardized functional observational battery for central nervous system function, were accomplished with Good Laboratory Practice standards.

Results: no significant difference in the tidal volume, but the respiratory rate and minute ventilation were reduced. The degree of inhibition was the most serious in the first 15 min after dosing and function fully recovered after 1 h. For male rats, the respiratory rate of male rats was reduced significantly at 15 min after injection with ET-26HCl (4 mg/kg, 28.6%, p ≤ 0.01; 8 mg/kg, 24.5%, p ≤ 0.01; 16 mg/kg, 44.5%, p ≤ 0.001), and the minute ventilation at 15 min was decreased by 20.1% (4 mg/kg, p = 0.034), 22.2% (8 mg/kg, p = 0.019), and 44.6% (16 mg/kg, p ≤ 0.001) as compared to control group. As with male rats, the respiratory rate of the female rats was reduced significantly at 15 min (4 mg/kg, 23.3%, p ≤ 0.01; 8 mg/kg, 29.2%, p ≤ 0.001; 16 mg/kg, 44.1%, p ≤ 0.001), and the minute ventilation was decreased by 25.2% (4 mg/kg, p ≤ 0.001), 23.0% (8 mg/kg, p ≤ 0.01), and 47.6% (16 mg/kg, p ≤ 0.001). Then, all the variations in cardiovascular functions were within the expected range for normal biological variation, we concluded that ET-26HCl, even at 10-fold ED₅₀, still does not exert toxicological effects on the cardiovascular system. For male beagle dogs, the systolic blood pressure after 24 h following administration of vehicle control or 8, 12, or 16 mg/kg ET-26HCl was 137.80 ± 5.55, 131.76 ± 10.03, 139.88 ± 8.35, and 141.28 ± 8.75 mmHg, respectively. The diastolic blood pressure was 71.16 ± 4.84, 66.52 ± 8.50, 73.64 ± 8.51, and 74.24 ± 8.68 mmHg, respectively. For female beagle dogs, the systolic blood pressure after 24 h following administration of vehicle control or 8, 12, or 16 mg/kg ET-26HCl was 128.28 ± 5.22, 124.76 ± 7.29, 134.88 ± 5.56, and 135.36 ± 8.72 mmHg, respectively. The diastolic blood pressure was 67.00 ± 4.10, 62.12 ± 7.87, 69.44 ± 6.40, and 70.20 ± 8.42 mmHg, respectively. In central nervous system function experiment, all the changes observed in the functional observational battery tests, including motor activity, behavior, coordination, and sensory and motor reflex responses, and reduced body temperature, were resulted in general anesthesia effect of ET-26HCl.

Conclusion: ET-26HCl exerts mild, reversible effects on respiratory, cardiovascular, and central nervous system function as verified by standard in vivo animal models.

Treatment of nasal tumours in dogs: a review

Nasal tumours are common neoplasms in dogs and often represent a diagnostic and therapeutic challenge due to their confined location within the nasal cavities. The main goal of this review is to extract the most relevant information from a wide and often confusing evidence-based medicine on the treatment of canine nasal tumours and conclude with current recommendations. This report highlights the different therapeutic modalities available and describes their technical aspects, interests and limitations. Megavoltage radiotherapy, as the most recent treatment and standard of care, is particularly examined, especially the different types of radiotherapy units, the main protocols used and their advantages and limits. Newer and non-conventional treatments are also discussed.

Preclinical Pharmacokinetics Study of a Novel Intravenous Anesthetic ET-26 Hydrochloride

BACKGROUND

ET-26 hydrochloride is a novel intravenous anesthetic, approved for clinical trials, that produces a desirable sedative-hypnotic effect with stable myocardial performance and mild adrenocortical suppression in rats and beagle dogs. The objective of this study was to assess the absorption, distribution, metabolism, and excretion of ET-26 hydrochloride.

METHODS

Hepatocytes from human, monkey, dog, rat, and mouse were used to determine the metabolites of ET-26 hydrochloride. Distribution and excretion were assessed in rats and pharmacokinetic studies were performed in beagle dogs.

RESULTS

The metabolic pathway and proposed structure of metabolites were fully assessed resulting from the biotransformation reactions of hydrolysis, dehydrogenation, demethylation and glucuronic acid conjugation. The main distribution of the drug was in fat (15067 ± 801 ng/ml) and liver (13647 ± 1126 ng/ml), and the kidney was the primary excretion route (4.47%-11.94%). The Cmax after injection with 1.045 mg/kg, 2.09 mg/kg, and 4.18 mg/kg was 1476.5 ± 138.9 ng/ml, 2846.1 ± 223.3 ng/ml, and 6233.3 ± 238.9 ng/ml, respectively. The t1/2 of the drug was similar across dose groups at 74.8 ± 10.8 min to 81.4 ± 4.2 min. The AUC0-t values were 30208.1 ± 2026.5 min*ng/ml, 62712.8 ± 1808.3 min*ng/ml, and 130465.2 ± 7457.4 min*ng/ml, respectively.

CONCLUSION

The metabolic pathway and the proposed structure of metabolites for ET-26 hydrochloride were fully assessed. The majority of distribution for ET-26 hydrochloride occurs in the fat and liver, while the primary route of excretion for ET-26 hydrochloride is through the kidney. In dogs, pharmacokinetic features of ET-26 hydrochloride had a linear relationship with dosage.

Metabolite identification, tissue distribution, excretion and preclinical pharmacokinetic studies of ET-26-HCl, a new analogue of etomidate

ET-26-HCl, a novel anaesthetic agent with promising pharmacological properties, lacks extensive studies on pharmacokinetics and disposition in vitro and in vivo. In this study, we investigated the metabolic stability, metabolite production and plasma protein binding (PPB) of ET-26-HCl along with its tissue distribution, excretion and pharmacokinetics in animals after intravenous administration. Ultra-high performance liquid chromatography–tandem quadrupole time-of-flight mass spectrometry identified a total of eight new metabolites after ET-26-HCl biotransformation in liver microsomes from different species. A hypothetical cytochrome P450-metabolic pathway including dehydrogenation, hydroxylation and demethylation was proposed. The PPB rate was highest in mouse and lowest in human. After intravenous administration, ET-26-HCl distributed rapidly to all tissues in rats and beagle dogs, with the highest concentrations in fat and liver. High concentrations of ET-26-acid, a major hydroxylation metabolite of ET-26-HCl, were found in liver, plasma and kidney. Almost complete clearance of ET-26-HCl from plasma occurred within 4 h after administration. Only a small fraction of the parent compound and its acid form were excreted via the urine and faeces. Taken together, the results added to a better understanding of the metabolic and pharmacokinetic properties of ET-26-HCl, which may contribute to the further development of this drug.

Preclinical safety evaluation of ET-26 hydrochloride, a novel intravenous anesthetic agent, in beagle dogs

ET-26 hydrochloride (ET-26HCl) is a novel etomidate analogue, approved for clinical trials, which has an effective sedative-hypnotic effect, a stable myocardial performance, and milder adrenocortical suppression than etomidate in rats and beagle dogs. Additionally, ET-26HCl showed similar hemodynamic stability as etomidate in the rat uncontrolled hemorrhagic shock model. Furthermore, ET-26HCl, in the rat lipopolysaccharide-induced sepsis model, was found to have a higher survival rate, a lower inflammatory reaction, and less organ injury. In the present study, we measured the potential adverse effects of ET-26HCl in beagle dogs in accordance with the Guidance on single- and repeated-dose toxicity published by the China Food and Drug Administration. In toxicity studies, single and repeated (14 days) intravenous doses of up to 16 mg/kg were well tolerated, with only pharmacologically related clinical signs seen in both studies. Thus, the no-observed-adverse-effect level (NOAEL) of ET-26HCl was found at 16 mg/kg/day. Toxicokinetic examination demonstrated that ET-26HCl showed a dose-dependent increase to exposure, no gender difference, and no evidence of accumulation. These results provide useful information for guiding a phase I clinical trial of ET-26HCl in healthy volunteers.

Cross-linked cartilage acellular matrix film decreases postsurgical peritendinous adhesions

Cartilage extracellular matrix contains antiadhesive and antiangiogenic molecules such as chondromodulin-1, thrombospondin-1, and endostatin. We have aimed to develop a cross-linked cartilage acellular matrix (CAM) barrier for peritendinous adhesion prevention. CAM film was fabricated using decellularized porcine cartilage tissue powder and chemical cross-linking. Biochemical analysis of the film showed retention of collagen and glycosaminoglycans after the fabrication process. Physical characterization of the film showed denser collagen microstructure, increased water contact angle, and higher tensile strength after cross-linking. The degradation time in vivo was 14 d after cross-linking. The film extract and film surface showed similar cell proliferation, while inhibiting cell migration and cell adhesion compared to standard media and culture plate, respectively. Application of the film after repair resulted in similar tendon healing and significantly less peritendinous adhesions in a rabbit Achilles tendon injury model compared to repair only group, demonstrated by histology, ultrasonography, and biomechanical testing. In conclusion, the current study developed a CAM film having biological properties of antiadhesion, together with biomechanical properties and degradation profile suitable for prevention of peritendinous adhesions.