Newer propofol, ketamine, and etomidate derivatives and delivery systems relevant to anesthesia practice

Etomidate enhances cerebellar CF-PC synaptic plasticity through CB1 receptor/PKA cascade in vitro in mice

Etomidate (ET) is a widely used intravenous imidazole general anesthetic, which depresses the cerebellar neuronal activity by modulating various receptors activity and synaptic transmission. In this study, we investigated the effects of ET on the cerebellar climbing fiber-Purkinje cells (CF-PC) plasticity in vitro in mice using whole-cell recording technique and pharmacological methods. Our results demonstrated that CF tetanic stimulation produced a mGluR1-dependent long-term depression (LTD) of CF-PC excitatory postsynaptic currents (EPSCs), which was enhanced by bath application of ET (10 µM). Blockade of mGluR1 receptor with JNJ16259685, ET triggered the tetanic stimulation to induce a CF-PC LTD accompanied with an increase in paired-pulse ratio (PPR). The ET-triggered CF-PC LTD was abolished by extracellular administration of an N-methyl-(D)-aspartate (NMDA) receptor antagonist, D-APV, as well as by intracellular blockade of NMDA receptors activity with MK801. Furthermore, blocking cannabinoids 1 (CB1) receptor with AM251 or chelating intracellular Ca2+ with BAPTA, ET failed to trigger the CF-PC LTD. Moreover, the ET-triggered CF-PC LTD was abolished by inhibition of protein kinase A (PKA), but not by inhibition of protein kinase C inhibiter. The present results suggest that ET acts on postsynaptic NMDA receptor resulting in an enhancement of the cerebellar CF-PC LTD through CB1 receptor/PKA cascade in vitro in mice. These results provide new evidence and possible mechanism for ET anesthesia to affect motor learning and motor coordination by regulating cerebellar CF-PC LTD.

The Modulation by Anesthetics and Analgesics of Respiratory Rhythm in the Nervous System

Rhythmic eupneic breathing in mammals depends on the coordinated activities of the neural system that sends cranial and spinal motor outputs to respiratory muscles. These outputs modulate lung ventilation and adjust respiratory airflow, which depends on the upper airway patency and ventilatory musculature. Anesthetics are widely used in clinical practice worldwide. In addition to clinically necessary pharmacological effects, respiratory depression is a critical side effect induced by most general anesthetics. Therefore, understanding how general anesthetics modulate the respiratory system is important for the development of safer general anesthetics. Currently used volatile anesthetics and most intravenous anesthetics induce inhibitory effects on respiratory outputs. Various general anesthetics produce differential effects on respiratory characteristics, including the respiratory rate, tidal volume, airway resistance, and ventilatory response. At the cellular and molecular levels, the mechanisms underlying anesthetic-induced breathing depression mainly include modulation of synaptic transmission of ligand-gated ionotropic receptors (e.g., γ-aminobutyric acid, N-methyl-D-aspartate, and nicotinic acetylcholine receptors) and ion channels (e.g., voltage-gated sodium, calcium, and potassium channels, two-pore domain potassium channels, and sodium leak channels), which affect neuronal firing in brainstem respiratory and peripheral chemoreceptor areas. The present review comprehensively summarizes the modulation of the respiratory system by clinically used general anesthetics, including the effects at the molecular, cellular, anatomic, and behavioral levels. Specifically, analgesics, such as opioids, which cause respiratory depression and the "opioid crisis", are discussed. Finally, underlying strategies of respiratory stimulation that target general anesthetics and/or analgesics are summarized.

The Development and Optimization of Lipid-Based Self-Nanoemulsifying Drug Delivery Systems for the Intravenous Delivery of Propofol

PURPOSE

Propofol is a relatively short-acting potent anesthetic lipophilic drug used during short surgical procedures. Despite the success of propofol intravenous emulsions, drawbacks to such formulations include inherent emulsion instability, the lack of a safe vehicle to prevent sepsis, and concern regarding hyperlipidemia-related side effects. The aim of the current investigation was to develop a novel, lipid-based self-nanoemulsifying drug delivery system (SNEDDS) for propofol with improved stability and anesthetic activity for human use.

METHODS

A series of SNEDDS formulations were developed using naturally obtained medium-chain/long-chain mono-, di-, and triglycerides, glyceryl monocaprylate, and water-soluble cosolvents with hydrogenated castor oil constructing ternary phase diagrams for propofol. The developed SNEDDS formulations were characterized using visual observation, particle size analysis, zeta potential, transmission electron microscopy, equilibrium solubility, in vitro dynamic dispersion and stability, and in vivo sleeping disorder studies in rats. The in vivo bioavailability of the SNEDDSs in rats was also studied to compare the representative formulations with the marketed product Diprivan^®.

RESULTS

Medium-chain triglycerides (M810) with mono-diglycerides (CMCM) as an oil blend and hydrogenated castor oil (KHS15) as a surfactant were selected as key ingredients in ternary phase diagram studies. The nanoemulsifying regions were identified from the studies and a number of SNEDDSs were formulated. Results from the characterization studies demonstrated the formation of efficient nanosized particles (28-45 nm globule size, 0.10-0.20 PDI) in the optimized SNEDDS with a drug loading of 50 mg/g, which is almost 500-fold higher than free propofol. TEM analysis showed the formation of spherical and homogeneous nanoparticles of less than 50 nm. The dissolution rate of the representative SNEDDS was faster than raw propofol and able to maintain 99% propofol in aqueous solution for around 24 h. The optimized liquid SNEDDS formulation was found to be thermodynamically stable. The intravenous administration of the SNEDDS in male Wistar rats induced a sleeping time of 73-88 min. The mean plasma concentrations after the IV administration of propofol nano-formulations PF2-SNEDDS and PF8-SNEDDS were 1348.07 ± 27.31 and 1138.66 ± 44.97 µg/mL, as compared to 891.44 ± 26.05 µg/mL (p = 0.05) observed after the IV administration of raw propofol.

CONCLUSION

Propofol-loaded SNEDDS formulations could be a potential pharmaceutical product with improved stability, bioavailability, and anesthetic activity.

A. The Valsalva Maneuver Is Not as Effective as Lidocaine for the Attenuation of Pain on Injection of Propofol: A Randomized Controlled Study

Background and objective

Lidocaine pretreatment is considered the gold standard for attenuating pain on injection of propofol. Valsalva maneuver (VM) causes baroreceptor reflex arc-induced antinociception by increasing the intrathoracic pressure. We aimed to evaluate the efficacy of VM in alleviating the pain on injection of propofol in this randomized comparative study.

Methods

A total of 90 patients were recruited for this randomized study. They were classified into two groups. Patients in group D received 5-mL 4% lidocaine in saline intravenously while the venous drainage was occluded. Then they were asked to press a rubber ball as hard as they could. Patients in group V received 5-ml saline pretreatment. They were then asked to perform VM by blowing into rubber tubing connected to a manometer and raising and holding the pressure up to 40 mmHg. The verbal response and behavioral signs were recorded with a score corresponding to no, mild, moderate, or severe pain. A t-test was performed to compare the mean of variables between the two groups. The Kolmogorov-Smirnov test was used for testing the equality of the distribution function of pain scores between the groups. Repeated measures analysis of variance (ANOVA) was performed to test the heart rate and mean arterial pressure (MAP) at different points of observation.

Results

The incidence of pain and pain scores were significantly higher among the patients in the VM group as compared to those in the lidocaine with distraction group.

Conclusions

VM performed immediately before the injection failed to attenuate the pain produced by propofol as compared to lidocaine pretreatment along with distraction.

Fast and reliable analysis of veterinary metomidate and etomidate in human blood samples by liquid chromatography-tandem mass spectrometry (LC-MS/MS) in a postmortem case

Metomidate and etomidate belong to the non-barbiturate imidazole family of sedative-hypnotics and elicit little analgesic action when used alone. Metomidate, in particular, has little analgesic activity in humans and is, therefore, used for veterinary purposes. In 2019, a Korean woman in her twenties was found unconscious in a motel bath and eventually died. Etomidate, alprazolam, escitalopram, and metomidate were detected in the postmortem specimens. To our knowledge, this is the first case of human metomidate abuse reported in the Republic of Korea. In this research, a simple and reliable method was developed for the analysis of metomidate and etomidate in human blood samples using liquid chromatography-tandem mass spectrometry (LC-MS/MS). Blood samples were deproteinized with acetonitrile, filtered, and analyzed by LC-MS/MS. Linear calibration curves were obtained with six concentrations ranging from 1 to 50 ng/ml for metomidate and 10 to 500 ng/ml for etomidate. The method was validated by assessing the selectivity, linearity, limit of detection (LOD), limit of quantitation (LOQ), intra- and inter-day precision and accuracy, matrix effect, and stability and successfully applied to the analysis of metomidate and etomidate in human blood samples. In a postmortem case, the concentrations of metomidate and etomidate were found to be 8 and 110 ng/ml in femoral blood and 6 and 210 ng/ml in cardiac blood, respectively.

Etomidate ameliorated advanced glycation end-products (AGEs)-induced reduction of extracellular matrix genes expression in chondrocytes

Osteoarthritis (OA) is a rheumatic disease common in the elderly. AGEs are the end products of glycation reactions and play an important role in the development of OA. Etomidate is a general anesthesia-inducing agent recently reported to exert significant anti-inflammatory effects. The present study aims to explore the protective effect of Etomidate against advanced glycation end-products (AGEs)-induced reduction of extracellular matrix gene expression in chondrocytes. In the present study, we found that AGEs significantly reduced the expression of Collagen II (COL2A1) and Aggrecan (ACAN) at the gene level. Furthermore, AGEs inhibited the expression of SRY-related high mobility group-box gene 9 (SOX-9), promoting the expression of COL2A1 and ACAN. COL2A1, ACAN, and SOX-9 in chondrocytes were significantly elevated by treatment with Etomidate alone. Consistently, Etomidate ameliorated AGEs-induced downregulation of COL2A1, ACAN, and SOX-9 in a dose-dependent manner. Importantly, we found that knockdown of SOX-9 eliminated the beneficial effects of Etomidate against AGEs-induced decrease in COL2A1 and ACAN genes. Based on these findings, we demonstrated that Etomidate could ameliorate AGEs-induced reduction of extracellular matrix gene expression in chondrocytes by upregulating SOX-9.

Facile design of gemini surfactant-like peptide for hydrophobic drug delivery and antimicrobial activity

Recently, many kinds of gemini-type amphiphilic peptides have been designed and shown their advantage as self-assembling nanomaterials. In this study, we proposed a simple strategy to design gemini surfactant-like peptides, which are only composed of natural amino acids and can be easily obtained by conventional peptide sythnesis. Taking two prolines as the turn-forming units, a peptide named APK was designed. The petide has a linear sequence but naturally takes the conformation like a gemini surfactant. Compared with a single-tailed surfactant-like peptide A6K, APK showed much stronger ability to undergo self-assembly and to encapsulate hydrophobic pyrene. Several hydrophobic drugs including paclitaxel, doxorubicin, etomidate and propofol were encapsulated by APK, and the corresponding formulations showed anti-tumor or anesthetic efficacy comparable to their respective clinical formulations. Furthermore, APK could inhibit the growth of different microorganisms including E. coli, S. aureus and C. albicans. Etomidate and propofol formulations encapsulated by APK also showed strong antimicrobial activity. Taking APK as an example, our study indicated a straightforward strategy to design gemini surfactant-like peptides, which could be potential nanomaterials for exploring hydrophobic drug formulations with efficacy, safety and self-antimicrobial activity.

Effects of continuous intravenous infusion of propofol on intestinal flora in rats

Under normal circumstances, the gut microbiota, host, and external environment establish a dynamic ecological balance and maintain human health. Once this balance is broken, the intestinal flora dysregulation will form, manifested by changes in the diversity, richness, proportion, location and biological characteristics of the gut microbiota. The hypothesis that propofol alters gut microbes was tested in a rat model with continuous intravenous infusion of propofol. Eight male wistar rats underwent tail vein puncture and catheterization respectively, and were continuously pumped with propofol for 3 h. Feces were collected from each rat before and on the 1 st, 3rd, 7th and 14th days after intervention. Finally, the effect of continuous intravenous infusion of propofol on the intestinal flora of rats was analyzed by high-throughput 16S rRNA gene amplification sequencing. Through high-throughput 16S rRNA gene amplicon sequencing analysis, we found that continuous intravenous infusion of propofol had little effect on intestinal flora in rats. Analysis of Alpha (shannon diversity index) showed that group A-7 was different from group P and group A-1 (P = 0.034), and recovered on the 14th day. Although the species diversity analysis showed a significant difference among the five groups (P = 0.049), the distribution of most fecal samples in the PCoA showed a clustered distribution, indicating similarity. In addition, no significant difference was found in the statistical KEGG difference pathway through LEfSe analysis.

Palonosetron Pretreatment is not as Effective as Lignocaine for Attenuation of Pain on Injection of Propofol

Objective

5-HT3 receptor antagonists are known to possess local anesthetic properties and are commonly used for the alleviation of pain following propofol injection. Palonosetron, a newer molecule, has shown contradictory results for this property. The aim of this study was to compare the effect of palonosetron pretreatment in alleviating propofol injection pain with that of lignocaine. Their comparative effect on various hemodynamic parameters was also evaluated.

Methods

A total of 100 adult patients were randomly assigned to one of two groups: group L received lignocaine 40 mg in 5 mL of 0.9% saline pretreatment solution and group P received 0.075 mg palonosetron in 5 mL 0.9% of saline pretreatment solution. After 2 minutes, the tourniquet was released and one-fourth of the total calculated dose of propofol was administered, after which the pain assessment was made. The Students t-test was used for comparing the difference of mean between the two groups after testing for equality of variance using F-statistics. Categorical variables were expressed as a percentage, and the Chi-square test was performed to assess the independence of attributes. Repeated-measure analysis of variance was used to compare the change in heart rate and mean arterial pressure over three time points between the two groups.

Results

The proportion of pain reported by the subjects in the lignocaine group was significantly lower as compared to the subjects in the palonosetron group (p=0.001). No significant difference of mean heart rate and mean arterial pressure was observed between the two groups following these interventions.

Conclusion

The efficacy of palonosetron in alleviating the pain on injection of propofol was significantly less than that of lignocaine.

Allosteric GABAA Receptor Modulators-A Review on the Most Recent Heterocyclic Chemotypes and Their Synthetic Accessibility

GABAA receptor modulators are structurally almost as diverse as their target protein. A plethora of heterocyclic scaffolds has been described as modulating this extremely important receptor family. Some made it into clinical trials and, even on the market, some were dismissed. This review focuses on the synthetic accessibility and potential for library synthesis of GABAA receptor modulators containing at least one heterocyclic scaffold, which were disclosed within the last 10 years.

mTOR Expression in Hippocampus and Prefrontal Cortex Is Downregulated in a Rat Model of Schizophrenia Induced by Chronic Administration of Ketamine

Schizophrenia is a severe chronic neuropsychiatric disorder, and it negatively affects individuals' quality of life, but the pathogenesis of schizophrenia remains unclear. This study aimed to explore whether the administration of ketamine in rats causes changes in mTOR (mechanistic/mammalian target of rapamycin) expression in the hippocampus and prefrontal cortex. Ketamine was used to establish an animal model of schizophrenia. Rats were randomly divided into four groups: control group (normal saline), low-dose group (15 mg/kg ketamine), middle-dose group (30 mg/kg ketamine), and high-dose group (60 mg/kg ketamine). The rats were intraperitoneally injected with ketamine or normal saline twice a day (9 AM and 9 PM) for 7 consecutive days. Immunohistochemistry was used to detect mTOR protein expression in the hippocampus and prefrontal cortex from rats at 13 h after the last treatment. Using immunohistochemistry, the expression of the mTOR protein was localized exclusively in the CA3 region of the hippocampus and in the Cg1 region of the prefrontal cortexes. Ketamine at 60 mg/kg decreased the expression of mTOR protein in the brain of rats. Ketamine successfully established a rat model of schizophrenia. This study helps elucidate the mechanisms of ketamine-induced schizophrenia and provides novel insights for drug discovery and development.

Effect of anesthesia with propofol plus remifentanil vs etomidate plus remifentanil on respiratory function and stress in elderly patients with esophageal leukoplakia treated by gastroscopy

BACKGROUND

With the development of society and the advancement of science and technology, the patient's requirements for comfort during gastroscopy are constantly increasing, and more attention has been paid to the possible adverse reactions. More and more patients choose to undergo painless gastroscopy. Elderly patients have vascular tolerance, significant organ function decline, and higher requirements for anesthetic drugs due to age and degenerative changes. Therefore, it is important to choose the correct anesthetic drugs during gastroscopy in elderly patients.

AIM

To compare the effects of anesthesia with propofol plus remifentanil and etomidate plus remifentanil on respiratory function and stress in elderly patients with esophageal leukoplakia.

METHODS

A total of 200 elderly patients (aged 62-73 years) with esophageal leukoplakia who underwent painless gastroscopy at the Endoscopy Center of our hospital from April 2018 to October 2018 were enrolled. The patients were randomly divided into either a control group or a study group, with 100 patients in each group. The control group was anesthetized with propofol and remifentanil, and the study group was anesthetized with etomidate and remifentanil. Serum oxygen saturation (SPO₂) and stress hormones (adrenocorticotropic hormone, glucocorticoid, and angiotensin) before and at the end of treatment were compared between the two groups. Hemodynamics during treatment, adverse reactions during treatment, and the difference in time to recovery of spontaneous breathing time were also compared.

RESULTS

Serum levels of stress hormones in the two groups were comparable before treatment. At the end of treatment, serum levels of stress hormones (adrenocorticotropic hormone, glucocorticoid, and angiotensin) in the study group were significantly lower than those in the control group (P < 0.05). Hemodynamics was more stable in the study group (P < 0.05). SPO₂ was significantly higher in the study group than in the control group (P < 0.05). The rate of adverse reactions was significantly reduced in the study group (P < 0.05). However, the time to recovery of spontaneous breathing was significantly shorter in the control group than in the study group (P < 0.05).

CONCLUSION

Compared with anesthesia with propofol plus remifentanil, etomidate plus remifentanil in elderly patients with esophageal leukoplakia can reduce inflammatory factors and stress hormones more significantly, maintain hemodynamics and intraoperative blood oxygenation saturation more stably, and have fewer adverse reactions, but is associated with longer time to recovery of spontaneous breathing.