Synergistic interaction between butorphanol and dexmedetomidine in antinociception

Modulation of spinal morphine pharmacokinetics and antinociception by α2-adrenergic agonists in the male rat

The synergistic antinociceptive effects of α2-adrenergic agonists and intrathecal (i.t.) opioids were initially linked to pharmacodynamics. However, the α2-agonist dexmedetomidine also enhances brain delivery of CSF-administered drugs by increasing glymphatic influx. Here, fadolmidine, a hydrophilic α2-agonist designed for spinal analgesia, was studied for its sedative, antinociceptive, and pharmacokinetic effects with co-administered lumbar intrathecal morphine. Subcutaneous and i.t. dexmedetomidine served as comparators. Forty-eight male Sprague-Dawley rats received i.t. lumbar catheters. Sedative effects of i.t. fadolmidine (1-10 μg) and i.t. dexmedetomidine (1-10 μg) were assessed by open field and rotarod tests. The antinociceptive effects of morphine alone (1.5 μg i.t.) and co-administered with i.t. fadolmidine (3 and 10 μg) were evaluated using the tail-flick test. Effects of i.t. fadolmidine and subcutaneous dexmedetomidine (0.2 mg/kg) on morphine concentration within CNS were assessed by liquid chromatography-tandem mass spectrometry at 60 min. While i.t. dexmedetomidine was sedating, i.t fadolmidine was not. The antinociceptive effects of other treatment regimens weaned at latest after 90 min, whereas the combination of fadolmidine 10 μg i.t. and morphine 1.5 μg i.t. provided antinociception until the end of the measurement period (%maximum possible effect of 77.5 ± 11.5 vs saline 10.6 ± 11.1, p = 0.0002 at 120 min). Subcutaneous dexmedetomidine effectively targeted lumbar morphine towards the injection site resulting in a 3335-fold (95% CI: 929-11978) lower brain-to-injection site ratio, versus a 355-fold (95% CI: 196-641) difference with saline. By improving spinal opioid targeting, α2-adrenergic agonists dexmedetomidine and fadolmidine may reduce supraspinal side effects, enabling safe and efficacious intrathecal analgesia.

Intranasal Atomized Dexmedetomidine in Combination With Intranasal Atomized Butorphanol for Dressing Change Sedation and Analgesia in Adult Burn Patients: A Randomized Clinical Trial

We aimed to evaluate the efficacy of the intranasal atomized dexmedetomidine (IAD) + intranasal atomized butorphanol (IAB) combination therapy on adult patients with burns undergoing dressing changes. Herein, 46 adult patients with burns were enrolled and randomly divided into 2 groups: dexmedetomidine-butorphanol (DB) and saline-butorphanol, treated with atomized dexmedetomidine + butorphanol and saline + butorphanol, respectively. The primary outcomes were the Ramsay Sedation Scale (RSS) and the Visual Analog Scale (VAS) scores. The secondary outcomes were mean blood pressure (MBP), heart rate, respiratory rate (RR), peripheral blood oxygen saturation (SpO2), total butorphanol consumption, and adverse effects. The 2 groups were comparable in age, sex, weight, and total burn surface area. During dressing changes, the DB group exhibited significantly lower RSS levels (P < .05). Besides, the 2 groups showed no significant differences in VAS scores across all measurement time points. Notably, the DB group exhibited decreased MBP at the beginning of the operation (P < .0001), 10 min after (P < .0001), and 20 min after (P = .0205). Heart rate decreased significantly at the beginning (P = .0005) and 10 min after (P = .0088) in the DB group. Furthermore, the 2 groups showed no significant differences in RR and SpO2 levels. In addition, the rescue butorphanol dose was lower in the DB group (P < .001). Finally, dizziness and nausea incidences were significantly lower in the DB group (P < .05). In conclusion, besides its hemodynamic adverse reactions, the IAD + IAB combination therapy exerted a better sedation effect in adult patients with burns than IAB treatment alone.

Enhancing fentanyl antinociception and preventing tolerance with α-2 adrenoceptor agonists in rats

Fentanyl (FEN) is a potent opioid analgesic used for pain management. Opioid analgesic tolerance poses a significant challenge to the clinical utility of opioid agonists. Preventing the development of tolerance to opioid analgesia is crucial for improving its efficacy and safety. The noradrenergic system is involved in pain regulation. This study examined the effects of α-2 adrenoceptor (AR) agonists, dexmedetomidine (DEX), and xylazine (XYL) on FEN tolerance and antinociception, and their impact on μ-opioid receptor (MOR) expression in the posterior horn of the spinal cord (SC). Male rats were divided into six groups and treated with different drug combinations for three consecutive days. Analgesia tests and motor performance assessments were conducted, followed by SC analysis using immunohistochemistry (IHC). Analgesia tests revealed the development of FEN tolerance on the second day, but the groups receiving combined drugs did not develop tolerance. Instead, FEN antinociception was enhanced, with a prolonged duration of its effects. None of the drugs caused sedation or motor impairment, and SC morphology appeared normal. MOR expression levels did not differ significantly between the groups based on IHC analysis. These findings suggest that changes in the secondary messenger system may play a role in the early development of FEN tolerance. Combining drugs can prevent tolerance, while enhancing FEN's antinociceptive effects. These results have promising implications for chronic pain management; however, further research is needed to explore the molecular effects of α-2 AR agonists on FEN tolerance. Overall, this study sheds light on the mechanism of FEN tolerance and identifies potential avenues for future research.

Synergistic interaction between DAMGO-NH2 and NOP01 in peripherally acting antinociception in two mouse models of formalin pain

The most commonly used opioid analgesics are limited by their severe side-effects in the clinical treatment of pain. Preliminary reports indicate that the combination of classical opioids and N/OFQ receptor (NOP) ligands may be an effective strategy to reduce unwanted side-effects and improve antinociception. But the interaction of these two receptor ligands in pain regulation at the peripheral level remains unclear. In this study, the antinociception of a designed amide analogue of the mu opioid receptor (MOP) peptide agonist DAMGO, DAMGO-NH₂, and its antinociceptive interaction with the peripherally limited NOP peptide agonist NOP01 was investigated in two mouse models of formalin pain. Our results showed that DAMGO-NH₂ acted as a MOP agonist in in vitro functional assays. Moreover, local subcutaneous or intraplantar injection of DAMGO-NH₂ exerted dose-related antinociception in both phases of the formalin orofacial and intraplantar pain, which could be mediated by the classical opioid receptor. Peripheral but not central pretreatment with the peripherally restricted opioid antagonist naloxone methiodide inhibited local DAMGO-NH₂-induced antinociception, supporting the involvement of the peripheral opioid receptor in local DAMGO-NH₂-induced antinociception. Furthermore, co-administration of the inactive doses of DAMGO-NH₂ and NOP01 produced effective antinociception. More importantly, isobolographic analysis indicates that the combination of DAMGO-NH₂ and NOP01 elicited supra-additive antinociception in these two models of formalin pain. In addition, the combination of DAMGO-NH₂ and NOP01 did not change motor function of mice in rotarod test. In conclusion, these data suggest that peripheral DAMGO-NH₂ and particularly its combination therapy with NOP01 may be effective for pain management.

Treatment of Pain in Rats, Mice, and Prairie Dogs

Recent myomorph and scuiromorph rodent analgesia studies are reviewed and evaluated for potential clinical application. Differences between laboratory animal studies and clinical use in diseased animals are discussed. Analgesia classes reviewed include local anesthetics, nonsteroidal anti-inflammatories, acetaminophen, opioids, and adjuvants such as anticonvulsants. Routes of administration including sustained-release mechanisms are discussed, as are reversal agents. Drug interactions are reviewed in the context of beneficial multimodal analgesia as well as potential adverse effects. Dosage recommendations for clinical patients are explored.

The Role of miRNAs in Dexmedetomidine's Neuroprotective Effects against Brain Disorders

There are limited neuroprotective strategies for various central nervous system conditions in which fast and sustained management is essential. Neuroprotection-based therapeutics have become an intensively researched topic in the neuroscience field, with multiple novel promising agents, from natural products to mesenchymal stem cells, homing peptides, and nanoparticles-mediated agents, all aiming to significantly provide neuroprotection in experimental and clinical studies. Dexmedetomidine (DEX), an α2 agonist commonly used as an anesthetic adjuvant for sedation and as an opioid-sparing medication, stands out in this context due to its well-established neuroprotective effects. Emerging evidence from preclinical and clinical studies suggested that DEX could be used to protect against cerebral ischemia, traumatic brain injury (TBI), spinal cord injury, neurodegenerative diseases, and postoperative cognitive disorders. MicroRNAs (miRNAs) regulate gene expression at a post-transcriptional level, inhibiting the translation of mRNA into functional proteins. In vivo and in vitro studies deciphered brain-related miRNAs and dysregulated miRNA profiles after several brain disorders, including TBI, ischemic stroke, Alzheimer's disease, and multiple sclerosis, providing emerging new perspectives in neuroprotective therapy by modulating these miRNAs. Experimental studies revealed that some of the neuroprotective effects of DEX are mediated by various miRNAs, counteracting multiple mechanisms in several disease models, such as lipopolysaccharides induced neuroinflammation, β-amyloid induced dysfunction, brain ischemic-reperfusion injury, and anesthesia-induced neurotoxicity models. This review aims to outline the neuroprotective mechanisms of DEX in brain disorders by modulating miRNAs. We address the neuroprotective effects of DEX by targeting miRNAs in modulating ischemic brain injury, ameliorating the neurotoxicity of anesthetics, reducing postoperative cognitive dysfunction, and improving the effects of neurodegenerative diseases.

Analgesic and Sedative Effects of Different Doses of Dexmedetomidine Combined with Butorphanol in Continuous Analgesia after a Cesarean Section

Objective

The present study is designed to study the analgesic and sedative effect of different doses of dexmedetomidine combined with butorphanol in continuous analgesia after a cesarean section.

Methods

A total of 60 puerperae undergoing a cesarean section recruited from a single center were divided into three groups according to the postoperative continuous analgesia protocol: control group (100 mL of normal saline containing 10 µg/kg fentanyl and 0.25 mg of palonosetron, 2 mL/h for continuous analgesia for 48 h), DB1 group (100 mL of normal saline containing 1.0 µg/kg dexmedetomidine, 4 mg of butorphanol, 10 µg/kg fentanyl, and 0.25 mg of palonosetron, 2 mL/h for continuous analgesia for 48 h), and DB2 group (100 mL normal saline containing 2.0 µg/kg dexmedetomidine, 4 mg of butorphanol, 10 µg/kg fentanyl, and 0.25 mg of palonosetron, 2 mL/h for continuous analgesia for 48 h). We compared the blood pressure, heart rate, oxygen saturation, VAS score, Ramsay score, and adverse reactions of puerperae among the three groups after surgery.

Results

The baseline data all have no significant difference in the three groups (p > 0.05). Compared with those in the control group, the systolic blood pressure, diastolic blood pressure, heart rate, and VAS score of the puerperae in the DB1 group and DB2 group were significantly decreased at 6, 24, and 48 h (P < 0.05), while the Ramsay scores of the puerperae in DB1 group and DB2 group were significantly increased at 6, 24, and 48 h (p < 0.05). At the same time, the systolic blood pressure, diastolic blood pressure, heart rate, and VAS score of the puerperae in the DB2 group were significantly lower than those in the DB1 group (P < 0.05), while the Ramsay scores of the puerperae in DB2 group were significantly higher than those in the DB1 group (P < 0.05). Also, there is no significant difference in oxygen saturation and adverse reactions of puerperae among the three groups after surgery (p > 0.05).

Conclusion

Dexmedetomidine combined with butorphanol can improve the analgesic and sedative effects in continuous analgesia after a cesarean section, and the analgesic and sedative effects of dexmedetomidine in the high-dose group are better than those in the low-dose group.

Pharmacokinetics and Pharmacodynamics of Butorphanol and Dexmedetomidine after Intranasal Administration in Broiler Chickens (Gallus gallus domesticus)

Butorphanol and dexmedetomidine (DXM) can produce analgesia in birds. Intranasal (IN) route of drug administration is easier, and free of risks such as pain and tissue damage compared with intravenous, intramuscular or subcutaneous routes in bird species, including wild birds. Although previous studies have demonstrated the use of IN route for producing sedation, no studies are available on the pharmacokinetics and pharmacodynamics of IN drugs in birds. This study analyzed the pharmacokinetics and sedative–analgesic efficacy of intranasal butorphanol (2 mg/kg), dexmedetomidine (80 µg/kg) and their combination (butorphanol, 2 mg/kg; DXM, 80 µg/kg) in healthy, male, Ross broiler chickens (n = 6/group) aged between 6 and 8 weeks. Maximum plasma concentration (Cmax, p = 0.01), area under the plasma concentration-time curve from time zero to 120 min (AUC0 to 120, p = 0.02) and apparent volume of distribution at steady state (Vss, p = 0.02) of DXM were significantly higher than that of DXM co-administered with butorphanol. The mechanical nociceptive thresholds and the sedation scores of DXM group were significantly higher than the baseline value. Dexmedetomidine (80 µg/kg, IN) was effective in chickens, and the drug absorption was more rapid than that of DXM with butorphanol. However, the duration of action of DXM was short. Lower value of Cmax and nociceptive thresholds showed the nonsignificant efficacy of butorphanol at a dose of 2 mg/kg after IN administration in broiler chickens.

Multiple pathways are responsible to the inhibitory effect of butorphanol on OGD/R-induced apoptosis in AC16 cardiomyocytes

Ischemic heart disease is the leading cause of cardiovascular mortality, which is related to cardiac myocyte apoptosis. Butorphanol is an opioid receptor agonist with potential cardioprotective function. The purpose of this work is to explore the function and mechanism of butorphanol in oxygen and glucose deprivation/reperfusion (OGD/R)-induced cardiomyocyte apoptosis. The overlapping targets of ischemic heart disease and butorphanol were analyzed according to GeneCards, ParmMapper, Cytoscape, and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis. Human cardiomyocyte AC16 cells were incubated with butorphanol and then stimulated with OGD/R. Cell injury was investigated by Cell Counting Kit-8, lactate dehydrogenase (LDH) assay kit, TUNEL staining, caspase-3 activity assay kit, and Western blotting. The proteins in signaling pathways were measured using Western blotting. A total of 93 overlapping targets of ischemic heart disease and butorphanol were obtained. Pathway analysis exhibited that these targets might be involved in multiple signaling pathways. Butorphanol alone showed little cytotoxicity to cardiomyocytes, and it protected against OGD/R-induced viability inhibition, LDH release, cell apoptosis, and increase of caspase-3 activity and expression levels of cleaved caspase-3 and Bim. Butorphanol promoted the activation of the phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt)/forkhead box O (FoxO) and hypoxia-inducible factor-1α (HIF-1α)/vascular endothelial growth factor (VEGF) pathways and attenuated the activation of the mitogen-activated protein kinase (MAPK) signaling in OGD/R-treated cardiomyocytes. In conclusion, butorphanol prevents OGD/R-induced cardiomyocyte apoptosis through activating the PI3K/Akt/FoxO and HIF-1α/VEGF pathways and inactivating the MAPK pathway.