Opioid Antagonist Research Articles

Artemisinin and deoxyartemisinin isolated from Artemisia annua L. promote distinct antinociceptive and anti-inflammatory effects in an animal model

Artemisia annua L., known for antimalarial activity, has demonstrated evidence of anti-inflammatory potential. Previously our research group reported the anti-inflammatory and antinociceptive effect of a sesquiterpene lactone-enriched fraction (Lac-FR) obtained from plant, containing artemisinin and deoxyartemisinin. Both the isolated compounds and Lac-FR evaluated on experimental animal models, in the formalin test showed that deoxyartemisinin reduced both neurogenic pain (56.55 %) and inflammatory pain (45.43 %). These findings were superior to the effect of artemisinin (reduction of 28.66 % and 33.35 %, respectively). In the tail flick test, the antinociceptive effect reported as a percentage of the maximum possible effect (%MPE), deoxyartemisinin showed a lower antinociceptive effect (41.57 %) compared to morphine (75.94 %) in 0.5 h. After 1.5 h, the MPE of deoxyartemisinin (87.99 %) exceeded the effect of morphine (47.55 %), without reversal with naloxone. The MPE of artemisinin (23.3 %) observed after 2 h was lower than deoxiartemisinin, without reversal with the opioid antagonist. Lac-FR and artemisinin demonstrated reductions in ear edema of 43.37 % and 48.19 %, respectively, higher than the effect of deoxyartemisinin (33.64 %). Artemisinin reduced tumor necrosis factor alpha (TNF-α) (76.96 %) more selectively when compared to interleukin-1beta (IL-1β) (48.23 %) and interleukin-6 (IL-6) (44.49 %). Lac-FR showed greater selectivity in IL-6 reduction (56.49 %) in relationship to TNF-α (46.71 %) and IL-1β (45.12 %), whereas deoxyartemisinin selectively reduced TNF-α (37.37 %). The results of our study indicate that the lactones isolated did not have relationship with the opioid system. Deoxyartemisinin showed a higher antinociceptive potential than artemisinin. Whereas, artemisinin showed a higher reduction of inflammation and mediators, with a better anti-inflammatory activity outcome.

Effects of chronic naltrexone treatment on relapse-related behavior and neural responses to fentanyl in awake nonhuman primates.

Naltrexone, an opioid antagonist that blocks the reinforcing properties of opioid agonists, is often prescribed to preclude relapse to opioid use disorder (OUD) following detoxification. However, few laboratory studies have directly investigated the ability of naltrexone to alter relapse-inducing effects of opioid agonists, including their priming strength in reinstatement studies and their impact in brain regions known to be involved in drug-induced reinforcement in MRI studies. Here we directly address this issue by investigating the effects of continuous exposure to naltrexone on 1) fentanyl-induced reinstatement of drug-seeking behavior, 2) fentanyl-induced patterns of blood oxygenation level dependent (BOLD) activation in the nucleus accumbens (NAcc), and 3) fentanyl-induced changes in NAcc functional connectivity (FC) in awake non-human primates that are engaged in ongoing opioid self-administration studies. We found that naltrexone antagonizes the priming strength of fentanyl as shown by a rightward shift in its reinstatement dose-effect curve and that naltrexone surmountably antagonizes the BOLD response induced by fentanyl. However, while naltrexone also countered fentanyl's effects on NAcc FC, the effects were not surmounted by a higher dose of fentanyl. Together, these data suggest that, in contrast to naltrexone's modulation of fentanyl's effects on behavior and BOLD responses, their interactive effects on FC between multiple brain regions do not reflect their receptor-mediated activity. Additionally, we demonstrated opposing effects in the absence and presence of naltrexone on NAcc FC at baseline (i.e., in the absence of any fentanyl prime) suggesting that naltrexone alters FC at baseline, even though naltrexone appears behaviorally silent in the absence of an agonist prime. Together these data provide additional insight into ways in which naltrexone interacts with opioid agonists, both behaviorally and in the brain. Further understanding the effects of opioid agonists on patterns of FC could help elucidate our understanding of the neural processes that contribute to the initiation of and relapse to opioid-seeking behavior in OUD.

Sustained fentanyl exposure inhibits neuronal activity in dissociated striatal neuronal-glial cocultures through actions independent of opioid receptors.

Besides having high potency and efficacy at the µ-opioid (MOR) and other opioid receptor types, fentanyl has some affinity for some adrenergic receptor types, which may underlie its unique pathophysiological differences from typical opioids. To better understand the unique actions of fentanyl, we assessed the extent to which fentanyl alters striatal medium spiny neuron (MSN) activity via opioid receptors or α1-adrenoceptors in dopamine type 1 or type 2 receptor (D1 or D2)-expressing MSNs. In neuronal and mixed-glial cocultures from the striatum, acute fentanyl (100 nM) exposure decreased the frequency of spontaneous action potentials. Overnight exposure of cocultures to 100 nM fentanyl severely reduced the proportion of MSNs with spontaneous action potentials, which was unaffected by coexposure to the opioid receptor antagonist naloxone (10 µM) but fully negated by coadministering the pan-α1-adrenoceptor inverse agonist prazosin (100 nM) and partially reversed by the selective α1A-adrenoceptor antagonist RS 100329 (300 nM). Acute fentanyl (100 nM) exposure modestly reduced the frequency of action potentials and caused firing rate adaptations in D2, but not D1, MSNs. Prolonged (2-5 h) fentanyl (100 nM) application dramatically attenuated firing rates in both D1 and D2 MSNs. To identify possible cellular sites of α1-adrenoceptor action, α1-adrenoceptors were localized in subpopulations of striatal astroglia and neurons by immunocytochemistry and Adra1a mRNA by in situ hybridization in astrocytes. Thus, sustained fentanyl exposure can inhibit striatal MSN activity via a nonopioid receptor-dependent pathway, which may be modulated via complex actions in α1-adrenoceptor-expressing striatal neurons and/or glia.NEW & NOTEWORTHY Acute fentanyl exposure attenuated the activity of striatal medium spiny neurons (MSNs) in vitro and in dopamine D2, but not D1, receptor-expressing MSNs in ex vivo slices. By contrast, sustained fentanyl exposure suppressed the spontaneous activity of MSNs cocultured with glia through a nonopioid receptor-dependent mechanism modulated, in part, by α1-adrenoceptors. Fentanyl exposure can affect striatal function via a nonopioid receptor mechanism of action that appears mediated by α1-adrenoreceptor-expressing striatal neurons and/or astroglia.

Off-Label Use of Lamotrigine and Naltrexone in the Treatment of Ketamine Use Disorder: A Case Report.

Ketamine is a dissociative anesthetic increasingly utilized in United States medical settings for the treatment of mental health conditions. Additionally, it is increasingly used in nonmedical settings for its dissociative properties. While nonmedical ketamine use and ketamine use disorder (KUD) have been observed internationally, KUD, and approaches to its treatment, have not been previously described in the US. We present the case of a 32-year-old man with KUD who experienced severe cravings despite receipt of residential and intensive outpatient substance use disorder treatment. He resumed use after an initial period of abstinence and was subsequently started on lamotrigine and naltrexone for treatment of depressive symptoms and cravings. This combination altered his experience while on ketamine, resulting in nausea and decreased hallucinogenic effects. In addition, it substantially decreased his cravings, aiding him in achieving longer-term abstinence in combination with receipt of dialectical behavioral therapy, familial support, and involvement in 12-step programming. KUD is a poorly described condition that may become more prevalent as US ketamine use increases. Combining treatment of depressive symptoms and cravings, in this case with lamotrigine and naltrexone, may be a promising pharmacotherapeutic strategy. Lamotrigine, an antiepileptic with glutamate modulating effects, has been utilized to decrease cravings in a variety of substance use disorders. Naltrexone is an opioid antagonist approved for alcohol use disorder and opioid use disorder and is used off-label for stimulant use disorder. This combination offers a possible pharmacotherapeutic option for KUD with more research needed to further evaluate.

Abstract We092: Naltrindole Attenuates Superoxide Release in Polymorphonuclear Leukocytes by a Novel Mechanism devoid of Delta opioid receptor antagonism Related to Reduced Intracellular Calcium Levels

Introduction: Naltrindole (NTI), known as a delta opioid receptor antagonist, inhibited phorbol 12-myristate 13-acetate (PMA) induced superoxide (SO) release in polymorphonuclear leukocytes (PMNs). PMNs do not express opioid receptors. We propose NTI reduces PMN SO by reducing intracellular calcium (Ca 2+ ). To test this hypothesis, we did experiments using KB-R7943 (KB) as a positive control, known to reduce intracellular Ca 2+ via inhibition of the reverse mode Na + /Ca 2+ exchanger. Naloxone (NX), a broad-spectrum opioid receptor antagonist, was used as a negative control. We predict that NTI will diminish PMA-induced PMN SO release similar to KB, while NX will have no effect, and that there will be no difference in cell viability compared to vehicle controls. Methods: Male Sprague Dawley (SD) rat PMNs (5x10 6 ) were incubated for 15 min at 37 o C in the presence or absence (dH 2 O vehicle control) of NTI (10 - 200 µM), KB (5-20 µM), and NX (100-200 µM). PMN SO release was measured by the change in absorbance at 550 nm over 420 sec via ferricytochrome c reduction after PMA stimulation (100 nM). The cell viability was determined microscopically by 0.2% trypan blue exclusion at the end of PMN SO release assay. Data were analyzed using ANOVA Fisher’s PLSD post-hoc test. Results: NTI significantly decreased PMN SO release at 200 μM (n=10, 0.196±0.06, p<0.05) compared to vehicle control (n=22, 0.731±0.07) or NX 100/200 μM (n=3, 0.593±0.06), and NTI at 100 μM (n=7, 0.461±0.08, p<0.05) versus vehicle control. Likewise, KB significantly decreased PMN SO release at 20 μM (n=7, 0.507±0.07), 10 μM (n=7, 0.552±0.07), and 5 μM (n=5, 0.615±0.11) compared to vehicle control (n=10, 0.908±0.07). Cell viability was statistically similar (80-90±5%) among all study groups. Conclusion: NTI (10-200 μM) and KB (5-20 µM) exhibited concentration-dependent effects in reducing PMN SO release without compromising cell viability. The results suggest that the novel effect of NTI maybe mediated through a reduction in intracellular Ca 2+ and independent of delta opioid receptor antagonism. These results are consistent with the effects of NTI, KB and NX in myocardial ischemia/reperfusion injuries. Future studies will assess the effects of NTI on ROS attenuation in human umbilical vein endothelial cells.

Exploring the analgesic potential of isorhamnetin: insights from formalin-induced pain and diabetic neuropathy models.

Isorhamnetin, a naturally occurring flavonoid compound, holds paramount importance as a primary constituent within several medicinal plants, exhibiting profound pharmacological significance. The aim of this study is to investigate the pain-relieving attributes of isorhamnetin in murine models through both formalin-induced pain and diabetic neuropathy scenarios. To achieve our objective, isorhamnetin was orally administered to mice at varying dosage levels (10 to 100 mg/kg). Pain-related behaviors were assessed using the formalin test during its secondary phase. Additionally, the potential pain-alleviating effect of isorhamnetin was evaluated in a diabetic neuropathy model induced by streptozotocin. Additionally, we carried out advanced interventions using naloxone, which is a well-known antagonist of opioid receptors, yohimbine, which blocks α2-adrenergic receptors, and methysergide, which inhibits serotonergic receptors, during the formalin test. The oral intake of isorhamnetin showed a decrease in behaviors associated with pain that was proportional to the dose observed during the second phase of the formalin test when induced by formalin. In the diabetic neuropathy model, isorhamnetin administration effectively reversed the reduced pain threshold observed. Notably, naloxone, the opioid receptor antagonist, effectively counteracted the pain-relieving effect produced by isorhamnetin in the formalin test, whereas yohimbine and methysergide did not yield similar outcomes. Isorhamnetin also led to a reduction in elevated spinal cyclic adenosine monophosphate (cAMP) response element binding protein (CREB) levels triggered by formalin, with this effect reversed by pre-treatment with naloxone. The compound also suppressed heightened spinal phosphorylated CREB (p-CREB) levels caused by diabetic neuropathy. This research determined that isorhamnetin has notable abilities to relieve pain in models of formalin-induced pain and diabetic neuropathy. The pain-relieving mechanism of isorhamnetin in the formalin-induced pain model seems to be connected to the activation of spinal opioid receptors and the adjustment of CREB protein amounts. This insight improves our knowledge of how isorhamnetin could be used therapeutically to treat pain conditions stemming from formalin-induced pain and diabetic neuropathy.

A novel cinnamic and caffeic acid-conjugated peptide analogs with anticonvulsant and analgesic potency: Comparative analyses of trans/cis isomers.

The novel cinnamic acid (CA) (H4-CA, H5-CA, and H7-CA) and caffeic acid (KA) (H4-KA, H5-KA, and H7-KA) hemorphin analogs have recently been synthesized and their trans isomers have been tested for antiseizure and antinociceptive activity. In the present study, the cis forms of these compounds were tested and compared with their trans isomers in seizure and nociception tests in mice. The cis-H5-CA and H7-CA compounds showed efficacy against psychomotor seizures, whereas the trans isomers were ineffective. Both the cis and trans KA isomers were ineffective in the 6-Hz test. In the maximal electroshock (MES) test, the cis isomers showed superior antiseizure activity to the trans forms of CA and KA conjugates, respectively. The suppression of seizure propagation by cis-H5-CA and the cis-H5-KA was reversed by a kappa opioid receptor (KOR) antagonist. Naloxone and naltrindole were not effective. The cis-isomers of CA conjugates and cis-H7-KA produced significantly stronger antinociceptive effects than their trans-isomers. The cis-H5-CA antinociception was blocked by naloxone in the acute phase and by naloxone and KOR antagonists in the inflammatory phase of the formalin test. The antinociception of the KA conjugates was not abolished by opioid receptor blockade. None of the tested conjugates affected the thermal nociceptive threshold. The results of the docking analysis also suggest a model-specific mechanism related to the activity of the cis-isomers of CA and KA conjugates in relation to opioid receptors. Our findings pave the way for the further development of novel opioid-related antiseizure and antinociceptive therapeutics.

Discriminative stimulus properties of two training doses of gabapentin in rats: Substitution by pregabalin, diazepam, and pentobarbital.

Gabapentin is used for the treatment of many conditions, including seizures, pain, and anxiety. Increasing reports of nonprescribed use suggest that gabapentin may elicit positive subjective effects. The present study was conducted to examine the subjective effects of gabapentin using rats trained to discriminate either a 30.0 mg/kg or 300.0 mg/kg dose of gabapentin versus vehicle on a two-choice drug discrimination task. Both doses of gabapentin were established as discriminative stimuli, and the 300.0 mg/kg dose was more readily established compared to the 30.0 mg/kg dose. Full substitution (> 80% gabapentin-lever responding) occurred by the training drug and by the gabapentinoid compound pregabalin. Partial substitution (> 20% gabapentin-lever responding) was shown by the opioid compounds morphine and fentanyl, and dose combinations of the opioid receptor antagonist naltrexone with the gabapentin training doses reduced the percentage of gabapentin-lever responding to below 80%. Partial substitution for both training doses of gabapentin occurred with the cannabinoid Δ⁹-tetrahydrocannabinol. The barbiturate compound pentobarbital and the benzodiazepine compound diazepam were only tested for substitution for the 300.0 mg/kg dose of gabapentin and these compounds produced full substitution. These findings demonstrate that gabapentin establishes a robust discriminative cue and exhibits stimulus effects closely similar to pregabalin, pentobarbital, and diazepam. Since pregabalin, pentobarbital, and diazepam carry a risk of problematic use and are classified as controlled substances, further evaluations of gabapentin's risks in this regard are warranted. (PsycInfo Database Record (c) 2024 APA, all rights reserved).

Opioid Use and the Risk of Ventricular Arrhythmias: A Systematic Review and Meta-Analysis.

The association between opioid use and the risk of ventricular arrhythmias (VA) is poorly understood. The objective of this study was to synthesize the evidence on the risk of VA associated with opioid use. We systematically searched the Cochrane Library, Embase, MEDLINE, and CINAHL databases in July 2022. Risk of bias was assessed using the Cochrane risk for bias tool for randomized controlled trials (RCTs) and ROBINS-I for observational studies. Certainty of evidence was assessed using GRADE. We included 15 studies (12 observational, 2 post hoc analyses of RCTs, 1 RCT). Most studies focused on opioid use for maintenance therapy (n = 9), comparing methadone to buprenorphine (n = 13), and reported QTc prolongation (n = 13). Six observational studies had a critical risk of bias, and one RCT was at high risk of bias. Two studies could not be included in the meta-analysis as they reported a different outcome and studied an opioid antagonist. Meta-analysis of 13 studies indicated that the use of methadone was associated with an increased risk of VA compared to the use of buprenorphine, morphine, placebo, or levacetylmethadol (risk ratio [RR], 2.39; 95% CI, 1.31-4.35; I2 = 60%). The pooled estimate varied greatly between observational studies (RR, 2.12; 95% CI, 1.15-3.91; I2 = 62%) and RCTs (RR, 14.09; 95% CI, 1.52-130.61; I2 = 0%), but both indicated an increased risk. In this systematic review and meta-analysis, we found that methadone use is associated with more than twice the risk of VA compared to comparators. However, our findings should be interpreted cautiously given the limited quality of the available evidence.

Buprenorphine/naloxone – one formulation that doesn’t fit all: a case report

BackgroundSublingual buprenorphine, approved for treatment of opioid use disorder since 2002, is most commonly available in co-formulation with naloxone. Naloxone is an opioid antagonist minimally absorbed when sublingual (SL) buprenorphine/naloxone is taken as prescribed; it is thought to reduce potential for misuse via intravenous administration. However, growing data and clinical experience demonstrate that previously accepted assumptions about the pharmacokinetics of these medications may not apply to all patients.Case presentationWe present a patient whose adverse post-administration side effects on SL buprenorphine/naloxone resolved with transition to SL buprenorphine monoproduct.DiscussionNaloxone can be detected in nearly all patients taking SL buprenorphine/naloxone, though with apparent variability in clinical effect. In a minority of patients, naloxone can contribute to adverse and potentially treatment-limiting side effects. Furthermore, the naloxone component is commonly misunderstood by patients and providers and can foster mistrust in the therapeutic relationship if providers are perceived to be withholding a more tolerable formulation. Prescribers should have a low threshold to offer buprenorphine alone when clinically appropriate.

Effects of Intranasal Naloxone on Hypoglycemia-Associated Autonomic Failure (HAAF) in Susceptible Individuals.

Hypoglycemia-associated autonomic failure (HAAF), defined as blunting of counter-regulatory hormone and symptom responses to recurrent hypoglycemia, remains a therapeutic challenge in diabetes treatment. The opioid system may play a role in HAAF pathogenesis since activation of opioid receptors induces HAAF. Blockade of opioid receptors with intravenous naloxone ameliorates HAAF experimentally, yet is not feasible therapeutically. To investigate the effects of opioid receptor blockade with intranasal naloxone on experimentally-induced HAAF. Randomized, double-blinded, placebo-controlled crossover study. Academic research center. Healthy non-diabetic volunteers. Paired two-day studies, 5-10 weeks apart, each consisting of three consecutive hypoglycemic episodes (hyperinsulinemic hypoglycemic clamps, glucose nadir: 54 mg/dL): two on day 1 with administration of intranasal naloxone vs. placebo, followed by the third episode on day 2. Differences in counter-regulatory hormones responses and hypoglycemia symptoms between first and third hypoglycemic episodes in naloxone vs. placebo studies. Out of 17 participants, 9 developed HAAF, confirming variable inter-individual susceptibility. Among participants susceptible to HAAF, naloxone maintained some hormonal and symptomatic responses to hypoglycemia and prevented the associated requirement for increased glucose infusion. Unexpectedly, naloxone reduced plasma epinephrine and growth hormone responses to the first hypoglycemic episode but prevented further reduction with subsequent hypoglycemia. This is the first study to report that intranasal naloxone, a widely used opioid receptor antagonist, may ameliorate some features of HAAF. Further investigation is warranted into mechanisms of variable inter-individual susceptibility to HAAF and the effects of intranasal naloxone in people with diabetes at risk for HAAF.

Endogenous opioid antagonism and the insulin response to oral glucose load in kidney failure patients: a randomized clinical trial.

Endogenous opioid antagonism and the insulin response to oral glucose load in kidney failure patients: a randomized clinical trial.

Evaluating drug withdrawal syndrome risks through food and drug administration adverse event reporting system: a comprehensive disproportionality analysis.

The study aims to identify the drugs associated with drug withdrawal syndrome in the Food and Drug Administration Adverse Event Reporting System (FAERS) and estimate their risks of causing withdrawal syndrome. All the data were collected from FAERS from the first quarter of 2004 to the third quarter of 2023. Disproportionality analyses of odds ratio (ROR) and proportional reported ratio were conducted to identify potential adverse effects signal of drug withdrawal syndrome. A total of 94,370 reports related to withdrawal syndrome from the data. The top 50 drugs with most frequency reported were analyzed, and 29 exhibited a positive signal based on the number of reports. The top three categories of drugs with positive signals included opioids, antidepressant drugs and antianxiety drugs. Other classifications included opioid antagonist, muscle relaxant, antiepileptic drugs, analgesics, hypnotic sedative drugs and antipsychotic drugs. Our analysis of FAERS data yielded a comprehensive list of drugs associated with withdrawal syndrome. This information is vital for healthcare professionals, including doctors and pharmacists, as it aids in better recognition and management of withdrawal symptoms in patients undergoing treatment with these medications.

Aticaprant, a kappa opioid receptor antagonist, and the recovered 'interest and pleasure' in the concept of major depressive disorder.

Lack of positive mood and anhedonia probably are the most specific depressive symptoms. Anhedonia is a multifaceted concept: the clinical language describes anticipatory/consummatory anhedonia and sensory/social anhedonia while the cognitive neuroscience language describes readiness for reward, energy expenditure to attain reward, updating reward presence and value. Mounting evidence supports the potential of kappa-opioid receptor (KOR) antagonists as novel pharmacotherapies for major depressive disorder : aticaprant is a potent, selective, short-acting KOR antagonist. The fast-fail approach evaluated the impact of aticaprant on the brain circuitry hypothesized to mediate anhedonia and significantly increased fMRI activation in the ventral striatal activation during reward anticipation as compared to placebo; the aticaprant induced changes in the self-reported psychological measures of anhedonia were rather inconsistent. The recently reported results of a phase 2a randomized, double-blind, placebo-controlled trial investigating the efficacy and safety of aticaprant, co-administered to an oral SSRI/SNRI antidepressant in depressed patients who had an inadequate response to 1 or 2 antidepressants. The improvement from baseline favoured the co-administration of aticaprant over the co-administration of placebo at all time points (during 6 weeks), and this was confirmed by higher response rates with aticaprant. A mid-split of patients with higher or lower than median anhedonia also showed that the patients with higher baseline anhedonia had the largest decrease on the MADRS. Tolerability and safety were reassuring. These promising results of the co-administration of aticaprant to an SSRI/SNRI in depressed patients with prominent anhedonia support he further investigation of aticaprant in larger trials.

Perioperative Naltrexone Management: A Scoping Review by the Perioperative Pain and Addiction Interdisciplinary Network.

Substance use disorders, including alcohol use disorder, are a public health concern that affect more than 150 million people globally. The opioid antagonist naltrexone is being increasingly prescribed to treat opioid use disorder, alcohol use disorder, and chronic pain. Perioperative management of patients on naltrexone is inconsistent and remains a controversial topic, with mismanagement posing a significant risk to the long-term health of these patients. This scoping review was conducted to identify human studies in which the perioperative management of naltrexone was described. This review includes a systematic literature search involving Medline, Medline In-Process, Embase, PsycINFO, and Web of Science. Seventeen articles that describe perioperative naltrexone management strategies were included, including thirteen guidelines, one case report, and three randomized trials. Despite its use in patients with alcohol use disorder and chronic pain, no clinical studies, case reports, or guidelines addressed naltrexone use in these clinical populations. All of the guideline documents recommended the preoperative cessation of naltrexone, irrespective of dose, indication, or route of administration. None of these guideline documents were designed on the basis of a systematic literature search or a Delphi protocol. As described by the primary studies, perioperative pain relief varied depending on naltrexone dose and route of administration, time since last naltrexone administration, and underlying substance use disorder. None of the studies commented on the maintenance of recovery for the patient's substance use disorder in the context of perioperative naltrexone management. The current understanding of the risks and benefits of continuing or stopping naltrexone perioperatively is limited by a lack of high-quality evidence. In patients with risk factors for return to use of opioids or alcohol, the discontinuation of naltrexone should have a strong rationale. Future studies and guidelines should seek to address both acute pain management and maintaining recovery when discussing perioperative naltrexone management strategies.

Exploring the antinociceptive potential of homoeriodictyol in nociception models

Context: Homoeriodictyol is a flavonoid with known antioxidant, anti-inflammatory, and anti-tumor properties found in various plants. However, its potential analgesic effects have not been explored. Aims: To investigate the pain-relieving properties of homoeriodictyol using different mouse models of nociception. Methods: Various doses of homoeriodictyol (50, 100, 150, and 200 µg/kg) were administered to mice and evaluated using the acetic acid-induced writhing test, the hot plate test, and the formalin-induced paw licking assay. These effects were compared with those of mice treated with acetylsalicylic acid or morphine, both with and without naloxone, an opioid receptor antagonist. Additionally, capsaicin- and glutamate-induced paw-licking tests were conducted to assess the involvement of the vanilloid and glutamatergic systems, respectively. Results: Homoeriodictyol demonstrated a significant and dose-dependent reduction in nociceptive behavior in the acetic acid-induced writhing test, achieving a 52.4% inhibition at a dose of 200 µg/kg. It also substantially increased the latency period in response to the hot plate test (65.8% at 200 µg/kg) and significantly suppressed both the neurogenic and inflammatory phases in the formalin-induced paw-licking test. Notably, the effects of homoeriodictyol in the hot plate test and formalin-induced paw-licking test were significantly reversed by naloxone. Furthermore, homoeriodictyol effectively reduced neurogenic nociception induced by intraplantar injections of glutamate and capsaicin (57.8% and 76.9%, respectively, at a dose of 200 µg/kg). Conclusions: This study concludes that homoeriodictyol exhibits antinociceptive activity in mice, acting through both central and peripheral pathways.

Leveraging the Electronic Medical Record in C. difficile Diagnostic Stewardship

Background: Clostridioides difficile PCR is extremely sensitive but cannot differentiate colonization versus active disease. Over diagnosis of C. difficile infection (CDI) has negative consequences including overuse of antibiotics targeting C. difficile, increased hospital-acquired (HA)-CDI rates, and increased healthcare costs. We describe the implementation of a Clinical Decision Support tool embedded in the C. difficile order and the result on testing, HA-CDI rates and healthcare costs. Methods: The C. difficile order was updated in June 2023 with 4 dynamic questions that reflex if specific criteria are identified in the electronic medical record in the prior 24 hours: less than 3 loose stools documented, receipt of laxative, opioid antagonist, oral contrast, or tube feed initiation. If any criteria are identified, an embedded alert triggers and the provider must choose “yes, high clinical suspicion” or “no (exit and cancel order)” in addition to providing an order indication. All inpatient C. difficile tests were reviewed from July 1 to Sept 30, 2022 (pre-update) and July 1 to Sept 30, 2023 (post-update). An order rate was calculated per 10,000 patient days as well as HA-CDI rate. Cost analysis was completed using direct lab costs and published costs of $35,000 per HA-CDI. Results of the order questions were reviewed post-update. Incident rate comparison was completed using medcalc. Results: Pre-update, 1147 tests were conducted, with an order rate of 104.3. Post-update, 919 tests were performed, with an order rate of 86.6. The positivity rate was 16.1% pre-update and 14.7% post-update. The incidence rate difference was 0.00177 (P 15 (145, 16%). 166 (18%) patients who received laxatives (18 positive, positivity rate 11%) were still tested. Conclusion: Implementation of a dynamic order led to a significant reduction in the total number of C. difficile PCR tests performed with associated reduction in HA-CDI and cost savings. Despite this, patients receiving laxatives were still being tested for C. difficile, highlighting the need for ongoing education and feedback. These results support the use of dynamic ordering for diagnostic stewardship, which can benefit both patients and hospitals.

Molecular docking, molecular dynamics simulation, preparation, and characterization of naltrexone-phospholipid complex: A novel cargo with improved loading into multivesicular liposomes

Naltrexone hydrochloride (NTX), a water-soluble opioid receptor antagonist, is prescribed widely for opioid and alcohol dependence and pain reduction. However, the significant limitations of NTX are low lipophilicity and extensive first-pass metabolism. This study aimed to design and prepare a novel phospholipid complex of NTX and load it into multivesicular liposomes (MVLs). In silico studies, including molecular docking and molecular dynamics (MD) simulation, were performed to determine the interactions between NTX and phospholipid and evaluate their best molar ratio to prepare the complex, respectively. The NTX phospholipid complex was prepared by solvent evaporation technique and characterized by PXRD, SEM, FTIR, 1HNMR, solubility study, and n-octanol/water partition coefficient analyses. NTX-SPC complex-loaded MVLs (NTX-SPC-MVLs) were prepared by the double-emulsion method and characterized by encapsulation efficiency (EE)%, size, PXRD, FTIR, SEM, and release pattern. MD simulation reported the 1:1.5 M ratio of NTX to phospholipid as the best molar ratio. Complexation led to reduced water solubility and enhanced n-octanol/water partition coefficient. Loading of NTX-SPC complex into MVLs enhanced EE and extended the release duration in comparison to NTX MVLs. Thus, the NTX-SPC complex may be an appropriate system to enhance the physicochemical features of NTX and improve the EE in vesicular drug delivery systems like MVLs.

A single exposure to the predator odor 2,4,5-trimethylthiazoline causes long-lasting affective behavioral changes in female mice: Modulation by kappa opioid receptor signaling

The volatile compound 2,4,5-trimethylthiazoline (TMT, a synthetic predator scent) triggers fear, anxiety, and defensive responses in rodents that can outlast the encounter. The receptor systems underlying the development and persistence of TMT-induced behavioral changes remain poorly characterized, especially in females. Kappa opioid receptors regulate threat generalization and fear conditioning and alter basal anxiety, but their role in unconditioned fear responses in females has not been examined. Here, we investigated the effects of the long-lasting kappa opioid receptor antagonist, nor-binalthorphinmine dihydrochloride (nor-BNI; 10mg/kg), on TMT-induced freezing and conditioned place aversion in female mice. We also measured anxiety-like behavior in the elevated plus maze three days after TMT and freezing behavior when returned to the TMT-paired context ten days after the single exposure. We found that 35μl of 10% TMT elicited a robust freezing response during a five-minute exposure in female mice. TMT evoked persistent fear as measured by conditioned place aversion, reduced entries into the open arm of the elevated plus maze, and increased general freezing behavior long after TMT exposure. In line with the known role of kappa-opioid receptors in threat generalization, we found that kappa-opioid receptor antagonism increased basal freezing but reduced freezing during TMT presentation. Together, these findings indicate that a single exposure to TMT causes long-lasting changes in fear-related behavioral responses in female mice and highlights the modulatory role of kappa-opioid receptor signaling on fear-related behavioral patterns in females.

Assessment of antinociceptive property of Cynara scolymus L. and possible mechanism of action in the formalin and writhing models of nociception in mice.

Cynara scolymus has bioactive constituents and has been used for therapeutic actions. The present study was undertaken to investigate the mechanisms underlying pain-relieving effects of the hydroethanolic extract of C. scolymus (HECS). The antinociceptive activity of HECS was assessed through formalin and acetic acid-induced writhing tests at doses of 50, 100 and 200 mg/kg intraperitoneally. Additionally, naloxone (non-selective opioid receptors antagonist, 2 mg/kg), atropine (non-selective muscarinic receptors antagonist, 1 mg/kg), chlorpheniramine (histamine HH1-receptor antagonist, 20 mg/kg), cimetidine (histamine H2-receptor antagonist, 12.5 mg/kg), flumazenil (GABAA/BDZ receptor antagonist, 5 mg/kg) and cyproheptadine (serotonin receptor antagonist, 4 mg/kg) were used to determine the systis implicated in HECS-induced analgesia. Impact of HECS on locomotor activity was executed by open-field test. Determination of total phenolic content (TPC) and total flavonoid content (TFC) was done. Evaluation of antioxidant activity was conducted iploying 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging assay. HECS (50, 100 and 200 mg/kg) significantly indicated dose dependent antinociceptive activity against pain-related behavior induced by formalin and acetic acid (P < 0.001). Pretreatment with naloxone, atropine and flumazenil significantly reversed HECS-induced analgesia. Antinociceptive effect of HECS riained unaffected by chlorpheniramine, cimetidine and cyproheptadine. Locomotor activity was not affected by HECS. TPC and TFC of HECS were 59.49 ± 5.57 mgGAE/g dry extract and 93.39 ± 17.16 mgRE/g dry extract, respectively. DPPH free radical scavenging activity (IC50) of HECS was 161.32 ± 0.03 μg/mL. HECS possesses antinociceptive activity which is mediated via opioidergic, cholinergic and GABAergic pathways.