Precipitated opioid withdrawal in a patient started on olanzapine/samidorphan.

BACKGROUND: Olanzapine/Samidorphan (Lybalvi®) is a novel oral agent for the treatment of schizophrenia and bipolar I disorder. It was designed to reduce weight gain associated with olanzapine. Samidorphan is an analog of naltrexone, initially intended to treat substance use disorders by antagonizing mu, delta, and kappa opioid receptors. CASE REPORT: We present the case of a 36-year-old who took their first dose of olanzapine/samidorphan shortly before calling for emergency services. The patient took diphenhydramine and an epinephrine autoinjector for what they thought was an allergic reaction but continued to have symptoms. EMS reported involuntary muscle movements thought to be due to dystonia from olanzapine. In the ED, they experienced generalized muscle spasms lasting for several seconds and diaphoresis. Initially, the staff treated for a presumed dystonic reaction to olanzapine and administered diphenhydramine 25 mg IV, diazepam 2 mg IV, midazolam 5 mg IV, and benztropine 1 mg IV without improvement. It was later determined that the patient took 16 mg of buprenorphine SL daily. With this information, precipitated opioid withdrawal was felt to be the likely cause of symptoms. The patient received 16 mg of buprenorphine for an initial Clinical Opiate Withdrawal Scale (COWS) score of 11 with repeat COWS of 6. Why should an emergency physician be aware of this? Initiating olanzapine/samidorphan in the setting of chronic opioid therapy may result in precipitated opioid withdrawal. Additional SL buprenorphine may be a reasonable treatment modality.

Pharmacological prevention and treatment of opioid-induced constipation in cancer patients: A systematic review and meta-analysis.

BACKGROUND: Cancer-related pain often requires opioid treatment with opioid-induced constipation (OIC) as its most frequent gastrointestinal side-effect. Both for prevention and treatment of OIC osmotic (e.g. polyethylene glycol) and stimulant (e.g. bisacodyl) laxatives are widely used. Newer drugs such as the peripherally acting µ-opioid receptor antagonists (PAMORAs) and naloxone in a fixed combination with oxycodone have become available for the management of OIC. This systematic review and meta-analysis aims to give an overview of the scientific evidence on pharmacological strategies for the prevention and treatment of OIC in cancer patients. METHODS: A systematic search in PubMed, Embase, Web of Science and the Cochrane Library was completed from inception up to 22 October 2022. Randomized and non-randomized studies were systematically selected. Bowel function and adverse drug events were assessed. RESULTS: Twenty trials (prevention: five RCTs and three cohort studies; treatment: ten RCTs and two comparative cohort studies) were included in the review. Regarding the prevention of OIC, three RCTs compared laxatives with other laxatives, finding no clear differences in effectivity of the laxatives used. One cohort study showed a significant benefit of magnesium oxide compared with no laxative. One RCT found a significant benefit for the PAMORA naldemedine compared with magnesium oxide. Preventive use of oxycodone/naloxone did not show a significant difference in two out of three other studies compared to oxycodone or fentanyl. A meta-analysis was not possible. Regarding the treatment of OIC, two RCTs compared laxatives, of which one RCT found that polyethylene glycol was significantly more effective than sennosides. Seven studies compared an opioid antagonist (naloxone, methylnaltrexone or naldemedine) with placebo and three studies compared different dosages of opioid antagonists. These studies with opioid antagonists were used for the meta-analysis. Oxycodone/naloxone showed a significant improvement in Bowel Function Index compared to oxycodone with laxatives (MD -13.68; 95 % CI -18.38 to -8.98; I2 = 58 %). Adverse drug event rates were similar amongst both groups, except for nausea in favour of oxycodone/naloxone (RR 0.51; 95 % CI 0.31-0.83; I2 = 0 %). Naldemedine (NAL) and methylnaltrexone (MNTX) demonstrated significantly higher response rates compared to placebo (NAL: RR 2.07, 95 % CI 1.64-2.61, I2 = 0 %; MNTX: RR 3.83, 95 % CI 2.81-5.22, I2 = 0 %). With regard to adverse events, abdominal pain was more present in treatment with methylnaltrexone and diarrhea was significantly more present in treatment with naldemedine. Different dosages of methylnaltrexone were not significantly different with regard to both efficacy and adverse drug event rates. CONCLUSIONS: Magnesium oxide and naldemedine are most likely effective for prevention of OIC in cancer patients. Naloxone in a fixed combination with oxycodone, naldemedine and methylnaltrexone effectively treat OIC in cancer patients with acceptable adverse events. However, their effect has not been compared to standard (osmotic and stimulant) laxatives. More studies comparing standard laxatives with each other and with opioid antagonists are necessary before recommendations for clinical practice can be made.

Efficacy and safety of naldemedine for opioid-induced constipation in older patients with cancer: a retrospective study.

BACKGROUND: Opioids are pain relievers that are often associated with opioid-induced constipation (OIC) that worsens with age. We performed a multicenter, retrospective analysis on the efficacy and safety of naldemedine, an opioid receptor antagonist, in treating OIC in patients with cancer (age >75 years). METHODS: The electronic medical records of cancer patients who received naldemedine at 10 Japanese institutions between 7 June 2017 and August 31, 2019, were retrieved. Patients aged ≥75 years who were treated with naldemedine for the first time and hospitalized for at least 7 days before and after initiating naldemedine therapy were included in this analysis. RESULTS: Sixty patients were observed for at least 7 days before and after starting naldemedine. The response rate was 68.3%, and the frequency of bowel movements increased significantly after naldemedine administration in the overall population ( P  < 0.0001) and among those who defecated <3 times/week before naldemedine administration ( P  < 0.0001). Diarrhea was the most frequent adverse event in all grades, observed in 45% of patients, of which 92.6% were Grade 1 or 2. Grade 4 or higher adverse events, including death, were not observed. CONCLUSION: Naldemedine exhibits significant efficacy and safety in OIC treatment in older patients with cancer.

TAAR1 agonist ulotaront delays gastric emptying of solids in patients with schizophrenia and concurrent metabolic syndrome with prediabetes.

BACKGROUND: Metabolic syndrome (MetS), which can be induced or exacerbated by the current class of antipsychotic drugs, is highly prevalent in patients with schizophrenia and presents significant challenges to lifetime disease management. Supported by initial clinical results, trace amine-associated receptor 1 (TAAR1) agonists have emerged as potential novel treatments for schizophrenia. Notably, non-clinical studies have also shown weight-lowering and glucoregulatory effects of TAAR1 agonists, including the investigational agent ulotaront. However, the translatability of these findings to humans has not been adequately assessed. Given that delayed gastric emptying (GE) was identified as a potential mechanism contributing to the metabolic benefits of TAAR1 agonists in rodents, the aim of this study was to evaluate the effect of ulotaront on GE in patients with schizophrenia and concurrent MetS with prediabetes. METHODS: Patients with schizophrenia were randomized to receive a single oral dose of ulotaront (150 mg) and their previous antipsychotic (PA) in an open-label, crossover, two-sequence design (NCT05402111). Eligible participants fulfilled at least three of five MetS criteria and had prediabetes defined by elevated glycated haemoglobin (5.7-6.4%) and/or fasting homeostatic model assessment of insulin resistance (i.e. ≥2.22). Following an overnight fast and 4 h post-dose, participants ingested a 99mTc-sulphur colloid radiolabelled egg meal (320 kcal, 30% fat). GE was measured by scintigraphy over 4 h. Endpoints included GE of solids half-time (T1/2) and percentage gastric retention at 1, 2 and 4 h. RESULTS: Thirty-one adults were randomized and 27 completed the study. Ulotaront significantly delayed GE of solids [median GE T1/2 ulotaront at 139 min (119, 182) vs. the participant's PA of 124 min (109, 132), p = .006]. A significant increase in gastric retention was seen in the ulotaront versus the PA group at 1 h (80% vs. 75%, p = .015), 2 h (61% vs. 50%, p = .023) and 4 h (17% vs. 7%, p = .002) post-meal. CONCLUSION: Ulotaront delayed the GE of solids in patients with schizophrenia and concurrent MetS with prediabetes. Additional studies are needed to assess whether treatment with TAAR1 agonists is associated with weight loss and glucoregulatory improvement.

Duration of the preemptive analgesic effects of low- and high-frequency transcutaneous electrical nerve stimulation in rats with acute inflammatory pain.

Transcutaneous electrical nerve stimulation (TENS) activates various pathways to induce antinociceptive effects, based on the frequencies used. This study evaluates the preemptive analgesic effects and their duration of low- (LT: 4 Hz) and high-frequency TENS (HT: 100 Hz) using a rat model of acute inflammatory pain. Acute inflammation was induced by injecting 1% formalin into the hind paws of rats. LT or HT was applied for 30 min before formalin injection. Pain-related behaviors, such as licking, flinching, and lifting, were recorded for 60 min postinjection. Immunohistochemistry was used to assess the number of phosphorylated extracellular signal-regulated kinase (pERK)- and c-fos-positive cells in the spinal cord. Naloxone, a µ-opioid receptors (MORs) antagonist, and naltrindole, a δ-opioid receptors (DORs) antagonist, were administered before TENS application. Pain behavior duration and pERK- and c-fos-positive cell expression were then measured. LT and HT pretreatment significantly reduced both pain behaviors and the number of pERK- and c-fos-positive cells postformalin injection. Naloxone and naltrindole partially reversed the effects of LT and HT, respectively. Notably, HT's analgesic effect lasted up to 120 min whereas that of LT persisted for 90 min. LT and HT effectively exerted their preemptive analgesic effects on acute inflammatory pain by inhibiting pERK and c-fos expression in the spinal cord. HT presented a longer-lasting effect compared to LT. MOR and DOR activation may contribute to LT and HT's analgesic mechanisms, respectively.

Stronger, longer, better opioid antagonists? Nalmefene is NOT a naloxone replacement.

The fatal overdose crisis claims nearly 200 lives daily in the United States (U.S). Evolutions in the illicit drug supply, such as the addition of sedative adulterants and a shift to synthetic opioids such as fentanyl, have driven increasing rates of both fatal and non-fatal overdose. Specifically, synthetic opioid usage of fentanyl was implicated in 68 % of the U.S. drug overdose deaths in 2022 alone. This has placed tremendous burden on communities, emergency medical services, and healthcare systems, and contributed to tragedy and grief both in the U.S. and worldwide. Despite the availability of effective opioid antagonist medications and standards of care, there has been increased interest in research and development of alternative opioid overdose reversal agents by the National Institutes of Health (NIH) in partnership with pharmaceutical manufacturers over the last decade. The U.S. Food and Drug Administration (FDA) recently approved nalmefene (Opvee) a mu-opioid receptor antagonist that boasts an extended half-life and stronger mu-receptor affinity compared to the standard of care use of naloxone for opioid reversal. In this article, we explore the medical need and ramifications of the introduction of longer-acting opioid antagonists in the current opioid overdose landscape. Existing data highlight the effectiveness of already available naloxone products as a safe and effective standard of care. These data support the notion that stronger, longer-acting agents may be unnecessary, and their existence may cause undue harm, such as more severe and/or prolonged withdrawal symptoms, lead to challenging patient interactions, and complicate the initiation of medications for opioid use disorder. More evidence is needed before healthcare professionals should implement the use of stronger, longer-acting opioid antagonists for reversing opioid overdose over evidence-based, cost-effective naloxone.

The Management of Opioid-Induced Constipation in Cancer and Advanced Illness: A Meta-Analysis.

CONTEXT: Constipation is a common problem among patients with cancer. By some accounts, about 60% of cancer patients experience constipation. There is limited empirical evidence of the clinical effectiveness of pharmacologic agents in opioid-induced constipation in advanced diseases. OBJECTIVES: We sought to quantitatively summarize the therapeutic effectiveness of the pharmacologic means of managing opioid-induced constipation. METHODS: Randomized control trials (RCTs) identified from medical literature databases that reported quantitative measures of the effect of pharmacotherapeutic agents to treat opioid induced constipation in patients with cancers and other advanced illnesses were included in this study. A conventional random effects meta-analysis was conducted including >3 trials with the same exposure and outcome assessed, and a network-meta-analysis was conducted for all placebo-controlled trials. RESULTS: Eighteen studies that examined the effect of various pharmacotherapeutic agents were included. The medications were Methylnatrexone (N = 5), Naldemedine (N = 5), other conventional agents (N = 4) and herbal medicines (N = 4). In conventional meta-analysis, methylnaltrexone increased the proportion achieving rescue-free laxation by 2.68 fold (95% CI: 1.34, 5.37; P = 0.0054) within 4 hours of the administration compared to placebo. In network meta-analysis, the pooled RR of the pharmacotherapeutic agents on rescue-free bowel movements as 2.26 (95% CI: 1.52, 3.36) for methylnaltrexone, 1.58 (95% CI: 0.94, 2.66) for naldemedine, and 0.74 (95% CI: 0.45, 1.23) for polyethylene glycol, compared to placebo. CONCLUSION: Methylnatrexone and Naldemedine have currently shown promise in randomized trials concerning opioid-induced constipation in cancer and advanced illness. It is imperative that future research ascertain not just the relative therapeutic efficacy but also the cost-benefit analyses of these newer regimens with more commonly used and accessible laxatives.

The safety and efficacy of methylnaltrexone in pediatric oncology patients: A single center experience.

INTRODUCTION: Peripherally acting µ-opioid receptor antagonists (PAMORAs) are used in the treatment of opioid induced constipation without impacting the actions of opioid analgesics. Subcutaneous methylnaltrexone was one of the first PAMORAs approved in April 2008 for the treatment of opioid induced constipation in adult patients. The safety and effectiveness of methylnaltrexone has not been established in pediatric patients. In this study, the use of subcutaneous methylnaltrexone in pediatric patients is analyzed and reviewed. The primary outcome is occurrence of a bowel movement within 24 h after methylnaltrexone (MNTX) administration and the number of bowel movements following treatment with methylnaltrexone. Secondary outcomes include safety in this patient cohort. METHODS: This is a retrospective study of 79 pediatric patients with opioid induced constipation. Patients were administered methylnaltrexone during their inpatient stay. Data on bowel activity after methylnaltrexone was obtained from the hospital information system. RESULTS: Out of the 79 patients who received methylnaltrexone, there were seven patients from whom data could not be analyzed. Of the 72 patients whose data was available, 38% (N = 27) were documented as having a bowel movement, 62% (N = 45) did not have a bowel movement. Reported adverse events were minimal with nausea (N = 3), vomiting (N = 1), and flatulence (N = 6). CONCLUSION: Methylnaltrexone appears safe in the pediatric population and produces bowel movements in more than a third of pediatric patients. It is a feasible and safe option for opioid induced constipation in pediatric patients.

A Retrospective Study of the Efficacy and Safety of Naldemedine for Treatment of Opioid-Induced Constipation in Patients with Hepatobiliary Pancreatic Cancer.

Background and Objectives: Opioid analgesics, which are used for cancer-related pain management, cause opioid-induced constipation (OIC). Naldemedine, a peripheral opioid receptor antagonist, is an OIC-modifying agent, but no focused efficacy and safety analysis has been conducted for its use in hepatobiliary pancreatic cancers. We performed a multi-institutional study on the efficacy and safety of naldemedine in patients with hepatobiliary pancreatic cancer using opioids in clinical practice. Materials and Methods: We retrospectively evaluated patients with hepatobiliary pancreatic cancer (including liver, biliary tract, and pancreatic cancers) treated with opioids and naldemedine during hospitalization at ten institutions in Japan from June 2017 to August 2019. We assessed the frequency of bowel movements before and after the initiation of naldemedine therapy. Responders were defined as patients who defecated ≥3 times/week, with an increase from a baseline of ≥1 defecations/week over seven days after the initiation of naldemedine administration. Results: Thirty-four patients were observed for one week before and one week after starting naldemedine. The frequency of bowel movements increased by one over the baseline frequency or to at least thrice per week in 21 patients. The response rate was 61.7% (95% confidence interval: 45.4-78.0%). The median number of weekly bowel movements before and after naldemedine treatment was 2 (range: 0-9) and 6 (range: 1-17), respectively, in the overall population (n = 34); the increase in the number of bowel movements following naldemedine administration was statistically significant (Wilcoxon signed-rank test, p < 0.0001). Diarrhea was the predominant gastrointestinal symptom, and 10 (29.4%) patients experienced grade 1, grade 2, or grade 3 adverse events. The only other adverse event included fatigue in one patient; grade 2-4 adverse events were absent. Conclusions: Naldemedine is effective, and its use may be safe in clinical practice for patients with hepatobiliary pancreatic cancer receiving opioid analgesics.

Effect of Sufentanil Combined with Nalmefene Assisted Surface Anesthesia on Transnasal Endotracheal Intubation Guided by Fiberoptic Bronchoscope.

In order to study the clinical effect of sufentanil combined with nalmefene in fiberoptic bronchoscopy tracheal intubation in airway patients, a method based on sufentanil combined with nalmefene-assisted topical anesthesia for fiberoptic bronchoscopy-guided nasotracheal intubation method is proposed. This method retrospectively analyzed 100 patients with difficult airways who underwent fiberoptic bronchoscope tracheal intubation in the Central Hospital from January 2021 to November 2021. The analysis results showed that compared with the control group, the patients in the study group had a significantly lower cough score, a higher Ramsay sedation score, a lower mean arterial pressure, and a lower number of patients with hypoxia (P < 0.05). There was no significant difference in postoperative hoarseness and sore throat between the two groups. Sufentanil combined with nalmefene has a better anesthesia effect and higher safety for bronchofiberscope intubation in patients with difficult airways.

Mu-opioid antagonists for opioid-induced bowel dysfunction in people with cancer and people receiving palliative care.

BACKGROUND: Opioid-induced bowel dysfunction (OIBD) is characterised by constipation, incomplete evacuation, bloating, and gastric reflux. It is one of the major adverse events (AEs) of treatment for pain in cancer and palliative care, resulting in increased morbidity and reduced quality of life. This review is a partial update of a 2008 review, and critiques as previous update (2018) trials only for people with cancer and people receiving palliative care. OBJECTIVES: To assess for OIBD in people with cancer and people receiving palliative care the effectiveness and safety of mu-opioid antagonists (MOAs) versus different doses of MOAs, alternative pharmacological/non-pharmacological interventions, placebo, or no treatment. SEARCH METHODS: We searched CENTRAL, MEDLINE, Embase, CINAHL, and Web of Science (December 2021), clinical trial registries and regulatory websites. We sought contact with MOA manufacturers for further data. SELECTION CRITERIA: Randomised controlled trials (RCTs) assessing the effectiveness and safety of MOAs for OIBD in people with cancer and people at a palliative stage irrespective of the type of terminal disease. DATA COLLECTION AND ANALYSIS: Two review authors assessed risk of bias and extracted data. The appropriateness of combining data from the trials depended upon sufficient homogeneity across trials. Our primary outcomes were laxation response, effect on analgesia, and AEs. We assessed the certainty of evidence using GRADE and created summary of findings tables. MAIN RESULTS: We included 10 studies (two new trials) randomising in-total 1343 adults with cancer irrespective of stage, or at palliative care stage of any disease. The MOAs were oral naldemedine and naloxone (alone or in combination with oxycodone), and subcutaneous methylnaltrexone. The trials compared MOAs with placebo, MOAs at different doses, or in combination with other drugs. Two trials of naldemedine and three of naloxone with oxycodone were in people with cancer irrespective of disease stage. The trial on naloxone alone was in people with advanced cancer. Four trials on methylnaltrexone were in palliative care where most participants had advanced cancer. All trials were vulnerable to biases; most commonly, blinding of the outcome assessor was not reported.  Oral naldemedine versus placebo Risk (i.e. chance) of spontaneous laxations in the medium term (over two weeks) for naldemedine was over threefold greater risk ratio (RR) 2.00, 95% confidence interval (CI) 1.59 to 2.52, 2 trials, 418 participants, I² = 0%. Number needed to treat for an additional beneficial outcome (NNTB) 3, 95% CI 3 to 4; moderate-certainty evidence). Earlier risk of spontaneous laxations and patient assessment of bowel change was not reported. Very low-certainty evidence showed naldemedine had little to no effect on opioid withdrawal symptoms. There was little to no difference in the risk of serious (non-fatal) AEs (RR 3.34, 95% CI 0.85 to 13.15: low-certainty evidence). Over double the risk of AEs (non-serious) reported with naldemedine (moderate-certainty evidence). Low-dose oral naldemedine versus higher dose Risk of spontaneous laxations was lower for the lower dose (medium term, 0.1 mg versus 0.4 mg: RR 0.69, 95% CI 0.53 to 0.89, 1 trial, 111 participants (low-certainty evidence)). Earlier risk of spontaneous laxations and patient assessment of bowel change not reported. Low-certainty evidence showed little to no difference on opioid withdrawal symptoms (0.1 mg versus 0.4 mg mean difference (MD) -0.30, 95% CI -0.85 to 0.25), and occurrences of serious AEs (0.1 mg versus 0.4 mg RR 0.25, 95% CI 0.03 to 2.17). Low-certainty evidence showed little to no difference on non-serious AEs. Oral naloxone versus placebo Risk of spontaneous laxations and AEs not reported. Little to no difference in pain intensity (very low-certainty evidence). Full data not given. The trial reported that no serious AEs occurred. Oral naloxone + oxycodone versus oxycodone Risk of spontaneous laxations within 24 hours and in the medium term not reported. Low-certainty evidence showed naloxone with oxycodone reduced the risk of opioid withdrawal symptoms. There was little to no difference in the risk of serious (non-fatal) AEs (RR 0.68, 95% CI 0.44 to 1.06), 3 trials, 362 participants, I² = 55%: very low-certainty evidence). There was little to no difference in risk of AEs (low-certainty evidence).  Subcutaneous methylnaltrexone versus placebo Risk of spontaneous laxations within 24 hours with methylnaltrexone was fourfold greater than placebo (RR 2.97, 95% CI 2.13 to 4.13. 2 trials, 287 participants, I² = 31%. NNTB 3, 95% CI 2 to 3; low-certainty evidence). Risk of spontaneous laxations in the medium term was over tenfold greater with methylnaltrexone (RR 8.15, 95% CI 4.76 to 13.95, 2 trials, 305 participants, I² = 47%. NNTB 2, 95% CI 2 to 2; moderate-certainty evidence). Low-certainty evidence showed methylnaltrexone reduced the risk of opioid withdrawal symptoms, and did not increase risk of a serious AE (RR 0.59, 95% CI 0.38 to 0.93. I² = 0%; 2 trials, 364 participants). The risk of AEs was higher for methylnaltrexone (low-certainty evidence). Lower-dose subcutaneous methylnaltrexone versus higher dose There was little to no difference in risk of spontaneous laxations in the medium-term (1 mg versus 5 mg or greater: RR 2.91, 95% CI 0.82 to 10.39; 1 trial, 26 participants very low-certainty evidence), or in patient assessment of improvement in bowel status (RR 0.98, 95% CI 0.71 to 1.35, 1 trial, 102 participants; low-certainty evidence). Medium-term assessment of spontaneous laxations and serious AEs not reported. There was little to no difference in symptoms of opioid withdrawal (MD -0.25, 95% CI -0.84 to 0.34, 1 trial, 102 participants) or occurrence of AEs (low-certainty evidence). AUTHORS' CONCLUSIONS: This update's findings for naldemedine and naloxone with oxycodone have been strengthened with two new trials, but conclusions have not changed. Moderate-certainty evidence for oral naldemedine on risk of spontaneous laxations and non-serious AEs suggests in people with cancer that naldemedine may improve bowel function over two weeks and increase the risk of AEs. There was low-certainty evidence on serious AEs. Moderate-certainty evidence for methylnaltrexone on spontaneous laxations over two weeks suggests subcutaneous methylnaltrexone may improve bowel function in people receiving palliative care, but certainty of evidence for AEs was low. More trials are needed, more evaluation of AEs, outcomes patients rate as important, and in children.

14-3-3γ mediates the long-term inhibition of peripheral kappa opioid receptor antinociceptive signaling by norbinaltorphimine.

Long-term inhibition of kappa opioid receptor (KOR) signaling in peripheral pain-sensing neurons is a potential obstacle for development of peripherally-restricted KOR agonists that produce analgesia. Such a long-term inhibitory mechanism is invoked from activation of c-Jun N-terminal kinase (JNK) that follows a single injection of the KOR antagonist norbinaltorphimine (norBNI). This effect requires protein synthesis of an unknown mediator in peripheral pain-sensing neurons. Using 2D difference gel electrophoresis with tandem mass spectrometry, we have identified that the scaffolding protein 14-3-3γ is upregulated in peripheral sensory neurons following activation of JNK with norBNI. Knockdown of 14-3-3γ by siRNA eliminates the long-term reduction in KOR-mediated cAMP signaling by norBNI in peripheral sensory neurons in culture. Similarly, knockdown of 14-3-3γ in the rat hind paw abolished the norBNI-mediated long-term reduction in peripheral KOR-mediated antinociception. Further, overexpression of 14-3-3γ in KOR expressing CHO cells prevented KOR-mediated inhibition of cAMP signaling. These long-term effects are selective for KOR as heterologous regulation of other receptor systems was not observed. These data suggest that 14-3-3γ is both necessary and sufficient for the long-term inhibition of KOR by norBNI in peripheral sensory neurons.

Possible mechanism for improving the endogenous immune system through the blockade of peripheral µ-opioid receptors by treatment with naldemedine.

BACKGROUND: It has been considered that activation of peripheral µ-opioid receptors (MORs) induces side effects of opioids. In this study, we investigated the possible improvement of the immune system in tumour-bearing mice by systemic administration of the peripheral MOR antagonist naldemedine. METHODS: The inhibitory effect of naldemedine on MOR-mediated signalling was tested by cAMP inhibition and ß-arrestin recruitment assays using cultured cells. We assessed possible changes in tumour progression and the number of splenic lymphocytes in tumour-bearing mice under the repeated oral administration of naldemedine. RESULTS: Treatment with naldemedine produced a dose-dependent inhibition of both the decrease in the cAMP level and the increase in ß-arrestin recruitment induced by the MOR agonists. Repeated treatment with naldemedine at a dose that reversed the morphine-induced inhibition of gastrointestinal transport, but not antinociception, significantly decreased tumour volume and prolonged survival in tumour-transplanted mice. Naldemedine administration significantly decreased the increased expression of immune checkpoint-related genes and recovered the decreased level of toll-like receptor 4 in splenic lymphocytes in tumour-bearing mice. CONCLUSIONS: The blockade of peripheral MOR may induce an anti-tumour effect through the recovery of T-cell exhaustion and promotion of the tumour-killing system.

OREX-1038: a potential new treatment for pain with low abuse liability and limited adverse effects.

Drugs targeting mu opioid receptors are the mainstay of clinical practice for treating moderate-to-severe pain. While they can offer excellent analgesia, their use can be limited by adverse effects, including constipation, respiratory depression, tolerance, and abuse liability. Multifunctional ligands acting at mu opioid and nociceptin/orphanin FQ peptide receptors might provide antinociception with substantially improved adverse-effect profiles. This study explored one of these ligands, OREX-1038 (BU10038), in several assays in rodents and nonhuman primates. Binding and functional studies confirmed OREX-1038 to be a low-efficacy agonist at mu opioid and nociceptin/orphanin FQ peptide receptors and an antagonist at delta and kappa opioid receptors with selectivity for opioid receptors over other proteins. OREX-1038 had long-acting antinociceptive effects in postsurgical and complete Freund's adjuvant (CFA)-induced thermal hyperalgesia assays in rats and a warm water tail-withdrawal assay in monkeys. OREX-1038 was active for at least 24 h in each antinociception assay, and its effects in monkeys did not diminish over 22 days of daily administration. This activity was coupled with limited effects on physiological signs (arterial pressure, heart rate, and body temperature) and no evidence of withdrawal after administration of naltrexone or discontinuation of treatment in monkeys receiving OREX-1038 daily. Over a range of doses, OREX-1038 was only transiently self-administered, which diminished rapidly to nonsignificant levels; overall, both OREX-1038 and buprenorphine maintained less responding than remifentanil. These results support the concept of dual mu and nociceptin/orphanin FQ peptide receptor partial agonists having improved pharmacological profiles compared with opioids currently used to treat pain.

Samidorphan for the treatment of weight gain associated with olanzapine in patients with schizophrenia and bipolar disorder.

INTRODUCTION: Olanzapine (OLZ) is one of the most effective antipsychotic agents, however, its clinical utility has been limited by weight gain. Samidorphan (SAM) is a µ-opioid receptor antagonist and it can reduce the weight gain associated with OLZ. A combination of OLZ and SAM (OLZ/SAM) has been developed to provide the antipsychotic efficacy of OLZ, while mitigating OLZ-associated weight gain. AREAS COVERED: A comprehensive literature search was conducted in PubMed. Key search terms included SAM and weight gain associated with OLZ. The pharmacological action, clinical efficacy, and safety of SAM were reviewed. EXPERT OPINION: OLZ can lead to weight gain. SAM is a new drug that acts as an opioid receptor antagonist that can decrease weight gain. SAM mitigates OLZ-associated weight gain while preserving the antipsychotic efficacy of OLZ. Clinical trials have confirmed that OLZ/SAM significantly improved psychotic symptoms, and resulted in significantly less weight gain than OLZ. OLZ/SAM was well tolerated. Therefore, it is a potential new treatment option for schizophrenia.