Insights into opioid action in the intestinal tract

The efficacy and safety of difelikefalin for pruritus in hemodialysis patients: a systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Chronic kidney disease-associated pruritus (CKD-ap) is a common complication that negatively affects the quality of life. Difelikefalin has emerged as a novel FDA-approved drug to manage CKD-ap. This systematic review and meta-analysis will assess the efficacy and safety of Difelikefalin versus placebo to manage CKD-ap.

METHODS

PubMed, Scopus, WOS, Central, and Embase were systematically searched until November 2023. RevMan was used to perform meta-analysis. Quality assessment was conducted using the Cochrane RoB 2.0 tool. Results were reported as risk ratio (RR) and mean difference (MD) with a 95% confidence interval (CI). PROSPERO ID: (CRD42023485979).

RESULTS

Five RCTs with a total of 896 participants were included. Difelikefalin significantly decreased the weekly mean WI-NRS score (MD: -0.99 [-1.22, -0.75], p ˂ .00001), 5-D itch scale total score (MD: -1.51 [-2.26, -0.76], p > .0001), and Skindex-10 total score (MD: -7.39 [-12.51, -2.28], p = .005), but showed significantly higher adverse events (RR: 1.26 [1.03, 1.55], p = .03), versus placebo. However, there was no significant difference between both groups in serious adverse events (RR: 1.42 [0.78, 2.57], p = .25) or death (RR: 0.81 [0.19, 3.34], p = .77).

CONCLUSION

Difelikefalin appears to be a promising agent for the management of CKD-induced pruritus in patients with end-stage renal disease. However, evidence is still underpowered due to the paucity of the current data; therefore, more robust RCTs are required to confirm the benefit of Difelikefalin.

Effects of opium tincture on gastrointestinal function and motility in healthy volunteers: A magnetic resonance imaging study

BACKGROUND

Opioids inhibit motility and secretion of the gut and have been used for antidiarrheal treatment for centuries. However, the underlying mechanisms of opium tincture are not evident.

AIM

To investigate the effects of opium tincture on gastrointestinal motility, intestinal volumes, and water content of different gut segments assessed by magnetic resonance imaging (MRI).

METHODS

Twenty healthy volunteers were included in a randomized, placebo-controlled, crossover study of 9 days of treatment with 30 drops of opium tincture per day. MRI was performed on day 1 (before treatment) and day 9 (during treatment). Measurements included assessments of gastric volume, gastric emptying, gastric motility, small bowel volume, small bowel water content, small bowel motility, colon volume, colon water content, and whole gut transit.

KEY RESULTS

Opium tincture delayed gastric emptying by a mean difference of 5.6 min [95% CI: 1.8-9.4], p = 0.004, and increased postprandial gastric meal volume (17-21%, p = 0.02). Small bowel endpoints did not change. Opium tincture delayed whole gut transit time (p = 0.027) and increased ascending colon volume by 59 mL [95% CI: 15-103], p = 0.004, and transverse colon volume by 48 mL [95% CI: 4-92], p = 0.027. T1-relaxation time of the descending colon chyme was decreased during opium treatment, indicating dryer feces (difference: -173 ms [95% CI: -336 -11], p = 0.03).

CONCLUSION AND INFERENCES

Opium tincture induced changes in the stomach and colon in healthy volunteers. An improved understanding of how opioids affect gut functions may lead to a better understanding and optimized management of diarrhea.

Differential impact of fentanyl and morphine doses on ticagrelor-induced platelet inhibition in ST-segment elevation myocardial infarction: a subgroup analysis from the PERSEUS randomized trial

Introduction

Among patients with ST-segment elevation myocardial infarction (STEMI) treated with primary percutaneous coronary intervention (PCI), intravenous fentanyl does not enhance ticagrelor-induced platelet inhibition within 2 h compared to morphine. The impact of the total dose of fentanyl and morphine received on ticagrelor pharmacodynamic and pharmacokinetic responses in patients with STEMI remains however undetermined.

Materials and methods

We performed a post-hoc subanalysis of the prospective, open-label, single-center, randomized PERSEUS trial (NCT02531165) that compared treatment with intravenous fentanyl vs. morphine among symptomatic patients with STEMI treated with primary PCI after ticagrelor pretreatment. Patients from the same population as PERSEUS were further stratified according to the total dose of intravenous opioids received. The primary outcome was platelet reactivity using P2Y12 reaction units (PRU) at 2 h following administration of a loading dose (LD) of ticagrelor. Secondary outcomes were platelet reactivity and peak plasma levels of ticagrelor and AR-C124910XX, its active metabolite, at up to 12 h after ticagrelor LD administration. Generalized linear models for repeated measures were built to determine the relationship between raw and weight-weighted doses of fentanyl and morphine.

Results

38 patients with STEMI were included between December 18, 2015, and June 22, 2017. Baseline clinical and procedural characteristics were similar between low- and high-dose opioid subgroups. At 2 h, there was a significant correlation between PRU and both raw [regression coefficient (B), 0.51; 95% confidence interval (CI), 0.02-0.99; p = 0.043] and weight-weighted (B, 0.54; 95% CI, 0.49-0.59; p < 0.001) doses of fentanyl, but not morphine. Median PRU at 2 h was significantly lower in patients receiving low, as compared to high, doses of fentanyl [147; interquartile range (IQR), 63-202; vs. 255; IQR, 183-274; p = 0.028], whereas no significant difference was found in those receiving morphine (217; IQR, 165-266; vs. 237; IQR, 165-269; p = 0.09). At 2 h, weight-weighted doses of fentanyl and morphine were significantly correlated to plasma levels of ticagrelor and AR-C124910XX.

Conclusion

In symptomatic patients with STEMI who underwent primary PCI after ticagrelor pretreatment and who received intravenous opioids, we found a dose-dependent relationship between the administration of intravenous fentanyl, but not morphine, and ticagrelor-induced platelet inhibition.

The impact of opioid administration on the incidence of postanaesthetic colic in horses

Effective management of postoperative pain is essential to ensure patient welfare, reduce morbidity and optimize recovery. Opioids are effective in managing moderate to severe pain in horses but concerns over their adverse effects on gastrointestinal (GI) motility and associated increased colic risk limit their widespread use. Studies investigating the impact of systemic opioids on both GI motility and colic incidence in horses have yielded inconclusive outcomes. Therefore, this retrospective study aims to assess the influence of systemic administration of butorphanol, morphine, and methadone on post-anaesthetic colic (PAC) incidence. Horses undergoing general anaesthesia for non-gastrointestinal procedures that were hospitalized for at least 72 h post-anaesthesia were included in this study. Anaesthetised horses were stratified by procedure type into horses undergoing diagnostic imaging without surgical intervention, emergency or elective surgery. In addition, patients were grouped by opioid treatment regime into horses receiving no opioids, intraanaesthetic, short- (<24 h) or long-term (>24 h) postoperative opioids. Administered opioids encompassed butorphanol, morphine and methadone. The number of horses showing signs of colic in the 72 h after anaesthesia was assessed for each group. A total of 782 horses were included, comprising 659 undergoing surgical procedures and 123 undergoing diagnostic imaging. The overall PAC incidence was 15.1%. Notably, horses undergoing diagnostic imaging without surgery had a significantly lower PAC rate of 6.5% compared to those undergoing surgery (16.7%, p = 0.0146). Emergency surgeries had a significantly lower PAC rate of 5.8% compared to elective procedures (18%, p = 0.0113). Of the 782 horses, 740 received intraoperative opioids and 204 postoperative opioids, 102 of which long-term (≥24 h). Neither intraoperative (p = 0.4243) nor short-term postoperative opioids (p = 0.5744) increased PAC rates. Notably, only the long-term (≥24 h) administration of morphine significantly increased PAC incidence to 34% (p = 0.0038). In contrast, long-term butorphanol (5.3% PAC, p = 0.8482) and methadone (18.4% PAC, p = 0.6161) did not affect PAC rates. In summary, extended morphine administration was the only opioid treatment associated with a significantly increased risk of PAC.

Anti-diarrheal effect of piperine possibly through the interaction with inflammation inducing enzymes: In vivo and in silico studies

Piperine is a natural alkaloid that possesses a variety of therapeutic properties, including anti-inflammatory, antioxidant, antibacterial, and anticarcinogenic activities. The present study aims to assess the medicinal benefits of piperine as an anti-diarrheal agent in a chick model by utilizing in vivo and in silico techniques. For this, castor oil was administered orally to 2-day-old chicks to cause diarrhea. Bismuth subsalicylate (10 mg/kg), loperamide (3 mg/kg), and nifedipine (2.5 mg/kg) were used as positive controls, while the vehicle was utilized as a negative control. Two different doses (25 and 50 mg/kg b.w.) of the test sample (piperine) were administered orally, and the highest dose was tested with standards to investigate the synergistic activity of the test sample. In our findings, piperine prolonged the latent period while reducing the number of diarrheal feces in the experimental chicks during the monitoring period (4 h). At higher doses, piperine appears to reduce diarrheal secretion while increasing latency in chicks. Throughout the combined pharmacotherapy, piperine outperformed bismuth subsalicylate and nifedipine in terms of anti-diarrheal effects with loperamide. In molecular docking, piperine exhibited higher binding affinities towards different inflammatory enzymes such as cyclooxygenase 1 (-7.9 kcal/mol), cyclooxygenase 2 (-8.4 kcal/mol), nitric oxide synthases (-8.9 kcal/mol), and L-type calcium channel (-8.8 kcal/mol), indicating better interaction of PP with these proteins. In conclusion, piperine showed a potent anti-diarrheal effect in castor oil-induced diarrheal chicks by suppressing the inflammation and calcium ion influx induced by castor oil.

Central glucagon-like peptide 1 receptor activation inhibits Toll-like receptor agonist-induced inflammation

Glucagon-like peptide-1 receptor agonists (GLP-1RAs) exert anti-inflammatory effects relevant to the chronic complications of type 2 diabetes. Although GLP-1RAs attenuate T cell-mediated gut and systemic inflammation directly through the gut intraepithelial lymphocyte GLP-1R, how GLP-1RAs inhibit systemic inflammation in the absence of widespread immune expression of the GLP-1R remains uncertain. Here, we show that GLP-1R activation attenuates the induction of plasma tumor necrosis factor alpha (TNF-α) by multiple Toll-like receptor agonists. These actions are not mediated by hematopoietic or endothelial GLP-1Rs but require central neuronal GLP-1Rs. In a cecal slurry model of polymicrobial sepsis, GLP-1RAs similarly require neuronal GLP-1Rs to attenuate detrimental responses associated with sepsis, including sickness, hypothermia, systemic inflammation, and lung injury. Mechanistically, GLP-1R activation leads to reduced TNF-α via α1-adrenergic, δ-opioid, and κ-opioid receptor signaling. These data extend emerging concepts of brain-immune networks and posit a new gut-brain GLP-1R axis for suppression of peripheral inflammation.

Insights into the Current and Possible Future Use of Opioid Antagonists in Relation to Opioid-Induced Constipation and Dysbiosis

Opioid receptor agonists, particularly those that activate µ-opioid receptors (MORs), are essential analgesic agents for acute or chronic mild to severe pain treatment. However, their use has raised concerns including, among others, intestinal dysbiosis. In addition, growing data on constipation-evoked intestinal dysbiosis have been reported. Opioid-induced constipation (OIC) creates an obstacle to continuing treatment with opioid analgesics. When non-opioid therapies fail to overcome the OIC, opioid antagonists with peripheral, fast first-pass metabolism, and gastrointestinal localized effects remain the drug of choice for OIC, which are discussed here. At first glance, their use seems to only be restricted to constipation, however, recent data on OIC-related dysbiosis and its contribution to the appearance of several opioid side effects has garnered a great of attention from researchers. Peripheral MORs have also been considered as a future target for opioid analgesics with limited central side effects. The properties of MOR antagonists counteracting OIC, and with limited influence on central and possibly peripheral MOR-mediated antinociception, will be highlighted. A new concept is also proposed for developing gut-selective MOR antagonists to treat or restore OIC while keeping peripheral antinociception unaffected. The impact of opioid antagonists on OIC in relation to changes in the gut microbiome is included.

A pharmacologically pre-contracted smooth muscle bowel model for the study of highly-potent opioid receptor agonists and antagonists

Isolated organ models are a versatile tool for pharmacological and toxicological research. Small bowel has been used to assess the inhibition of smooth muscle contraction by opioids. In the present study, we set out to establish a pharmacologically stimulated rat bowel model. The effects of carfentanil, remifentanil and the new synthetic opioid U-48800 and their respective antagonists naloxone, nalmefene and naltrexone were studied in a small bowel model in rats. The IC₅₀ values of the tested opioids were as follows: carfentanil (IC₅₀ = 0.02 µmol/L, CI 0.02-0.03 µmol/L) ≫ remifentanil (IC₅₀ = 0.51 µmol/L, CI 0.40-0.66 µmol/L) ≫ U-48800 (IC₅₀ = 1.36 µmol/L, CI 1.20-1.54 µmol/L). The administration of the opioid receptor antagonists naloxone, naltrexone and nalmefene led to progressive, parallel rightward shifts of the dose-response curves. Naltrexone was most potent in antagonizing the effects of U-48800, whereas naltrexone and nalmefene were most effective in antagonizing the effects of carfentanil. In summary, the current model seems to be a robust tool to study opioid effects in a small bowel model without the necessity of using electrical stimulation.

Determination of Region-Specific Roles of the M3 Muscarinic Acetylcholine Receptor in Gastrointestinal Motility

BACKGROUND

The specific role of the M₃ muscarinic acetylcholine receptor in gastrointestinal motility under physiological conditions is unclear, due to a lack of subtype-selective compounds.

AIMS

The objective of this study was to determine the region-specific role of the M₃ receptor in gastrointestinal motility.

METHODS

We developed a novel positive allosteric modulator (PAM) for the M₃ receptor, PAM-369. The effects of PAM-369 on the carbachol-induced contractile response of porcine esophageal smooth muscle and mouse colonic smooth muscle (ex vivo) and on the transit in mouse small intestine and rat colon (in vivo) were examined.

RESULTS

PAM-369 selectively potentiated the M₃ receptor under the stimulation of its orthosteric ligands without agonistic or antagonistic activity. Half-maximal effective concentrations of PAM activity for human, mouse, and rat M₃ receptors were 0.253, 0.345, and 0.127 μM, respectively. PAM-369 enhanced carbachol-induced contraction in porcine esophageal smooth muscle and mouse colonic smooth muscle without causing any contractile responses by itself. The oral administration of 30 mg/kg PAM-369 increased the small intestinal transit in both normal motility and loperamide-induced intestinal dysmotility mice but had no effects on the colonic transit, although the M₃ receptor mRNA expression is higher in the colon than in the small intestine.

CONCLUSIONS

This study provided the first direct evidence that the M₃ receptor has different region-specific roles in the motility function between the small intestine and colon in physiological and pathophysiological contexts. Selective PAMs designed for targeted subtypes of muscarinic receptors are useful for elucidating the subtype-specific function.

Naloxone Versus Methylnaltrexone for Opioid-Induced Constipation in Critically Ill Patients

Background:

Opioid-induced constipation (OIC) may occur in up to 81% of critically ill patients and can lead to many complications. Opioid antagonists are a reasonable approach and may be used for managing OIC.

Objective:

The purpose of this study was to assess the efficacy of enteral naloxone (NLX) versus subcutaneous methylnaltrexone (MNTX) for the management of OIC in critically ill patients.

Methods:

A retrospective analysis was conducted on adult patients who received NLX or MNTX and a continuous opioid infusion for at least 48 hours. The primary end point was time to resolution of constipation, defined as hours to first bowel movement (BM) after the first dose of an opioid antagonist. Reversal of analgesia was assessed by comparing the total number of morphine milligram equivalents (MME) 24 hours preopioid and postopioid antagonist administration. Univariate and multivariate analyses were conducted to assess treatment response within 48 hours.

Results:

Baseline characteristics were similar between patients receiving NTX (n = 89) and MNTX (n = 71). However, the time to the first BM with NLX was 18 hours compared with 41 hours with MNTX ( P = 0.004). There was no difference in MME requirements 24 hours pre/post NLX or MNTX administration. Naloxone administration was identified as a statistically significant predictor of BM within 48 hours (odds ratio [OR] = 2.68 [1.33-5.38]).

Conclusion and Relevance:

The time to first BM was shorter with enteral NLX. Both NLX and MNTX appear to be effective for the management of OIC without causing reversal of analgesia. Future controlled, prospective trials comparing these agents are warranted.

Opioid Use, Gut Dysbiosis, Inflammation, and the Nervous System

Opioid use disorder (OUD) is defined as the chronic use or misuse of prescribed or illicitly obtained opioids and is characterized by clinically significant impairment. The etiology of OUD is multifactorial as it is influenced by genetics, environmental factors, stress response and behavior. Given the profound role of the gut microbiome in health and disease states, in recent years there has been a growing interest to explore interactions between the gut microbiome and the central nervous system as a causal link and potential therapeutic source for OUD. This review describes the role of the gut microbiome and opioid-induced immunopathological disturbances at the gut epithelial surface, which collectively contribute to OUD and perpetuate the vicious cycle of addiction and relapse.

Do gluten peptides stimulate weight gain in humans?

Observations from animal and in vitro laboratory research, and anecdotal evidence, have led to the suggestion that gluten consumption stimulates weight gain by the presence of peptides expressing opioid activity. Another proposed mechanism is that gluten peptides decrease resting energy expenditure resulting in a positive energy balance. In order to induce such effects in vivo, intact food peptides must be absorbed in sufficient quantities, remain intact in the blood for sufficient time to have long-lasting biological activity and bind to receptors involved in appetite, satiety and energy regulation. However, although peptides from food may pass from the intestine into the blood in extremely low quantities, they are generally rapidly degraded by plasma and vasculum-bound aminopeptidases, resulting in very short half-lives and loss of bioactivity. At present, gluten peptide sequences that influence regulators of energy metabolism have not been identified. Furthermore, data on the quantitative absorption of gluten peptides in the blood stream, their stability and lasting bioactivity are also lacking. Therefore, there is no evidence for proposed effects on driving appetite by the brain, nor on energy expenditure and weight gain. Furthermore, the level of overweight observed in various countries appears to be independent of the level of wheat consumption, and abundant observational evidence in humans shows that the levels of gluten consumption are neither related to daily calorie intake nor to BMI. This narrative review therefore discusses the proposed effects of gluten on bodyweight (BW) and putative biological mechanisms in the light of the current evidence.

Establishing Minimal Clinically Important Differences in Quality of Life Measures in Opioid-Induced Constipation

BACKGROUND & AIMS

Opioids have a role in chronic pain management. However, opioid-induced constipation may cause patients to skip or reduce opioid doses, leading to inadequate pain relief and negatively impacting quality of life. We sought to establish a minimal clinically important difference to understand whether changes in quality of life scores are of value to patients.

METHODS

Integrated data from the double-blind, controlled, phase 3 COMPOSE-1 and COMPOSE-2 trials of naldemedine in chronic noncancer pain and opioid-induced constipation were used to determine minimal clinically important differences using Patient Assessment of Constipation Symptoms (PAC-SYM) and Patient Assessment of Constipation Quality of Life (PAC-QOL) questionnaires. Patients completed the questionnaires (5-point Likert scale; predose, Weeks 2, 4, and 12), kept a daily log of Bowel Movement and Constipation Assessment, and rated satisfaction at end of study. Minimal clinically important differences were computed using an anchor-based method with 6 anchors: 5 from the Bowel Movement and Constipation Assessment and 1 from patient satisfaction. Threshold values for each anchor were set to define responders versus nonresponders based on score definitions. Clinically meaningful cutoff values for changes in PAC-SYM and PAC-QOL scores were determined using receiver operating characteristic curves.

RESULTS

Data from 1095 patients (549, naldemedine; 546, placebo) were analyzed. The area under the curve for the receiver operating characteristic curves (ranges, 0.719 to 0.798 for PAC-SYM and 0.734 to 0.833 for PAC-QOL) indicated that both instruments can discriminate responders and nonresponders for each anchor. PAC-SYM cutoff values ranged from -1.04 to -0.83; PAC-QOL cutoff values ranged from -0.93 to -0.82.

CONCLUSIONS

Based on data derived from the anchor method, reductions in PAC-SYM and PAC-QOL scores of >1.0 in patients with chronic noncancer pain and opioid-induced constipation are clinically meaningful.

CLINICALTRIALS

gov Registration: NCT01965158; NCT01993940.

Chronic opioid use is associated with obstructive and spastic disorders in the esophagus

BACKGROUND AND AIMS

Chronic opioid effects on the esophagus are poorly understood. We investigated whether opioids were associated with increased prevalence of esophageal motility disorders.

METHODS

A retrospective study of all patients undergoing high-resolution manometry (HREM) at the Yale Gastrointestinal Motility Lab between January 2014 and August 2019. Data were extracted from the electronic medical record after studies were reviewed by two motility specialists using the Chicago Classification v.3.0. We compared the manometric results of patients who use opioids to those who do not and adjusted for type and dose of opioids using a 24 h Morphine Milligram Equivalents (MME) scale to compare patients taking low or high amounts of opioids.

RESULTS

Four manometric abnormalities were significantly different between the opioid and non-opioid users. Achalasia type III, esophagogastric junction outflow obstruction (EGJOO), and distal esophageal spasm (DES) (p < 0.005, p < 0.01, and p < 0.005, respectively) were common among opioid users, whereas ineffective esophageal motility (IEM) was more common among non-opioid users (p < 0.01). The incidence of EGJOO was significantly higher in opioid users compared to non-opioid users (p < 0.001). Lastly, IRP, DCI, and distal latency were significantly different between the two groups. Patients in the high MME group had significantly greater IRP, DCI, and lower distal latency than non-opioids (p < 0.001). Also, achalasia type III and DES were more common in the high but not the low MME group.

CONCLUSIONS

Opioid use is associated with multiple abnormalities on esophageal motility and these effects may be dose-dependent.

The Guts of the Opioid Crisis

Bidirectional interactions of the gut epithelium with commensal bacteria are critical for maintaining homeostasis within the gut. Chronic opioid exposure perturbs gut homeostasis through a multitude of neuro-immune-epithelial mechanisms, resulting in the development of analgesic tolerance, a major underpinning of the current opioid crisis. Differences in molecular mechanisms of opioid tolerance between the enteric and central pain pathways pose a significant challenge for managing chronic pain without untoward gastrointestinal effects.

Management of Opioid-Induced Constipation and Bowel Dysfunction: Expert Opinion of an Italian Multidisciplinary Panel

The prescribing and use of opioid analgesics is increasing in Italy owing to a profusion in the number and types of opioid analgesic products available, and the increasing prevalence of conditions associated with severe pain, the latter being related to population aging. Herein we provide the expert opinion of an Italian multidisciplinary panel on the management of opioid-induced constipation (OIC) and bowel dysfunction. OIC and opioid-induced bowel dysfunction are well-recognised unwanted effects of treatment with opioid analgesics that can profoundly affect quality of life. OIC can be due to additional factors such as reduced mobility, a low-fibre diet, comorbidities, and concomitant medications. Fixed-dose combinations of opioids with mu (μ) opioid receptor antagonists, such as oxycodone/naloxone, have become available, but have limited utility in clinical practice because the individual components cannot be independently titrated, creating a risk of breakthrough pain as the dose is increased. A comprehensive prevention and management strategy for OIC should include interventions that aim to improve fibre and fluid intake, increase mobility or exercise, and restore bowel function without compromising pain control. Recommended first-line pharmacological treatment of OIC is with an osmotic laxative (preferably polyethylene glycol [macrogol]), or a stimulant laxative such as an anthraquinone. A second laxative with a complementary mechanism of action should be added in the event of an inadequate response. Second-line treatment with a peripherally acting μ opioid receptor antagonist (PAMORA), such as methylnaltrexone, naloxegol or naldemedine, should be considered in patients with OIC that has not responded to combination laxative treatment. Prokinetics or intestinal secretagogues, such as lubiprostone, may be appropriate in the third-line setting, but their use in OIC is off-label in Italy, and should therefore be restricted to settings such as specialist centres and clinical trials.

Impact of food-derived bioactive peptides on gut function and health

The gastrointestinal tract (GIT) is the largest interface between our body and the environment. It is an organ system extending from the mouth to the anus and functions for food intake, digestion, transport and absorption of nutrients, meanwhile providing protection from environmental factors, like toxins, antigens, and pathogens. Diet is one of the leading factors modulating the function of the GIT. Bioactive peptides presenting naturally in food or derived from food proteins during digestion or processing have been revealed multifunctional in diverse biological processes, including maintaining gut health and function. This review summarizes the available evidence regarding the effects of food-derived bioactive peptides on gut function and health. Findings and insights from studies based on in vitro and animal models are discussed. The gastrointestinal mucosa maintains a delicate balance between immune tolerance to nutrients and harmful components, which is crucial for the digestive system's normal functions. Dietary bioactive peptides positively impact gastrointestinal homeostasis by modulating the barrier function, immune responses, and gut microbiota. However, there is limited clinical evidence on the safety and efficacy of bioactive peptides, much less on the applications of dietary peptides for the treatment or prevention of diseases related to the GIT. Further study is warranted to establish the applications of bioactive peptides in regulating gut health and function.

Paracellular Filtration Secretion Driven by Mechanical Force Contributes to Small Intestinal Fluid Dynamics

Studies of fluid secretion by the small intestine are dominated by the coupling with ATP-dependent generation of ion gradients, whereas the contribution of filtration secretion has been overlooked, possibly by the lack of a known mechanistic basis. We measured apical fluid flow and generation of hydrostatic pressure gradients by epithelia of cultured mouse enterocytes, Caco-2 and T-84 cells, and fibroblasts exposed to mechanical force provided by vigorous aeration and in response to ion gradients, inhibitors of ion channels and transporters and in vitro using intact mouse and rat small intestine. We describe herein a paracellular pathway for unidirectional filtration secretion that is driven by mechanical force, requires tight junctions, is independent of ionic and osmotic gradients, generates persistent hydrostatic pressure gradients, and would contribute to the fluid shifts that occur during digestion and diarrhea. Zinc inhibits the flow of fluid and the paracellular marker fluorescein isothyocyanate conjugated dextran (MW = 4 kD) across epithelia of cultured enterocytes (>95%; p < 0.001) and intact small intestine (>40%; p = 0.03). We propose that mechanical force drives fluid secretion through the tight junction complex via a “one-way check valve” that can be regulated. This pathway of filtration secretion complements chloride-coupled fluid secretion during high-volume fluid flow. The role of filtration secretion in the genesis of diarrhea in intact animals needs further study. Our findings may explain a potential linkage between intestinal motility and intestinal fluid dynamics.

Current overview of opioids in progression of inflammatory bowel disease; pharmacological and clinical considerations

Inflammatory bowel diseases (IBD) belong to a subgroup of persistent, long-term, progressive, and relapsing inflammatory conditions. IBD may spontaneously develop in the colon, resulting in tumor lesions in inflamed regions of the intestine, such as invasive carcinoma. The benefit of opioids for IBD treatment is still questionable, thereby we investigated databases to provide an overview in this context. This review demonstrates the controversial role of opioids in IBD therapy, their physiological and pharmacological functions in attenuating the IBD symptoms, and in improving inflammatory, oxidative stress, and the quality of life factors in IBD subjects. Data were extracted from clinical, in vitro, and in vivo studies in English, between 1995 and 2019, from PubMed, Google Scholar, Scopus, and Cochrane library. Based on recent reports, there are promising opportunities to target the opioid system and control the IBD symptoms. This study suggests a novel approach for future treatment of functional and inflammatory disorders such as IBD.

Prevalence and management of constipation in pediatric acute lymphoblastic leukemia in U.S. children's hospitals

BACKGROUND

Children with acute lymphoblastic leukemia (ALL) suffer from a litany of chemotherapy-induced side effects. Constipation secondary to vinca alkaloids, environmental changes, and opioid use is a common issue for children newly diagnosed with leukemia.

PROCEDURE

We analyzed data from 48 children's hospitals in the Pediatric Health Information System, extracting patients 1-21 years of age with ALL hospitalized from October 2015 through September 2019. Our objective was to investigate the prevalence, risk factors, and treatment of constipation in hospitalized children with ALL.

RESULTS

We identified 4647 unique patients with an ALL induction admission. Constipation was the most common gastrointestinal diagnosis with 1576 (33.9%; 95% confidence interval [CI]: 32.6%-35.3%) patients diagnosed during induction admission and 19.8% in post-induction admissions. The most commonly administered constipation medications were poly-ethyl glycol (n = 3385, 89.6%), followed by senna (n = 1240, 32.8%), lactulose (n = 916, 24.2%), and docusate (n = 914, 24.2%). Multivariate logistic regression revealed the following variables to be significantly associated with the presence of a constipation diagnosis: age < 6 years at induction (compared with those ≥12 years; odds ratios [OR] = 1.32 [95% CI: 1.13-1.55]; P = < 0.001), female sex (OR = 1.16 [95% CI: 1.02-1.31]; P = 0.024), increased length of hospitalization (OR = 1.03 [95% CI: 1.02-1.04]; P < 0.0001), use of non-fentanyl opioids for one or two days (OR = 1.28 [95% CI: 0.99-1.65]; P = 0.056), and use of non-fentanyl opioids > 2 days (OR = 1.53 [95% CI: 1.19-1.95]; P < 0.001).

CONCLUSIONS

A large portion of hospitalized children with ALL experience constipation and required medications. Increased attention should be paid to constipation prophylaxis and treatment in ALL patients, particularly at the start of induction therapy.

Intranasal Low-Dose Naltrexone Against Opioid Side Effects: A Preclinical Study

Opioids are broad spectrum analgesics that are an integral part of the therapeutic armamentarium to combat pain in the clinical practice. Unfortunately, together with analgesia, a number of adverse effects can occur such as nausea, vomiting, constipation, gastrointestinal alterations and cognitive impairments. Naltrexone is a competitive antagonist of opioid receptors commonly used to treat opioid addiction; its oral use against agonists side effects is limited by the decrease of opioids-therapeutic efficacy and own adverse effects. The intranasal delivery of naltrexone could offer a quick and effective achievement of CNS based on extracellular mechanisms including perineural and perivascular transport. The aim of the study was to test the efficacy of intranasal low-dose naltrexone in reducing intraperitoneal morphine and oxycodone side effects in rodents. In mice, 1 μg naltrexone intranasally administered 30 min before opioids reduced cognitive impairments and motor alteration induced by 10 mg kg^-1 morphine and 60 mg kg^-1 oxycodone in the Passive avoidance and Rota rod tests, respectively. Moreover, naltrexone rebalanced opioid-induced reduction of the intestinal transit and latency of feces expulsion as well as food intake inhibition. Importantly, 1 μg naltrexone instillation did not block analgesia as demonstrated by the Hot plate test. In rats, intranasal naltrexone counteracted the opioid-induced pica phenomenon related to emesis and increased water and palatable food intake. The effects were comparable to that achieved by metoclopramide used as reference drug. Treatments did not influence body weight. Lastly, the safety of the intranasal delivery has been checked by hematoxylin-eosin staining that did not show histological alterations of the nasal cavity. In conclusion, intranasal low-dose naltrexone counteracted morphine and oxycodone induced gastrointestinal and CNS side effects without impairing opioid analgesia. It is a candidate to be a valid clinical strategy deserving deep analysis.

Tramadol Effects on Lameness Score After Inhibition of P-GP by Ivermectin Administration in Horses: Preliminary Results

This study aimed to evaluate the effects and lameness degree in horses administered tramadol after the P-glycoprotein (P-gp) enteric inhibitor ivermectin. Six horses were randomly distributed into three groups, which received two different doses of tramadol by a nasogastric tube: 1 mg/kg (tramadol group 1(GT1)), 4 mg/kg (tramadol group 4 (GT4)), and tramadol 1 mg/kg combined with ivermectin 0.2 mg/kg PO (ivermectin tramadol group (GT1 + Ive)), with one-week washout interval. Heart rate (HR), respiratory rate (RR), intestinal motility, body temperature, and the degree of lameness were evaluated for 360 minutes. The blood gas parameters were evaluated at 0, 60 minutes, and 120 minutes. There were no differences in HR and the degree of lameness. Hypomotility occurred in GT1 and GT4 only at the end of the evaluation period, and RR increased in all groups. We conclude that inhibition of enteric P-gp by ivermectin did not alter the effects of tramadol, suggesting that tramadol is not a substrate for P-gp. However, future studies should be conducted to assess the interaction between P-gp inhibitors on the pharmacokinetics of tramadol.

A retrospective evaluation of the effect of perianesthetic hydromorphone administration on the incidence of postanesthetic signs of colic in horses

OBJECTIVE

To describe the incidence of postanesthetic signs of colic (PASC) in horses and determine if perianesthetic administration of hydromorphone was associated with an increased risk of PASC.

STUDY DESIGN

Retrospective, cohort study.

ANIMALS

A total of 409 horses.

METHODS

Anesthesia and clinical records of horses admitted for various procedures from July 2018 to September 2019 were reviewed. Signs of colic and interventions were recorded up to 48 hours after anesthesia. A binomial logistic regression model was used to evaluate the association between the type of surgery, administration of hydromorphone, the duration of anesthesia and the incidence of PASC.

RESULTS

Overall, 25 (6.1%) horses developed PASC within 48 hours of general anesthesia. Of 60 horses that underwent colic surgery, 16 (26.7%) developed PASC. Of 349 horses that underwent noncolic procedures, nine (2.6%) developed PASC. Thus, the incidence of PASC was higher in horses that underwent colic surgery than in horses that underwent noncolic procedures [odds ratio (OR) = 13.74 (5.73-32.95)]. No effect of hydromorphone on the incidence of PASC was identified [OR = 1.61 (0.71-3.62)]. Longer procedures (>2 hours) were identified as an independent risk factor for PASC [OR = 4.13 (1.52-11.22)].

CONCLUSIONS

No association between hydromorphone and an increase in the incidence of PASC was identified. Anesthesia for colic surgery and duration of anesthesia were associated with an increased risk of PASC.

CLINICAL RELEVANCE

Hydromorphone did not increase the incidence of PASC in this population.

Delta-opioid receptor antagonist naltrindole reduces oxycodone addiction and constipation in mice

Oxycodone, a widely prescribed and very potent oral opioid analgesic agent, is highly addictive and has many side effects, including troublesome constipation. Our studies in mice indicated that pretreatment of naltrindole did not significantly affect the analgesic efficacy of oxycodone but attenuated the tolerance and withdrawal induced by chronic oxycodone administration. Naltrindole also attenuated the oxycodone-induced rewarding and re-instatement behaviors, as shown by the conditioned place preference test. Further, oxycodone-induced decrease in intestinal transit (i.e., constipation) was reduced by naltrindole. However, naltrindole did not block the respiratory depression produced by oxycodone. Taken together, these data suggest that naltrindole can attenuate some major side effects while retaining the analgesic efficacy of oxycodone in mice. Naltrindole and oxycodone may have the potential to be a potent analgesic combination with much lower levels of oxycodone's side effects of addictive liability and constipation.

Enkephalinase inhibitors, potential therapeutics for the future treatment of diarrhea predominant functional gastrointestinal disorders

The endogenous opioid system (EOS) is considered being a crucial element involved in the pathophysiology of irritable bowel syndrome (IBS) as it regulates gastrointestinal (GI) homeostasis through modulation of motility and water and ion secretion/absorption. Along with opioid receptors (ORs), the following components of EOS can be distinguished: 1. endogenous opioid peptides (EOPs), namely enkephalins, endorphins, endomorphins and dynorphins, and 2. peptidases, which regulate the metabolism (synthesis and degradation) of EOPs. Enkephalins, which are δ-opioid receptors agonists, induce significant effects in the GI tract as they act as potent pro-absorptive neurotransmitters. The action of enkephalins and other EOPs is limited, since EOPs are easily and rapidly inactivated by a natural metalloendopeptidase (enkephalinase/neprilysin) and aminopeptidase N. Studies show that the activity of EOPs can be enhanced by inhibition of these enzymes. In this review, we discuss the antidiarrheal and antinociceptive potential of enkephalinase inhibitors. Furthermore, our review is to answer the question whether enkephalinase inhibitors may be helpful in the future treatment of diarrhea predominant functional GI disorders.

Optimal treatment of opioid induced constipation in daily clinical practice - an observational study

Background

Opioids are prescribed in over 40% of patients with advanced cancer, but side effects occur frequently. In this study we evaluated the development and treatment of opioid induced constipation (OIC), and OIC resolving effect of methylnaltrexone for different opioid subtypes in daily clinical practice.

Methods

Patients with cancer using opioids were included in a retrospective chart analysis. Baseline characteristics, data on opioid use, laxative use, and OIC were collected. Patients with OIC who were prescribed methylnaltrexone, were included in a prospective observational trial (NCT01955213).

Results

Thirty-nine of 327 patients (pts) with cancer who were treated with opioids suffered from OIC (overall prevalence 12%; 95%-CI: 8–15%). The prevalence of OIC was similar in patients treated with oxycodone or fentanyl (12 of 81 pts. vs. 18 of 110 pts., RR 0.9; 95%CI 0.4–2.0). The morphine equivalent daily dose did not significantly differ between opioid subtypes (fentanyl 89 mg (IQR 60–180) vs. oxycodone 40 mg (40–80), P = 0.231). Twenty-two individual patients (7%) were admitted for OIC. Most effective laxatives in admitted patients were enemas, methylnaltrexone, or 4-l polyethylene-glycol solution. In the prospective observational study, the effect of methylnaltrexone could be evaluated in 23 patients. Eleven patients achieved the primary endpoint of ≥2 laxation responses out of the first four doses methylnaltrexone, independent of opioid subtype.

Conclusions

OIC is a burdensome clinical problem independent of opioid subtype. Timely intensification of prophylactic laxative treatment, especially when opioid doses increase, may help to prevent OIC. Clinically overt OIC requires a more intensive laxative regimen with for example methylnaltrexone.

Trial registration

NCT01955213.

Methylation Products of 6β- N-Heterocyclic Substituted Naltrexamine Derivatives as Potential Peripheral Opioid Receptor Modulators

Two 6β- N-heterocyclic naltrexamine derivatives, NAP and NMP, have been identified as peripherally selective mu opioid receptor (MOR) antagonists. To further enhance the peripheral selectivity of both compounds, the 17-amino group and the nitrogen atom of the pyridine ring in both NAP and NMP were methylated to obtain dMNAP and dMNMP, respectively. Compared with NAP and NMP, the binding affinities of dMNAP and dMNMP shifted to MOR and KOR (kappa opioid receptor) dual selective and they acted as moderate efficacy partial agonists. The results from radioligand binding studies were further confirmed by molecular docking studies. In vivo studies demonstrated that dMNAP and dMNMP did not produce antinociception nor did they antagonize morphine's antinociceptive activity, indicating that these compounds did not act on the central nervous system. Meanwhile, both dMNAP and dMNMP significantly slowed down fecal excretion, which indicated that they were peripherally acting opioid receptor agonists. All together, these results suggested that dMNAP and dMNMP acted as peripheral mu/kappa opioid receptor modulators and may be applicable in the treatment of diarrhea in patients with bowel dysfunction.

Oral methylnaltrexone does not negatively impact analgesia in patients with opioid-induced constipation and chronic noncancer pain

Purpose

An oral formulation of methylnaltrexone has been developed for treating opioid-induced constipation (OIC). This manuscript examines the impact of oral methylnaltrexone, a peripherally acting µ-opioid receptor antagonist, on opioid analgesia.

Methods

This Phase III, randomized, double-blind, placebo-controlled trial, evaluated changes in pain intensity scores (0= no pain to 10= worst possible pain) and opioid use in adults with chronic noncancer pain. Patients taking ≥50 mg/day oral morphine equivalent dose (MED) for ≥14 days before screening with less than three rescue-free bowel movements/week received oral methylnaltrexone 150 mg/day (n=201), 300 mg/day (n=201), 450 mg/day (n=200), or placebo (n=201) once daily for 4 weeks followed by 8 weeks of oral methylnaltrexone as needed.

Results

The primary condition requiring opioid use was back pain (68.2% of 803 patients). Baseline pain intensity scores were similar among treatment groups (mean range, 6.2–6.4) and remained stable throughout the 4-week double-blind (mean range, 6.1–6.5) and 8-week as needed (mean range, 6.3–6.5) periods. Baseline mean MED was comparable between oral methylnaltrexone 150 mg (200.0 mg/day), methylnaltrexone 450 mg (218.0 mg/day), and placebo (209.7 mg/day), but was slightly higher in the oral methylnaltrexone 300-mg group (252.6 mg/day). Nonsignificant, minimal changes in mean MED were observed after 4 weeks of treatment (214.5–235.6 mg/day) and at the end of the as needed phase (202.3–234.9 mg/day). The percentage of patients who initiated new opioid medications during the 4-week, once-daily dosing period was generally similar among the oral methylnaltrexone 150-mg, 300-mg, and 450-mg groups (44.8%, 43.3%, and 35.0%, respectively), the oral methylnaltrexone combined group (41.0%), and the placebo group (39.8%). The most common newly initiated opioid medications during this once-daily period were oxycodone (oral methylnaltrexone groups combined, 14.6%; placebo, 12.4%) and morphine (oral methylnaltrexone combined, 10.1%; placebo, 7.0%).

Conclusion

Oral methylnaltrexone does not elicit opioid withdrawal or interfere with opioid analgesia.

Peripherally Acting μ-Opioid Receptor Agonists Attenuate Ongoing Pain-associated Behavior and Spontaneous Neuronal Activity after Nerve Injury in Rats

BACKGROUND

Ongoing neuropathic pain is difficult to treat. The authors examined whether dermorphin [D-Arg2, Lys4] (1-4) amide, a peripherally acting µ-opioid receptor agonist, attenuates ongoing pain-associated manifestations after nerve injury in rats and mice.

METHODS

Using conditioned place preference assay, the authors tested whether animals show a preference to the environment associated with drug treatment. Wide-dynamic range and dorsal root ganglion neuronal activities were measured by electrophysiology recording and calcium imaging.

RESULTS

Nerve-injured animals stayed longer in dermorphin [D-Arg2, Lys4] (1-4) amide-paired chamber after conditioning than during preconditioning (rats: 402.4 ± 61.3 vs. 322.1 ± 45.0 s, 10 mg/kg, n = 9, P = 0.009; mice: 437.8 ± 59.4 vs. 351.3 ± 95.9 s, 2 mg/kg, n = 8, P = 0.047). Topical ganglionic application of dermorphin [D-Arg2, Lys4] (1-4) amide (5 μM, 1 μl, n = 5) reduced the numbers of small-diameter dorsal root ganglion neurons that showed spontaneous activity (1.1 ± 0.4 vs. 1.5 ± 0.3, P = 0.044) and that were activated by test stimulation (15.5 ± 5.5 vs. 28.2 ± 8.2, P = 0.009) after injury. In neuropathic rats, dermorphin [D-Arg2, Lys4] (1-4) amide (10 mg/kg, n = 8) decreased spontaneous firing rates in wide-dynamic range neurons to 53.2 ± 46.6% of predrug level, and methylnaltrexone (5 mg/kg, n = 9) blocked dermorphin [D-Arg2, Lys4] (1-4) amide-induced place preference and inhibition of wide-dynamic range neurons. Dermorphin [D-Arg2, Lys4] (1-4) amide increased paw withdrawal threshold (17.5 ± 2.2 g) from baseline (3.5 ± 0.7 g, 10 mg/kg, n = 8, P = 0.002) in nerve-injured rats, but the effect diminished after repeated administrations.

CONCLUSIONS

Peripherally acting μ-opioids may attenuate ongoing pain-related behavior and its neurophysiologic correlates. Yet, repeated administrations cause antiallodynic tolerance.

Prosecretory effect of loperamide in ileal and colonic mucosae of mice displaying high or low swim stress-induced analgesia associated with high and low endogenous opioid system activity

BACKGROUND

Irritable bowel syndrome (IBS) is characterized by abdominal pain, bloating, and changes in bowel habit. The aim of this study was to characterize the effect of loperamide hydrochloride (LOP) and naloxone hydrochloride (NLX), an opioid agonist and antagonist, respectively, on electrolyte equilibrium in ileal and colonic mucosae and to estimate the possible influence of divergent activity of the endogenous opioid system (EOS) on IBS therapy.

METHODS

Two mouse lines bidirectionally selected for high (HA) and low (LA) swim stress-induced analgesia associated with high and low EOS activity were used in this study. To assess the effect of LOP and NLX on HA/LA lines in vivo, we used the castor oil-induced diarrhea model. Changes in electrolyte equilibrium were determined on the basis of short-circuit current (ΔI_sc ) in isolated mouse ileum and colon exposed to LOP and NLX and stimulated by forskolin (FSK), veratridine (VER), and bethanechol (BET).

KEY RESULTS

In vivo, we found that LOP significantly prolonged time to appearance of diarrhea in HA and LA lines. In vitro, LOP and NLX increased ΔI_sc in FSK- and VER-stimulated colonic tissue, respectively, in HA line. In the ileum, LOP increased ΔI_sc in FSK- and VER-stimulated tissue and decreased ΔI_sc in BET-stimulated tissues in HA line.

CONCLUSIONS & INFERENCES

Individual differences in EOS activity may play a crucial role in the response to the IBS-D therapy, thus some patients may be at an increased risk of side effects such as constipation or diarrhea.

Updates in palliative care - recent advancements in the pharmacological management of symptoms

Symptom management is an important part of both palliative care and end-of-life care. This article will examine the recent research evidence about drugs commonly used for symptom management in adult patients receiving palliative care. In particular, the management of symptoms where recent palliative care-based evidence has changed recommended practice will be reviewed. This includes: breathlessness, delirium, nausea and vomiting in bowel obstruction, opioid-induced constipation and upper respiratory tract secretions. For each symptom, a review of recent pharmacological evidence has been undertaken, with emphasis on potential important changes to physicians' practice.

Progress in understanding mechanisms of opioid-induced gastrointestinal adverse effects and respiratory depression

Opioids evoke analgesia through activation of opioid receptors (predominantly the μ opioid receptor) in the central nervous system. Opioid receptors are abundant in multiple regions of the central nervous system and the peripheral nervous system including enteric neurons. Opioid-related adverse effects such as constipation, nausea, and vomiting pose challenges for compliance and continuation of the therapy for chronic pain management. In the post-operative setting opioid-induced depression of respiration can be fatal. These critical limitations warrant a better understanding of their underpinning cellular and molecular mechanisms to inform the design of novel opioid analgesic molecules that are devoid of these unwanted side-effects. Research efforts on opioid receptor signalling in the past decade suggest that differential signalling pathways and downstream molecules preferentially mediate distinct pharmacological effects. Additionally, interaction among opioid receptors and, between opioid receptor and non-opioid receptors to form signalling complexes shows that opioid-induced receptor signalling is potentially more complicated than previously thought. This complexity provides an opportunity to identify and probe relationships between selective signalling pathway specificity and in vivo production of opioid-related adverse effects. In this review, we focus on current knowledge of the mechanisms thought to transduce opioid-induced gastrointestinal adverse effects (constipation, nausea, vomiting) and respiratory depression.

Eluxadoline Demonstrates a Lack of Abuse Potential in Phase 2 and 3 Studies of Patients With Irritable Bowel Syndrome With Diarrhea

BACKGROUND & AIMS

Eluxadoline is approved by the Food and Drug Administration for the treatment of adults with irritable bowel syndrome with diarrhea (IBS-D). Eluxadoline is a locally acting mixed μ-opiod and κ-opioid receptor agonist and δ-opioid receptor antagonist. The abuse potential of eluxadoline was evaluated as part of the Phase 2 and 3 clinical trials assessing the efficacy, safety, and tolerability of the drug.

METHODS

One Phase 2 (IBS-2001) and two Phase 3 (IBS-3001 and IBS-3002) randomized controlled trials enrolled patients meeting Rome III criteria for IBS-D. Patients received oral twice-daily double-blind treatment with eluxadoline or placebo for 12, 26, or 52 weeks. The primary end point of these studies was the proportion of patients who had a composite response of decrease in abdominal pain and improvement in stool consistency on the same day for at least 50% of days. Safety data were pooled, and specific adverse event terms potentially related to abuse were assessed descriptively. Adverse events reported during a 2-week post-treatment period (IBS-3001) and a 4-week single-blind washout period (IBS-3002) were assessed for signs of opioid withdrawal. Potential withdrawal effects were assessed by using the Subjective Opiate Withdrawal Scale.

RESULTS

Overall, 807 and 1032 patients received 1 or more doses of eluxadoline (75 or 100 mg, respectively), and 975 patients received placebo. The overall incidence of adverse events potentially related to abuse did not differ significantly among the groups given placebo, eluxadoline 75 mg, or eluxadoline 100 mg (2.8%, 2.7%, and 4.3%, respectively). The most common adverse events potentially related to abuse were anxiety and somnolence, which occurred in less than 2% of patients in each group. Median overall Subjective Opiate Withdrawal Scale scores did not differ significantly among the groups given placebo, eluxadoline 75 mg, or eluxadoline 100 mg (3.0, 2.0, and 3.0, respectively).

CONCLUSIONS

In an analysis of data from Phase 2 and Phase 3 trials of eluxadoline (75 or 100 mg) for patients with IBS-D, data revealed no signs of abuse potential for eluxadoline. ClinicalTrials.gov numbers: NCT01130272, NCT01553591, NCT01553747.

Effect of methylnaltrexone and naloxone on esophageal motor function in man

BACKGROUND

Endogenous opioids (EO) acting on μ-opiod receptors in central and enteric nervous system (ENS) control gastrointestinal motility but it is still unclear whether EO in ENS may control esophageal function in man, thus we will study the effects of methylnaltrexone (MNTX), a peripherally selective, and naloxone (NA), a non-selective μ-opiod receptor antagonist, on esophageal motility in healthy subjects.

METHODS

Fifteen HV (6 M; 34.1 ± 0.6 years; BMI: 22.1 ± 0.1 kg/m² ) underwent three esophageal high-resolution manometry impedance (HRiM) studies with 10 saline swallows administered every 30 minutes: drug was administered after 30 minutes (MNTX subcutaneously/NA or saline intravenously), a solid meal after 90 minutes; measurements continued for 120 minutes postprandially.

KEY RESULTS

Methylnaltrexone did not significantly decrease the upper esophageal sphincter (UES) percentage of relaxation preprandially (72.5 ± 5 vs 66.9 ± 4.6 and 73 ± 3.8%, ANOVA between placebo, MNTX and NA, P=NS) and postprandially (60 minutes: 68.2 ± 5.6 vs 61 ± 5.5 and 67.1 ± 5.6%; 120 minutes: 68 ± 5.9 vs 59.3 ± 5.2 and 67.7 ± 4.7%; ANOVA between placebo, MNTX and NA, P=NS). MNTX and NA did not significantly alter preprandial and postprandial LES resting pressures and integrated relaxation pressure (ANOVA between placebo, MNTX and NA, all P=NS). Peak front velocity and distal contractile integral were not altered pre- and postprandially by MNTX and NA (ANOVA between placebo, MNTX and NA, P=NS). Transient lower esophageal sphincter relaxations (TLESRs') number was not altered by MNTX and NA (ANOVA between placebo, MNTX and NA, all P=NS).

CONCLUSIONS AND INFERENCES

The peripheral selective and non-selective μ-opioid receptor antagonists MNTX and NA, respectively, do not alter TLESRs occurrence and esophageal peristalsis.

Methyl-orvinol-Dual activity opioid receptor ligand inhibits gastrointestinal transit and alleviates abdominal pain in the mouse models mimicking diarrhea-predominant irritable bowel syndrome

BACKGROUND

Diarrhea-predominant irritable bowel syndrome (IBS-D) is a functional disorder of the gastrointestinal (GI) tract. The major IBS-D symptoms include diarrhea, abdominal pain and discomfort. High density of opioid receptors (ORs) in the GI tract and their participation in the maintenance of GI homeostasis make ORs ligands an attractive option for developing new anti-IBS-D treatments. The aim of this study was to characterize the effect of methyl-orvinol on the GI motility and secretion and in mouse models mimicking symptoms of IBS-D.

METHODS

In vitro, the effects of methyl-orvinol on electrical field stimulated smooth muscle contractility and epithelial ion transport were characterized in the mouse colon. In vivo, the following tests were used to determine methyl-orvinol effect on mouse GI motility: colonic bead expulsion, whole GI transit and fecal pellet output. An antinociceptive action of methyl-orvinol was assessed in the mouse model of visceral pain induced by mustard oil.

RESULTS

Methyl-orvinol (10^-10 to 10^-6M) inhibited colonic smooth muscle contractions in a concentration-dependent manner. This effect was reversed by naloxone (non-selective opioid antagonist) and β-funaltrexamine (selective MOP antagonist). Experiments with a selective KOP receptor agonist, U50488 revealed that methyl-orvinol is a KOP receptor antagonist in the GI tract. Methyl-orvinol enhanced epithelial ion transport. In vivo, methyl-orvinol inhibited colonic bead expulsion and prolonged GI transit. Methyl-orvinol improved hypermotility and reduced abdominal pain in the mouse models mimicking IBS-D symptoms.

CONCLUSION

Methyl-orvinol could become a promising drug candidate in chronic therapy of functional GI diseases such as IBS-D.

Opioids and GI Motility-Friend or Foe?

OPINION STATEMENT

The use of opioids for the treatment of chronic non-cancer pain is growing at an alarming rate. Opioid-induced bowel dysfunction (OBD) is a common adverse effect of long-term opioid treatment manifesting as constipation, nausea, and vomiting. These effects are primarily mediated by peripheral μ-opioid receptors with resultant altered GI motility and function. As a result, patients may present with opioid-induced constipation (OIC), opioid-induced nausea and vomiting (OINV), and/or narcotic bowel syndrome (NBS). This often leads to decreased quality of life and in many cases, discontinuation of opioid therapy. There is limited evidence to support the use of traditional anti-emetics and laxatives in the treatment of OBD. Tapering the dose of opioids, switching to transdermal application, opioid rotation, or dual-action opioids, such as tapentadol, may be helpful in the treatment of OBD. Novel agents, such as peripherally acting μ-opioid receptor antagonists which target the cause of OIC, show promise in the treatment of OBD and should be considered when conventional laxatives fail. This chapter will review the pathophysiology of OBD, including OINV and OIC, and treatment options available.

A Case of Stercoral Perforation Detected on CT Requiring Proctocolectomy in a Heroin-Dependent Patient

Stercoral perforation of the colon is rare but carries with it significant morbidity and mortality. Stercoral perforation usually occurs in elderly, immobile patients with chronic constipation. In this manuscript, we report the case of stercoral perforation in a patient due to chronic heroin dependence. We report the case of a 56-year-old male patient with stercoral perforation, diagnosed by computed tomography, secondary to heroin dependence, requiring proctocolectomy and an end ileostomy. There are very few reports in the literature describing cases of stercoral perforation and questions have been asked about the importance of preoperative cross-sectional imaging. In our case, the diagnosis of stercoral perforation was made only on CT. Although this is not the first such case to be reported, it is significant as preoperative CT imaging was influential not only in determining the aetiology of the abdominal distension seen on the plain film, but also in detecting the pneumoperitoneum which was not evident clinically or on plain radiographs.

The Effect of DA-9701 in Opioid-induced Bowel Dysfunction of Guinea Pig

Background/Aims

Opioid induced bowel dysfunction (OIBD) is associated with decreased gastrointestinal (GI) propulsive activity due to intake of opioid analgesics. DA-9701, a novel prokinetic agent formulated with Pharbitis Semen and Corydalis Tuber has promising effects on GI motor function. Therefore, we aim to evaluate the prokinetic effects of DA-9701 in an OIBD model of guinea pig.

Methods

The ileal and distal colon muscle contraction in presence of different doses of DA-9701, morphine, and combination (morphine + DA-9701) was measured by tissue bath study. The prokinetic effect of DA-9701 was assessed by charcoal transit and fecal pellet output assay in an OIBD model of guinea pig.

Results

DA-9701 significantly increased the amplitude and area under the curve of ileal muscle contraction, while there was insignificant effect on the distal colon compared to the control. The maximal amplitude of ileal muscle contraction was acquired at a concentration of 10 μg/mL of DA-9701. In contrast, morphine significantly decreased the amplitude of ileal and distal colon muscle contraction compared to the control. Morphine delayed both upper (P < 0.01) and lower (P < 0.05) GI transit, and delayed GI transit was restored by the administration of DA-9701. Morphine induced reduction of contractility was significantly ameliorated by addition of DA-9701 in both ileal and distal colon muscles.

Conclusions

DA-9701 significantly increased the amplitude of contraction of the ileal muscle, however the distal colon muscle contraction was insignificant. Additionally, it restored delayed upper and lower GI transit in an OIBD model of guinea pig, and it might prove to be a useful candidate drug in a clinical trial for OIBD.

Opioid-induced bowel dysfunction in healthy volunteers assessed with questionnaires and MRI

OBJECTIVE

Opioid treatment is associated with numerous gastrointestinal adverse effects collectively known as opioid-induced bowel dysfunction (OIBD). Most current knowledge of the pathophysiology derives from animal studies limited by species differences and clinical studies, which have substantial confounders that make evaluation difficult. An experimental model of OIBD in healthy volunteers in a controlled setting is therefore highly warranted. The aim of this study was to assess bowel function in healthy volunteers during opioid treatment using subjective and objective methods.

METHODS

Twenty-five healthy men were assigned randomly to oxycodone or placebo for 5 days in a cross-over design. The analgesic effect was assessed with muscle pressure algometry and adverse effects were measured using questionnaires including the bowel function index, gastrointestinal symptom rating scale, patient assessment of constipation symptoms and the Bristol stool form scale. Colorectal volumes were determined using a newly developed MRI method.

RESULTS

Compared with baseline, oxycodone increased pain detection thresholds by 8% (P=0.02). Subjective OIBD was observed as increased bowel function index (464% increase; P<0.001), gastrointestinal symptom rating scale (37% increase; P<0.001) and patient assessment of constipation symptoms (198% increase; P<0.001). Objectively, stools were harder and drier during oxycodone treatment (P<0.001) and segmental colorectal volumes increased in the caecum/ascending colon by 41% (P=0.005) and in the transverse colon by 20% (P=0.005). No associations were detected between questionnaire scores and colorectal volumes.

CONCLUSION

Experimental OIBD in healthy volunteers was induced during oxycodone treatment. This model has potential for future interventional studies to discriminate the efficacies of different laxatives, peripheral morphine antagonists and opioid treatments.

Acquired causes of intestinal malabsorption

This review focuses on the acquired causes, diagnosis, and treatment of intestinal malabsorption. Intestinal absorption is a complex process that depends on many variables, including the digestion of nutrients within the intestinal lumen, the absorptive surface of the small intestine, the membrane transport systems, and the epithelial absorptive enzymes. Acquired causes of malabsorption are classified by focussing on the three phases of digestion and absorption: 1) luminal/digestive phase, 2) mucosal/absorptive phase, and 3) transport phase. Most acquired diseases affect the luminal/digestive phase. These include short bowel syndrome, extensive small bowel inflammation, motility disorders, and deficiencies of digestive enzymes or bile salts. Diagnosis depends on symptoms, physical examination, and blood and stool tests. There is no gold standard for the diagnosis of malabsorption. Further testing should be based on the specific clinical context and the suspected underlying disease. Therapy is directed at nutritional support by enteral or parenteral feeding and screening for and supplementation of deficiencies in vitamins and minerals. Early enteral feeding is important for intestinal adaptation in short bowel syndrome. Medicinal treatment options for diarrhoea in malabsorption include loperamide, codeine, cholestyramine, or antibiotics.

The Impact of Opioid Treatment on Regional Gastrointestinal Transit

Background/Aims

To employ an experimental model of opioid-induced bowel dysfunction in healthy human volunteers, and evaluate the impact of opioid treatment compared to placebo on gastrointestinal (GI) symptoms and motility assessed by questionnaires and regional GI transit times using the 3-dimensional (3D)-Transit system.

Methods

Twenty-five healthy males were randomly assigned to oxycodone or placebo for 5 days in a double blind, crossover design. Adverse GI effects were measured with the bowel function index, gastrointestinal symptom rating scale, patient assessment of constipation symptom questionnaire, and Bristol stool form scale. Regional GI transit times were determined using the 3D-Transit system, and segmental transit times in the colon were determined using a custom Matlab^® graphical user interface.

Results

GI symptom scores increased significantly across all applied GI questionnaires during opioid treatment. Oxycodone increased median total GI transit time from 22.2 to 43.9 hours (P < 0.001), segmental transit times in the cecum and ascending colon from 5.7 to 9.9 hours (P = 0.012), rectosigmoid colon transit from 2.7 to 9.0 hours (P = 0.044), and colorectal transit time from 18.6 to 38.6 hours (P = 0.001). No associations between questionnaire scores and segmental transit times were detected.

Conclusions

Self-assessed GI adverse effects and increased GI transit times in different segments were induced during oxycodone treatment. This detailed information about segmental changes in motility has great potential for future interventional head-to-head trials of different laxative regimes for prevention and treatment of constipation.

The effect of opioid agonists and antagonists on gastrointestinal motility in mice selected for high and low swim stress-induced analgesia

BACKGROUND

The opioid system in the gastrointestinal (GI) tract plays an important physiological role, but is also responsible for the side effect of opioid drugs, including troublesome constipation in chronic pain treatment. The aim of this study was to characterize and validate a new mouse model to study the effects of opioid agonists and antagonists in the GI tract.

METHODS

Six-week-old male Swiss-Webster mice, divergently bred for high (HA) and low (LA) swim stress-induced analgesia (SSIA), were used in the study. To assess the influence of opioid agonists (morphine and loperamide) and antagonists (naloxone hydrochloride, NLX and naloxone methiodide, NLXM) on GI motility, whole GI transit (whole GIT) and upper GIT assays were conducted. To evaluate the expression of opioid receptors in the ileum and colon of HA and LA mice, immune staining was performed.

KEY RESULTS

The effect of morphine was more pronounced in HA line, whereas loperamide exerted a stronger effect in LA mice. Furthermore, NLX and NLXM differentially abolished the inhibitory action of the central and peripheral opioid system on whole and upper GIT in HA and LA mice. The differences in GI motility between HA and LA mice coexisted with parallel changes in the expression of opioid receptors in the ileum and colon.

CONCLUSIONS & INFERENCES

Differences in the activity of the endogenous opioid system are responsible for the vulnerability to changes in GI motility during treatment with opioids. Our findings validate the HA/LA model for further studies on opioids in the GI tract.