Role of opiate receptors in the regulation of colonic transit

Acute colonic pseudo-obstruction in polytrauma patients

BACKGROUND

Acute colonic pseudo-obstruction (ACPO) is characterized by severe colonic distension without mechanical obstruction. It has an uncertain pathogenesis and poses diagnostic challenges. This study aimed to explore risk factors and clinical outcomes of ACPO in polytrauma patients and contribute information to the limited literature on this condition.

METHODS

This retrospective study, conducted at a Level 1 trauma center, analyzed data from trauma patients with ACPO admitted between July 2009 and June 2018. A control cohort of major trauma patients was used. Data review encompassed patient demographics, abdominal imaging, injury characteristics, analgesic usage, interventions, complications, and mortality. Statistical analyses, including logistic regression and correlation coefficients, were employed to identify risk factors.

RESULTS

There were 57 cases of ACPO, with an incidence of 1.7 per 1,000 patients, rising to 4.86 in major trauma. Predominantly affecting those older than 50 years (75%) and males (75%), with motor vehicle accidents (50.8%) and falls from height (36.8%) being the commonest mechanisms. Noteworthy associated injuries included retroperitoneal bleeds (RPBs) (37%), spinal fractures (37%), and pelvic fractures (37%). Analysis revealed significant associations between ACPO and shock index >0.9, Injury Severity Score >18, opioid use, RPBs, and pelvic fractures. A cecal diameter of ≥12 cm had a significant association with cecal ischemia or perforation.

CONCLUSION

This study underscores the significance of ACPO in polytrauma patients, demonstrating associations with risk factors and clinical outcomes. Clinicians should maintain a high index of suspicion, particularly in older patients with RPBs, pelvic fractures, and opioid use. Early supportive therapy, vigilant monitoring, and timely interventions are crucial for a favorable outcome. Further research and prospective trials are warranted to validate these findings and enhance understanding of ACPO in trauma patients.

LEVEL OF EVIDENCE

Prognostic and Epidemiological; Level IV.

Effects of Codeine on Esophageal Peristalsis in Patients With Ineffective Esophageal Motility: Studies Using High-resolution Manometry

Background/Aims

This study aims to evaluate the effects of acute codeine administration on primary and secondary esophageal peristalsis in patients with ineffective esophageal motility (IEM).

Methods

Eighteen IEM patients (8 women; mean age 37.8 years, range 23-64 years) were enrolled in the study. The patients underwent high-resolution manometry exams, consisting of 10 single wet swallows, multiple rapid swallows, and ten 20 mL rapid air injections to trigger secondary peristalsis. All participants completed 2 separate sessions, including acute administration of codeine (60 mg) and placebo, in a randomized order.

Results

Codeine significantly increased the distal contractile integral (566 ± 81 mmHg∙s∙cm vs 247 ± 36 mmHg∙s∙cm, P = 0.001) and shortened distal latency (5.7 ± 0.2 seconds vs 6.5 ± 0.1 seconds, P < 0.001) for primary peristalsis compared with these parameters after placebo treatment. The mean total break length decreased significantly after codeine treatment compared with the length after placebo (P = 0.003). Codeine significantly increased esophagogastric junction-contractile integral (P = 0.028) but did not change the 4-second integrated relaxation pressure (P = 0.794). Codeine significantly decreased the frequency of weak (P = 0.039) and failed contractions (P = 0.009), resulting in increased frequency of normal primary peristalsis (P < 0.136). No significant differences in the ratio of impaired multiple rapid swallows inhibition and parameters of secondary peristalsis were detected.

Conclusions

In IEM patients, acute administration of codeine increases contraction vigor and reduces distal latency of primary esophageal peristalsis, but has no effect on secondary peristalsis. Future studies are required to further elucidate clinical relevance of these findings, especially in the setting of gastroesophageal reflux disease with IEM.

Practicing Digital Gastroenterology through Phonoenterography Leveraging Artificial Intelligence: Future Perspectives Using Microwave Systems

Production of bowel sounds, established in the 1900s, has limited application in existing patient-care regimes and diagnostic modalities. We review the physiology of bowel sound production, the developments in recording technologies and the clinical application in various scenarios, to understand the potential of a bowel sound recording and analysis device-the phonoenterogram in future gastroenterological practice. Bowel sound production depends on but is not entirely limited to the type of food consumed, amount of air ingested and the type of intestinal contractions. Recording technologies for extraction and analysis of these include the wavelet-based filtering, autoregressive moving average model, multivariate empirical mode decompression, radial basis function network, two-dimensional positional mapping, neural network model and acoustic biosensor technique. Prior studies evaluate the application of bowel sounds in conditions such as intestinal obstruction, acute appendicitis, large bowel disorders such as inflammatory bowel disease and bowel polyps, ascites, post-operative ileus, sepsis, irritable bowel syndrome, diabetes mellitus, neurodegenerative disorders such as Parkinson's disease and neonatal conditions such as hypertrophic pyloric stenosis. Recording and analysis of bowel sounds using artificial intelligence is crucial for creating an accessible, inexpensive and safe device with a broad range of clinical applications. Microwave-based digital phonoenterography has huge potential for impacting GI practice and patient care.

The effects of loperamide on excitatory and inhibitory neuromuscular function in the human colon

BACKGROUND

In most animal species, opioids alter colonic motility via the inhibition of excitatory enteric motor neurons. The mechanisms by which opioids alter human colonic motility are unclear. The aim of this study was to describe the effects of loperamide on neuromuscular function in the human colon.

METHODS

Tissue specimens of human colon from 10 patients undergoing an anterior resection were divided into three inter-taenial circular muscle strips. Separate organ baths were used to assess: (1) excitatory transmission (selective blockade of inhibitory transmission: L-NOARG/MRS2179); (2) inhibitory transmission (selective blockade of excitatory transmission: hyoscine hydrobromide); and (3) a control bath (no drug additions). Neuromuscular function was assessed using force transducer recordings and electrical field stimulation (EFS; 20 V, 10 Hz, 0.5 ms, 10 s) prior to and following loperamide and naloxone.

KEY RESULTS

In human preparations with L-NOARG/MRS2179, loperamide had no significant effects on isometric contractions. In preparations with hyoscine hydrobromide, loperamide reduced isometric relaxation during EFS (median difference + 0.60 g post-loperamide, Z = -2.35, p = 0.019).

CONCLUSIONS AND INFERENCES

Loperamide had no effect on excitatory neuromuscular function in human colonic circular muscle. These findings suggest that loperamide alters colonic function by acting primarily on inhibitory motor neurons, premotor enteric neurons, or via alternative non-opioid receptor pathways.

Update on the role of naldemedine in opioid-induced constipation in patients with chronic noncancer pain

Chronic noncancer pain (CNCP) affects up to 20% of adults and can interfere with activities of daily living. Up to 4% of adults in the United States receive chronic opioid therapy and up to 57% of patients on long-term opioids for CNCP report opioid-induced constipation (OIC). OIC is essentially constipation occurring after starting opioid treatment. While laxatives are traditionally the first-line therapy for OIC, 81% of patients taking daily laxatives and opioids still reported OIC and considered that it negatively affected their quality of life. Naldemedine is a peripherally acting µ-opioid receptor antagonists (PAMORA) approved for the treatment of OIC in patients with CNCP. This article reviews the mechanism of action, efficacy, and safety of naldemedine in CNCP patients. Naldemedine improves OIC in patients with CNCP by acting as an opioid receptor antagonist in the gastrointestinal tract. It does not interfere with the analgesic properties of opioids or cause withdrawal symptoms since these effects are centrally mediated, and naldemedine does not cross the blood brain barrier. Naldemedine showed significant and sustained improvement in frequency of bowel movements, quality of life, and constipation-related symptoms. It is generally well tolerated with a higher incidence of gastrointestinal adverse events of mild or moderate severity such as diarrhea, abdominal pain, or vomiting compared to placebo. While there are no randomized, controlled trials that compare head-to-head pharmacological therapies used for treatment of OIC, network meta-analysis shows that naldemedine has an overall good benefit-risk profile compared to the other approved medications.

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.

Pre-induction Ultrasonographic Evaluation of Gastric Residual Volume in Elective Gastrointestinal Cancer Surgeries

Pulmonary aspiration of gastric contents during elective surgery remains a major cause of airway-related mortality and morbidity. The preoperative fasting times for solids and liquids have been standardized across various anesthesia society guidelines. Enhanced Recovery After Surgery (ERAS) guidelines now advocate liberal clear fluid intake with carbohydrate loading up to 2 h preoperatively. The aim of the study was to assess whether practicing both ASA fasting guidelines and ERAS protocol makes the patients prone to a full stomach. The supine position standard curvilinear ultrasound probe (2-5 MHz) with Sonosite M-Turbo ©system was used to obtain the images. Gastric residual volume (GRV) was derived from the cross-sectional area (CSA) using the Perlas and colleagues model. A total of 102 patients were recruited and analyzed. The mean age and BMI were 50.65 years ± 13.35 years and 22.23 kg/m² ± 3.7 kg/m², respectively. A total of four patients (3.92%) had gastric volume > 1.5 ml/kg; out of these four patients, three were female and one was male. We did not observe any case of pulmonary aspiration in any of our patients. In conclusion, even though for elective surgeries, the current fasting guidelines are adequate, these findings cannot be extrapolated to patients with risk factors for high gastric residual volume where further studies need to be performed.

Effects of codeine on esophageal peristalsis in humans using high resolution manometry

BACKGROUND AND AIM

Opioid receptors agonists have been demonstrated to impair lower esophageal sphincter (LES) relaxation and induce spastic esophageal dysmotility, but little was known for their impact on distension-induced secondary peristalsis. The aim of the study was to investigate the hypothesis whether acute administration of codeine can influence physiological characteristics of primary and secondary peristalsis in healthy adults.

METHODS

Eighteen healthy volunteers (13 men, mean age 27.5 years, aged 20-43 years) underwent high resolution manometry (HRM) with a catheter containing an injection port in mid-esophagus. Secondary peristalsis was performed with 10 and 20 mL rapid air injections. Two different sessions including acute administration of codeine (60 mg) or the placebo were randomly performed.

RESULTS

Codeine significantly increased 4-s integrated relaxation pressure (IRP-4s) (P = 0.003) and shortened distal latency (DL) (P = 0.003) of primary peristalsis. The IRP-4s of secondary peristalsis was also significantly higher after codeine than the placebo during air injections with 10 mL (P = 0.048) and 20 mL (P = 0.047). Codeine significantly increased the frequency of secondary peristalsis during air injections with 10 mL than the placebo (P = 0.007), but not for air injection with 20 mL (P = 0.305).

CONCLUSIONS

In addition to impair LES relaxation and reduce distal latency of primary peristalsis, codeine impairs LES relaxation of secondary peristalsis and increases secondary peristaltic frequency. Our study supports the notion in human esophagus that the impact of opioids on peristaltic physiology appears to be present in both primary and secondary peristalsis.

Can Naloxegol Therapy Improve Quality of Life in Patients with Advanced Cancer?

This observational study aims to evaluate the efficacy of naloxegol therapy in resolving opioid-induced constipation (OIC) and in improving the quality of life in a home palliative care cancer setting. Advanced cancer patients with OIC (Rome IV criteria) not relieved by laxatives started a naloxegol therapy 25 mg/day for 4 weeks. Quality of life was evaluated by Patient Assessment of Constipation Quality-of-Life (PAC-QoL) at day 0 and day 28; background pain by Numerical Rating Scale, number of weekly spontaneous bowel movements and Bowel Function Index (BFI) were evaluated at day 0 and every week. Seventy-eight patients who completed the 4-week study improved all four PAC-QoL dimensions (physical and psychological discomfort, worries/concerns and satisfaction level). Weekly spontaneous bowel movements increased and BFI improved. Background pain reduced after seven days and remained lower during the following weeks. Seventy-two patients dropped out the study before day 28 with a reduced survival compared to patients completing the study. Even in these patients, an improvement of bowel function was observed after two weeks. Naloxegol was effective in improving the quality of life, resolving OIC and reducing overall pain in patients with advanced cancer.

Association between opioid usage and rectal dysfunction in constipation: A cross-sectional study of 2754 patients

BACKGROUND

Opioid use has reached epidemic proportions. In contrast to the known effect of opioids on gut transit, the effect on rectal sensorimotor function has not been comprehensively investigated.

METHODS

Cross-sectional (hypothesis-generating) study of anorectal physiology studies in 2754 adult patients referred to a tertiary unit (2004-2016) for investigation of functional constipation (defined by "derived" Rome IV core criteria). Statistical associations between opioid usage, symptoms, and anorectal physiological variables were investigated. Opioids were sub-classified as prescriptions for mild-moderate or moderate-severe pain.

KEY RESULTS

A total of 2354 patients (85.5%) were classified as non-opioid users, 162 (5.9%) as opioid users for mild-moderate pain, and 238 (8.6%) for moderate-severe pain. Opioids for moderate-severe pain were associated with increased symptomatic severity (Cleveland Clinic constipation score 18.5 vs 15.1; mean difference 2.9 [95%-CI 2.3-3.6]; P < .001), rectal hyposensitivity (odds ratio 1.74 [95%-CI 1.23-2.46]; P = .002), functional evacuation disorders (odds ratio 1.73 [95%-CI 1.28-2.34]; P < .001), and delayed whole-gut transit (odds ratio 1.68 [95%-CI 1.19-2.37]; P = .003). Differences in anorectal variables between opioid users for mild-moderate pain and non-opioid users were not statistically significant. Hierarchical opioid use (non vs mild-moderate vs moderate-severe) was associated with decreasing proportions of patients with no physiological abnormality on testing (40.2% vs 38.1% vs 29.2%) and increasing proportions with both delayed whole-gut transit and rectal sensorimotor dysfunction (16.6% vs 17.5% vs 28.5%).

CONCLUSIONS AND INFERENCES

Opioid use is over-represented in patients referred for investigation of constipation. Opioids for moderate-severe pain are associated with rectal sensorimotor abnormalities. Further studies are required to determine whether this association indicates causation.

Systematic review with meta-analysis: efficacy and safety of treatments for opioid-induced constipation

BACKGROUND

When opioid-induced constipation is treated with centrally acting opioid antagonists, there may be opioid withdrawal or aggravation of pain due to inhibition of μ-opioid analgesia. This led to the development of peripherally acting μ-opioid receptor antagonists (PAMORAs).

AIM

To evaluate the efficacy of available PAMORAs and other approved or experimental treatments for relieving constipation in patients with opioid-induced constipation, based on a systematic review and meta-analysis of published studies.

METHODS

A search of MEDLINE, EMBASE and EBM Reviews Cochrane Central Register of Controlled Trials was completed in July 2019 for randomised trials compared to placebo. FDA approved doses or highest studied dose was evaluated. Efficacy was based on diverse endpoints, including continuous variables (the bowel function index, number of spontaneous bowel movements and stool consistency based on Bristol Stool Form Scale), or responder analysis (combination of >3 spontaneous bowel movements or complete spontaneous bowel movements plus 1 spontaneous bowel movement or complete spontaneous bowel movements, respectively, over baseline [so-called FDA endpoints]). Adverse effects evaluated included central opioid withdrawal, serious adverse events, abdominal pain and diarrhoea.

RESULTS

We included 35 trials at low risk of bias enrolling 13 566 patients. All PAMORAs demonstrated efficacy on diverse patient response endpoints. There was greater efficacy with approved doses of the PAMORAs (methylnaltrexone, naloxegol and naldemidine), with lower efficacy or lower efficacy and greater adverse effects with combination oxycodone with naloxone, lubiprostone and linaclotide.

CONCLUSIONS

Therapeutic response in opioid-induced constipation is best achieved with the PAMORAs, methylnaltrexone, naloxegol and naldemidine, which are associated with low risk of serious adverse events.

Comparison of early and on-demand maternal feeding after Caesarean delivery: a prospective randomised trial

INTRODUCTION

This study aimed to compare early and on-demand maternal feeding after Caesarean delivery in terms of gastrointestinal complaints and patient satisfaction.

METHODS

A total of 262 women with uncomplicated singleton term pregnancies who underwent a Caesarean section under regional anaesthesia were randomised to a soft food diet served at Postoperative Hour 2 (early feeding group) or eating whenever they wanted to upon return to the ward (on-demand group). Patient satisfaction scores at the time of discharge and gastrointestinal complaints were compared.

RESULTS

The fed-early group comprised 133 (50.8%) women and the on-demand group comprised 129 (49.2%) women. Major characteristics and surgical procedures were comparable between the two groups. No significant between-group differences in demographic criteria or surgical procedures were evident (p > 0.05). The mean time to the first feeding was 120.00 ± 00.00 minutes for the early feeding group as compared to 236.59 ± 107.74 minutes for the on-demand feeding group (p = 0.001). Satisfaction levels did not differ significantly between the two groups (p = 0.366). Duration to first breastfeeding, analgesia on the ward, passage of flatus, defecation, mobilisation and urination after catheter removal did not differ significantly between the two groups (p > 0.05).

CONCLUSION

Early initiation of solid food in low-risk women after Caesarean delivery under regional anaesthesia was associated with high satisfaction and did not increase gastrointestinal complaints. We suggest having flexibility in terms of postoperative feeding time. This may shorten hospitalisation time and reduce hospitalisation costs.

Sacral nerve stimulation with appropriate parameters improves constipation in rats by enhancing colon motility mediated via the autonomic-cholinergic mechanisms

Although sacral nerve stimulation (SNS) has been applied for treating constipation, its parameters were adopted from SNS for fecal incontinence, its effects are limited, and mechanisms are largely unknown. We investigated the effects and mechanism of SNS with appropriate parameters on constipation in rats treated with loperamide. First, using rectal compliance as an outcome measure, an experiment was performed to derive effective SNS parameters. Then, a 7-day SNS was performed in rats with constipation induced by loperamide. Autonomic functions were assessed by spectral analysis of heart rate variability (HRV) derived from an electrocardiogram. Serum levels of pancreatic polypeptide (PP), norepinephrine (NE), and acetylcholine (ACh) in colon were assessed. 1) Acute SNS at 5 Hz, 100 µs was found effective in enhancing rectal compliance and accelerating distal colon transit (P < 0.05 vs. sham SNS). 2) The 7-day SNS normalized loperamide-induced constipation, assessed by the number, weight, and water content of fecal pellets, and accelerated the distal colon transit (29.4 ± 3.7 min with sham SNS vs. 16.4 ± 5.3 min with SNS but not gastric emptying or intestinal transit. 3) SNS significantly increased vagal activity (P = 0.035) and decreased sympathetic activity (P = 0.012), assessed by spectral analysis of HRV as well as by the serum PP. 4) SNS increased ACh in the colon tissue; atropine blocked the accelerative effect of SNS on distal colon transit. We concluded that SNS with appropriate parameters improves constipation induced by loperamide by accelerating distal colon motility, mediated via the autonomic-cholinergic function.NEW & NOTEWORTHY Although sacral nerve stimulation (SNS) has been applied for treating constipation, its parameters were adopted from SNS for fecal incontinence, effects are limited, and mechanisms are largely unknown. This paper shows that SNS with appropriate parameters improves constipation induced by loperamide by accelerating distal colon motility mediated via the autonomic-cholinergic function.

Opioid-Induced Esophageal Dysfunction: Differential Effects of Type and Dose

OBJECTIVE

Data regarding opioid effects on esophageal function are limited. We previously demonstrated an association between chronic opioid use and esophageal motor dysfunction characterized by esophagogastric junction outflow obstruction, distal esophageal spasm, achalasia type III, and possibly Jackhammer esophagus. Our aim was to characterize the influence of different opioids and doses on esophageal dysfunction.

METHODS

Retrospective review of 225 patients prescribed oxycodone, hydrocodone, or tramadol for >3 months, who completed high-resolution manometry from 2012 to 2017. Demographic and manometric data were extracted from a prospectively maintained motility database. Frequency of opioid-induced esophageal dysfunction (OIED, defined as distal esophageal spasm, esophagogastric junction outflow obstruction, achalasia type III, or Jackhammer esophagus on high-resolution manometry, was compared among different opioids. The total 24-hour opioid doses for oxycodone, hydrocodone, and tramadol were converted to a morphine equivalent for dose effect analysis.

RESULTS

OIED was present in 24% (55 of 225) of opioid users. OIED was significantly more prevalent with oxycodone or hydrocodone use compared with tramadol (31% vs 28% vs 12%, P = 0.0162), and for oxycodone alone vs oxycodone with acetaminophen (43% vs 21%, P = 0.0482). There was no difference in OIED for patients taking hydrocodone alone vs hydrocodone with acetaminophen. Patients with OIED were taking a higher median 24-hour opioid dose than those without OIED (45 vs 30 mg, P = 0.058).

DISCUSSION

OIED is more prevalent in patients taking oxycodone or hydrocodone compared with tramadol. There is greater likelihood of OIED developing with higher doses. Reducing the opioid dose or changing to tramadol may reduce OIED in opioid users.

Efficacy of pharmacological therapies for the treatment of opioid-induced constipation: systematic review and network meta-analysis

OBJECTIVE

Opioids are increasingly prescribed in the West and have deleterious GI consequences. Pharmacological therapies to treat opioid-induced constipation (OIC) are available, but their relative efficacy is unclear. We performed a systematic review and network meta-analysis to address this deficit in current knowledge.

DESIGN

We searched MEDLINE, EMBASE, EMBASE Classic and the Cochrane central register of controlled trials through to December 2017 to identify randomised controlled trials (RCTs) of pharmacological therapies in the treatment of adults with OIC. Trials had to report a dichotomous assessment of overall response to therapy, and data were pooled using a random effects model. Efficacy and safety of pharmacological therapies was reported as a pooled relative risk (RR) with 95% CIs to summarise the effect of each comparison tested and ranked treatments according to their P-score.

RESULTS

Twenty-seven eligible RCTs of pharmacological therapies, containing 9149 patients, were identified. In our primary analysis, using failure to achieve an average of ≥3 bowel movements (BMs) per week with an increase of ≥1 BM per week over baseline or an average of ≥3 BMs per week, to define non-response, the network meta-analysis ranked naloxone first in terms of efficacy (RR=0.65; 95% CI 0.52 to 0.80, P-score=0.84), and it was also the safest drug. When non-response to therapy was defined using failure to achieve an average of ≥3 BMs per week, with an increase of ≥1 BM per week over baseline, naldemedinewas ranked first (RR=0.66; 95% CI 0.56 to 0.77, P score=0.91) and alvimopan second (RR=0.74; 95% CI 0.57 to 0.94, P-score=0.71).

CONCLUSION

In network meta-analysis, naloxone and naldemedine appear to be the most efficacious treatments for OIC. Naloxone was the safest of these agents.

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 is efficacious and well tolerated for the treatment of opioid-induced constipation in patients with chronic noncancer pain receiving concomitant methadone

Purpose

To evaluate the safety and efficacy of oral methylnaltrexone for opioid-induced constipation (OIC).

Patients and methods

This was a post hoc analysis of patients receiving methadone in a randomized, double-blind, placebo-controlled, Phase 3 trial. The trial included adults with chronic noncancer pain for ≥2 months receiving opioid doses ≥50 mg/day of oral morphine equivalents for ≥14 days and with a history of OIC. Patients were assigned to oral methylnaltrexone (150, 300, or 450 mg) or placebo once daily (QD) for 4 weeks followed by 8 weeks as needed. Percentage of dosing days that resulted in a rescue-free bowel movement (RFBM) within 4 hours of dosing was assessed during QD dosing (primary efficacy endpoint). Other endpoints included percentage of responders (ie, ≥3 RFBMs/week, with an increase of ≥1 RFBM/week from baseline for ≥3 of the 4 weeks) during QD dosing and change in weekly number of RFBMs. Adverse events were assessed.

Results

Concomitant methadone was reported in 120 patients (oral methylnaltrexone: 150 mg [n=33], 300 mg [n=30], and 450 mg [n=31]; placebo [n=26]). Oral methylnaltrexone-treated patients had significant increases in mean percentage of dosing days with RFBMs within 4 hours of dosing during weeks 1–4 with 300 mg (33.6%; P<0.01) and 450 mg (38.2%; P<0.001) vs placebo; improvements with 150 mg (20.0%) vs placebo (15.1%) did not reach statistical significance. The percentage of responders was greater vs placebo, but not significant, for the higher doses during the QD period (150 mg [39.4%], 300 mg [60.0%], 450 mg [67.7%], and placebo [38.5%]). Change from baseline in the mean number of weekly RFBMs (weeks 1–4) was significantly greater with oral methylnaltrexone 450 mg vs placebo (least-squares mean difference vs placebo, 1.2; P=0.04); no significant differences were found for 300 or 150 mg. Oral methylnaltrexone was well tolerated at all doses; few patients discontinued treatment.

Conclusion

Oral methylnaltrexone, particularly 450 mg, was efficacious and safe for treating OIC in these patients.

Opioid receptors in the GI tract: targets for treatment of both diarrhea and constipation in functional bowel disorders?

Opioids have been used for centuries, mostly as a sedative and to treat pain. Currently, they are used on a global scale for the treatment of acute and chronic pain in diseases as osteoarthritis, fibromyalgia, and low back pain. Binding of opioids on opioid receptors can cause a range of different effects such as changes in stress response, analgesia, motor activity and autonomic functions. This review provide a synthetic summary of the most recent literature on the use of drugs acting on mu-receptors to treat two prevalent functional bowel disorders, presenting with opposite bowel habit. Eluxadoline and naloxegol, methylnaltrexone and naldemedine are recently FDA and/or EMA approved drugs demonstrated to be effective and safe for treatment respectively of irritable bowel syndrome subtype diarrhea and opioid induced constipation.

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.

Effects of naloxegol on whole gut transit in opioid-naïve healthy subjects receiving codeine: A randomized, controlled trial

BACKGROUND

Nausea, vomiting, and constipation (OIC) are common adverse effects of acute or chronic opioid use. Naloxegol (25 mg) is an approved peripherally active mu-opiate opioid receptor antagonist.

AIM

To compare the effects on pan-gut transit of treatment with codeine, naloxegol, or combination in healthy volunteers.

METHODS

We conducted a randomized, double-blind, placebo-controlled, single-center, parallel-group study in 72 healthy opioid-naïve adults, randomized to: codeine (30 mg q.i.d.), naloxegol (25 mg daily), codeine and naloxegol, or matching placebo. During 3 days of treatment, we measured gastric emptying (GE) T1/2 , colonic filling at 6 hours (CF6), colonic geometric center at 24 and 48 hours, and ascending colon emptying (ACE) T1/2 .

KEY RESULTS

Participants were 59.7% women, median BMI 25.0 kg/m2 , and median age 33.8 years. Codeine significantly retarded GE T1/2, CF6, overall colonic transit, and ACE T1/2 . There was significant difference (P = .026) in GE T1/2 between codeine (144.0 min [IQR 110.5-238.6]) and naloxegol (95.5 min [89.1-135.4]). There was a significant overall group difference in CF6 (P = .023), with significant difference (P = .019) between codeine (11.0% [0.0-45.0]) and naloxegol (51% [18.8-76.2]). However, no significant differences were found between codeine-treated participants concomitantly receiving placebo or naloxegol.

CONCLUSIONS AND INFERENCES

Short-term administration of naloxegol (25 mg) in healthy, opioid-naïve volunteers does not reverse the retardation of gastric, small bowel, or colonic transit induced by acute administration of codeine. Further studies with naloxegol at higher dose are warranted to assess the ability to reverse the retardation of transit caused by acute administration of codeine in opioid-naïve subjects.

Insights on efficacious doses of PAMORAs for patients on chronic opioid therapy or opioid-naïve patients

BACKGROUND

Opioid-induced constipation (OIC) is a major side effect of opioid use. Centrally acting antagonists result in opioid withdrawal or worsening of pain and lead to use of peripherally acting mu-opioid receptor antagonists (PAMORAs). The required doses of the PAMORAs, methylnaltrexone and naloxegol, in the treatment of OIC are well established in chronic opioid users. OIC may occur after short duration of opioid treatment; the required doses of naloxone, naltrexone, and PAMORAs in opioid-naïve subjects (with no opioid use for at least 3 months) are unclear. The aim of this review was to evaluate the PAMORA dose required for opioid-naïve subjects to achieve similar beneficial effects on symptoms or valid surrogates to those observed in chronic opioid users.

METHODS

A PubMed search of μ-opioid antagonists to counter μ-opioid effects included terms: naloxone, naltrexone, methylnaltrexone, alvimopan, and naloxegol, as well as OIC and colonic transit.

KEY RESULTS

The approved dose of methylnaltrexone in chronic opioid users, 0.3 mg/kg subcutaneous (SQ), did not affect motility in opioid-naïve subjects. Trials investigating the required dose of alvimopan showed 0.5-1 mg dose was efficacious in treating OIC; a 10-fold higher dose (12 mg) of alvimopan is needed to block effects of codeine on small bowel and colonic transit in opioid-naïve subjects compared to chronic opioid users. Opioid-naïve users need 125 mg of naloxegol to reverse the effects of opioids on transit; this is in contrast to the 12.5 to 25 mg needed to treat OIC in chronic opioid users.

CONCLUSIONS & INFERENCES

Opioid-naïve subjects require a higher dose of PAMORA than chronic opioid users to achieve μ-opioid antagonist effect.

Diabetics on Narcotics Are Less Likely to Achieve Excellent Bowel Preparation Than Are Patients with Either Condition

BACKGROUND

Diabetes and chronic narcotic use negatively affect the quality of bowel preparation before colonoscopy.

AIM

To investigate whether narcotic use and diabetes have an additive negative impact on bowel preparation.

PATIENTS AND METHODS

We performed a retrospective study of 2841 patients (mean age 61 ± 10.2; 94% male) who received outpatient colonoscopies at our Veterans Affairs Medical Center between June 2012 and December 2014. We collected information related to demographics, body mass index, indications, and medical/surgical history (diabetes mellitus, stroke, cirrhosis, dementia, constipation, hypothyroidism, and use of narcotics or antidepressants/anxiolytics for more than three months). Patients were classified into four groups: (1) diabetics on narcotics, (2) diabetics only, (3) on narcotics only, and (4) neither diabetic nor using narcotics. Quality of the bowel preparation was scored using the Boston Bowel Preparation Scale (BBPS) and categorized as either excellent (BBPS ≥7, with no individual segment scoring <2) or not excellent (BBPS <7). Multivariate logistic regression analysis was performed to identify the combined impact of narcotic use and diabetes on bowel preparation.

RESULTS

Bowel preparation quality was excellent in 49%. Thirty-eight percent of patients with diabetes who were using narcotics (adjusted OR 0.6, CI [0.4, 0.8]) achieved excellent bowel preparation compared with 44% (adjusted OR 0.7, CI [0.6, 0.9]) of patients on narcotics only, 48% (adjusted OR 0.8, CI [0.7, 0.9]) of diabetics only, and 54% of patients with neither condition.

CONCLUSION

Concomitant narcotic use and diabetes have a compounding effect on the quality of bowel preparation prior to colonoscopy.

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.

Opioid-induced constipation: rationale for the role of norbuprenorphine in buprenorphine-treated individuals

Buprenorphine and buprenorphine–naloxone fixed combinations are effective for managing patients with opioid dependence, but constipation is one of the most common side effects. Evidence indicates that the rate of constipation is lower when patients are switched from sublingual buprenorphine–naloxone tablets or films to a bilayered bioerodible mucoadhesive buccal film formulation, and while the bilayered buccal film promotes unidirectional drug flow across the buccal mucosa, the mechanism for the reduced constipation is unclear. Pharmacokinetic simulations indicate that chronic dosing of sublingually administered buprenorphine may expose patients to higher concentrations of norbuprenorphine than buprenorphine, while chronic dosing of the buccal formulation results in higher buprenorphine concentrations than norbuprenorphine. Because norbuprenorphine is a potent full agonist at mu-opioid receptors, the differences in norbuprenorphine exposure may explain the observed differences in treatment-emergent constipation between the sublingual formulation and the buccal film formulation of buprenorphine–naloxone. To facilitate the understanding and management of opioid-dependent patients at risk of developing opioid-induced constipation, the clinical profiles of these formulations of buprenorphine and buprenorphine-naloxone are summarized, and the incidence of treatment-emergent constipation in clinical trials is reviewed. These data are used to propose a potential role for exposure to norbuprenorphine, an active metabolite of buprenorphine, in the pathophysiology of opioid-induced constipation.

Opioid-induced bowel dysfunction: epidemiology, pathophysiology, diagnosis, and initial therapeutic approach

Opioids affect motor and sensory function throughout the gastrointestinal tract, and are frequently associated with a number of gastrointestinal symptoms including constipation, which impairs the quality of life and may limit the dose of opioid or result in discontinuation altogether. Patients with opioid-induced constipation should be assessed by careful history and physical examination, and in some cases where the diagnosis is unclear with select diagnostic tests. Few clinical studies have been conducted to assess the efficacy of various treatments. However, it is generally recommended that first-line therapy begin with opioid rotation, as well as with low-cost and low-risk approaches such as lifestyle changes, consumption of fiber-rich food, stool softeners, and laxatives.

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.

Prediction of Prolonged Postoperative Ileus After Radical Gastrectomy for Gastric Cancer: A Scoring System Obtained From a Prospective Study

Currently, there is a paucity of study investigating postoperative ileus in gastric cancer surgery. This prospective study aims to identify the risk factors for prolonged postoperative ileus (PPOI) and to use these risk factors to generate a risk stratification scoring system for the occurrence of PPOI.Patients who underwent radical gastrectomy for gastric cancer were included in this study. A multivariate logistic analysis was applied to identify independent risk factors for PPOI and to generate the scoring system. A receiver operating characteristic curve was generated and the area under the curve was calculated to demonstrate the predictive power of the scoring system.Finally, 296 patients were included and analyzed, of whom 96 (32.4%) developed PPOI. The multivariate analysis showed that age ≥65 years, operative duration ≥4 hours, tumor-node-metastasis (TNM) stage = III, open/converted operative technique, and total postoperative opiates dose (TOD) ≥0.3 mg/kg were independent risk factors for PPOI. Based on these factors, a risk stratification scoring system was generated, classified by low-risk (score 0-2), moderate-risk (score 3-4), and high-risk (score 5-6) groups. The incidence of PPOI increased by 7.5-fold from low-risk to high-risk group. The area under the curve of the scoring system was 0.841 (95% CI, 0.793-0.890), indicating a good predictive capability for the occurrence of PPOI.We have identified independent risk factors for the occurrence of PPOI and used these factors to construct a risk stratification scoring system.

Opioid-Induced Esophageal Dysfunction (OIED) in Patients on Chronic Opioids

OBJECTIVES

Bowel dysfunction has been recognized as a predominant side effect of opioid use. Even though the effects of opioids on the stomach and small and large intestines have been well studied, there are limited data on opioid effects on esophageal function. The aim of this study was to compare esophageal pressure topography (EPT) of patients taking opioids at the time of the EPT (≤24 h) with chronic opioid users who were studied off opioid medications for at least 24 h using the Chicago classification v3.0.

METHODS

A retrospective review identified 121 chronic opioid users who completed EPT between March 2010 and August 2012. Demographic and manometric data were compared between the two groups using general linear models or χ(2).

RESULTS

Of the 121 chronic opioid users, 66 were studied on opioid medications (≤24 h) and 55 were studied off opioid medications for at least 24 h. Esophagogastric junction (EGJ) outflow obstruction was significantly more prevalent in patients using opioids within 24 h compared with those who did not (27% vs. 7%, P=0.004). Mean 4 s integrated relaxation pressure was also significantly higher in patients studied on opioids (10.71 vs. 6.6 mm Hg, P=0.025). Resting lower esophageal sphincter pressures tended to be higher on opioids (31.61 vs. 26.98 mm Hg, P=0.25). Distal latency was significantly lower in patients studied on opioids (6.15 vs. 6.74 s, P=0.044).

CONCLUSIONS

Opioid use within 24 h of EPT is associated with more frequent EGJ outflow obstruction and spastic peristalsis compared with when opioid use is stopped for at least 24 h before the study.

Morphine-Induced Constipation Develops With Increased Aquaporin-3 Expression in the Colon via Increased Serotonin Secretion

Aquaporin-3 (AQP3) is a water channel that is predominantly expressed in the colon, where it plays a critical role in the regulation of fecal water content. This study investigated the role of AQP3 in the colon in morphine-induced constipation. AQP3 expression levels in the colon were analyzed after oral morphine administration to rats. The degree of constipation was analyzed after the combined administration of HgCl(2) (AQP3 inhibitor) or fluoxetine (5-HT reuptake transporter [SERT] inhibitor) and morphine. The mechanism by which morphine increased AQP3 expression was examined in HT-29 cells. AQP3 expression levels in rat colon were increased during morphine-induced constipation. The combination of HgCl(2) and morphine improved morphine-induced constipation. Treatment with morphine in HT-29 cells did not change AQP3 expression. However, 5-HT treatment significantly increased the AQP3 expression level and the nuclear translocation of peroxisome proliferator-activated receptor gamma (PPARγ) 1 h after treatment. Pretreatment with fluoxetine significantly suppressed these increases. Fluoxetine pretreatment suppressed the development of morphine-induced constipation and the associated increase in AQP3 expression in the colon. The results suggest that morphine increases the AQP3 expression level in the colon, which promotes water absorption from the luminal side to the vascular side and causes constipation. This study also showed that morphine-induced 5-HT secreted from the colon was taken into cells by SERT and activated PPARγ, which subsequently increased AQP3 expression levels.

Ogilvie's syndrome-acute colonic pseudo-obstruction

Ogilvie's syndrome describes an acute colonic pseudo-obstruction (ACPO) consisting of dilatation of part or all of the colon and rectum without intrinsic or extrinsic mechanical obstruction. It often occurs in debilitated patients. Its pathophysiology is still poorly understood. Since computed tomography (CT) often reveals a sharp transition or "cut-off" between dilated and non-dilated bowel, the possibility of organic colonic obstruction must be excluded. If there are no criteria of gravity, initial treatment should be conservative or pharmacologic using neostigmine; decompression of colonic gas is also a favored treatment in the decision tree, especially when cecal dilatation reaches dimensions that are considered at high risk for perforation. Recurrence is prevented by the use of a multiperforated Faucher rectal tube and oral or colonic administration of polyethylene glycol (PEG) laxative. Alternative therapeutic methods include: epidural anesthesia, needle decompression guided either radiologically or colonoscopically, or percutaneous cecostomy. Surgery should be considered only as a final option if medical treatments fail or if colonic perforation is suspected; surgery may consist of cecostomy or manually-guided transanal pan-colorectal tube decompression at open laparotomy. Surgery is associated with high rates of morbidity and mortality.

Emerging treatments in neurogastroenterology: a multidisciplinary working group consensus statement on opioid-induced constipation

BACKGROUND

Opioids are effective for acute and chronic pain conditions, but their use is associated with often difficult-to-manage constipation and other gastrointestinal (GI) effects due to effects on peripheral μ-opioid receptors in the gut. The mechanism of opioid-induced constipation (OIC) differs from that of functional constipation (FC), and OIC may not respond as well to most first-line treatments for FC. The impact of OIC on quality of life (QoL) induces some patients to decrease or stop their opioid therapy to relieve or avoid constipation.

PURPOSE

At a roundtable meeting on OIC, a working group developed a consensus definition for OIC diagnosis across disciplines and reviewed current OIC treatments and the potential of treatments in development. By consensus, OIC is defined as follows: 'A change when initiating opioid therapy from baseline bowel habits that is characterized by any of the following: reduced bowel movement frequency, development or worsening of straining to pass bowel movements, a sense of incomplete rectal evacuation, or harder stool consistency'. The working group noted the prior validation of a patient response outcome and end point for clinical trials and recommended future efforts to create treatment guidelines and QoL measures specific for OIC. Details from the working group's discussion and consensus recommendations for patient care and research are presented in this article.

Oxycodone/Naloxone: role in chronic pain management, opioid-induced constipation, and abuse deterrence

The use of opioids in the treatment of chronic pain is widespread; the prevalence of specific opioids varies from country to country and depends on product availability, national formulary systems, and provider preferences. Patients often receive opioids for legitimate treatment of pain conditions, but on the opposite side of the spectrum, nonmedical use of opioids is a significant public health concern. Opioids are associated with several side effects, and constipation is the most commonly reported and persistent symptom. Unlike some adverse effects associated with opioid use, tolerance does not develop to constipation. Opioid-induced constipation (OIC) is the most prevalent patient complaint associated with opioid use and has been associated with declines in various quality of life measures. OIC can be extremely difficult for patients to tolerate and may prompt patients to decrease or discontinue opioid treatment. Current management strategies for OIC are often insufficient. A prolonged-release formulation of oxycodone/naloxone (OXN) has been investigated for the treatment of nonmalignant and cancer pain and mitigation of OIC, and evidence is largely favorable. Studies have demonstrated the capability of OXN to alleviate OIC while maintaining pain control comparable to oxycodone-only regimens. There is insufficient evidence for OXN efficacy for patients with mild OIC or patients maintained on high doses of opioids, and use in these populations is controversial. The reduction of costs associated with OIC may provide overall cost effectiveness with OXN. Additionally, the presence of naloxone may deter abuse/misuse by those seeking to misuse the formulation by modes of administration other than oral ingestion. Most studies to date have occurred in European countries, and phase 3 trials continue in the United States. This review will include current therapeutic options for pain and constipation, unique characteristics of OXN, evidence related to use of OXN and its place in therapy, discussion of opioid abuse/misuse, and various abuse-deterrent mechanisms, and areas of continuing research.

Pain therapy with oxycodone/naloxone prolonged-release combination: case report

Pain afflicts patients suffering from many chronic diseases and is present in 80% of cases of patients with advanced cancer who suffer from persistent pain. The aim of the pain treatment is to achieve the maximum analgesic effect while minimizing side effects. The main analgesic agent - morphine is unfortunately a therapy associated with gastrointestinal side effects. It appears that the combination of oxycodone and naloxone available as Targin(®) (Mundipharma) is an alternative. The paper presents a case of a 45-year-old patient who was treated effectively with oxycodone/naloxone prolonged-release tablets. This treatment has proven to be effective in providing pain and constipation control.

Efficacy of pharmacological therapies for the treatment of opioid-induced constipation: systematic review and meta-analysis

OBJECTIVES

There has been no definitive synthesis of the evidence for any benefit of available pharmacological therapies in opioid-induced constipation (OIC). We conducted a systematic review and meta-analysis to address this deficit.

METHODS

We searched MEDLINE, EMBASE, EMBASE Classic, and the Cochrane central register of controlled trials through to December 2012 to identify placebo-controlled trials of μ-opioid receptor antagonists, prucalopride, lubiprostone, and linaclotide in the treatment of adults with OIC. No minimum duration of therapy was required. Trials had to report a dichotomous assessment of overall response to therapy, and data were pooled using a random effects model. Effect of pharmacological therapies was reported as relative risk (RR) of failure to respond to therapy, with 95% confidence intervals (CIs).

RESULTS

Fourteen eligible randomized controlled trials (RCTs) of μ-opioid receptor antagonists, containing 4,101 patients, were identified. These were superior to placebo for the treatment of OIC (RR of failure to respond to therapy=0.69; 95% CI 0.63-0.75). Methylnaltrexone (six RCTs, 1,610 patients, RR=0.66; 95% CI 0.54-0.84), naloxone (four trials, 798 patients, RR=0.64; 95% CI 0.56-0.72), and alvimopan (four RCTs, 1,693 patients, RR=0.71; 95% CI 0.65-0.78) were all superior to placebo. Total numbers of adverse events, diarrhea, and abdominal pain were significantly commoner when data from all RCTs were pooled. Reversal of analgesia did not occur more frequently with active therapy. Only one trial of prucalopride was identified, with a nonsignificant trend toward higher responder rates with active therapy. Two RCTs of lubiprostone were found, with significantly higher responder rates with lubiprostone in both, but reporting of data precluded meta-analysis.

CONCLUSIONS

μ-Opioid receptor antagonists are safe and effective for the treatment of OIC. More data are required before the role of prucalopride or lubiprostone in the treatment of OIC are clear.

A randomised, placebo-controlled trial comparing the effects of tapentadol and oxycodone on gastrointestinal and colonic transit in healthy humans

BACKGROUND

Tapentadol is a mu-opioid receptor agonist and norepinephrine reuptake inhibitor. In clinical trials, tapentadol provided somatic pain relief comparable to mu-opioids such as oxycodone, with significantly less gastrointestinal adverse effects. The acute effects of tapentadol on gastrointestinal and colonic transit are unclear.

AIM

To compare acute effects of oral tapentadol and oxycodone on gastric, small bowel and colonic transit of solids in 38 healthy human subjects.

METHODS

In a randomised, parallel-group, double-blind, placebo-controlled study of the effects of identical-appearing tapentadol immediate release (IR), 75 mg t.d.s., or oxycodone IR, 5 mg t.d.s., for 48 h, we measured gastric (GE), small bowel (SBT measured as colonic filling at 6 h) and colonic transit by validated scintigraphy. Drug was commenced on the evening before the start of the transit test. The primary endpoints were overall colonic transit (geometric centre, GC) at 24 h and GE half-time (t1/2 ). ancova of transit data included gender or BMI as covariates. Adverse effects were summarised.

RESULTS

At the doses tested, oxycodone and tapentadol significantly delayed GE t1/2 and SBT, but not overall colonic transit, compared to placebo. Transit profiles in all regions were not significantly different between oxycodone and tapentadol at the doses tested. Both oxycodone and tapentadol were associated with nausea and central effects attributable to central opiate effects.

CONCLUSIONS

Tapentadol significantly delayed gastric emptying t1/2 and small bowel transit, similar to oxycodone. These data suggest that acute administration of tapentadol may not have significant advantages over standard mu-opioids, in terms of the potential to avoid upper gastrointestinal motor dysfunction.

A randomized, placebo-controlled phase 3 trial (Study SB-767905/013) of alvimopan for opioid-induced bowel dysfunction in patients with non-cancer pain

The balance between the pain relief provided by opioid analgesics and the side effects caused by such agents is of particular significance to patients who take opioids for the long-term relief of non-cancer pain. The spectrum of signs and symptoms affecting the gastrointestinal (GI) tract associated with opioid use is known as opioid-induced bowel dysfunction. Alvimopan is an orally administered, systemically available, peripherally acting mu-opioid receptor (PAM-OR) antagonist, approved in the US for the management of postoperative ileus in patients undergoing bowel resection (short-term, in-hospital use only). Alvimopan was under clinical development for long-term treatment of opioid-induced constipation (OIC) but this program has been discontinued. This double-blind, placebo-controlled trial, part of the former OIC development program, enrolled patients (N = 485) receiving opioids for non-cancer pain. Patients were randomized to receive alvimopan .5 mg once daily, alvimopan .5 mg twice daily, or placebo, for 12 weeks. The primary efficacy endpoint was the proportion of patients who experienced ≥ 3 spontaneous bowel movements (SBMs; bowel movements with no laxative use in the previous 24 hours) per week over the treatment period, and an average increase from baseline of ≥ 1 SBM per week. There were greater proportions of SBM responders in both alvimopan treatment groups (63% in both groups) compared with placebo (56%), although these differences were not statistically significant. Secondary efficacy analyses indicated that alvimopan was numerically superior to placebo in improving opioid-induced bowel dysfunction symptoms and patients' global assessment of opioid-induced bowel dysfunction, and reduced the requirement for rescue laxatives. Active treatment was well tolerated and alvimopan did not antagonize opioid analgesia.

PERSPECTIVE

Although the primary endpoint was not met in this study, the magnitude of alvimopan-induced improvements versus baseline, together with previous study results, suggest that a PAM-OR antagonist has the potential to improve OIC.

A randomized, placebo-controlled phase 3 trial (Study SB-767905/012) of alvimopan for opioid-induced bowel dysfunction in patients with non-cancer pain

Gastrointestinal (GI) side effects are common with opioid medication, and constipation affects ∼40% of patients. Such symptoms considerably impair patients' quality of life. Alvimopan is an orally administered, systemically available, peripherally acting mu-opioid receptor (PAM-OR) antagonist approved in the US for short-term, in-hospital management of postoperative ileus in patients undergoing bowel resection. This double-blind, placebo-controlled trial was conducted as part of a recently discontinued clinical program, in which alvimopan was being developed for opioid-induced constipation (OIC). Patients (N = 518) receiving opioids for non-cancer pain were randomized to receive alvimopan .5 mg once daily, alvimopan .5 mg twice daily, or placebo for 12 weeks. The primary efficacy endpoint was the proportion of patients experiencing ≥ 3 spontaneous bowel movements (SBMs; bowel movements with no laxative use in the previous 24 hours) per week over the treatment period and an average increase from baseline of ≥ 1 SBM per week. A significantly greater proportion of patients in the alvimopan .5 mg twice-daily group met the primary endpoint compared with placebo (72% versus 48%, P < .001). Treatment with alvimopan twice daily improved a number of other symptoms compared with placebo and reduced the requirement for rescue laxative use. The opioid-induced bowel dysfunction Symptoms Improvement Scale (SIS) responder rate was 40.4% in the alvimopan .5 mg twice daily group, versus 18.6% with placebo (P < .001). In general, alvimopan .5 mg once daily produced qualitatively similar but numerically smaller responses than twice-daily treatment. Active treatment did not increase the requirement for opioid medication or increase average pain intensity scores. Over the 12-week treatment period, alvimopan appeared to be well tolerated.

PERSPECTIVE

These results demonstrate the potential for a PAM-OR antagonist to improve the symptoms of OIC without antagonizing opioid analgesia.

Risk factors for postoperative ileus

Purpose

This study aimed to examine extended postoperative ileus and its risk factors in patients who have undergone abdominal surgery, and discuss the techniques of prevention and management thereof the light of related risk factors connected with our study.

Methods

This prospective study involved 103 patients who had undergone abdominal surgery. The effects of age, gender, diagnosis, surgical operation conducted, excessive small intestine manipulation, opioid analgesic usage time, and systemic inflammation on the time required for the restoration of intestinal motility were investigated. The parameters were investigated prospectively.

Results

Regarding the factors that affected the restoration of gastrointestinal motility, resection operation type, longer operation period, longer opioid analgesics use period, longer nasogastric catheter use period, and the presence of systemic inflammation were shown to retard bowel motility for 3 days or more.

Conclusion

Our study confirmed that unnecessary analgesics use in patients with pain tolerance with non-steroid anti-inflammatory drugs, excessive small bowel manipulation, prolonged nasogastric catheter use have a direct negative effect on gastrointestinal motility. Considering that an exact treatment for postoperative ileus has not yet been established, and in light of the risk factors mentioned above, we regard that prevention of postoperative ileus is the most effective way of coping with intestinal dysmotility.

Neostigmine for the treatment of gastrointestinal atony: a report of one case

BACKGROUND

A case of severe constipation is described in a 75-year- old cancer patient receiving methadone for pain. Her constipation was refractory to the current treatment and she suffered severe discomfort and cognitive impairment. Due to the severity of the clinical situation and after excluding mechanical obstruction, low doses of subcutaneous neostigmine were administered, having bowel movements with evacuation of stools in a few hours after its administration.

DISCUSSION

The results suggest that subcutaneous neostigmine could be an alternative choice in a group of selected patients with advanced cancer and opioid-induced constipation.