Opioid-induced gastrointestinal dysfunction

Perioperative management protocol for pediatric endoluminal functional lumen imaging probe in esophageal motility disorders

OBJECTIVES

Lower esophageal sphincter achalasia is associated with a higher risk of aspiration during anesthesia. Endoluminal Functional Lumen Imaging Probe (EndoFLIP) is used as an adjunctive tool in both the diagnosis and treatment of achalasia, for which all children require anesthesia. Anesthesia may affect the parameters of the EndoFLIP due to its effect on gut motility. There are no standard anesthesia protocols to help decrease the risk of aspiration and the undesirable effect of anesthesia on EndoFLIP parameters. This study aims to standardize an anesthesia protocol to target both goals.

METHODS

A protocol was developed to address perioperative management in patients undergoing EndoFLIP for any indication to minimize both anesthetic effect on the esophageal motility as well as perioperative complications. A retrospective data analysis was conducted on patients who underwent EndoFLIP at Cincinnati Children's Hospital Medical Center; pre- and post-protocol implementation data including adverse events was compared.

RESULTS

Pre-protocol implementation: 60 cases (median age of 13.8 years, 30 [50%] females) with 2 cases of adverse events (3.3%). Post-protocol implementation: 71 cases (median age of 14.6 years, 37 [52.1%] females) with no adverse events (0/71 = 0%). In comparison between pre- and post-protocol cases, no significant difference was noted in gender, age, and adverse events. Post-protocol procedures were found to be significantly shorter (median time of 89 vs. 79 min, p = 0.004).

CONCLUSIONS

Our anesthesia protocol provides a standardized way of administering anesthesia minimizing impact on EndoFLIP parameters and aspiration for patients with achalasia.

Expression and function of transient receptor potential melastatin 3 in the spinal afferent innervation of the mouse colon

Abdominal pain is a cardinal symptom of inflammatory bowel disease (IBD). Transient receptor potential (TRP) channels contribute to abdominal pain in preclinical models of IBD, and TRP melastatin 3 (TRPM3) has recently been implicated in inflammatory bladder and joint pain in rodents. We hypothesized that TRPM3 is involved in colonic sensation and is sensitized during colitis. We used immunohistochemistry, ratiometric Ca2+ imaging, and colonic afferent nerve recordings in mice to evaluate TRPM3 protein expression in colon-projecting dorsal root ganglion (DRG) neurons, as well as functional activity in DRG neurons and colonic afferent nerves. Colitis was induced using dextran sulfate sodium (DSS) in drinking water. TRPM3 protein expression was observed in 76% of colon-projecting DRG neurons and was often colocalized with calcitonin gene-related peptide. The magnitudes of intracellular Ca2+ transients in DRG neurons in response to the TRPM3 agonists CIM-0216 and pregnenolone sulfate sodium were significantly greater in neurons from mice with colitis compared with controls. In addition, the percentage of DRG neurons from mice with colitis that responded to CIM-0216 was significantly increased. CIM-0216 also increased the firing rate of colonic afferent nerves from control and mice with colitis. The TRPM3 inhibitor isosakuranetin inhibited the mechanosensitive response to distension of wide dynamic range afferent nerve units from mice with colitis but had no effect in control mice. Thus, TRPM3 contributes to colonic sensory transduction and may be a potential target for treating pain in IBD.NEW & NOTEWORTHY This is the first study to characterize TRPM3 protein expression and function in colon-projecting DRG neurons. A TRPM3 agonist excited DRG neurons and colonic afferent nerves from healthy mice. TRPM3 agonist responses in DRG neurons were elevated during colitis. Inhibiting TRPM3 reduced the firing of wide dynamic range afferent nerves from mice with colitis but had no effect in control mice.

Impact of opioids on esophageal motility

Opioids are well known to cause adverse effects on the gastrointestinal tract including nausea, vomiting, and constipation. Data regarding how opioids affect the esophagus are more limited. Opioid-induced esophageal dysfunction (OIED) is a clinical syndrome defined by chronic opioid use (≥3 months), esophageal symptoms (mainly dysphagia), and esophageal motility abnormalities diagnosed by manometry including achalasia type III, hypercontractile esophagus, distal esophageal spasm, and esophagogastric junction outflow obstruction. Up until now, the effect of opioids on esophageal motility assessed by the functional lumen imaging probe (FLIP) had not been described. In this issue of NGM, Patel et al. report that FLIP assessment in patients with esophageal symptoms showed that chronic opioid users have a significant increase in repetitive retrograde contractions, but no significant reduction in distensibility at the esophagogastric junction compared to non-users. Additionally, perceptive symptoms were higher, and quality of life metrics were lower in the chronic opioid users. This review article will discuss our current understanding of OIED and provide context for this latest study in chronic opioid users. Further investigation with larger prospective studies is needed to understand the pathophysiology, diagnosis, and management of OIED.

Magnesium hydroxide versus macrogol/electrolytes in the prevention of opioid-induced constipation in incurable cancer patients: study protocol for an open-label, randomized controlled trial (the OMAMA study)

BACKGROUND

Opioid-induced constipation (OIC) is a common symptom in cancer patients treated with opioids with a prevalence of up to 59%. International guidelines recommend standard laxatives such as macrogol/electrolytes and magnesium hydroxide to prevent OIC, although evidence from randomized controlled trials is largely lacking. The aim of our study is to compare magnesium hydroxide with macrogol /electrolytes in the prevention of OIC in patients with incurable cancer and to compare side-effects, tolerability and cost-effectiveness.

METHODS

Our study is an open-label, randomized, multicenter study to examine if magnesium hydroxide is non-inferior to macrogol/electrolytes in the prevention of OIC. In total, 330 patients with incurable cancer, starting with opioids for pain management, will be randomized to treatment with either macrogol/electrolytes or magnesium hydroxide. The primary outcome measure is the proportion of patients with a score of < 30 on the Bowel Function Index (BFI), measured on day 14. The Rome IV criteria for constipation, side effects of and satisfaction with laxatives, pain scores, quality of life (using the EQ-5D-5L), daily use of laxatives and escape medication, and cost-effectiveness will also be assessed.

DISCUSSION

In this study we aim to examine if magnesium hydroxide is non-inferior to macrogol/electrolytes in the prevention of OIC. The outcome of our study will contribute to prevention of OIC and scientific evidence of guidelines on (opioid-induced) constipation.

TRIAL REGISTRATION

This trial is registered at clinicaltrials.gov: NCT05216328 and in the Dutch trial register: NTR80508. EudraCT number 2022-000408-36.

Opioid-Associated Anorectal Dysfunction in Chronic Constipation

INTRODUCTION

The role of anorectal and defecatory dysfunction in opioid-related constipation is unclear. We aimed to evaluate the relationship between opioid use and rectal sensation, defecatory function, and balloon expulsion on anorectal physiology testing.

METHODS

This was a retrospective cohort study of consecutive adults undergoing high-resolution anorectal manometry (HRAM) at a tertiary center for constipation. Clinical characteristics, medication use, and HRAM findings were obtained. Statistical analyses were performed using Fisher-exact/student t-test for univariate analyses and logistic/general linear regression for multivariable analyses to compare patients with no opioid use, recent (< 3 months) use, and distant (> 3 months) use.

RESULTS

424 patients (49.8 ± 17.2 years; 85.6% female) were included. Compared to those without opioid history, patients with recent use had increased volumes for first rectal sensation (70.4 mL vs 59.4, p = 0.043), urge (120.5 mL vs 101.5, p = 0.017), and maximal tolerance (170.2 mL vs 147.2, p = 0.0018), but not patients with distant use. Recent opioid use was associated with increased risk of dyssynergic defecation (DD) (61.8% vs 46.4%, p = 0.035), but not failed balloon expulsion. On multivariable models controlling for potential confounders, recent opioid use, but not distant use, remained independently correlated with increased volumes for first rectal sensation (β-coefficient 9.78, p = 0.019), urge (β-coefficient 16.7, p = 0.0060), and maximal tolerance (β-coefficient 22.9, p = 0.0032), and higher risk for DD (aOR = 2.18, p = 0.026).

CONCLUSION

Recent opioid use was an independent risk factor for rectal hyposensitivity and DD on HRAM in patients with constipation, but that effect may decrease with discontinuation of use. Anorectal physiology testing should be considered in patients with opioid-associated constipation.

Medical marijuana for inflammatory bowel disease: the highs and lows

Increased interest in cannabis as a potential treatment and/or adjuvant therapy for inflammatory bowel disease (IBD) has been driven by patients with refractory disease seeking relief as well those who desire alternatives to conventional therapies. Available data have shown a potential role of cannabis as a supportive medication, particularly in pain reduction; however, it remains unknown whether cannabis has any impact on the underlying inflammatory process of IBD. The purpose of this review article is to summarize the available literature concerning the use of cannabis for the treatment of IBD and highlight potential areas for future study.

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.

Association between potentially inappropriate medication and adverse drug reactions in hospitalized elderly patients

WHAT IS KNOWN AND OBJECTIVE

The Beers, European Union (EU) and Screening Tool of Older Persons' potentially inappropriate Prescription (STOPP) criteria were developed to improve the safe use of medicines in the elderly. However, the predictive validity of existing criteria to detect adverse drug reactions (ADRs) remains unexplored. The objective of the current study was to determine whether the 2019 Beers, 2015 STOPP or 2015 EU potentially inappropriate medicine (PIM) criteria were associated with ADRs.

METHODS

A retrospective, cross-sectional investigation was conducted among older persons (≥60 years of age) admitted to a tertiary hospital in China between April 2019 and December 2019. PIMs were identified as per the Beers, EU and STOPP criteria definitions. ADRs were retrospectively evaluated by two clinical pharmacists using the Naranjo algorithm. Multivariate logistic regression was used to evaluate the factors associated with ADRs in the hospitalized patients.

RESULTS AND DISCUSSION

The study participants included 560 hospitalized patients (mean age 72.05 ± 8.15). The prevalence of patients receiving at least one PIM was 52.1%, 37.0% and 42.9% according to the Beers, EU and STOPP criteria, respectively. Univariate analysis showed that ADRs were associated with PIMs listed in the Beers criteria (OR: 2.093, 95% CI: 1.028-4.263, 0.042), but not with the STOPP-listed (OR: 0.536, 95% CI: 0.255-1.123, 0.098) and EU-listed PIMs (OR: 0.258, 95% CI: 0.118-0.563, 0.001).

WHAT IS NEW AND CONCLUSION

In contrast to the STOPP and EU criteria on PIMs, the Beers criteria were significantly associated with avoidable ADRs in hospitalized older persons.

Opioid-induced esophageal dysfunction

PURPOSE OF REVIEW

Chronic opioid use is common and can cause opioid-induced esophageal dysfunction (OIED). We will discuss the pathophysiology, diagnosis, and management of OIED.

RECENT FINDINGS

OIED is diagnosed based on symptoms, opioid use, and manometric evidence of distal esophageal spasm, esophagogastric junction outflow obstruction, achalasia type III, or jackhammer esophagus. Chronic opioid use appears to interfere with inhibitory signals involved in control of esophageal motility, allowing for unchecked excitatory stimuli, and leading to spastic contractility and impaired esophagogastric junction relaxation. Patients may present with dysphagia and chest pain. OIED is significantly more prevalent in patients taking the stronger opioids oxycodone and hydrocodone compared with the weaker opioid tramadol. Based on 24-h morphine equivalent doses, patients with OIED take higher opioid doses than those without OIED. Impaired inhibitory signaling was recently demonstrated in a study showing reduced deglutitive inhibition during multiple rapid swallows in patients taking opioids.

SUMMARY

OIED is frequent in chronic opioid users undergoing manometry for esophageal symptoms, especially at higher doses or with stronger opioids. OIED appears to be due to impaired inhibitory signals in the esophagus. Opioid cessation or dose reduction is recommended, but studies examining management of OIED are lacking.

Anticholinergic, anti-depressant and other medication use is associated with clinically relevant oesophageal manometric abnormalities

BACKGROUND

Medications can affect gastrointestinal tract motility. However, their effects on oesophageal motility in particular are often not as widely known or may be underestimated.

AIM

To review the effect of existing medication use on high-resolution oesophageal manometry (HRM) in a 'real-world' setting.

METHODS

Adult patients with upper gut symptoms and normal endoscopy or imaging who had HRM over a 22-month period were analysed. Achalasia and major disorders of peristalsis were excluded. All medications taken within 24 hours of the procedure were prospectively recorded and compared with HRM results, controlling for age, gender and proton pump inhibitor use.

RESULTS

A total of 502 patients (323 female, mean age 51) were recruited. Of these, 41.2% had normal oesophageal HRM, while 41.4% had ineffective oesophageal motility (IOM) and 7.6% had oesophagogastric junction outflow obstruction (OGJOO). Serotonin/norepinephrine reuptake inhibitors (SNRI) and opioids were associated with significantly higher resting lower oesophageal sphincter pressure. Benzodiazepines and opioids were associated with elevated integrated relaxation pressure. SNRI and inhaled beta-agonists were associated with increased distal contractile index, whereas calcium channel blockers were associated with a lower distal contractile index. Odds ratio of being on anticholinergics was higher in IOM patients vs normal (3.6, CI 1.2-10.8). Odds ratio for anticholinergics, inhaled beta-agonists, anticonvulsants, SNRIs and opioids (trend) were all > 3 for OGJOO patients vs normal.

CONCLUSION

Many medication classes are associated with abnormal HRM variables and diagnoses such as OGJOO and IOM; some of these associations are probably causal. These possible links should be taken into consideration during manometry interpretation.

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.

Increasing Prescription of Opiates and Mortality in Patients With Inflammatory Bowel Diseases in England

BACKGROUND & AIMS

The prescription of opiate medications is increasing. Individuals with inflammatory bowel diseases (IBD) can develop serious complications from opiate use, but few data are available on the prescription of these drugs to patients with IBD. We examined trends in prescriptions of opiates and their association with all-cause mortality in individuals with IBD.

METHODS

We performed a retrospective cohort study of 3517 individuals with Crohn's disease (CD) and 5349 with ulcerative colitis (UC) using the primary care database ResearchOne, which holds de-identified clinical and administrative information from the health records of approximately 6 million persons (more than 10% of the total population) in England. We explored trends in prescriptions of all opiates, codeine, tramadol, or strong opiates, separately from 1990 through September 14, 2014. Associations between opiates and all-cause mortality were examined using propensity score-matched analysis.

RESULTS

There was a statistically significant increase in the prescription of opiate medications, with 10% of subjects receiving an opiate prescription from 1990 through 1993 compared to 30% from 2010 through 2013 (chi-square for trend, P < .005). Prescription of strong opiates was significantly associated with increased premature mortality of patients with CD (heavy use) or UC (moderate or heavy use). There was a significant association between heavy use of any opiate or codeine alone and premature mortality of patients with UC. Use of tramadol alone, or in combination with codeine, was not associated with premature mortality in patients with CD or UC.

CONCLUSIONS

In an analysis of primary care patients with IBD in England, we found prescriptions for opiate drugs to have increased significantly from 1990 through 2013. Heavy use of strong opiates among patients with IBD associates with increased all-cause premature mortality.

Opioid-Induced Constipation and Bowel Dysfunction: A Clinical Guideline

OBJECTIVE

To formulate timely evidence-based guidelines for the management of opioid-induced bowel dysfunction.

SETTING

Constipation is a major untoward effect of opioids. Increasing prescription of opioids has correlated to increased incidence of opioid-induced constipation. However, the inhibitory effects of opioids are not confined to the colon, but also affect higher segments of the gastrointestinal tract, leading to the coining of the term "opioid-induced bowel dysfunction."

METHODS

A literature search was conducted using Medline, EMBASE, and EMBASE Classic, and the Cochrane Central Register of Controlled Trials. Predefined search terms and inclusion/exclusion criteria were used to identify and categorize relevant papers. A series of statements were formulated and justified by a comment, then labeled with the degree of agreement and their level of evidence as judged by the Strength of Recommendation Taxonomy (SORT) system.

RESULTS

From a list of 10,832 potentially relevant studies, 33 citations were identified for review. Screening the reference lists of the pertinent papers identified additional publications. Current definitions, prevalence, and mechanism of opioid-induced bowel dysfunction were reviewed, and a treatment algorithm and statements regarding patient management were developed to provide guidance on clinical best practice in the management of patients with opioid-induced constipation and opioid-induced bowel dysfunction.

CONCLUSIONS

In recent years, more insight has been gained in the pathophysiology of this "entity"; new treatment approaches have been developed, but guidelines on clinical best practice are still lacking. Current knowledge is insufficient regarding management of the opioid side effects on the upper gastrointestinal tract, but recommendations can be derived from what we know at present.

Quality of life and healthcare resource in patients receiving opioids for chronic pain: a review of the place of oxycodone/naloxone

In patients managed with opioids for chronic pain, opioid-induced bowel dysfunction—specifically, opioid-induced constipation (OIC)—is a common side effect, which has a significant impact on quality of life (QoL). The most recent developments for management of OIC are opioid antagonists, including naloxone, a competitive antagonist of peripheral opioid receptors that reverses opioid-induced peripheral gastrointestinal (GI) effects. A prolonged-release formulation of naloxone is available in combination with oxycodone (OXN PR). To review the specific role of OXN PR in the management of chronic pain and OIC and its impact on QoL and healthcare costs, a review of available relevant literature was conducted. Healthcare costs can be up to ten times higher for patients with GI events than for those without. Assessment of QoL in patients with OIC is essential, and multiple tools for its evaluation are available. The Bowel Function Index (BFI), a tool that was specifically developed and validated to measure bowel function in patients with OIC, can be an indication of QoL. In patients with moderate-to-severe chronic pain, randomized trials have demonstrated that OXN PR has equal analgesic efficacy and safety, but results in improved bowel function, compared with prolonged-release oxycodone (Oxy PR) alone. In conclusion, randomized studies using the BFI, as well as real-world clinical practice observations, have demonstrated improved QoL for patients taking OXN PR. This combination should allow more patients to benefit from the analgesic efficacy of opioid therapy and should minimize the side effects of constipation that correspond to improvements in QoL and healthcare offsets.

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.

Lubiprostone vs Senna in postoperative orthopedic surgery patients with opioid-induced constipation: A double-blind, active-comparator trial

AIM: To investigate the efficacy of lubiprostone compared to Senna on bowel symptoms and constipation in post-operative orthopedic patients treated with opioids.

METHODS: In this double blind, randomized, active comparator trial, adults who required opioids for analgesia following orthopedic procedures and who were admitted in inpatient rehabilitation were randomized following baseline assessments to lubiprostone (Amitza^®), orally twice a day or Senna (generic) two capsules administered daily for six days. Subjects were assessed using the patient assessment of constipation (PAC)-symptoms (PAC-SYM) and the PAC-quality of life (PAC-QOL) scales measured at baseline and Day 7; Subjects were assessed daily for secondary measures included the Bristol stool scale bowel consistency, specific bowel symptom score (Nausea, cramping, straining, completeness, abdominal pain, time per lavatory attempt, assistance needed), adverse events and rescue medications required. Function was measured using the functional independence measure (FIM) at admission and discharge; length of stay (LOS) and missed treatments due to gastrointestinal symptoms were also assessed.

RESULTS: 64 adults were enrolled; 56 participants (28 in each group) had baseline and follow up measures and were included in the intention to treat (ITT) analyses. 43 participants completed the study, 21 in the active lubiprostone and 22 in the active Senna group. The mean age of the participants was 71.5 years (SD = 11.4 years, range: 28-96 years). In the ITT analyses, participants showed significant improvement in bowel symptoms as measured by the PAC-SYM (mean ± SD, -0.28 ± 0.60, range: -1-2.33) and PAC-QOL (mean ± SD, 0.33 ± 0.81, range: -1.5-2.0) over time, but there were no significant differences between the lubiprostone and Senna groups in mean change in the PAC-SYM (-0.20 ± 0.60 vs -0.36 ± 0.61, P = 0.61 respectively) or the PAC-QOL (0.29 ± 0.76 vs 0.37 ± 0.87, P = 0.61 respectively). The mean change in each bowel symptom also did not significantly differ between treatment groups on ITT analyses, except for completeness of bowel movement, with the Senna group showing greater negative mean change in bowel movement completeness (-0.56 ± 1.01 vs -2.00 ± 1.41, P = 0.03) and for reduction of abdominal pain, favoring Senna (-0.14 ± 0.73 vs -0.73 ± 1.08, P = 0.04). Fifteen (75%) participants in the lubiprostone and in the Senna group requested rescue treatments. Participants made significant functional improvement from admission to discharge over a median LOS of 12 d, with a mean FIM change of 29.13 ± 13.58 and no significant between group differences (27.0 ± 9.2 vs 31.5 ± 16.6, P = 0.27).

CONCLUSION: Both lubiprostone and Senna improved constipation-related symptoms and QOL in opioid-induced constipation, with no significant between-group differences.

Opioid-induced bowel dysfunction

Opioid-induced bowel dysfunction (OIBD) is a potentially debilitating side effect of chronic opioid use. It refers to a collection of primarily gastrointestinal motility disorders induced by opioids, of which opioid-induced constipation (OIC) is the most common. Management of OIBD is difficult, and affected patients will often limit their opioid intake at the expense of experiencing more pain, to reduce the negative impact of OIBD on their quality of life. Effective pharmacologic therapy for OIC is considered an unmet need and several agents have recently been given priority review and approval for OIC. Furthermore, multiple agents currently in development show promise in treating OIC without significant impact on analgesia or precipitation of withdrawal symptoms. The approval and availability of such medications would represent a significant improvement in the management of OIC and OIBD in patients with chronic pain.

Prevalence and impact of constipation and bowel dysfunction induced by strong opioids: a cross-sectional survey of 520 patients with cancer pain: DYONISOS study

OBJECTIVE

To describe the prevalence of opioid-induced constipation (OIC) in patients with cancer pain according to the Knowles-Eccersley-Scott symptom score (KESS), the different symptoms of opioid-induced bowel dysfunction (OIBD), and to assess the impact of OIBD on patient's quality-of-life.

METHODS

A cross-sectional observational study, using the KESS questionnaire and the physician's subjective assessment of constipation, and other questionnaires and questions on constipation, OIBD, and quality-of-life, carried out on 1 day at oncology day centres and hospitals.

RESULTS

Five hundred and twenty patients were enrolled at 77 centres in France; 61.7% of patients (n = 321) showed a degree of constipation that is problematic for the patient according to KESS (between 9-39). Even more patients, 85.7% (n = 438), were considered constipated according to the physician's subjective assessment-despite laxative use (84.7% of patients). Quality-of-life was significantly reduced in constipated vs non-constipated patients for both PAC-QoL (p < 0.0001 for total score and each dimension) and the SF-12 questionnaires (statistically significant for all dimensions except physical state and role physical). OIC and OIBD led to hospitalization (16% of patients), pain (75% of patients), and frequent changes in opioid and laxative treatment.

KEY LIMITATIONS

This cross-sectional study, in a selected population of cancer patients, has measured prevalence and impact of OIBD. Further confirmation could be sought through the use of longitudinal studies, and larger populations, such as non-cancer pain patients treated with opioids.

CONCLUSIONS

Cancer patients taking opioids for pain are very frequently constipated, even if they are prescribed laxatives. This leads to relevant impairments of quality-of-life.

Opioid induced nausea and vomiting

Opioids are broad spectrum analgesics that are an integral part of the therapeutic armamentarium to combat pain in the palliative care population. Unfortunately, among the adverse effects of opioids that may be experienced along with analgesia is nausea, vomiting, and/or retching. Although it is conceivable that in the future, using combination agents (opioids combined with agents which may nullify emetic effects), currently nausea/vomiting remains a significant issue for certain patients. However, there exists potential current strategies that may be useful in efforts to diminish the frequency and/or intensity of opioid-induced nausea/vomiting (OINV).

Pharmacologic treatment of opioid-induced constipation

Opioids are potent analgesics for treating moderate to severe pain, but their use is associated with a number of adverse effects, especially opioid-induced constipation (OIC). If the centrally mediated analgesia of opioids could be separated from their peripherally mediated gastrointestinal effects, by a peripherally acting opioid receptor antagonist, opioid-induced bowel dysfunction could be prevented or reversed. There has been considerable interest in peripherally acting opioid antagonists or other compounds to treat OIC. Subcutaneous methylnaltrexone is the first approved therapeutic agent for treatment of OIC, and studies have been conducted using the oral formulation. This editorial contains a brief overview of other selected compounds to treat OIC. Other potential uses of peripherally acting opioid antagonist in clinical practice are also discussed.

Associations between medication use and functional gastrointestinal disorders: a population-based study

BACKGROUND

Functional GI syndromes are known to be very prevalent, but this may be linked to unrecognized medications use. We aimed to estimate the prevalence of PPI, antidepressant, and narcotic use in the general population, and to evaluate the association between each medication and functional GI syndromes adjusting for potential confounders.

METHODS

In 2008 and 2009, newly revised versions of a validated bowel disease questionnaire were mailed to a community-based cohort (total mailed = 8006) of Olmsted County, MN residents; 3831 returned the questionnaire (response rate = 48.0%). Medication usage, specifically PPIs, narcotics, and antidepressants in the last year, was elicited via three separate questions on the questionnaire. The association between each medication and GI symptom complexes was assessed using multiple variable logistic regression models.

KEY RESULTS

A total of 3515 of the respondents (92%) had complete data (mean age: 61 ± 15; 54% female). The overall proportion reporting PPI use was 20% (95% CI: 19, 22), narcotic use 12% (95% CI: 11, 13), and antidepressant use 15% (95% CI: 14, 16). PPI use was significantly associated with IBS status (OR = 1.4, 95% CI 1.1, 1.7) as well as with GERD (OR = 3.5, 95% CI 2.7, 4.4) and dyspepsia (OR = 2.0, 95% CI 1.5, 2.7). The association of PPI use with IBS was not explained by coexistent GERD or dyspepsia. Antidepressant use was significantly associated only with bloating (OR = 1.6, 1.1, 2.2).

CONCLUSIONS & INFERENCES

Some medications that may alter intestinal transit or bowel flora are commonly utilized by the general population, and PPI use appears to be linked to IBS.

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.

Narcotic bowel syndrome

BACKGROUND

Narcotic bowel syndrome is characterized by chronic or recurrent abdominal pain associated with escalating doses of narcotic pain medications. It may occur in as many as 4% of all patients taking opiates, and yet few physicians are aware that the syndrome exists.

OBJECTIVES

The objectives of this case report are to raise awareness of narcotic bowel syndrome among emergency physicians, as well as review the clinical features, diagnosis, pathophysiology, and emergency department (ED) management of the syndrome.

CASE REPORT

We report a case of narcotic bowel syndrome diagnosed in a 24-year-old woman after > 1 year of ED visits for recurrent abdominal pain of unknown origin.

CONCLUSIONS

It is particularly important for emergency physicians to be familiar with this syndrome, as many patients with narcotic bowel syndrome seek evaluation and treatment in the ED. Although the diagnosis is unlikely to be made in the ED, timely referral for evaluation of this syndrome may help patients to receive definitive treatment for their recurrent and chronic pain.

Prescription drug abuse: epidemiology, regulatory issues, chronic pain management with narcotic analgesics

The epidemic of prescription drug abuse has reached a critical level, which has received national attention. This article provides insight into the epidemiology of prescription drug abuse, explains regulatory issues, and provides guidelines for the assessment and management of pain, particularly with long-term opioid therapy. Using informed consent forms, treatment agreements, and risk documentation tools and regularly monitoring the 4 A's help to educate patients and guide management based on treatment goals. By using universal precautions, and being aware of aberrant behaviors, physicians may feel more confident in identifying and addressing problematic behaviors.

The relationship between opioid and sugar intake: review of evidence and clinical applications

Opioid dependence poses significant public health risks arising from associated morbidity and mortality caused by accidents, infectious diseases, and social ramifications of crime and unemployment, among other complications. Opioid use, acute and chronic, is also associated with weight gain, glycemic dysregulation, and dental pathology. The literature supporting the connection between opiate use and development of preference for sweet tastes is reviewed, and further association with dental pathology, weight gain, and loss of glycemic control are considered. Additionally, the impact of sweet tastes on the endogenous opioid system, as pertaining to analgesia, is also discussed. The authors discuss the clinical implications in relation to the aforementioned conditions while treating the opiate-dependent patient.

Efficacy and safety of prucalopride in patients with chronic noncancer pain suffering from opioid-induced constipation

BACKGROUND

Opioid-induced constipation (OIC) has negative effects on quality of life (QOL). Prucalopride is a new, selective 5-HT(4) agonist and enterokinetic with strong clinical data in chronic constipation. This study investigated the efficacy, safety, and tolerability of prucalopride in patients with noncancer pain and OIC.

METHODS

A phase II, double-blind, placebo-controlled study of 196 patients randomized to placebo (n = 66), prucalopride 2 mg (n = 66) or 4 mg (n = 64), for 4 weeks, was carried out. The primary endpoint was the proportion of patients with increase from baseline of ≥ 1 spontaneous complete bowel movement (SCBM)/week. Secondary endpoints [proportion of patients with ≥ 3 SCBM/week, weekly frequency of (SC)BM, severity of constipation, and efficacy of treatment], adverse events (AEs), and safety parameters were also monitored.

RESULTS

More patients had an increase from baseline of ≥ 1 SCBM per week (weeks 1-4) in the prucalopride groups [35.9% (2 mg) and 40.3% (4 mg)] versus placebo (23.4%), reaching statistical significance in week 1. Over weeks 1-4, more patients in the prucalopride groups achieved an average of ≥ 3 SBM per week versus placebo (60.7% and 69.0% versus 43.3%), reaching significance at week 1. Prucalopride 4 mg significantly improved patient-rated severity of constipation and effectiveness of treatment versus placebo. Patient Assessment of Constipation-Symptom (PAC-SYM) total scores and Patient Assessment of Constipation-Quality of Life (PAC-QOL) total and satisfaction subscale scores were improved. The most common AEs were abdominal pain and nausea. There were no clinically relevant differences between groups in vital signs, laboratory measures or electrocardiogram parameters.

CONCLUSION

In this population with OIC, prucalopride improved bowel function and was safe and well tolerated.

Methylnaltrexone: a novel approach for the management of opioid-induced constipation in patients with advanced illness

In April 2008, the US FDA granted approval to methylnaltrexone (Relistor), the first peripheral micro-opioid-receptor antagonist for the treatment of opioid-induced constipation in advanced-illness patients receiving palliative care and for whom other laxative therapies failed to achieve adequate results. Methylnaltrexone, a quaternary derivative of naltrexone, introduces a novel mechanism of action that selectively antagonizes the peripheral micro-receptors in the GI tract without effects on the CNS. In clinical trials, subcutaneous methylnaltrexone reversed opioid-induced constipation after the first dose in approximately 50-60% of the patients. In most of the cases, effective laxation occurred within 1 h. The therapeutic benefit was sustained in multiple-dose studies. Owing to the nature of the population studied, safety data are available for approximately 4 months of use. Although it is not the focus of this article, methylnaltrexone's mechanism of action suggests it could be beneficial for other peripheral, opioid-induced adverse effects, such as opioid-related nausea, vomiting, urinary retention, pruritus or postoperative ileus.

Opioid bowel dysfunction and narcotic bowel syndrome: a population-based study

OBJECTIVES

Opioid prescription use is increasing. Narcotic bowel syndrome (NBS) refers to chronic abdominal pain aggravated by narcotic use. Despite increasing narcotic use, NBS may be under-recognized. The aim of this study was to assess whether gastrointestinal (GI) symptoms in the community are associated with chronic narcotic use and estimate the likely prevalence of NBS.

METHODS

Validated self-report GI symptom questionnaires were mailed to 4,898 randomly selected people in the community. The medical charts of all respondents were reviewed to identify participants who had used narcotics and to determine whether they were taking an opioid for > 5 weeks for the treatment of chronic pain (malignant or nonmalignant). NBS was defined as abdominal pain developing in those taking chronic narcotics. The associations between GI symptoms and chronic narcotics use were assessed using logistic regression analysis.

RESULTS

A total of 2,913 respondents returned a completed questionnaire (overall response rate 59%, mean age 62, 52% female); 117 participants (4.1%, 95% confidence interval (CI): 3.3, 4.5) were taking narcotics. Five participants (0.17%; 95% CI: 0.06, 0.40%) met the criteria for NBS. Participants using narcotics had an increased use of laxatives (17 vs. 8% in those not using narcotics, P < 0.05). GI symptom reporting was more common in participants on narcotics, although the adjusted (for age, gender, somatic symptom complaints, and use of laxatives) odds ratios (ORs) were significantly increased only for frequent abdominal pain and stool frequency.

CONCLUSIONS

NBS may be relatively uncommon. Those on narcotics report additional GI symptoms (abdominal pain and stool frequency) and use more laxatives.

Prevalence of opioid dispensings and concurrent gastrointestinal medications in Quebec

BACKGROUND

Opioids are frequently prescribed for moderate to severe pain. A side effect of opioid usage is the inhibition of gastrointestinal (GI) motility, known as opioid-induced bowel dysfunction (OBD). OBD is typically treated prophylactically with laxatives and/or acid suppressants.

AIM

The present study describes the prevalence of outpatient opioid dispensing, opioid patient demographics, and concomitant dispensing of opioids and GI medications in the Quebec Public Prescription Drug Insurance Plan in 2005.

METHODS

Using a retrospective cohort design, opioid dispensings were identified using claims and reimbursement data. Laxative and acid suppressant dispensings were also identified. Concurrent use was defined as having at least one 'GI medication-exposed day' overlapping an 'opioid-exposed day'.

RESULTS

More than 11% of the drug plan population was dispensed an opioid in 2005, and dispensings increased with age. Approximately two-thirds of patients who received an opioid were given codeine. Approximately one-third of opioid patients were concomitantly dispensed a GI medication, yet only 2% were dispensed a laxative.

CONCLUSIONS

Although the GI side effects of opioids are well known, these side effects appear to increase with age and duration of opioid use. Opioid-related side effects, particularly OBD, should be effectively managed so as not to lead to the cessation of opioid therapy.

Methylnaltrexone, a new peripherally acting mu-opioid receptor antagonist being evaluated for the treatment of postoperative ileus

Postoperative ileus (POI), a transient impairment of bowel function, is considered an inevitable response after open abdominal surgery. It leads to significant patient morbidity and increased hospital costs and length of stay. The pathophysiology is multifactorial, involving neurogenic, hormonal, inflammatory and pharmacologic mediators. Several treatments have been shown to reduce the duration of POI, and a multimodal approach combining several of these interventions seems to be the most effective treatment option. Various drug therapies have been evaluated for the treatment of POI, although most have not shown any benefit. Peripherally active mu-opioid receptor antagonists are a new class of compounds that selectively block the peripheral (i.e., gastrointestinal [GI]) effects of opioids while preserving centrally mediated analgesia. Recently, alvimopan was approved in the US for the treatment of POI after abdominal surgery with bowel resection. Methylnaltrexone is a peripherally active mu-opioid receptor antagonist that has been shown to antagonize the inhibitory effects of opioids on GI transit without impairing analgesia. Phase II data indicated that methylnaltrexone was effective for improving GI recovery, reducing POI and shortening the time to discharge readiness in patients who underwent segmental colectomy. Two Phase III trials have been completed, and one is underway at present. Preliminary results from the two completed trials indicate that methylnaltrexone was not better than placebo for the primary or secondary outcomes. Further analyses of these data, clinical trial designs and the various dosage forms are necessary to determine the potential role of methylnaltrexone in the treatment of POI.

The prevalence, severity, and impact of opioid-induced bowel dysfunction: results of a US and European Patient Survey (PROBE 1)

OBJECTIVE

This multinational, Internet-based survey was designed to assess the prevalence, frequency, severity, and impact of opioid-induced bowel dysfunction (OBD) in patients receiving opioid therapy for chronic pain and taking laxatives.

DESIGN

In total, 322 patients taking daily oral opioids and laxatives completed the 45-item questionnaire. At the time of the survey, 45% of patients reported <3 bowel movements per week. The most prevalent opioid-induced side effects were constipation (81%) and straining to pass a bowel movement (58%). Those side effects considered most bothersome by patients were (in order of rank) constipation, straining, fatigue, small or hard bowel movements, and insomnia.

RESULTS

Most of the OBD symptoms specified in the questionnaire were experienced by the majority of patients >or=4 times a week. Constipation was the OBD symptom that was most often reported as severe. Most patients reported that their OBD symptoms had at least a moderate negative impact on their overall quality of life and activities of daily living. A third of patients had missed, decreased or stopped using opioids in order to make it easier to have a bowel movement.

CONCLUSION

The survey findings confirm that OBD occurs frequently, despite the use of laxatives, in individuals taking daily oral opioids for chronic pain. These gastrointestinal symptoms add to the burden already experienced by chronic pain patients, negatively impacting quality of life and, in some cases, affecting opioid treatment itself.

Evidence-informed management of chronic low back pain with opioid analgesics

The management of chronic low back pain (CLBP) has proven to be very challenging in North America, as evidenced by its mounting socioeconomic burden. Choosing among available nonsurgical therapies can be overwhelming for many stakeholders, including patients, health providers, policy makers, and third-party payers. Although all parties share a common goal and wish to use limited health-care resources to support interventions most likely to result in clinically meaningful improvements, there is often uncertainty about the most appropriate intervention for a particular patient. To help understand and evaluate the various commonly used nonsurgical approaches to CLBP, the North American Spine Society has sponsored this special focus issue of The Spine Journal, titled Evidence-Informed Management of Chronic Low Back Pain Without Surgery. Articles in this special focus issue were contributed by leading spine practitioners and researchers, who were invited to summarize the best available evidence for a particular intervention and encouraged to make this information accessible to nonexperts. Each of the articles contains five sections (description, theory, evidence of efficacy, harms, and summary) with common subheadings to facilitate comparison across the 24 different interventions profiled in this special focus issue, blending narrative and systematic review methodology as deemed appropriate by the authors. It is hoped that articles in this special focus issue will be informative and aid in decision making for the many stakeholders evaluating nonsurgical interventions for CLBP.

The narcotic bowel syndrome: clinical features, pathophysiology, and management

Narcotic bowel syndrome (NBS) is a subset of opioid bowel dysfunction that is characterized by chronic or frequently recurring abdominal pain that worsens with continued or escalating dosages of narcotics. This syndrome is underrecognized and may be becoming more prevalent. In the United States this may be the result of increases in using narcotics for chronic nonmalignant painful disorders, and the development of maladaptive therapeutic interactions around its use. NBS can occur in patients with no prior gastrointestinal disorder who receive high dosages of narcotics after surgery or acute painful problems, and among patients with functional gastrointestinal disorders or other chronic gastrointestinal diseases who are managed by physicians who are unaware of the hyperalgesic effects of chronic opioids. The evidence for the enhanced pain perception is based on the following: (1) activation of excitatory antianalgesic pathways within a bimodal opioid regulation system, (2) descending facilitation of pain at the rostral ventral medulla and pain facilitation via dynorphin and cholecystokinin activation, and (3) glial cell activation that produces morphine tolerance and enhances opioid-induced pain. Treatment involves early recognition of the syndrome, an effective physician-patient relationship, graded withdrawal of the narcotic according to a specified withdrawal program, and the institution of medications to reduce withdrawal effects.

Opioid-induced bowel dysfunction: prevalence, pathophysiology and burden

As a result of the undesired action of opioids on the gastrointestinal (GI) tract, patients receiving opioid medication for chronic pain often experience opioid-induced bowel dysfunction (OBD), the most common and debilitating symptom of which is constipation. Based on clinical experience and a comprehensive MEDLINE literature review, this paper provides the primary care physician with an overview of the prevalence, pathophysiology and burden of OBD. Patients with OBD suffer from a wide range of symptoms including constipation, decreased gastric emptying, abdominal cramping, spasm, bloating, delayed GI transit and the formation of hard dry stools. OBD can have a serious negative impact on quality of life (QoL) and the daily activities that patients feel able to perform. To relieve constipation associated with OBD, patients often use laxatives chronically (associated with risks) or alter/abandon their opioid medication, potentially sacrificing analgesia. Physicians should have greater appreciation of the prevalence, symptoms and burden of OBD. In light of the serious negative impact OBD can have on QoL, physicians should encourage dialogue with patients to facilitate optimal symptomatic management of the condition. There is a pressing need for new therapies that act upon the underlying mechanisms of OBD.

Methylnaltrexone mechanisms of action and effects on opioid bowel dysfunction and other opioid adverse effects

OBJECTIVE

To review the mechanisms of action of methylnaltrexone and its effects on opioid bowel dysfunction, as well as its effects on other opioid-induced adverse effects (ADEs), and its potential roles in clinical practice.

DATA SOURCES

A literature search using the MEDLINE and Cochrane Collaboration databases for articles published between 1966 and March 2007 was performed. Additional data sources were obtained from manual searches of recent journal articles, book chapters, and monographs. An updated literature search showed no additional publications.

STUDY SELECTION AND DATA EXTRACTION

Abstracts and original preclinical and clinical research reports published in the English language were identified for review. Review articles, commentaries, and news reports of this compound were excluded. Literature related to opioids, opioid receptors, opioid antagonists, methylnaltrexone, opioid-induced bowel dysfunction, constipation, nausea, and vomiting was evaluated and selected based on consideration of the support shown for the proof of concept, mechanistic findings, and timeliness. Fifty-eight original articles from preclinical studies and clinical trials using methylnaltrexone were identified. Pharmacologic action, benefits, and ADEs of methylnaltrexone were reviewed, with a focus on its effects on bowel dysfunction after opioids. Emphases were placed on its receptor binding activities and therapeutically relevant sites of action (peripheral vs central), in which peripheral opioid receptors in the body contribute to physiological and drug-induced effects.

DATA SYNTHESIS

Morphine and related opioids are associated with a number of limiting ADEs, including opioid-induced bowel dysfunction. Methylnaltrexone, a quaternary derivative of naltrexone, blocks peripheral effects of opioids while sparing central analgesic effects. It is currently under late-stage clinical investigation for the treatment of opioid-induced constipation in patients with advanced illness. Reported results showed the drug to be generally well-tolerated. The rapid reversal of constipation is very encouraging. Hastening postoperative discharge may also be possible.

CONCLUSIONS

Methylnaltrexone has the potential to prevent or treat opioid-induced peripherally mediated ADEs on bowel dysfunction without interfering with central analgesia. The study of methylnaltrexone leads to a greater understanding of the mechanisms of action of opioid pharmacology.

Indium-Labeled Macrocyclic Conjugates of Naltrindole: High-Affinity Radioligands for In Vivo Studies of Peripheral δ Opioid Receptors

We have identified a series of hydrophilic indium-labeled DOTA and DO3A conjugates of naltrindole (NTI) that are suited to in vivo studies of peripheral delta opioid receptors. Indium(III) complexes, linked to the indole nitrogen of NTI by six- to nine-atom spacers, display high affinities (0.1-0.2 nM) and excellent selectivities for binding to delta sites in vitro. The [111In]-labeled complexes can be prepared in good isolated yields ( approximately 65%) with high specific radioactivities (>3300 mCi/mumol). The spacers serve as pharmacokinetic modifiers, and log D7.4 values range from -2.74 to -1.79. These radioligands exhibit a high level of specific binding (75-94%) to delta opioid receptors in mouse gut, heart, spleen, and pancreas in vivo. Uptakes of radioactivity are saturable by the non-radioactive complexes, inhibited by naltrexone, and blocked by NTI. Thus, these radiometal-labeled NTI analogues warrant further study by single-photon emission computed tomography.

Effects of nociceptin/orphanin FQ on rats with cathartic colon

AIM

To demonstrate the change and effect of nociceptin/orphanin FQ in the colon of rats with cathartic colon.

METHODS

The cathartic colon model was established by feeding rats rhubarb for 3 mo, the changes of colonic electromyography were investigated by both suspension muscle strips test and serosal recordings of colonic myoelectrical activity. Immunohistochemical staining (S-P methods) and image analysis were used to determine the changes of nociceptin/orphanin FQ in the proximal colon and distal colon of rats with cathartic colon.

RESULTS

Suspension muscle strips test in vitro showed OFQ (10(-9)-10(-6) mol/L) concentration dependently caused an immediate tonic contraction in the isolated colon. But the increase of tension in cathartic colon was less than control groups (P < 0.01). Intravenous administration of OFQ (1 microg/kg) caused phasic contractions in the proximal colon, while the amplitude of phasic contractions caused by OFQ in cathartic colon was much lower than that in the control groups (2.58 +/- 0.41 vs 4.16 +/- 0.53, t = -2.6, P = 0.012). OFQ was highly expressed in the myenteric plexus of the rat colon but not in the muscle cells. The immunoreactivity of OFQ in the proximal colon in cathartic colon rats decreased significantly compared with the control group (P = 0.001).

CONCLUSION

Colonic smooth muscle of cathartic colon showed low sensitivity to the stimulation of OFQ, suggesting that it might be caused by the abnormal distribution of OFQ or the abnormalities of receptors, leading to the disorganization of dynamic and incoordinated contractions.