Reversal of opioid-induced gastric dysfunction in a critically ill burn patient after methylnaltrexone

Successful Use of Intravenous Methylnaltrexone for Opioid-Induced Constipation in Critically Ill Pediatric Patients

Objectives  Methylnaltrexone is U.S. Food and Drug Administration (FDA) approved as a subcutaneous injection for adults with opioid-induced constipation (OIC). Case series have described the use of methylnaltrexone for OIC in the pediatric oncology population. There are limited data describing its intravenous use in critically ill pediatric patients. Methods  We conducted a retrospective observational study at St. Louis Children's Hospital. Patients less than 18 years old who received at least one dose of intravenous methylnaltrexone while admitted to an intensive care unit between January 2016 and August 2019 were included. The primary outcome was documented laxation within 24 hours of methylnaltrexone administration. Results  Sixteen patients received a total of 34 doses of intravenous methylnaltrexone. Patients received a median of 1.69 (interquartile range [IQR], 0.9-4.86) morphine milligram equivalents per kilogram per 24 hours, over a median of 14 days (IQR, 11-30), before methylnaltrexone administration. The median dose of methylnaltrexone was 0.15 mg/kg (IQR, 0.15-0.16). Ten patients (63%) responded to the first dose of methylnaltrexone, and 14 patients (88%) responded to at least one dose. Overall, 26 doses (76%) led to patient response. Four patients (25%) experienced adverse events (emesis, abdominal pain) after methylnaltrexone administration. No signs or symptoms of opioid withdrawal were documented. Conclusions  Intravenous methylnaltrexone appears to be safe and effective in treating OIC in critically ill pediatric patients. No serious adverse events or signs of opioid withdrawal were observed after single and repeat dosing. Patients responded to methylnaltrexone with varying opioid dosing and durations prior to administration.

Peripherally-active mu-opioid receptor antagonists for constipation in critically ill patients receiving opioids: A case-series and a systematic review and meta-analysis of the literature

BACKGROUND

Constipation is frequent in critically ill patients, and potentially related to adverse outcomes. Peripherally-active mu-opioid receptor antagonists (PAMORAs) are approved for opioid-induced constipation, but information on their efficacy and safety in critically ill patients is limited. We present a single-center, retrospective, case-series of the use of naldemedine for opioid-associated constipation, and we systematically reviewed the use of PAMORAs in critically ill patients.

METHODS

Case-series included consecutive mechanically-ventilated patients; constipation was defined as absence of bowel movements for >3 days. Naldemedine was administered after failure of the local laxation protocol. Systematic review: PubMed was searched for studies of PAMORAs to treat opioid-induced constipation in adult critically ill patients.

PRIMARY OUTCOMES

time to laxation, and number of patients laxating at the shortest follow-up.

SECONDARY OUTCOMES

gastric residual volumes and adverse events.

KEY RESULTS

A total of 13 patients were included in the case-series; the most common diagnosis was COVID-19 ARDS. Patients had their first bowel movement 1 [0;2] day after naldemedine. Daily gastric residual volume was 725 [405;1805] before vs. 250 [45;1090] mL after naldemedine, p = 0.0078. Systematic review identified nine studies (two RCTs, one prospective case-series, three retrospective case-series and three case-reports). Outcomes were similar between groups, with a trend toward a lower gastric residual volume in PAMORAs group.

CONCLUSIONS & INFERENCES

In a highly-selected case-series of patients with refractory, opioid-associated constipation, naldemedine was safe and associated to reduced gastric residuals and promoting laxation. In the systematic review and meta-analysis, the use of PAMORAs (mainly methylnaltrexone) was safe and associated with a reduced intolerance to enteral feeding but no difference in the time to laxation.

Opioid Use and Potency Are Associated With Clinical Features, Quality of Life, and Use of Resources in Patients With Gastroparesis

BACKGROUND & AIMS

Many patients with gastroparesis are prescribed opioids for pain control, but indications for opioid prescriptions and the relationship of opioid use to gastroparesis manifestations are undefined. We characterized associations of use of potent vs weaker opioids and presentations of diabetic and idiopathic gastroparesis.

METHODS

We collected data on symptoms, gastric emptying, quality of life, and health care resource use from 583 patients with gastroparesis (>10% 4-h scintigraphic retention) from the National Institute of Diabetes and Digestive and Kidney Diseases Gastroparesis Consortium, from January 2007 through November 2016. Patients completed medical questionnaires that included questions about opioid use. The opioid(s) were categorized for potency relative to oral morphine. Symptom severities were quantified by Patient Assessment of Upper Gastrointestinal Disorders Symptoms questionnaires. Subgroup analyses compared patients on potent vs weaker opioids and opioid effects in diabetic vs idiopathic etiologies.

RESULTS

Forty-one percent of patients were taking opioids; 82% of these took potent agents (morphine, hydrocodone, oxycodone, methadone, hydromorphone, buprenorphine, or fentanyl). Abdominal pain was the reason for prescription for 61% of patients taking opioids. Mean scores for gastroparesis, nausea/vomiting, bloating/distention, abdominal pain, and constipation scores were higher in opioid users (P ≤ .05). Opioid use was associated with greater levels of gastric retention, worse quality of life, increased hospitalization, and increased use of antiemetic and pain modulator medications compared with nonusers (P ≤ .03). Use of potent opioids was associated with worse gastroparesis, nausea/vomiting, upper abdominal pain, and quality-of-life scores, and more hospitalizations compared with weaker opioids (tapentadol, tramadol, codeine, or propoxyphene) (P ≤ .05). Opioid use was associated with larger increases in gastric retention in patients with idiopathic vs diabetic gastroparesis (P = .008).

CONCLUSIONS

Opioid use is prevalent among patients with diabetic or idiopathic gastroparesis, and is associated with worse symptoms, delays in gastric emptying, and lower quality of life, as well as greater use of resources. Potent opioids are associated with larger effects than weaker agents. These findings form a basis for studies to characterize adverse outcomes of opioid use in patients with gastroparesis and to help identify those who might benefit from interventions to prevent opioid overuse.

Protocol for a randomised control trial of methylnaltrexone for the treatment of opioid-induced constipation and gastrointestinal stasis in intensive care patients (MOTION)

INTRODUCTION

Gastrointestinal dysmotility and constipation are common problems in intensive care patients. The majority of critical care patients are sedated with opioids to facilitate tolerance of endotracheal tubes and mechanical ventilation, which inhibit gastrointestinal motility and lead to adverse outcomes. Methylnaltrexone is a peripheral opioid antagonist that does not cross the blood-brain barrier and can reverse the peripheral side effects of opioids without affecting the desired central properties. This trial will investigate whether methylnaltrexone can reverse opioid-induced constipation and gastrointestinal dysmotility.

METHODS

This is a single-centre, multisite, double-blind, randomised, placebo-controlled trial. 84 patients will be recruited from 4 intensive care units (ICUs) within Imperial College Healthcare NHS Trust. Patients will receive intravenous methylnaltrexone or placebo on a daily basis if they are receiving opioid infusion to facilitate mechanical ventilation and have not opened their bowels for 48 hours. All patients will receive standard laxatives as per the clinical ICU bowel protocol prior to randomisation. The primary outcome of the trial will be time to significant rescue-free laxation following randomisation. Secondary outcomes will include tolerance of enteral feed, gastric residual volumes, incidence of pneumonia, blood stream and Clostridium difficile infection, and any reversal of central opioid effects.

ETHICS AND DISSEMINATION

The trial protocol, the patient/legal representative information sheets and consent forms have been reviewed and approved by the Harrow Research Ethics Committee (REC Reference 14/LO/2004). An independent Trial Steering Committee and Data Monitoring Committee are in place, with patient representation. On completion, the trial results will be published in peer-reviewed journals and presented at national and international scientific meetings.

TRIAL REGISTRATION NUMBER

2014-004687-37; Pre-results.

Use of methylnaltrexone to induce laxation in acutely injured patients with burns and necrotizing soft-tissue infections

The routine use of high-dose opioids for analgesia in patients with acute burns and soft-tissue injuries often leads to the development of opioid-induced constipation. The opioid antagonist methylnaltrexone (MLTX) reverses narcotic-related ileus without affecting systemic pain treatment. The authors' burn center developed a bowel protocol that included administration of MLTX for relief of opioid-induced constipation after other methods failed. The authors performed a retrospective review of patients with acute burns or necrotizing soft-tissue infections, who had been given subcutaneous MLTX to induce laxation. All patients who received MLTX were included and all administrations of the drug were included in the analysis. The primary outcome examined was time to laxation from drug administration. Forty-eight patients received MLTX a total of 112 times. Six patients were admitted with soft-tissue injuries and the rest suffered burns with an average TBSA of 17%. The median patient age was 41 years and the majority (75%) were men. Administration of a single dose of MLTX resulted in laxation within 4 hours in 38% of cases, and within 24 hours in 68%. Patients given MLTX received an average of 174 mg morphine equivalents daily for pain control. MLTX was given after an average of 52 hours since the last bowel movement. As this experience has evolved, it has been incorporated into an organized bowel protocol, which includes MLTX administration after other laxatives have failed. MLTX is an effective laxation agent in patients with burn and soft-tissue injuries, who have failed conventional agents.

Electroacupuncture improves burn-induced impairment in gastric motility mediated via the vagal mechanism in rats

BACKGROUND

Delayed gastric emptying (GE) is common in patients with severe burns. This study was designed to investigate effects and mechanisms of electroacupuncture (EA) on gastric motility in rats with burns.

METHODS

Male rats (intact and vagotomized) were implanted with gastric electrodes, chest and abdominal wall electrodes for investigating the effects of EA at ST-36 (stomach-36 or Zusanli) on GE, gastric slow waves, autonomic functions, and plasma interleukin 6 (IL-6) 6 and 24 h post severe burns.

KEY RESULTS

(i) Burn delayed GE (P < 0.001). Electroacupuncture improved GE 6 and 24 h post burn (P < 0.001). Vagotomy blocked the EA effect on GE. (ii) Electroacupuncture improved burn-induced gastric dysrhythmia. The percentage of normal slow waves was increased with EA 6 and 24 h post burn (P = 0.02). (iii) Electroacupuncture increased vagal activity assessed by the spectral analysis of heart rate variability (HRV). The high-frequency component reflecting vagal component was increased with EA 6 (P = 0.004) and 24 h post burn (P = 0.03, vs sham-EA). (iv) Electroacupuncture attenuated burn-induced increase in plasma IL-6 at both 6 (P = 0.03) and 24 h post burn (P = 0.003).

CONCLUSIONS & INFERENCES

Electroacupuncture at ST-36 improves gastric dysrhythmia and accelerates GE in rats with burns. The improvement seems to be mediated via the vagal pathway involving the inflammatory cytokine IL-6.

Management of opioid-induced constipation in cancer patients: focus on methylnaltrexone

Opioids are one of the most widely used therapies for the palliative treatment of cancer pain; however, despite their proven analgesic efficacy, they are associated with several adverse effects. Associated with psychological distress and multiple concomitant clinical concerns, constipation is the most commonly occurring adverse effect of chronic opioid therapy in cancer patients. Whilst prophylaxis remains the first-line management option, methylnaltrexone is a recommended treatment option for opioid-related constipation if administration of laxatives is ineffective. Due to its inability to cross the blood-brain barrier, methylnaltrexone exerts a peripheral inhibition of opioid-related effects without influencing the opioid-induced central effects; as a result, the analgesic effect of opioids is unaffected. Moreover, multiple clinical trials, albeit not always conducted specifically in cancer patients, have demonstrated that up to 4 months' treatment with either intravenous or subcutaneous methylnaltrexone provides effective relief from opioid-related constipation and is well tolerated. Preliminary evidence indicates that the addition of methylnaltrexone to standard care for opioid-related constipation may also be advantageous from a pharmacoeconomic perspective. In addition, preliminary data suggest that methylnaltrexone could be associated with some further clinical benefits other than the treatment of opioid-related constipation, such as the improvement of gastric emptying, the relief of nausea/vomiting, and the reduction of the risk of regurgitation and pulmonary aspiration. This narrative review examines the most recent evidence and evaluates the current role of methylnaltrexone in the management of opioid-related constipation, and its potential efficacy in cancer patients. The pharmacokinetics, pharmacodynamics, efficacy and tolerability of methylnaltrexone are discussed.

Motility disorders of the upper gastrointestinal tract in the intensive care unit: pathophysiology and contemporary management

Upper gastrointestinal (GI) dysmotility, an entity commonly found in the intensive care unit setting, can lead to insufficient nutrient intake while increasing the risk of infection and mortality. Further, overcoming the altered motility with early enteral feeding is associated with a reduced incidence of infectious complications in intensive care unit patients. Upper GI dysmotility in critical care patients is a common occurrence, and there are many causes for this problem, which affects a very heterogenous population with a multitude of underlying medical abnormalities. Therefore, it is of utmost importance to identify this widespread problem and subsequently institute a proper therapy as rapidly as possible. Prokinetic pharmacotherapies are currently the mainstay for the management of disordered upper GI motility. Future therapies, aimed at the underlying pathophysiology of this complex problem, are under investigation. These aim is to reduce the side effects of the currently available options, while improving on nutrition delivery in the critically ill. This review discusses the pathophysiology, clinical manifestations, diagnosis, and treatment of upper GI motility disturbances in the critically ill.

Use of methylnaltrexone for the treatment of opioid-induced constipation in critical care patients

Gastrointestinal dysmotility and constipation are common problems in critical care patients. The majority of critical care patients are treated with opioids, which inhibit gastrointestinal (GI) motility and lead to adverse outcomes. We reasoned that methylnaltrexone (MNTX), a peripheral opioid antagonist approved for the treatment of opioid-induced constipation in patients with advanced illness receiving palliative care when response to laxative therapy has not been sufficient, could improve GI function in critically ill patients. The present study included all patients in our intensive care unit who required rescue medication for GI stasis during the 10-week period from September 1 to November 15, 2009. We compared conventional rescue therapy with subcutaneous MNTX. We performed a retrospective chart review of the 88 nonsurgical critical care patients receiving fentanyl infusions, 15 (17%) of whom met the criteria of absence of laxation within 72 hours of intensive care unit admission despite treatment with senna and sodium docusate. Eight of these 15 patients subsequently received conventional rescue therapy (combination of sodium picosulfate [5 mg] and 2 glycerin suppositories [4-g mold]), and 7 patients received MNTX (subcutaneous injection, 0.15 mg/kg). Laxation occurred within 24 hours in 6 of the 7 MNTX patients (86%) but in none of the 8 patients receiving conventional rescue therapy (P=.001). The median difference in time to laxation between the 2 groups was 3.5 days (P<.001). Although not statistically significant, all 7 patients treated with MNTX, but only 4 of 8 (50%) who received conventional rescue therapy, progressed to full target enteral feeding (P=.08). Intensive care unit mortality was 2 of 7 MNTX patients (29%) vs 4 of 8 (50%) in the standard therapy group (P=.61). We hypothesize that MNTX may play an important role in restoration of bowel function in critically ill patients.

Pain in the ICU: a psychiatric perspective

Pain is abundant in the intensive care unit (ICU). Successful analgesia demands a comprehensive appreciation for the etiologies of pain, vigilant clinical assessment, and personalized treatments. For the critically ill, frequent threats to mental and bodily integrity magnify the experience of pain, challenging clinicians to respond swiftly and thoughtfully. Because pain is difficult to predict and physiologic correlates are not specific, self-report remains the gold standard assessment. When communication is limited by intubation or cognitive deficits, behavioral pain scales prove useful. Patient-tailored analgesia aspires to mitigate suffering while optimizing alertness and cognitive capacity. Mindfulness of the neuropsychiatric features of pain helps the ICU clinician to clarify limits of traditional analgesia and identify alternative approaches to care. Armed with empirical data and clinical practice recommendations to better conceptualize, identify, and treat pain and its neuropsychiatric comorbidities, the authors (psychiatric consultants, by trade) reinforce holistic approaches to pain management in the ICU. After all, without attempts to understand and relieve suffering on all fronts, pain will remain undertreated.

Creating the animated intensive care unit

Critical care medicine has matured greatly as a field in the past decade. Much has been learned concerning the institution of life support therapies to sustain patients with diverse and multiple organ failures, thus providing patients with a window of opportunity to recover from potentially life-ending insults. The management of critically ill patients has increasingly involved creation of a highly controlled environment by care providers, with patients immobilized, tethered to devices, and receiving multiple drugs to facilitate the entire process. Although it has been assumed that such control of the patient has been necessary to implement essential therapies and to tailor life support systems such as mechanical ventilation, this assumption may be unfounded or at least overplayed, as knowledge of the adverse effects of this approach have been identified and quantified. Extant information, based on observational studies and a few interventional trials, would suggest a radically different approach to care is warranted, even given the difficulties in reversing the current culture of critical care management. Specifically, methods to avoid entirely, or minimize, neuromuscular blockade and sedation are supported by recent literature. These methods include the use of noninvasive ventilation in appropriately selected patients, the development of mechanical ventilators more synchronous with patient efforts and needs, and the use of sedation strategies to avoid drug accumulations with protracted effects. These methods, in turn, afford opportunities to avoid extreme immobilization and institute physiotherapy earlier than previously had been thought possible. In addition to the neuropsychiatric and neuromuscular benefits that could derive from minimizing opiate administration in critically ill patients, gut hypomotility could be avoided. This, in turn, could facilitate earlier and more complete enteral nutrition. Even when opioids have to be administered in generous amounts for control of pain that may accompany critical illness, it is now possible to block the peripheral actions of these medications with the μ-receptor antagonist methylnaltrexone. Other new drugs being introduced into the critical care unit such as dexmedetomidine may also provide a greater ability to achieve analgesia and anxiolysis without some of the adverse concomitant effects seen with more traditional drug regimens. The ultimate goal of this multipronged program to facilitate the maintenance of patients who are more interactive with their care providers, and the life support provided in the intensive care unit would be to speed the pace of recovery and to diminish the need for the protracted rehabilitation that often follows survival from critical illness.

The effects of methylnaltrexone alone and in combination with acutely administered codeine on gastrointestinal and colonic transit in health

BACKGROUND

The short-term effects of methylnaltrexone (MNTX), a peripherally acting mu-opioid receptor antagonist, on gastrointestinal and colonic transit remain unclear.

AIM

To compare the effects of placebo, codeine, subcutaneous (s.c.) MNTX and codeine with s.c. MNTX on gastrointestinal and colonic transit of solids in healthy humans.

METHODS

In a randomized, parallel-group, double-blind, placebo-controlled trial of 48 healthy volunteers, effects of 6 consecutive days of placebo [s.c. and p.o. (orally), n = 8], codeine (p.o. 30 mg q.d.s., n = 8), MNTX (s.c. 0.30 mg/kg, n = 16) and combined MNTX and codeine (same doses and routes, n = 16) on gastrointestinal and colonic transit were assessed. A validated scintigraphic method was used to measure transit during the last 48 h of treatment. Bowel function was estimated during treatment as well as 1 week preceding treatment using standard diaries. Analysis of covariance was used to assess treatment effects.

RESULTS

Codeine delayed colonic transit [geometric centre at 24 h (P = 0.04) and ascending colon t(1/2) (P = 0.02)] and reduced stool frequency (P = 0.002), but had no effect on stool form. MNTX did not affect transit, stool frequency or stool form, either alone or with codeine (P > 0.3). No drug interaction effects were detected (P > 0.15).

CONCLUSION

Methylnaltrexone does not alter gastrointestinal or colonic transit and does not reverse acute codeine-associated delayed gut transit in health.

Methylnaltrexone: the evidence for its use in the management of opioid-induced constipation

Introduction:

Constipation is a distressing side effect of opioid treatment, being so irksome in some cases that patients would rather suffer the pain than the side effect of opioid analgesics. Stool softeners or stimulating laxatives are often ineffective or even aggravate the situation. A new efficacious and safe drug is needed to limit the frequently observed side effects induced by effective opioid-based analgesic therapy and to improve the quality of life for patients, most of whom are impaired by a severe disease.

Aims:

The purpose of this article is to assess current evidence supporting the use of the peripherally acting μ-opioid receptor antagonist, methylnaltrexone, to restrict passage across the blood–brain barrier in patients with opioid-induced bowel dysfunction.

Evidence review:

There are now convincing data from phase II and multicenter phase III randomized, double-blind, placebo-controlled trials that methylnaltrexone induces laxation in patients with long-term opioid use without affecting central analgesia or precipitation of opioid withdrawal. Onset of the effect is rapid and improvement is maintained for at least 3 months during the drug treatment. The action of methylnaltrexone is dose dependent. Weight-related dosing appeared to be effective. There were no severe side effects or signs of opioid withdrawal. Adverse events, most frequently abdominal cramping or nausea, were usually mild to moderate. Methylnaltrexone is contraindicated in patients with known or suspected mechanical intestinal stenosis. Patients receiving methylnaltrexone must be monitored.

Place in therapy:

Methylnaltrexone applied subcutaneously every other day may be given to patients suffering from chronic constipation due to opioid therapy for whom laxatives do not provide adequate relief of their symptoms.

Mechanisms of burn-induced impairment in gastric slow waves and emptying in rats

Delayed gastric emptying is common following severe large cutaneous burns; however, the mechanisms of burn-induced delayed gastric emptying remain unknown. The aim of this study was to explore the possible involvement of hyperglycemia and cyclooxygenase-2 receptors in the burn-induced gastric dysrhythmias. Gastric slow waves and gastric emptying were assessed in rats 6 h following sham or burn injury. Animals were randomized to one sham-burn and seven burn groups: untreated; two groups of saline treated (control); insulin treated (5 IU/kg); cyclooxygenase-2 inhibitor treated (10 mg/kg); ghrelin treated (2 nmol/rat); and gastric electrical stimulation treated. It was found that 1) severe burn injury impaired gastric slow waves postprandially and delayed gastric emptying; 2) the impairment in gastric slow waves included a decrease in the slow-wave frequency and in the percentage of normal slow waves, and an increase in the percentage of bradygastria (P = 0.001, 0.01, and 0.01, respectively vs. preburn values). None of the gastric slow-wave parameters was significantly correlated with gastric emptying; 3) cyclooxygenase-2 inhibitor normalized burn-induced delayed gastric emptying (P = 0.3 vs. sham-burn), but not gastric dysrhythmias (P < 0.002 vs. sham), whereas insulin normalized both gastric emptying (P = 0.4 vs. sham-burn) and gastric dysrhythmias (P = 0.3 vs. sham-burn); 4) both gastric electrical stimulation and ghrelin accelerated burn-induced delayed gastric emptying (P = 0.002 and 0.04, respectively, vs. untreated burn). In conclusion, hyperglycemia alters gastric slow-wave activity and delayed gastric emptying, while cyclooxygenase-2 inhibition delays gastric emptying without altering gastric slow-wave activity.

Methylnaltrexone: the answer to opioid-induced constipation?

Opioid-induced constipation is a significant problem particularly for end stage cancer patients, methadone users, patients suffering from chronic pain as well as surgical patients. Until recently, there were few efficacious treatment options that did not have significant side effects. Methylnaltrexone is a promising drug for the treatment of opioid-induced constipation. It is an opioid-receptor antagonist that blocks the peripheral gastrointestinal opioid receptors responsible for opioid-induced bowel dysfunction. Due to the drug's polarity, it does not cross the blood-brain barrier; therefore, it does not block the central opioid receptors, thus, retaining effective analgesia. Methylnaltrexone has been recently approved by the FDA in the subcutaneous form for the treatment of opioid-induced bowel dysfunction, whereas the intravenous and oral forms remain under investigation.