A double-blind, randomized, placebo-controlled phase III study of the safety of alvimopan in patients who undergo simple total abdominal hysterectomy

Alvimopan for postoperative ileus following abdominal surgery: a systematic review

BACKGROUND

Postoperative ileus (POI) is a common complication following abdominal surgery, often leading to extended hospital stays and a higher risk of post-operative complications, leading to poorer patient outcomes. Alvimopan, a peripherally acting µ-opioid receptor antagonist, has been shown to aid in the recovery of normal bowel function after surgery. While its benefits are well-established in open abdominal surgeries, its efficacy in laparoscopic procedures had not been conclusively determined. However, recent clinical trials involving laparoscopic surgeries have since been conducted. This review aims to reassess the efficacy of Alvimopan by incorporating findings from these new studies, potentially providing further insight into its clinical benefits.

METHODS

A comprehensive search of PubMed, Google Scholar, EMBASE, and the Cochrane Library was conducted. Studies were included based on the PICO framework, focusing on Alvimopan's impact on postoperative gastrointestinal recovery. Primary outcomes were time to gastrointestinal function recovery (GI-3) and hospital stay duration.

RESULTS

Ten studies met the inclusion criteria, with seven focusing on the use of Alvimopan in open abdominal surgeries and three in laparoscopic procedures. Collectively, these studies involved 18,822 patients undergoing various types of abdominal Administration of Alvimopan 6 mg accelerated gastrointestinal function recovery by an average of 14 h (Hazard ratio: 1.62, p = 0.002) and reduced hospital stays by 5.2 h (Hazard ratio: 1.52, p = 0.04) compared to placebo. Similarly, Alvimopan 12 mg reduced GI-3 recovery time by 13.5 h (Hazard ratio: 1.58, p = 0.02) and hospital stay duration by 6.2 h (Hazard ratio: 1.46, p = 0.018).

CONCLUSION

Alvimopan shows promise in reducing POI and hospital stay durations following abdominal surgeries. The incorporation of the recent studies in laparoscopic abdominal procedures further supports these findings. Integrating Alvimopan into perioperative care protocols may enhance patient outcomes and help lower healthcare costs.

Updates on enhanced recovery after surgery for radical cystectomy

Enhanced Recovery after Surgery (ERAS) is a multimodal pathway that provides evidence-based guidance for improving perioperative care and outcomes in patients undergoing surgery. In 2013, the ERAS society released its original guidelines for radical cystectomy (RC) for bladder cancer (BC), adopting much of its supporting data from colorectal literature. In the last decade, growing interest in ERAS has increased RC-specific ERAS research, including prospective randomized controlled trials (RCTs). Collective data suggest ERAS contributes to improved complication rates, decreased hospital length-of-stay, and/or time to bowel recovery. Various institutions have adopted modified versions of the ERAS pathway, yet there remains a lack of consensus on the efficacy of specific ERAS items and standardization of the protocol. In this review, we summarize updated evidence and practice patterns of ERAS pathways for RC since the introduction of the original 2013 guidelines. Novel target interventions, including use of immunonutrition, prehabilitation, alvimopan, and methods of local analgesia are reviewed. Finally, we discuss barriers to implementing and future steps in advancing the ERAS movement.

Use of naldemedine is associated with reduced incidence of hyperactive delirium in cancer patients with opioid-induced constipation: a nationwide retrospective cohort study in Japan

BACKGROUND

Medical benefits of peripherally-acting mu-opioid receptor antagonists other than improving opioid-induced constipation remain unclear. Our aim was to evaluate the association between the use of naldemedine and incidence of hyperactive delirium in cancer patients receiving chemotherapy and opioid therapy.

METHODS

We conducted a propensity score-matched analysis using a nationwide inpatient database in Japan. Cancer patients receiving both inpatient chemotherapy and opioid therapy from June 1, 2017 to March 31, 2018 were included. Patients receiving naldemedine were matched to control patients by propensity score. Our primary outcome was the incidence of hyperactive delirium during hospitalization, and secondary outcomes were the length of hospital stay, hospital costs, in-hospital mortality, and incidence of ileus.

RESULTS

Of 34,031 patients receiving inpatient chemotherapy and opioid therapy, 1905 (5.6%) were included in the naldemedine group. After one-to-four propensity score matching, 1904 patients were included in the naldemedine group and 7616 in the control group. Naldemedine users had significantly reduced incidence of hyperactive delirium compared with the control patients (19.4% vs 23.3%; risk difference, -3.9 [95% confidence interval, -5.9 - -1.9]; risk ratio, 0.83 [0.75-0.92]; P<0.001; subdistribution hazard ratio, 0.85 [0.75-0.97]; P=0.015). The median length of hospital stay was significantly shorter in the naldemedine group compared with the control group (12 days [interquartile range, 6-23] vs 14 days [6-26]; P=0.001). The median hospital costs were also significantly lower in the naldemedine group compared with the control group (US $6179 [3351-10,026] vs US $6576 [3436-11,107]; P<0.001). No significant differences were found for in-hospital mortality or incidence of ileus between the groups.

CONCLUSIONS

Our findings suggest that the use of naldemedine may have benefits in preventing hyperactive delirium, shortening hospital stay, and decreasing hospital costs in cancer patients receiving chemotherapy and opioid therapy.

Peripherally Acting μ-Opioid Receptor Antagonists in the Management of Postoperative Ileus: a Clinical Review

Postoperative ileus (POI) and constipation are common secondary effects of opioids and carry significant clinical and economic impacts. μ-Opioid receptors mediate opioid analgesia in the central nervous system (CNS) and gastrointestinal-related effects in the periphery. Peripherally acting μ-opioid receptor antagonists (PAMORAs) block the peripheral effects of opioids in the gastrointestinal tract, while maintaining opioid analgesia in the CNS. While most are not approved for POI or postoperative opioid-induced constipation (OIC), PAMORAs have a potential role in these settings via their selective effects on the μ-opioid receptor. This review will discuss recent clinical trials evaluating the safety and efficacy of PAMORAs, with a focus on alvimopan (Entereg^®) and methylnaltrexone (Relistor^®) in patients with POI or postoperative OIC. We will characterize potential factors that may have impacted the efficacy observed in phase 3 trials and discuss future directions for the management and treatment of POI.

The association of alvimopan treatment with postoperative outcomes after abdominal surgery: A systematic review across different surgical procedures and contexts of perioperative care

BACKGROUND

Alvimopan is a Food and Drug Administration-approved treatment to accelerate gastrointestinal recovery after abdominal surgery; however, benefits may vary across different procedures and contexts of care. The purpose of this study is to summarize the evidence regarding the effect of alvimopan on postoperative outcomes after abdominal surgery.

METHODS

Major databases (Medline, Embase, Biosis, Cochrane, Web of Science, and Scopus) were searched for randomized controlled trials and nonrandomized studies comparing alvimopan versus control. Risk of bias was assessed using Cochrane's risk of bias tool 2.0 (for randomized controlled trials) and Risk of Bias in Nonrandomized Studies-of Intervention tool (for nonrandomized studies). Results were appraised descriptively as heterogeneity in reporting and risk of bias hindered meta-analysis. Quality of evidence across different surgical procedures and contexts of care (ie, open versus minimally invasive surgery, traditional care versus enhanced recovery pathway) was evaluated using Grading of Recommendations Assessment, Development, and Evaluation.

RESULTS

Nine randomized controlled trials and 35 nonrandomized studies were identified. Evidence of low to moderate certainty supports that alvimopan reduces length of stay and improves gastrointestinal recovery after open bowel resection and open radical cystectomy. Limited evidence supports alvimopan for surgeries not listed in Food and Drug Administration labels (ie, total abdominal hysterectomy and retroperitoneal lymph node dissection). Similar effects were observed in traditional and enhanced recovery pathway settings, but enhanced recovery pathway elements varied across studies. There is very low certainty of evidence supporting alvimopan for patients undergoing minimally invasive surgery.

CONCLUSION

Evidence supports that alvimopan improves outcomes after open bowel resection and open radical cystectomy. Benefits for patients undergoing minimally invasive surgery and treated in contemporary enhanced recovery pathway settings remain uncertain. These findings contribute important new knowledge to inform evidence-based alvimopan prescribing.

The Impact of Alvimopan on Return of Bowel Function After Major Spine Surgery - A Prospective, Randomized, Double-Blind Study

BACKGROUND

Pain management following major spine surgery requires high doses of opioids and is associated with a risk of opioid-induced constipation. Peripheral mu-receptor antagonists decrease the gastrointestinal complications of perioperative systemic opioid administration without antagonizing the analgesic benefits of these drugs.

OBJECTIVE

To investigate the impact of alvimopan in opioid-naive patients undergoing major spine surgery.

METHODS

Patients undergoing >3 levels of thoracic and/or lumbar spine surgery were enrolled in this prospective, randomized, double-blind study to receive either alvimopan or placebo prior to and following surgery. Opioid consumption; pain scores; and time of first oral intake, flatus, and bowel movement were recorded.

RESULTS

A total of 24 patients were assigned to the active group and 25 were assigned to the placebo group. There was no significant difference in demographics between the groups. Postoperatively, the alvimopan group reported earlier time to first solid intake [median (range): alvimopan: 15 h (3-25) vs placebo: 17 h (3-46), P < .001], passing of flatus [median (range): alvimopan: 22 h (7-63) vs placebo: 28 h (10-58), P < .001], and first bowel movement [median (range): alvimopan: 50 h (22-80) vs placebo: 64 h (40-114), P < .001]. The alvimopan group had higher pain scores (maximum, minimum, and median); however, there was no significant difference between the groups with postoperative opioid use.

CONCLUSION

This study shows that the perioperative use of alvimopan significantly reduced the time to return of bowel function with no increase in postoperative opioid use despite a slight increase in pain scores.

Effect of Chewing Gum on Gastrointestinal Function Recovery After Surgery of Gynecological Cancer Patients at Rajavithi Hospital: A Randomized Controlled Trial

Objective:

To evaluate the efficacy of postoperative gum-chewing compare with routine postoperative care on the recovery of gastrointestinal function after comprehensive surgical staging for gynecological cancer.

Materials and Methods:

A total of 82 patients who underwent comprehensive surgical staging for gynecological cancer at Rajavithi Hospital between October 1st, 2018 and June 30th, 2019 were randomly allocated into two groups: Gum-chewing group (n=40) and control group (n=42). In the gum-chewing group, patients were assigned to chew sugar-free gum for 30 minutes starting from the first postoperative morning then every 8 hours until the first passage of flatus. In the control group, patients have received routine postoperative care. The primary endpoint was time to first flatus after surgery. The secondary endpoints were time to first bowel sound, time to first defecation, time to first walk, postoperative analgesia and anti-emetic drug requirement, ileus symptoms, length of a hospital stay, and potential adverse events of gum-chewing, including dry mount, choking, and aspiration.

Results:

Chewing gum was statistically significant in reducing time to first flatus compared with routine postoperative care (median 24.7 (range 2.2-86.5) vs 35.4 (range 7.2-80.9) hours, p=0.025). The length of a hospital stay was also significantly shorter in the gum-chewing group (median 3.0 (range 1.0-8.8) vs 3.5 (range 1.8-50.0) days, p=0.023). There were no significant differences in time to first bowel sound, time to first defecation, time to first walk, postoperative analgesia and anti-emetic drug requirement, and ileus symptoms between both two groups. No adverse events related to postoperative gum-chewing were observed.

Conclusion:

Gum-chewing was associated with early recovery of gastrointestinal function in patients undergoing surgery for gynecological cancer. It is an inexpensive and physiologic intervention that appears to be reasonably safe and should be recommended as an adjunct in postoperative care of gynecological cancer surgery.

Surgical technical evidence review for gynecologic surgery conducted for the Agency for Healthcare Research and Quality Safety Program for Improving Surgical Care and Recovery

BACKGROUND

The Agency for Healthcare Research and Quality, in partnership with the American College of Surgeons and the Armstrong Institute at Johns Hopkins, developed the Safety Program for Improving Surgical Care and Recovery, which integrates principles of implementation science into adoption of enhanced recovery pathways and promotes evidence-based perioperative care.

OBJECTIVE

The objective of this study is to review the enhanced recovery pathways literature in gynecologic surgery and provide the framework for an Improving Surgical Care and Recovery pathway for gynecologic surgery.

STUDY DESIGN

We searched PubMed and Cochrane Central Register of Controlled Trials databases from 1990 through October 2017. Studies were included in hierarchical and chronological order: meta-analyses, systematic reviews, randomized controlled trials, and interventional and observational studies. Enhanced recovery pathways components relevant to gynecologic surgery were identified through review of existing pathways. A PubMed search for each component was performed in gynecologic surgery and expanded to include colorectal surgery as needed to have sufficient evidence to support or deter a process. This review focuses on surgical components; anesthesiology components are reported separately in a companion article in the anesthesiology literature.

RESULTS

Fifteen surgical components were identified: patient education, bowel preparation, elimination of nasogastric tubes, minimization of surgical drains, early postoperative mobilization, early postoperative feeding, early intravenous fluid discontinuation, early removal of urinary catheters, use of laxatives, chewing gum, peripheral mu antagonists, surgical site infection reduction bundle, glucose management, and preoperative and postoperative venous thromboembolism prophylaxis. In addition, 14 components previously identified in the colorectal Improving Surgical Care and Recovery pathway review were included in the final pathway.

CONCLUSION

Evidence and existing guidelines support 29 protocol elements for the Agency for Healthcare Research and Quality Safety Program for Improving Surgical Care and Recovery in gynecologic surgery.

The Efficacy of Peripheral Opioid Antagonists in Opioid-Induced Constipation and Postoperative Ileus: A Systematic Review of the Literature

Opioid-induced constipation has a negative impact on quality of life for patients with chronic pain and can affect more than a third of patients. A related but separate entity is postoperative ileus, which is an abnormal pattern of gastrointestinal motility after surgery. Nonselective μ-opioid receptor antagonists reverse constipation and opioid-induced ileus but cross the blood-brain barrier and may reverse analgesia. Peripherally acting μ-opioid receptor antagonists target the μ-opioid receptor without reversing analgesia. Three such agents are US Food and Drug Administration approved. We reviewed the literature for randomized controlled trials that studied the efficacy of alvimopan, methylnaltrexone, and naloxegol in treating either opioid-induced constipation or postoperative ileus. Peripherally acting μ-opioid receptor antagonists may be effective in treating both opioid-induced bowel dysfunction and postoperative ileus, but definitive conclusions are not possible because of study inconsistency and the relatively low quality of evidence. Comparisons of agents are difficult because of heterogeneous end points and no head-to-head studies.

Preemptive analgesia for postoperative hysterectomy pain control: systematic review and clinical practice guidelines

OBJECTIVE

The objective of the study was to investigate the effectiveness of preemptive analgesia at pain control in women undergoing total abdominal hysterectomy.

DATA SOURCES

Eligible studies, published through May 31, 2016, were retrieved through Medline, Cochrane Central Register for Controlled Trials, and Cochrane Database of Systematic Reviews.

STUDY ELIGIBILITY

We included randomized controlled trials with the primary outcome of pain control in women receiving a preemptive medication prior to total abdominal hysterectomy. Comparators were placebo, different doses of the same medication as intervention, or other nonnarcotic or narcotic medication.

STUDY APPRAISAL AND SYNTHESIS METHODS

Study data were extracted by one reviewer and confirmed by a second reviewer. For each outcome we graded the quality of the evidence. Studies were classified by the type of medication used and by outcome type.

RESULTS

Eighty-four trials met eligibility, with 69 included. Among nonnarcotic medications, paracetamol, gabapentin, and rofecoxib combined with gabapentin resulted in improvements in pain assessment compared with placebo and other nonnarcotic medications. Patient satisfaction was higher in patients who were given gabapentin combined with paracetamol compared with gabapentin alone. Use of preemptive paracetamol, gabapentin, bupivacaine, and phenothiazine resulted in less narcotic usage than placebo. All narcotics (ketamine, morphine, fentanyl) resulted in improved pain control compared with placebo. Narcotics had a greater reduction in pain assessment scores compared with nonnarcotics, and their use resulted in lower total narcotic usage.

CONCLUSION

Preemptive nonnarcotic and narcotic medications prior to abdominal hysterectomy decrease total narcotic requirements and improve patient postoperative pain assessment and satisfaction scores.

Alvimopan combined with enhanced recovery strategy for managing postoperative ileus after open abdominal surgery: a systematic review and meta-analysis

BACKGROUND

To assess the efficacy and safety of alvimopan in conjunction with enhanced recovery strategy, compared with this strategy alone, in management of postoperative ileus in patients undergoing open abdominal surgery.

METHODS

Electronic databases were comprehensively searched for relevant randomized controlled trials. We were interested in doses of 6 and 12 mg. The efficacy end points included the time to recovery of full gastrointestinal (GI) function (a composite end point measured by the time to first toleration of solid food [SF] and the time to first passage of stool, GI-2), the recovery of upper (SF) or the lower (the time to first bowel movement, BM) GI function, and the length of hospital stay (the time to discharge order written). Safety end points included GI-related, non-GI-related, and serious adverse events. These parameters were all analyzed by RevMan 5.3 software.

RESULTS

Nine randomized controlled trials involving 4075 patients were enrolled in this study. The pooled results showed that alvimopan significantly decreased the time to GI-2 recovery (6 mg, hazard ratio [HR] = 1.45, P < 0.00001; 12 mg, HR = 1.59, P < 0.00001), BM (6 mg, HR = 1.54, P < 0.00001; 12 mg, HR = 1.74, P = 0.0002), and the time to discharge order written (6 mg, HR = 1.37, P < 0.00001; 12 mg, HR = 1.34, P < 0.00001) compared with the placebo group. However, SF was significantly reduced in 6 mg group (HR = 1.23, P = 0.008) rather than 12 mg group (HR = 1.14, 95% confidence interval 1.00, 1.30, P = 0.04). The incidence of some GI-related and serious adverse events were significantly lower in the alvimopan group than the placebo group, and the dose of 12 mg was superior to 6 mg in this regard.

CONCLUSIONS

Alvimopan can accelerate recovery of GI function (especially for the lower GI tract), shorten the length of hospital stay, and reduce postoperative ileus-related morbidity without compromising opioid analgesia in an enhanced recovery setting.

Gastrointestinal dysmotility disorders in critically ill dogs and cats

OBJECTIVE

To review the human and veterinary literature regarding gastrointestinal (GI) dysmotility disorders in respect to pathogenesis, patient risk factors, and treatment options in critically ill dogs and cats.

ETIOLOGY

GI dysmotility is a common sequela of critical illness in people and small animals. The most common GI motility disorders in critically ill people and small animals include esophageal dysmotility, delayed gastric emptying, functional intestinal obstruction (ie, ileus), and colonic motility abnormalities. Medical conditions associated with the highest risk of GI dysmotility include mechanical ventilation, sepsis, shock, trauma, systemic inflammatory response syndrome, and multiple organ failure. The incidence and pathophysiology of GI dysmotility in critically ill small animals is incompletely understood.

DIAGNOSIS

A presumptive diagnosis of GI dysmotility is often made in high-risk patient populations following detection of persistent regurgitation, vomiting, lack of tolerance of enteral nutrition, abdominal pain, and constipation. Definitive diagnosis is established via radioscintigraphy; however, this diagnostic tool is not readily available and is difficult to perform on small animals. Other diagnostic modalities that have been evaluated include abdominal ultrasonography, radiographic contrast, and tracer studies.

THERAPY

Therapy is centered at optimizing GI perfusion, enhancement of GI motility, and early enteral nutrition. Pharmacological interventions are instituted to promote gastric emptying and effective intestinal motility and prevention of complications. Promotility agents, including ranitidine/nizatidine, metoclopramide, erythromycin, and cisapride are the mainstays of therapy in small animals.

PROGNOSIS

The development of complications related to GI dysmotility (eg, gastroesophageal reflux and aspiration) have been associated with increased mortality risk. Institution of prophylaxic therapy is recommended in high-risk patients, however, no consensus exists regarding optimal timing of initiating prophylaxic measures, preference of treatment, or duration of therapy. The prognosis for affected small animal patients remains unknown.

Delayed gastrointestinal recovery after abdominal operation - role of alvimopan

Postoperative Ileus (POI), which occurs after surgical manipulation of the bowel during abdominal operations, is associated with prolonged hospital stay, increasing medical costs, and delayed advancement of enteral diet, which contributes to a significant economic burden on the healthcare system. The use of accelerated care pathways has shown to positively impact gut function, but inevitable postoperative opioid use contributes to POI. Alvimopan is a peripherally acting μ-opioid receptor antagonist designed to mitigate antimotility effects of opioids. In our review, we examined ten trials on alvimopan’s use after abdominal operations. Several of the earlier studies on patients undergoing bowel resection showed correlations between the study group and GI recovery as defined by passage of flatus, first bowel movement, and time to readiness for discharge. Data in patients undergoing total abdominal hysterectomy showed similarly decreased GI recovery time. Additionally, data within the past few years shows alvimopan is associated with more rapid GI recovery time in patients undergoing radical cystectomy. Based on our review, use of alvimopan remains a safe and potentially cost-effective means of reducing POI in patients following open GI surgery, radical cystectomy, and total abdominal hysterectomy, and should be employed following these abdominal operations.

Off-label uses of alvimopan and methylnaltrexone

PURPOSE

Off-label uses of the peripheral μ-opioid receptor antagonists alvimopan and methylnaltrexone are reviewed.

SUMMARY

Alvimopan is approved by the Food and Drug Administration (FDA) for postoperative ileus after surgeries that include partial bowel resection with primary anastomosis, while methylnaltrexone is approved for the treatment of opioid-induced constipation (OIC) in patients with advanced illness who are receiving palliative care. Literature describing the off-label use of alvimopan in the treatment of OIC and of methylnaltrexone in postoperative ileus was reviewed and included retrospective studies and prospective Phase II-IV trials. Randomized controlled trials did not demonstrate consistent benefit of alvimopan in OIC nor of methylnaltrexone in postoperative ileus. A greater proportion of patients receiving alvimopan for OIC experienced severe adverse cardiovascular events, leading to a risk evaluation and mitigation strategy and discontinuation of its study in this condition. Data are limited and unreplicated for the off-label use of alvimopan for postoperative ileus in patients undergoing abdominal hysterectomy. Individual studies suggest benefit with methylnaltrexone for OIC in unlabeled populations, including patients with non-cancer-related pain, opioid dependence, opioid sedation, and opioid use after orthopedic surgery; however, confirmatory evaluations have not been performed.

CONCLUSION

Trials of alvimopan in the FDA-approved use of methylnaltrexone (OIC) indicate potentially serious cardiovascular safety concerns and conflicting findings of efficacy. Similarly, trials of methylnaltrexone in the FDA-approved use of alvimopan (postoperative ileus) consistently showed no benefit. Evaluations of both drugs in their labeled conditions in populations not endorsed in their product labeling have been limited and largely unreplicated.

Facilitating return of bowel function after colorectal surgery: alvimopan and gum chewing

Postoperative ileus is common after colorectal surgery, and has a huge impact on hospital LOS. With the impeding cost crisis in the United States, safely reducing length of stay is essential. Chewing gum and pharmacological treatment with alvimopan are safe, simple tools to reduce postoperative ileus and its associated costs. Future research will determine if integrating these tools with laparoscopic procedures and enhanced recovery pathways is a best practice in colorectal surgery.

Physiology, signaling, and pharmacology of opioid receptors and their ligands in the gastrointestinal tract: current concepts and future perspectives

Opioid receptors are widely distributed in the human body and are crucially involved in numerous physiological processes. These include pain signaling in the central and the peripheral nervous system, reproduction, growth, respiration, and immunological response. Opioid receptors additionally play a major role in the gastrointestinal (GI) tract in physiological and pathophysiological conditions. This review discusses the physiology and pharmacology of the opioid system in the GI tract. We additionally focus on GI disorders and malfunctions, where pathophysiology involves the endogenous opioid system, such as opioid-induced bowel dysfunction, opioid-induced constipation or abdominal pain. Based on recent reports in the field of pharmacology and medicinal chemistry, we will also discuss the opportunities of targeting the opioid system, suggesting future treatment options for functional disorders and inflammatory states of the GI tract.

Methylnaltrexone for the treatment of opioid-induced constipation

Opioids are the drugs of choice for treating moderate-to-severe pain, especially for patients in the end stage of cancer or other advanced illnesses, and also in critical care or for the treatment of chronic pain. Side effects such as nausea, pruritus, dizziness and constipation have to be controlled in order to use these drugs to their full potential. Opioid-induced bowel syndrome and constipation caused by activation of μ-receptors in the gut can have such distressing effects that some patients prefer to forego adequate pain control. Methylnaltrexone is a μ-opioid receptor antagonist that, unlike naltrexone or naloxone, does not pass the blood-brain barrier, and therefore does not impair the centrally mediated analgesic effect of opioids. It is licensed for the treatment of opioid-induced constipation in palliative care in more than 50 countries. This article presents practically relevant pharmacological data, basic research results and evidence from clinical research about methylnaltrexone, and outlines potential future therapeutic options for this promising drug.

A meta-analysis of the effectiveness of the opioid receptor antagonist alvimopan in reducing hospital length of stay and time to GI recovery in patients enrolled in a standardized accelerated recovery program after abdominal surgery

BACKGROUND

Despite accelerated recovery programs and the widespread uptake of laparoscopic surgery, postoperative ileus remains a significant factor affecting length of stay after abdominal surgery. Alvimopan, an opioid-receptor antagonist, may reduce the incidence of postoperative ileus and expedite hospital discharge.

OBJECTIVE

The aim of this study was to perform a meta-analysis to determine the role of alvimopan in accelerating GI recovery and hospital discharge after laparoscopic and open abdominal surgery performed within an accelerated recovery program.

DATA SOURCES AND STUDY SELECTION

Cochrane (1999-2010), Embase (1980-2010), MEDLINE (1980-2010), and International Pharmaceutical Abstracts (1970-2010) were searched for relevant double-blinded, randomized controlled trials.

INTERVENTIONS

Twelve milligrams of alvimopan and placebo were given to patients enrolled in an accelerated recovery program after abdominal surgery.

MAIN OUTCOME MEASURES

The primary outcomes measured were the length of stay as defined by the writing of the hospital discharge order and GI-3 and GI-2 GI tract recovery.

RESULTS

: Three trials were included that reported on a pooled modified intention-to-treat population of 1388 patients; 685 (49%) patients received alvimopan. On meta-analysis, alvimopan reduced time to the hospital discharge order (HR 1.37 (1.21, 1.62), p < 0.0001), GI-3 recovery (HR 1.42 (1.25, 1.62), p < 0.001), and GI-2 recovery (HR 1.49 (1.32, 1.68), p < 0.0001).

LIMITATIONS

The search criteria identified only a small number of trials of alvimopan after abdominal surgery with no randomized trials of alvimopan after laparoscopic surgery. In addition, the use of length of hospital stay as the primary outcome measure may be inappropriate, because it is open to many confounding factors. Finally, adverse events, in particular, adverse cardiovascular events, were not considered.

CONCLUSIONS

Alvimopan 12 mg can further reduce time to GI recovery and hospital discharge in patients undergoing abdominal surgery within an accelerated recovery program. Investigation into the effect of alvimopan following laparoscopic surgery and additional cost-benefit analyses are required to further define the role of this intervention.

Analgesic effects of melatonin: a review of current evidence from experimental and clinical studies

Melatonin is an endogenous indoleamine, produced mainly by the pineal gland. Melatonin has been proven to have chronobiotic, antioxidant, antihypertensive, anxiolytic and sedative properties. There are also experimental and clinical data supporting an analgesic role of melatonin. In experimental studies, melatonin shows potent analgesic effects in a dose-dependent manner. In clinical studies, melatonin has been shown to have analgesic benefits in patients with chronic pain (fibromyalgia, irritable bowel syndrome, migraine). The physiologic mechanism underlying the analgesic actions of melatonin has not been clarified. The effects may be linked to G(i) -coupled melatonin receptors, to G(i) -coupled opioid μ-receptors or GABA-B receptors with unknown downstream changes with a consequential reduction in anxiety and pain. Also, the repeated administration of melatonin improves sleep and thereby may reduce anxiety, which leads to lower levels of pain. In this paper, we review the current evidence regarding the analgesic properties of melatonin in animals and humans with chronic pain.

Management of postoperative ileus: focus on alvimopan

Postoperative ileus (POI) is a transient loss of coordinated peristalsis precipitated by surgery and exacerbated by opioid pain medication. Ileus causes a variety of symptoms including bloating, pain, nausea, and vomiting, but particularly delays tolerance of oral diet and liquids. Thus POI is a primary determinant of hospital stay after surgery. ‘Fast-track’ recovery protocols, opioid sparing analgesia, and laparoscopic surgery reduce but do not eliminate postoperative ileus. Alvimopan is a mu opioid receptor antagonist that blocks the effects of opioids on the intestine, while not interfering with their centrally mediated analgesic effect. Several large randomized clinical trials have demonstrated that alvimopan accelerates the return of gastrointestinal function after surgery and subsequent hospital discharge by approximately 20 hours after elective open segmental colectomy. However, it has not been tested in patients undergoing laparoscopic surgery and is less effective in patients receiving nonsteroidal anti-inflammatory agents in a narcotic sparing postoperative pain control regimen. Safety concerns seen with chronic low dose administration of alvimopan for opioid bowel dysfunction have not been noted with its acute use for POI.

Immunosuppressive effects of opioids--clinical relevance

Opioid-induced immunosuppression has been demonstrated in cell culture experiments and in animal models. This is in striking contrast to the paucity of confirmatory studies in humans. This review describes the basic pharmacokinetics and -dynamics of opioid use in patients. It summarizes the major findings on opioid use and infectious complications in intensive care unit (ICU) patients, in patients with acute or chronic non-malignant pain, and in intravenous drug users (IDU). The limitations of studies in each area are discussed. For example, ethical concerns may complicate randomized placebo-controlled trials (RCT) in acute postoperative pain and for a large part of ICU patients. Importantly, most studies in patients with chronic (non-malignant) pain only inadequately report infectious complications in relation to opioid use since their incidence is usually not considered to be drug related. Infectious complications in IDUs are very frequent but cannot easily be distinguished from risk behavior or risk environment. In summary, convincing clinical evidence is lacking that opioids per se increase the rate of infectious complications in most patient categories. From a clinical standpoint, important unresolved issues are i) selection of relevant animal models, ii) opioid selection and discontinuation, and iii) the role of coexisting diseases and concomitant other medications.

Novel opioid antagonists for opioid-induced bowel dysfunction

INTRODUCTION

Adverse effects frequently limit the therapeutic benefits of opioid analgesics. Gastrointestinal adverse effects are common, burdensome, and can compromise the quality of life. It is estimated that up to 81% of patients still report constipation despite regular use of laxatives. Thus, the development of opioid antagonists that selectively target receptors in the gut without affecting central analgesia has provided new perspectives on the treatment of opioid-induced gastrointestinal adverse effects.

AREAS COVERED

In this paper, we review the pathophysiology, prevalence, and burden of opioid-induced bowel dysfunction (OBD). In addition, this study aims to provide a better understanding of the mechanism of action and reviews the efficacy, safety and the latest research on novel opioid antagonists for OBD.

EXPERT OPINION

Two strategies effectively relieve OBD without interfering with centrally mediated analgesia: the administration of opioid antagonists with limited systemic absorption and peripherally acting mu-opioid receptor antagonists (PAMORA) that selectively target mu-receptors in the gastrointestinal tract. Methylnaltrexone and alvimopan are two recently marketed PAMORA and provide a new mechanism-based approach for the treatment of opioid-induced gastrointestinal dysfunction. However, its use in clinical practice is limited by various reasons such as its relatively low response rates and higher costs. Nevertheless, at least four new oral PAMORA (NKTR-118, TD-1211, ADL-7445, and ADL-5945) are under clinical development, further expanding the possibilities for a new paradigm for OBD management.

Opioid antagonists for prevention and treatment of opioid-induced gastrointestinal effects

PURPOSE OF REVIEW

The therapeutic action of opioid analgesics is compromised by peripheral adverse effects, among which constipation is the most disabling as laxatives often fail to provide satisfactory relief. This review highlights recent advances in the specific control of opioid-induced constipation by opioid receptor antagonists with limited systemic bioavailability or a peripherally restricted site of action.

RECENT FINDINGS

The specific management of opioid-induced bowel dysfunction is currently based on three drug entities: oral alvimopan for the shortening of postoperative ileus associated with opioid-induced pain control after bowel resection, subcutaneous methylnaltrexone for the reduction of opioid-induced constipation in patients with advanced illness, and a fixed combination of oral prolonged-release naloxone with prolonged-release oxycodone for the treatment of noncancer and cancer pain. All three drug entities have been shown to attenuate opioid-induced motor stasis in the gut with a favorable adverse effect profile, while the analgesic effect of opioids remains unabated.

SUMMARY

The availability of opioid receptor antagonists with restricted access to the central nervous system provides a novel opportunity to specifically control opioid-induced constipation and other peripheral adverse effects of opioid analgesics. Further studies are needed to evaluate the long-term efficacy, safety and cost-effectiveness of this approach.

Recent Advances in Pharmacotherapy

Many unique and clinically important medications were approved by the Food and Drug Administration from December 2007 through May 2008 for various conditions encountered in an internal medicine setting. These new treatments dramatically vary in their targeted body system and include agents for the cardiovascular system (nebivolol), central nervous system (desvenlafaxine), gastrointestinal tract (certolizumab, methylnaltrexone, and alvimopan), immunological function (etravirine), and metabolic function (sapropterin). This article discusses medications by their respective body system. Each review is comprised of an overview of the Food and Drug Administration–approved indication and the drug’s role in treatment of that disease state. Current dosing guidance, clinical efficacy and clinically relevant adverse drug reactions, drug interactions, contraindications, and precautions are also presented. This review is designed to focus on the new molecular entities and biological approvals clinicians may potentially encounter in an internal medicine practice.

Recent advances in the use of opioids for cancer pain

Opioids are the mainstay of treatment for moderate to severe cancer pain. In recent years there have been many advances in the use of opioids for cancer pain. Availability and consumption of opioids have increased and opioids other than morphine (including methadone, fentanyl, oxycodone) have become more widely used. Inter-individual variation in response to opioids has been identified as a significant challenge in the management of cancer pain. Many studies have been published demonstrating the benefits of opioid switching as a clinical maneuver to improve tolerability. Constipation has been recognized as a significant burden in cancer patients on opioids. Peripherally restricted opioid antagonists have been developed for the prevention and management of opioid induced constipation. The phenomenon of breakthrough pain has been characterized and novel modes of opioid administration (transmucosal, intranasal, sublingual) have been explored to facilitate improved management of breakthrough cancer pain. Advances have also been made in the realm of molecular biology. Pharmacogenetic studies have explored associations between clinical response to opioids and genetic variation at a DNA level. To date these studies have been small but future research may facilitate prospective prediction of response to individual drugs.

[Opioid-induced bowel dysfunction: a literature analysis on pathophysiology and treatment]

Bowel dysfunction is a frequent and serious side effect of opioid analgetics. In spite of its common occurrence, in the course of clinical routine, it is frequently ignored or underestimated. Authors of the analysed literature widely agree that a prophylactic and routine pharmacotherapy is necessary. For this purpose, laxatives, enemas and suppositories, prokinetic agents and opioid antagonists can be considered. Bulk-forming laxatives did not prove to be effective, since the quantity of fluid intake required for the action usually cannot be provided. Furthermore, the benefit of emollient agents is doubted. As a monotherapy they are not sufficient. By contrast, stimulant and osmotic laxatives proved to be active. Prokinetic drugs are not recommended because of their serious side effects. Effective abatement of opioid-induced obstipation by opioid antagonists has been proven in numerous studies. However, the loss of analgesia and opioid withdrawal symptoms were described as adverse effects. Development of quaternary opioid antagonists such as methylnaltrexone was allowed for mitigating these adverse effects.

Peripherally acting mu-opioid receptor antagonists and postoperative ileus: mechanisms of action and clinical applicability

Postoperative ileus (POI), a transient cessation of coordinated bowel function after surgery, is an important health care problem. The etiology of POI is multifactorial and related to both the surgical and anesthetic pathways chosen. Opioids used to manage surgical pain can exacerbate POI, delaying gastrointestinal (GI) recovery. Peripherally acting mu-opioid receptor (PAM-OR) antagonists are designed to mitigate the deleterious effects of opioids on GI motility. This new class is investigational for POI management with the goal of accelerating the recovery of upper and lower GI tract function after bowel resection. In this review, we summarize the mechanisms by which POI occurs and the role of opioids and opioid receptors in the enteric nervous system, discuss the mechanism of action of PAM-OR antagonists, and review clinical pharmacology and Phase II/III POI trial results of methylnaltrexone and alvimopan. Finally, the role of anesthesiologists in managing POI in the context of a multimodal approach is discussed.

Novel opioid antagonists for opioid-induced bowel dysfunction and postoperative ileus

Peripherally acting mu-opioid receptor antagonists methylnaltrexone and alvimopan are a new class of drugs designed to reverse opioid-induced side-effects on the gastrointestinal system without compromising pain relief. This article gives an overview of the pharmacology, the efficacy, and adverse effects of these drugs. Both compounds seem to be generally well tolerated and effective for the treatment of opioid-related bowel dysfunction and postoperative ileus. Methylnaltrexone recently received approval by the US Food and Drug Administration (FDA) and the European Medicines Agency for treatment of opioid-related bowel dysfunction in patients with advanced illness. Alvimopan was recently approved by the FDA for treatment of postoperative ileus, but the use of the drug is restricted to inpatients because it has been associated with an increased rate of myocardial infarction. Further research should assess the effectiveness and safety of these drugs in clinical practice.

Safety and efficacy update: Alvimopan in postoperative ileus

Postoperative ileus (POI) in patients undergoing abdominal surgery is associated with significant morbidity. In 2008, alvimopan (Entereg®) was approved by the Food and Drug Administration (FDA), and is the only available POI therapy in the United States for patients undergoing bowel resection. Data from preclinical studies demonstrate that alvimopan and its primary metabolite, ADL 08-0011, behave as potent μ. opioid receptor antagonists. In animals, alvimopan and ADL 08-0011 attenuate opioid agonist-induced reductions in gastrointestinal (GI) transit. Higher doses of alvimopan are required to inhibit opioid-induced analgesia as a result of its inability to penetrate the central nervous system (CNS). ADL 08-0011 is also peripherally selective, although to a lesser degree than alvimopan. In multiple species, including humans, alvimopan has low oral bioavailability, while ADL 08-0011, following its generation by human gut microflora, is more readily absorbed and achieves higher exposures. Three Phase 2 and five Phase 3 clinical trials have been conducted to investigate the efficacy and tolerability of alvimopan in patients undergoing bowel resection. An additional Phase 3 study was conducted in hysterectomy patients. In the majority of the studies, statistically significant, and clinically meaningful, acceleration of GI recovery has been demonstrated. Consistent with animal data, alvimopan has no effect on opioid agonist-induced analgesia in healthy human subjects and POI patients. Clinical experience to date in POI patients indicates that alvimopan is well tolerated when used according to its approved dosing regimen (12 mg b.i.d. for up to 7 days). In this article, the preclinical and clinical properties of alvimopan are reviewed.

Alvimopan

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Through the cooperation of The Formulary, Hospital Pharmacy publishes selected reviews in this column. If you would like information about The Formulary Monograph Service or The FIX., call The Formulary at 800-322-4349. The October 2008 monograph topics are on clevidipine butyrate injectable emulsion, tetrabenazine, tenofovir disoproxil fumarate tablets, ferumoxytol, and saxagliptin. The DUE is on clevidipine butyrate injectable emulsion.

Alvimopan and COX-2 inhibition reverse opioid and inflammatory components of postoperative ileus

Our objective was to investigate the therapeutic potential of peripheral opioid antagonism with alvimopan and anti-inflammatory cyclooxygenase 2 (COX-2) inhibition in an animal model of postoperative ileus with pain management. Intestinal manipulation was conducted in mice and rats with or without postoperative morphine injection. Rodents were orally fed non-digestible fluorescein (FITC)-labelled dextran and transit measured after a period of 90 min. The immunomodulatory effects of morphine and alvimopan were determined on nitric oxide released from the organ cultured muscularis externa. Surgical manipulation of the intestine resulted in a delay in gastrointestinal transit after 24 h that worsened with exogenous morphine. Alvimopan did not significantly alter transit of control or manipulated animals, but significantly antagonized the transit delaying effects of morphine. However, when the inflammatory component was robust enough to obscure a further opioid induced delay in gastrointestinal transit, alvimopan ceased to be effective in improving postoperative intestinal function. Cyclooxygenase 2 inhibition significantly diminished the inflammatory component of postoperative ileus. Surgical manipulation resulted in an increased release of nitric oxide from the inflamed isolated muscularis externa in 24-h organ culture which was not altered by morphine or alvimopan. Two distinct mechanisms exist which participate in postoperative bowel dysfunction: a local inflammatory response which is antagonized by COX-2 inhibition, and a morphine-induced alteration in neural function which can be blocked with alvimopan.

Mu-opioid antagonists for opioid-induced bowel dysfunction

BACKGROUND

Opioid-induced bowel dysfunction (OBD) is characterized by constipation, incomplete evacuation, bloating, and increased gastric reflux. OBD occurs both acutely and chronically, in multiple disease states, resulting in increased morbidity and reduced quality of life.

OBJECTIVES

To compare the efficacy and safety of traditional and peripherally active opioid antagonists versus conventional interventions for OBD.

SEARCH STRATEGY

We searched MEDLINE, the Cochrane Central Register of Controlled Trials and EMBASE in January 2007. Additional reports were identified from the reference lists of retrieved papers.

SELECTION CRITERIA

Studies were included if they were randomized controlled trials that investigated the efficacy of mu-opioid antagonists for OBD.

DATA COLLECTION AND ANALYSIS

Data were extracted by two independent review authors and included demographic variables, diagnoses, interventions, efficacy, and adverse events.

MAIN RESULTS

Twenty-three studies met inclusion criteria and provided data on 2871 opioid antagonist-treated patients. The opioid antagonists investigated were alvimopan (nine studies), methylnaltrexone (six), naloxone (seven), and nalbuphine (one). Meta-analysis demonstrated that methylnaltrexone and alvimopan were better than placebo in reversing opioid-induced increased gastrointestinal transit time and constipation, and that alvimopan appears to be safe and efficacious in treating postoperative ileus. The incidence of adverse events with opioid antagonists was similar to placebo and generally reported as mild-to-moderate.

AUTHORS' CONCLUSIONS

Insufficient evidence exists for the safety or efficacy of naloxone or nalbuphine in the treatment of OBD. Long-term efficacy and safety of any of the opioid antagonists is unknown, as is the incidence or nature of rare adverse events. Alvimopan and methylnaltrexone both show promise in treating OBD, but further data will be required to fully assess their place in therapy.

Systemic prokinetic pharmacologic treatment for postoperative adynamic ileus following abdominal surgery in adults

BACKGROUND

Postoperative adynamic bowel atony interferes with recovery following abdominal surgery. Prokinetic pharmacologic drugs are widely used to accelerate postoperative recovery.

OBJECTIVES

To evaluate the benefits and harms of systemic acting prokinetic drugs to treat postoperative adynamic ileus in patients undergoing abdominal surgery.

SEARCH STRATEGY

Trials were identified by computerised searches of the Cochrane Central Register of Controlled Trials, MEDLINE, EMBASE, and the Cochrane Colorectal Cancer Group specialised register. The reference lists of included trials and review articles were tracked and authors contacted.

SELECTION CRITERIA

Randomised controlled parallel-group trials (RCT) comparing the effect of systemically acting prokinetic drugs against placebo or no intervention.

DATA COLLECTION AND ANALYSIS

Four reviewers independently extracted the data and assessed trial quality. Trial authors were contacted for additional information if needed.

MAIN RESULTS

Thirty-nine RCTs met the inclusion criteria contributing a total of 4615 participants. Most trials enrolled a small number of patients and showed moderate to poor (reporting of) methodological quality, in particular regarding allocation concealment and intention-to-treat analysis. Fifteen systemic acting prokinetic drugs were investigated and ten comparisons could be summarized. Six RCTs support the effect of Alvimopan, a novel peripheral mu receptor antagonist. However, the trials do not meet reporting guidelines and the drug is still in an investigational stage. Erythromycin showed homogenous and consistent absence of effect across all included trials and outcomes. The evidence is insufficient to recommend the use of cholecystokinin-like drugs, cisapride, dopamine-antagonists, propranolol or vasopressin. Effects are either inconsistent across outcomes, or trials are too small and often of poor methodological quality. Cisapride has been withdrawn from the market due to adverse cardiac events in many countries. Intravenous lidocaine and neostigmine might show a potential effect, but more evidence on clinically relevant outcomes is needed. Heterogeneity among included trials was seen in 10 comparisons. No major adverse drug effects were evident.

AUTHORS' CONCLUSIONS

Alvimopan may prove to be beneficial but proper judgement needs adherence to reporting standards. Further trials are needed on intravenous lidocaine and neostigmine. The remaining drugs can not be recommended due to lack of evidence or absence of effect.

Emerging pharmacologic options for treating postoperative ileus

PURPOSE

Characteristics of the ideal drug therapy for postoperative ileus (POI); the pharmacology, efficacy, and safety of currently available nonselective opioid antagonists and the new peripherally selective opioid antagonists methylnaltrexone and alvimopan for the treatment of POI; and formulary considerations associated with the introduction of these new POI drug therapies are discussed.

SUMMARY

The ideal drug therapy for treating POI would selectively antagonize the inhibitory effects on the gastrointestinal (GI) tract of all of the potential factors implicated in the pathophysiology of POI (neurogenic, inflammatory, hormonal, and pharmacologic mediators). The most promising target to date is inhibition of the adverse GI effects of endogenous and exogenous opioids. Selective inhibition of the mu-opioid receptors in the GI tract, without reversing centrally mediated opioid-induced analgesia, may be beneficial in reducing POI. The nonselective opioid antagonists naloxone and nalmefene have not been studied for POI, and they cross the blood-brain barrier. Therefore, they are not appropriate for preventing or treating POI. The peripherally selective opioid antagonist methylnaltrexone shortens the duration of POI and the hospital length of stay (LOS). Alvimopan, a more extensively studied peripherally selective opioid antagonist, has been shown to reduce the duration of POI, frequency of postoperative nausea and vomiting, and hospital LOS. Both methylnaltrexone and alvimopan also appear effective for treating opioid-induced constipation. Preliminary results of a long-term study of alvimopan safety have revealed some potential concerns, and the significance of the adverse effects must be understood before the most appropriate role of alvimopan in patient care can be determined. Restricting the prescribing of new POI drug therapies to certain types of patients, surgeries, and prescribers; incorporating these therapies into preoperative and postoperative policies, procedures, and protocols; and the potential cost savings from reducing hospital LOS are among the considerations in adding these agents to health-system formularies.

CONCLUSION

Peripherally selective opioid receptor antagonists are promising new drug therapies that can reduce the clinical and economic burden of POI.

Treatment of opioid-induced gut dysfunction

Opioid analgesics are the mainstay in the treatment of moderate-to-severe pain, yet their use is frequently associated with adverse effects, the most common and debilitating being constipation. Opioid-induced motor stasis results from blockade of gastrointestinal peristalsis and fluid secretion, and reflects the action of the endogenous opioid system in the gut. Methylnaltrexone and alvimopan are new investigational drugs that selectively target peripheral mu-opioid receptors because they are poorly absorbed in the intestine and do not enter the brain. Clinical studies have proved the concept that these drugs prevent opioid-induced bowel dysfunction without interfering with analgesia. As reviewed in this article, opioid receptor antagonists with a peripherally restricted site of action also hold therapeutic promise in postoperative ileus and chronic constipation due to the fact that they have been found to stimulate intestinal transit.

Meta-analysis: Alvimopan vs. placebo in the treatment of post-operative ileus

BACKGROUND

Alvimopan is a selective, competitive mu-opioid receptor antagonist with limited oral bioavailability which may be used to reduce length of post-operative ileus.

AIM

The study compared alvimopan with placebo following bowel resection or total abdominal hysterectomy.

METHODS

A meta-analysis of randomized-controlled trials published between 2001 and 2006 of alvimopan vs. placebo was performed. The primary efficacy end-points were composite measures of passage of flatus, stool, and tolerance of solid food (GI-3) and passage of stool and tolerance of solid food (GI-2). The incidence of treatment emergent adverse events was assessed.

RESULTS

Five trials matched the selection criteria, reporting on 2195 patients. A total of 1521 (69.3%) had alvimopan and 674 (30.7%) placebo. GI-3 significantly improved (hazard ratio 1.30; 95% confidence intervals 1.16, 1.45, P < 0.001), as did GI-2 (hazard ratio 1.61; 95% confidence intervals 1.26, 2.05, P < 0.001) on alvimopan 12 mg. Time to discharge (hazard ratio 1.26; 95% confidence intervals 1.13, 1.40, P < 0.001), time to bowel motion (hazard ratio 1.74; 95% confidence intervals 1.29, 2.35, P < 0.001), and time to solid food (hazard ratio 1.14; 95% confidence intervals 1.01, 1.30, P < 0.04) also improved significantly. No difference was noted in the incidence of treatment emergent adverse events.

CONCLUSIONS

Alvimopan showed significant advantages over placebo in restoring gastro-intestinal function, and reduced time to discharge following major abdominal surgery, with acceptable side effects.