Evaluation of the effect of Naloxegol on cardiac repolarization: a randomized, placebo- and positive-controlled crossover thorough QT/QTc study in healthy volunteers

Evaluating the Safety and Efficacy of Naloxegol in Critically Ill Opioid-Induced Constipation Patients

Background Opioid-induced constipation (OIC) has become more common in the intensive care unit (ICU) due to increased opioid utilization. Traditional laxatives often prove ineffective against OIC, leading to the increased utilization of naloxegol. However, further research is needed to confirm naloxegol's effectiveness and safety in critical care. This study aimed to explore the safety and efficacy of this intervention in critically ill OIC patients. Methods A single-center retrospective study was conducted on 353 patients who received one or more doses of naloxegol from January 1, 2019, to June 30, 2020, for OIC at a tertiary care center. The primary endpoint of this study was to evaluate serious adverse events such as reduced analgesic effect, gastrointestinal perforation, seizure, acute myocardial infarction (AMI), or ventricular arrhythmias using Naranjo Scale in critically ill patients. The secondary goal was to assess the efficacy of naloxegol, measured by the time of the first bowel movement. Results The average duration of naloxegol use was three days, with the first bowel movement occurring at an average of 11.3 hours. Furthermore, 59.8% of individuals had their first bowel movement within 20 hours of receiving naloxegol. There was a low level of causality between naloxegol use and adverse events such as gastrointestinal perforation, seizures, AMI, cardiovascular mortality, stroke, and ventricular arrhythmia. Additionally, reduction in analgesia showed no strong relationship with naloxegol use indicated by the Naranjo Scale assessment. Conclusion Naloxegol showed promising safety and efficacy profiles in treating OIC amongst critically ill patients, though our findings require further validation through prospective studies. This research paves the way for further investigation into naloxegol's role in OIC management, emphasizing the necessity of personalized treatment strategies in critical care settings.

Insights into the Use of Peripherally Acting μ-Opioid Receptor Antagonists (PAMORAs) in Oncologic Patients: from Scientific Evidence to Real Clinical Practice

OPINION STATEMENT

Management of chronic pain is crucial to improve the quality of life of cancer and palliative care patients. Opioid-based treatments used to control pain can be prolonged over time. Unfortunately, constipation is one of the most disturbing adverse effects of long-term use of opioids. Opioid-induced constipation (OIC) occurs when opioids bind to the specific receptors present in the gastrointestinal (GI) tract, and can affect any patients receiving chronic opioid therapy, including cancer patients. The limited efficacy of laxatives to treat OIC symptoms prompted the search for new therapeutic strategies. Peripherally acting μ-opioid receptor antagonists (PAMORAs) have recently emerged as new effective drugs for OIC management due to their specific binding to enteric μ-receptors. Little information is available on the use of PAMORAs in real-life practice for OIC treatment in cancer patients. In this paper, a panel of experts specializing in cancer and palliative care pools their clinical experience with PAMORAs in cancer patients presenting OIC and highlights the importance of timing and choice of therapy in achieving prompt OIC management and benefitting patients.

The Use of Peripheral μ-Opioid Receptor Antagonists (PAMORA) in the Management of Opioid-Induced Constipation: An Update on Their Efficacy and Safety

Peripherally acting μ-opioid receptor antagonists (PAMORAs) constitute a class of drugs which reverse opioid-induced constipation (OIC) with similar opioid analgesic effects. OIC differs from other forms of constipation in that it is an iatrogenic condition that occurs when an opioid acts on the dense network of μ-opioid receptors in the enteric system, which affect a variety of functions including gastrointestinal motility, secretion, and other factors that can cause bowel dysfunction. Unfortunately, laxative products, bowel regimens, dietary changes, and lifestyle modifications have limited effectiveness in preventing OIC, Opioid-associated adverse effect which occurs in 40% to 80% of opioid patients and may led to cessation of the treatment. PAMORAs are μ-receptor opioid antagonists specifically developed so that they have very limited ability to cross the blood-brain barrier and thus they are able to antagonize peripheral but not central μ-opioid receptors. PAMORAs are designed to have no effect on the analgesic benefits of opioid pain relievers but to relieve but antagonizing the effects of the opioid in the gastrointestinal system. The three main PAMORAS are methyltrexone (oral or parenteral), naldemedine (oral only), and naloxegol (oral only). Clinical studies demonstrate the safety and efficacy of these agents for alleviating constipation without diminishing the analgesic effect of opioid therapy. The aim of this narrative review to update the current status of PAMORAs for treating OIC in terms of safety and efficacy.

Opioid-Induced Constipation in Oncological Patients: New Strategies of Management

OPINION STATEMENT

Cancer-associated pain has traditionally been treated with opioid analgesics, often in escalating doses. Opioid-induced constipation (OIC) is a common problem associated with chronic use of opioid analgesics. Typical treatment strategies to alleviate constipation are based on dietary changes, exercise, and laxatives. However, laxatives have a nonspecific action and do not target underlying mechanisms of OIC. This article will review prevalent, clinical presentation and recommendations for the treatment of OIC. An independent literature search was carried out by the authors. We reviewed the literature for randomized controlled trials that studied the efficacy of laxatives, naloxone, and naloxegol in treating OIC. Newer strategies addressing the causal pathophysiology of OIC are needed for a more effective assessment and management of OIC. Finally, traditional recommended therapies are appraised and compared with the latest pharmacological developments. Future research should address whether naloxegol is more efficacious by its comparison directly with first-line treatments, including laxatives.

Clinical Overview and Considerations for the Management of Opioid-induced Constipation in Patients With Chronic Noncancer Pain

OBJECTIVES

Opioid analgesics may be associated with chronic adverse effects, such as opioid-induced constipation (OIC). Available and emerging prescription medications for OIC in patients with chronic noncancer pain are described, including concerns and challenges associated with OIC management.

METHODS

Narrative review.

RESULTS

OIC is characterized by a change in bowel habits and defecation patterns that occurs when initiating opioid therapy and is associated with reduced bowel frequency, straining, sensation of incomplete evacuation, and/or patient distress related to bowel habits. Prescription medications are indicated when OIC persists despite conservative approaches (eg, increased fiber and fluid intake, exercise, over-the-counter laxatives and stool softeners). Phase 3 studies have demonstrated the efficacy of peripherally acting µ-opioid receptor antagonists (PAMORA; methylnaltrexone, naloxegol, naldemedine), and a chloride channel activator (lubiprostone) for improving OIC in patients with chronic noncancer pain. Although head-to-head studies are lacking, a meta-analysis demonstrated that μ-opioid receptor antagonists were more effective than placebo for the treatment of OIC. The most common adverse effects associated with prescription medications for OIC are gastrointestinal related (eg, nausea, diarrhea, abdominal pain, or distention), with most being mild or moderate in severity. Therapy currently in development for OIC includes the PAMORA axelopran.

DISCUSSION

Health care providers should be aware of this complication in patients receiving opioids and should monitor and address constipation-related symptoms to optimize pain management and improve patient quality of life.

Effects of Nemonoxacin on Thorough ECG QT/QTc Interval: A Randomized, Placebo- and Positive-controlled Crossover Study in Healthy Chinese Adults

PURPOSE

Nemonoxacin, a nonfluorinated quinolone, has been approved in Taiwan and mainland China for the treatment of bacterial infection. Whether nemonoxacin is associated with the adverse events of other quinolones, such as the risk for QT-interval prolongation, which has led to the withdrawal of several fluoroquinolones from the market, needs to be elucidated.

METHODS

The effects of nemonoxacin on thorough QT/QTc interval was investigated in this randomized, placebo- and positive-controlled crossover study conducted according to the International Conference on Harmonisation E14 guideline. Forty-eight healthy adults received a single oral dose of nemonoxacin 500 mg (therapeutic dose), nemonoxacin 750 mg (supratherapeutic dose), moxifloxacin 400 mg (positive control), or placebo in 1 of 4 cohorts (Williams Latin square design) in the fasted condition. After a 7-day washout, 6 male and 6 female subjects were orally administered a 500-mg dose of nemonoxacin after high-fat food intake. The primary end point was the change in QT interval corrected for heart rate using the Fridericia formula (QTcF). The secondary end point was the change in QT interval corrected for heart rate using the Bazett formula (QTcB).

FINDINGS

The study revealed that nemonoxacin was classified as not likely dangerous at the therapeutic dose (500 mg) and as potentially dangerous at the supratherapeutic dose (750 mg). The T_max of nemonoxacin was 1 to 2 hours after administration, and the elimination half-life was 5 to 7 hours, in the fasted conditions. High-fat food intake had significant effects on the T_max, C_max, AUC_0-∞, and QT/QTc interval of nemonoxacin compared with these values in the fasted condition. A correlation between QTcF and the plasma drug concentration of nemonoxacin was not observed.

IMPLICATIONS

Nemonoxacin at the clinically therapeutic and supratherapeutic doses had a prolongation effect on QT/QTc. ClinicalTrials.gov identifier: NCT03362853.

Gastroparesis: pharmacotherapy and cardiac risk

BACKGROUND

Gastroparesis is characterized by abnormal gastric motility and delayed emptying with symptoms of early satiety, postprandial fullness, bloating, nausea, vomiting and abdominal pain. Pharmacological discovery has been lagging because potential drugs often are associated with abnormalities of electrical conduction of the myocardium due to interaction with cardiac ion channels leading to limited pharmaceutical options for development of new drugs.

OBJECTIVE

Addresses the safety of drugs for gastroparesis in terms of cardiotoxicity related to the clinical use of prokinetics and antiemetics.

METHODS

Survey of QT drugs List and review of current literature.

RESULTS

Many prokinetic drugs are associated with cardiac adverse events and manifest as prolongation of ventricular repolarization, i.e., QT-interval prolongation of the electrocardiogram. This disturbance may develop into a potentially fatal polymorphic ventricular tachyarrhythmia; Torsade de Pointes. Co-administration of prokinetics with other drugs affecting the repolarization process, pharmacokinetic interactions leading to increased blood levels, or the presence of clinical risk factors could further increase the risk for cardiac arrhythmias.

CONCLUSIONS

It is important that clinicians managing gastroparesis are aware of the arrhythmogenic potential of drugs used clinically and risk factors that contribute to QT prolongation to safeguard patients at risk for drug-induced cardiac arrhythmia.

Cardiovascular Safety of the Selective μ-Opioid Receptor Antagonist Naloxegol: A Novel Therapy for Opioid-Induced Constipation

Background:

Naloxegol is a novel selective, peripherally acting μ-opioid receptor antagonist for treating opioid-induced constipation (OIC) in patients with chronic pain syndromes. We analyzed the cardiovascular (CV) safety of naloxegol based on data from its development program prior to approval by the US Food and Drug Administration in 2015.

Methods:

Comprehensive CV safety analyses were performed in 4 clinical studies of naloxegol (12.5 and/or 25 mg) in patients with noncancer pain and OIC: two 12-week, double-blind, randomized studies; a 12-week, double-blind, extension study; and a 52-week, randomized, open-label study versus usual care. Evaluations of baseline CV risk were obtained from medical histories and clinical findings at the time of study initiation.

Results:

Across the 4 studies (N = 2135), 68% of patients had ≥1 CV risk factor and 41% had a history of CV disease, diabetes, or ≥2 other CV risk factors. There were no increases in blood pressure, heart rate, or the rate-pressure product with naloxegol versus placebo. The rates of major adverse cardiovascular events (MACE) per 100 patient-years of exposure were 1.13 (95% confidence interval [CI], 0.31-2.89) for placebo/usual care and 0.75 (95% CI, 0.24-1.75) for naloxegol. The relative risk of MACE for all doses of naloxegol versus placebo was 0.67 (95% CI, 0.14-3.36).

Conclusion:

These data demonstrate that naloxegol has a CV safety profile comparable to placebo/usual care in patients with OIC. Although the observed number of events was low, the data show no CV signal in patients with OIC treated with naloxegol.

Clinical Pharmacokinetics and Pharmacodynamics of Naloxegol, a Peripherally Acting µ-Opioid Receptor Antagonist

Naloxegol is a peripherally acting µ-opioid receptor antagonist approved for use as an orally administered tablet (therapeutic doses of 12.5 and 25 mg) for the treatment of opioid-induced constipation. Over a wide dose range (i.e. single supratherapeutic doses up to 1000 mg in healthy volunteers), the pharmacokinetic properties of naloxegol appear to be time- and dose-independent. Naloxegol is rapidly absorbed, with mean time to maximum plasma concentration of <2 h. Following once-daily administration, steady state is achieved within 2-3 days and minimal accumulation is observed. The primary route of naloxegol elimination is via hepatic metabolism, with renal excretion playing a minimal role. In clinical studies, six metabolites were found in feces, urine or plasma, none of which have been identified as unique or disproportionate human metabolites. The major plasma circulating species is naloxegol. There are small effects of mild and moderate renal impairment, age, race, and body mass index on the systemic exposure of naloxegol; however, gender has no effect on the pharmacokinetics of this agent. Naloxegol is a sensitive substrate of cytochrome P450 (CYP) 3A4 and its exposure can be significantly altered by strong or moderate CYP3A modulators. Food increases the bioavailability of naloxegol, and the relative bioavailability of the tablet formulation was not limited by dissolution. Naloxegol in the dose range of 8-125 mg can antagonize morphine-induced peripheral effects without impacting the effect of morphine on the central nervous system, consistent with a peripheral mode of action.

Naloxegol in opioid-induced constipation: a new paradigm in the treatment of a common problem

Opioid-induced constipation (OIC) imposes a significant burden for patients taking pain medications, often resulting in decreased quality of life. Treatment of OIC with traditional medications for functional constipation can be incompletely effective, leading to nonadherence with opioid treatment and undertreated pain. An emerging class of medications that counteract the adverse effects of opioids in the gastrointestinal tract while preserving central nervous system-based pain relief may represent a paradigm shift in the prevention and treatment of OIC. One of these medications, naloxegol, is a once-daily, oral opioid antagonist that is effective, well-tolerated, and approved for treatment of OIC in patients with noncancer pain. More studies are needed to demonstrate this same utility in patients with cancer-related pain.

The role of naloxegol in the management of opioid-induced bowel dysfunction

Opioid-induced constipation (OIC) and other gastrointestinal (GI) symptoms of opioid-induced bowel dysfunction (OIBD) significantly deteriorate patients' quality of life and may lead to noncompliance with opioid schedule and undertreatment of pain. Although traditional oral laxatives are the first-line treatment of OIC, they do not address OIBD pathophysiology, and display numerous adverse effects. OIC treatment includes prokinetics (lubiprostone), opioid switch, and changing route of opioid administration. Targeted management of OIBD comprises the use of purely peripherally acting μ-opioid receptor antagonists (PAMORA): naloxegol and methylnaltrexone. Naloxegol (NKTR-118) is a polymer conjugate of the opioid antagonist naloxone. The polyethylene glycol limits naloxegol capacity to cross the blood-brain barrier (BBB). Naloxegol is substrate for the P-glycoprotein (P-gp) transporter. The central nervous system penetration of naloxegol is negligible due to reduced permeability and its increased efflux across the BBB, related to P-gp transporter. Naloxegol antagonizes μ- and κ-opioid receptors and displays low affinity to δ-opioid receptors in the GI tract, thereby decreasing OIBD symptoms without reversing central analgesic effects. Naloxegol is metabolised through CYP3A4 to six metabolites, with the majority of the dose (68%) excreted with faeces and less (16%) with urine. The dose of naloxegol equals 25 mg administered orally once daily on a fasting condition. Mild or moderate hepatic impairment has no impact on naloxegol dosing; naloxegol was not studied and is not recommended in patients with hepatic failure. Dose reduction (12.5 mg once daily) and caution is recommended in patients with moderate-to-severe renal impairment. Efficacy (bowel movement in 42-49% of patients not responsive to laxatives) and safety of naloxegol were confirmed in studies conducted in patients with OIC and nonmalignant pain. Naloxegol may be useful for cancer patients with OIC, although studies in this population are lacking.

Naloxegol

Opioid-related bowel dysfunction is a common and potentially severe adverse effect from treatment with opioid analgesics. Its development is not dose related, nor do patients develop tolerance. Opioid-induced constipation (OIC) can lead to fecal impaction, bowel obstruction, and bowel perforation as well as noncompliance with opioid analgesics and poor quality of life. Routine administration of laxatives is necessary to maintain bowel function, and, in refractory cases, other modalities must be pursued. Available options are limited but include peripherally acting μ-opioid receptor antagonists (PAMORAs), including methylnaltrexone. Naloxegol is a newly developed PAMORA that is available through the oral route. At the therapeutic dose of 25 mg daily, naloxegol is effective and safe, with a limited side effect profile and is associated with preservation of centrally mediated analgesia. In this article, we discuss the pharmacokinetics, pharmacodynamics, adverse effects, clinical trials, and cost considerations of naloxegol. Finally, we discuss its potential role as a novel key treatment for OIC in palliative medicine patients.

New Options in Constipation Management

Constipation is common in the general population and for those on opioids and/or who are suffering from advanced cancer. Self-management consists of dietary changes, exercise, and laxatives. However, responses to self-management efforts are often inadequate to relieve the subjective and objective experience of constipation. Multiple new anti-constipating medications have recently been tested in randomized trials and the following are available commercially: probiotics, prucalopride, lubiprostone, linaclotide, elobixibat, antidepressants, methylnaltrexone, alvimopan, and naloxegol. This review will discuss the evidence-based benefits of these medications and outline an approach to managing constipation.

Opioid-induced constipation: advances and clinical guidance

Currently opioids are the most frequently used medications for chronic noncancer pain. Opioid-induced constipation is the most common adverse effect associated with prolonged use of opioids, having a major impact on quality of life. There is an increasing need to treat opioid-induced constipation. With the recent approval of medications for the treatment of opioid-induced constipation, there are several therapeutic approaches. This review addresses the clinical presentation and diagnosis of opioid-induced constipation, barriers to its diagnosis, effects of opioids in the gastrointestinal tract, differential tolerance to opiates in different gastrointestinal organs, medications approved and in development for the treatment of opioid-induced constipation, and a proposed clinical management algorithm for treating opioid-induced constipation in patients with noncancer pain.

Naloxegol: a review of its use in patients with opioid-induced constipation

Oral naloxegol (Movantik™, Moventig(®)), a peripherally acting μ-opioid receptor antagonist, inhibits opioid binding in μ-opioid receptors in the gastrointestinal tract. This article reviews the pharmacological properties of naloxegol and its clinical efficacy and tolerability in patients with opioid-induced constipation. It demonstrated clinical efficacy and was well tolerated in placebo-controlled trials in patients with non-cancer pain and opioid-induced constipation, including those with an inadequate response to laxatives, and was well tolerated in a long-term safety study. As a PEGylated naloxone derivative, naloxegol is associated with significant improvements in spontaneous bowel movements, while maintaining levels of opioid-related analgesia (a result of its reduced ability to cross the blood-brain barrier). Naloxegol is a useful option in the treatment of opioid-induced constipation.

Naloxegol: First oral peripherally acting mu opioid receptor antagonists for opioid-induced constipation

Opioid-induced constipation (OIC) is one of the most troublesome and the most common effects of opioid use leading to deterioration in quality of life of the patients and also has potentially deleterious repercussions on adherence and compliance to opioid therapy. With the current guidelines advocating liberal use of opioids by physicians even for non-cancer chronic pain, the situation is further complicated as these individuals are not undergoing palliative care and hence there cannot be any justification to subject these patients to the severe constipation brought on by opioid therapy which is no less debilitating than the chronic pain. The aim in these patients is to prevent the opioid-induced constipation but at the same time allow the analgesic activity of opioids. Many drugs have been used with limited success but the most specific among them were the peripherally acting mu opioid receptor antagonists (PAMORA). Methylnaltrexone and alvimopan were the early drugs in this group but were not approved for oral use in OIC. However naloxegol, the latest PAMORA has been very recently approved as the first oral drug for OIC. This article gives an overview of OIC, its current management and more specifically the development and approval of naloxegol, including pharmacokinetics, details of various clinical trials, adverse effects and its current status for the management of OIC.

Effect of Retosiban on Cardiac Repolarization in a Randomized, Placebo- and Positive-controlled, Crossover Thorough QT/QTc Study in Healthy Men and Women

PURPOSE

Retosiban is a small molecule oxytocin receptor antagonist that is under evaluation in clinical studies for treatment of spontaneous preterm labor. A Thorough QT/QTc study was conducted to evaluate the effect of retosiban on cardiac repolarization according to International Conference on Harmonization E14 guidance. This was a randomized, placebo- and positive-controlled, single-dose, crossover study of healthy men and women.

METHODS

All study participants received a 100 mg dose of retosiban (therapeutic target exposure), a 800 mg dose of retosiban (supratherapeutic target exposure), a 400 mg dose of moxifloxacin (positive control), and placebo with an appropriate washout. Holter monitoring data at baseline (predose) and at 13 subsequent time points during the next 24 hours were extracted and manually read by a central ECG reader who was blinded to the treatment assignment and corrected for heart rate by using the Fridericia formula (QTcF). A linear exposure-QTc response model was developed: ΔΔQTcF=RI+Cp,R⋅RS+MI+Cp,M⋅MS, where RI and MI are intercept terms for retosiban and moxifloxacin, respectively, RS and MS are slope terms for retosiban and moxifloxacin, respectively, and Cp,R and Cp,M are plasma concentrations for retosiban and moxifloxacin, respectively.

FINDINGS

A total of 52 healthy men (n = 27) and women (n = 25), with a mean age of 32 years, were enrolled in the study, and 43 (83%) completed all treatment periods and assessments. Mean placebo-corrected change from baseline QT (ΔΔQTcF) for the 2 retosiban dose groups revealed statistically significant decreases in ΔΔQTcF between 2 and 3 hours after administration, reaching a value of -2.5 msec for both retosiban dose groups. The 400 mg moxifloxacin group had a statistically significant increase in the ΔΔQTcF value at 0.75 hours after administration, reaching a maximal increase of 11.10 msec at 4 hours after administration. Results of the exposure-QTc response modeling revealed that there was no significant effect of retosiban on the ΔΔQTcF at therapeutic exposures. For the supratherapeutic exposure of retosiban, there was a slight negative effect, with a mean decrease of -3.05 msec. The moxifloxacin arm had a mean increase in ΔΔQTcF of 10.7 msec.

IMPLICATIONS

At therapeutic and supratherapeutic exposures, retosiban had no significant effect on cardiac repolarization, as estimated by the ΔΔQTcF. However, both doses of retosiban had a minor shortening effect. This is not considered to be clinically significant. CLINICALTRIALS.

GOV IDENTIFIER

NCT01702376.

Clinical utility of naloxegol in the treatment of opioid-induced constipation

Opioids are a class of medications frequently used for the treatment of acute and chronic pain, exerting their desired effects at central opioid receptors. Agonism at peripherally located opioid receptors, however, leads to opioid-induced constipation (OIC), one of the most frequent and debilitating side effects of prolonged opioid use. Insufficient relief of OIC with lifestyle modification and traditional laxative treatments may lead to decreased compliance with opioid regimens and undertreated pain. Peripherally acting mu-opioid receptor antagonists (PAMORAs) offer the reversal of OIC without loss of central pain relief. Until recently, PAMORAs were restricted to subcutaneous route or to narrow patient populations. Naloxegol is the first orally dosed PAMORA indicated for the treatment of OIC in noncancer patients. Studies have suggested its efficacy in patients failing traditional constipation treatments; however, insufficient evidence exists to establish its role in primary prevention of OIC at this time.

Naloxegol , a new drug for the treatment of opioid-induced constipation

INTRODUCTION

With increasing chronic opioid use, opioid-induced constipation (OIC) is becoming a relevant clinical challenge. Presently, only few treatments have been demonstrated to be more effective than placebo in treating OIC but most of them have a restricted clinical application because of side effects. Naloxegol , an orally administered, peripherally acting, μ-opioid receptor antagonist (PAMORA), was developed for the treatment of OIC.

AREA COVERED

This review summarizes published information and presentations at meetings on the effects of naloxegol in OIC. Pharmacodynamic studies have demonstrated that naloxegol inhibits gastrointestinal opioid effects while preserving central analgesic actions. Phase II and Phase III studies in patients with non-cancer OIC have confirmed the efficacy of naloxegol to inhibit OIC, and the most consistent efficacy was seen with the 25 mg dose once daily. Adverse events were mainly gastrointestinal in origin and usually transient and mild. There were no signs of opioid withdrawal in the studies. Safety and tolerability were also shown in a long-term safety study. Regulatory authorities have recently approved the use of naloxegol in OIC.

EXPERT OPINION

Naloxegol is the first approved, orally available PAMORA. The drug has the potential to substantially improve management of OIC patients.

Naloxegol: treatment for opioid-induced constipation in chronic non-cancer pain

OBJECTIVE

To describe the effectiveness of naloxegol for the treatment of opioid-induced constipation (OIC) in chronic non-cancer pain patients.

DATA SOURCES

Citations in PubMed, Google Scholar, Cochrane Library, CINAHL, ScienceDirect, and ProQuest were obtained. Reference lists from individual articles obtained were reviewed for additional sources.

STUDY SELECTION AND DATA EXTRACTION

All English-language publications available as poster presentations, abstracts, and peer-reviewed articles ranging from preclinical to phase III trials and published between 2007 and September 14, 2014, were reviewed and summarized.

DATA SYNTHESIS

Naloxegol was shown to be effective for increasing the average weekly number of spontaneous bowel movements (SBMs) in a single phase II trial enrolling 208 patients. Phase III trials (KODIAC-04/-05) enrolling a total of 1352 patients developed a new primary end point with a more strict responder criteria. This entailed a mean increase in SBMs, at least 3 SBMs per week, efficacy in 9 of 12 weeks, and efficacy in 3 of the final 4 weeks of the study period. Both groups receiving naloxegol 25 mg had significant improvement over the placebo group. The improvement was similar in patients who reported failure with laxatives in the past and regardless of daily opioid dose. A long-term trial (KODIAC-08) showed safety over 52 weeks.

CONCLUSION

OIC affects many individuals treated with opioids for chronic non-cancer pain. Previous over-the-counter or prescription treatment options were limited by a lack of adequate and well-controlled studies, multiple daily dosing, or need for injections. Cost issues may limit therapy with naloxegol to select patients.

Endogenous opiates and behavior: 2013

This paper is the thirty-sixth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2013 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides, opioid receptors, opioid agonists and opioid antagonists. The particular topics that continue to be covered include the molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors related to behavior, and the roles of these opioid peptides and receptors in pain and analgesia; stress and social status; tolerance and dependence; learning and memory; eating and drinking; alcohol and drugs of abuse; sexual activity and hormones, pregnancy, development and endocrinology; mental illness and mood; seizures and neurologic disorders; electrical-related activity and neurophysiology; general activity and locomotion; gastrointestinal, renal and hepatic functions; cardiovascular responses; respiration and thermoregulation; and immunological responses.

Naloxegol for the treatment of opioid-induced constipation

With increasing chronic opioid use, opioid-induced constipation (OIC) is a rapidly increasing clinical challenge. Naloxegol, an orally administered, peripherally-acting, µ-opioid receptor antagonist, was developed for the treatment of OIC. This drug profile summarizes published information and presentations at meetings on the effects of naloxegol in OIC. In animal studies, naloxegol was able to inhibit gastrointestinal opioid effects while preserving central analgesic actions and human pharmacodynamic studies were in agreement with such mode of action. Phase II and Phase III studies in patients with non-cancer OIC confirmed the efficacy of naloxegol to inhibit OIC, and the most consistent efficacy was seen with the 25 mg dose once daily. There were no signs of opioid withdrawal in these studies. Side effects were mainly gastrointestinal in origin, and usually transient and mild. A long-term safety study showed no new adverse events. The US FDA and EMA are currently evaluating the use of naloxegol in OIC.

Clinical potential of naloxegol in the management of opioid-induced bowel dysfunction

Opioid-induced bowel dysfunction (OIBD) is a burdensome condition which limits the therapeutic benefit of analgesia. It affects the entire gastrointestinal tract, predominantly by activating opioid receptors in the enteric nervous system, resulting in a wide range of symptoms, such as reflux, bloating, abdominal cramping, hard, dry stools, and incomplete evacuation. The majority of studies evaluating OIBD focus on constipation experienced in approximately 60% of patients. Nevertheless, other presentations of OIBD seem to be equally frequent. Furthermore, laxative treatment is often insufficient, which in many patients results in decreased quality of life and discontinuation of opioid treatment. Novel mechanism-based pharmacological approaches targeting the gastrointestinal opioid receptors have been marketed recently and even more are in the pipeline. One strategy is prolonged release formulation of the opioid antagonist naloxone (which has limited systemic absorption) and oxycodone in a combined tablet. Another approach is peripherally acting, μ-opioid receptor antagonists (PAMORAs) that selectively target μ-opioid receptors in the gastrointestinal tract. However, in Europe the only PAMORA approved for OIBD is the subcutaneously administered methylnaltrexone. Alvimopan is an oral PAMORA, but only approved in the US for postoperative ileus in hospitalized patients. Finally, naloxegol is a novel, oral PAMORA expected to be approved soon. In this review, the prevalence and pathophysiology of OIBD is presented. As PAMORAs seem to be a promising approach, their potential effect is reviewed with special focus on naloxegol's pharmacological properties, data on safety, efficacy, and patient-focused perspectives. In conclusion, as naloxegol is administered orally once daily, has proven efficacious compared to placebo, has an acceptable safety profile, and can be used as add-on to existing pain treatment, it is a welcoming addition to the targeted treatment possibilities for OIBD.