Low-dose oral naloxone reverses opioid-induced constipation and analgesia

Definition, diagnosis and treatment strategies for opioid-induced bowel dysfunction–Recommendations of the Nordic Working Group

Background and aims

Opioid-induced bowel dysfunction (OIBD) is an increasing problem due to the common use of opioids for pain worldwide. It manifests with different symptoms, such as dry mouth, gastro-oesophageal reflux, vomiting, bloating, abdominal pain, anorexia, hard stools, constipation and incomplete evacuation. Opioid-induced constipation (OIC) is one of its many symptoms and probably the most prevalent. The current review describes the pathophysiology, clinical implications and treatment of OIBD.

Methods

The Nordic Working Group was formed to provide input for Scandinavian specialists in multiple, relevant areas. Seven main topics with associated statements were defined. The working plan provided a structured format for systematic reviews and included instructions on how to evaluate the level of evidence according to the GRADE guidelines. The quality of evidence supporting the different statements was rated as high, moderate or low. At a second meeting, the group discussed and voted on each section with recommendations (weak and strong) for the statements.

Results

The literature review supported the fact that opioid receptors are expressed throughout the gastrointestinal tract. When blocked by exogenous opioids, there are changes in motility, secretion and absorption of fluids, and sphincter function that are reflected in clinical symptoms. The group supported a recent consensus statement for OIC, which takes into account the change in bowel habits for at least one week rather than focusing on the frequency of bowel movements. Many patients with pain receive opioid therapy and concomitant constipation is associated with increased morbidity and utilization of healthcare resources. Opioid treatment for acute postoperative pain will prolong the postoperative ileus and should also be considered in this context. There are no available tools to assess OIBD, but many rating scales have been developed to assess constipation, and a few specifically address OIC. A clinical treatment strategy for OIBD/OIC was proposed and presented in a flowchart. First-line treatment of OIC is conventional laxatives, lifestyle changes, tapering the opioid dosage and alternative analgesics. Whilst opioid rotation may also improve symptoms, these remain unalleviated in a substantial proportion of patients. Should conventional treatment fail, mechanism-based treatment with opioid antagonists should be considered, and they show advantages over laxatives. It should not be overlooked that many reasons for constipation other than OIBD exist, which should be taken into consideration in the individual patient.

Conclusion and implications

It is the belief of this Nordic Working Group that increased awareness of adverse effects and OIBD, particularly OIC, will lead to better pain treatment in patients on opioid therapy. Subsequently, optimised therapy will improve quality of life and, from a socio-economic perspective, may also reduce costs associated with hospitalisation, sick leave and early retirement in these patients.

Bowel Disorders

Functional bowel disorders are highly prevalent disorders found worldwide. These disorders have the potential to affect all members of society, regardless of age, gender, race, creed, color or socioeconomic status. Improving our understanding of functional bowel disorders (FBD) is critical as they impose a negative economic impact to the global health care system in addition to reducing quality of life. Research in the basic and clinical sciences during the past decade has produced new information on the epidemiology, etiology, pathophysiology, diagnosis and treatment of FBDs. These important findings created a need to revise the Rome III criteria for FBDs, last published in 2006. This manuscript classifies the FBDs into five distinct categories: irritable bowel syndrome (IBS); functional constipation (FC); functional diarrhea (FDr); functional abdominal bloating/distention (FAB/D); and unspecified FBD (U-FBD). Also included in this article is a new sixth category, opioid induced constipation (OIC) which is distinct from the functional bowel disorders (FBDs). Each disorder will first be defined, followed by sections on epidemiology, rationale for changes from prior criteria, clinical evaluation, physiologic features, psychosocial features and treatment. It is the hope of this committee that this new information will assist both clinicians and researchers in the decade to come.

Opioid-induced constipation in chronic noncancer pain

PURPOSE OF REVIEW

Opioid-based management of noncancer pain has become much more prevalent over the last 2 decades and is responsible for a wide range of side-effects, particularly affecting the intestinal tract causing opioid-induced constipation (OIC). This review will consider results of recent clinical trials that have provided evidence of new pharmacological management options for the treatment of OIC.

RECENT FINDINGS

Supportive use of conventional agents, such as stool softeners, osmotic laxatives, and stimulating laxatives in OIC has limited efficacy. The peripheral μ-opioid receptor antagonist (PAMORA) methylnaltrexone (MNTX) was first FDA approved for OIC in patients with advanced illness and later also for OIC in noncancer pain patients; clinical trial results indicated MNTX did not reverse opioid analgesia and did not trigger central opioid withdrawal. Another PAMORA, the orally available naloxegol, has also gained recent FDA approval for the treatment of OIC in adults with chronic, noncancer pain. Lubiprostone, a bicyclical fatty acid acting via activation of intestinal chloride channel-2 (ClC-2), was also approved for OIC treatment in patients with noncancer pain.

SUMMARY

PAMORA MNTX and naloxegol and the intestinal chloride channel-2 (ClC-2) activator lubiprostone represent additional possible therapeutic options for the management of OIC in patients with chronic noncancer pain.

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.

Opioid-induced constipation reversal in response to placebo in a patient with a history of IBS receiving methadone maintenance therapy

Opioid-induced constipation (OIC) is one of the major side effects in patients receiving methadone maintenance treatment (MMT). Quite often, constipation becomes a factor significantly affecting therapeutic options and choices. Currently used approaches are symptomatic and in many cases ineffective. At the same time, it is well known that the gastrointestinal system is a subject for psychosomatic influences. In this case report, we describe an unexpected outcome of placebo administration in a patient suffering from OIC since her participation in MMT. The patient participated in a triple-blind randomised placebo-controlled trial of naloxone for treatment of OIC. As part of the study crossover design, the patient received 1 week of placebo followed by 1 week of naloxone, and had significant improvement in her bowel functioning when receiving placebo, then returned to baseline during the second week of the study.

Safety, tolerability, pharmacokinetics, and pharmacodynamic effects of naloxegol at peripheral and central nervous system receptors in healthy male subjects: A single ascending-dose study

This randomized, double-blind, placebo-controlled, ascending-dose, crossover study evaluated single oral doses of naloxegol (NKTR-118; 8, 15, 30, 60, 125, 250, 500, and 1000 mg), a PEGylated derivative of naloxone, for safety and tolerability, antagonism of peripheral and central nervous system (CNS) effects of intravenous morphine, and pharmacokinetics. Healthy men were randomized 1:1 to naloxegol or naloxegol-matching placebo administered with morphine and lactulose in a 2-period crossover design. Periods were separated by a 5- to 7-day washout. Assessments included safety, tolerability, orocecal transit time (OCTT), pupillary miosis, and pharmacokinetics. The study was completed by 46 subjects. The most common adverse events were somnolence, dizziness, headache, and nausea. Greater reversal of morphine-induced delay in OCTT occurred with increasing naloxegol dose, demonstrating dose-ordered antagonism of morphine's peripheral gastrointestinal effects. Forty-four subjects showed no reversal of pupillary miosis; 2 showed potential partial reversal at 250 and 1000 mg, indicating negligible antagonism of morphine's CNS effects at doses ≤ 125 mg. Rapid absorption, linear pharmacokinetics up to 1000 mg, and low to moderate between-subject pharmacokinetic variability was observed. The pharmacokinetics of morphine or its glucuronide metabolites were unaltered by concurrent naloxegol administration. Naloxegol was generally safe and well tolerated at single doses up to 1000 mg.

Chronic opioid induced constipation in patients with nonmalignant pain: challenges and opportunities

With the recent introduction and approval of medications directed at the treatment of opioid induced constipation (OIC) in patients with nonmalignant pain, there is increased interest and understanding of the unmet need and opportunities to enhance patient management. The high incidence of OIC is associated with rapid increase of narcotic analgesic prescriptions for nonmalignant chronic pain. This review addresses briefly the mechanisms of action of opioids that lead to OIC, the differential tolerance of gastrointestinal organs to the effects of opioids, the size and scope of the problem, the definition and outcome measures for OIC, current differential diagnosis and management algorithms, and the pharmacology and efficacy of treatments for OIC in patients with nonmalignant pain.

Laxatives for the management of constipation in people receiving palliative care

BACKGROUND

This article describes the second update of a Cochrane review on the effectiveness of laxatives for the management of constipation in people receiving palliative care. Previous versions were published in 2006 and 2010 where we also evaluated trials of methylnaltrexone; these trials have been removed as they are included in another review in press. In these earlier versions, we drew no conclusions on individual effectiveness of different laxatives because of the limited number of evaluations. This is despite constipation being common in palliative care, generating considerable suffering due to the unpleasant physical symptoms and the availability of a wide range of laxatives with known differences in effect in other populations.

OBJECTIVES

To determine the effectiveness and differential efficacy of laxatives used to manage constipation in people receiving palliative care.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL; The Cochrane Library), MEDLINE, EMBASE, CINAHL and Web of Science (SCI & CPCI-S) for trials to September 2014.

SELECTION CRITERIA

Randomised controlled trials (RCTs) evaluating laxatives for constipation in people receiving palliative care.

DATA COLLECTION AND ANALYSIS

Two authors assessed trial quality and extracted data. The appropriateness of combining data from the studies depended upon clinical and outcome measure homogeneity.

MAIN RESULTS

We identified five studies involving the laxatives lactulose, senna, co-danthramer, misrakasneham, docusate and magnesium hydroxide with liquid paraffin. Overall, the study findings were at an unclear risk of bias. As all five studies compared different laxatives or combinations of laxatives, it was not possible to perform a meta-analysis. There was no evidence on whether individual laxatives were more effective than others or caused fewer adverse effects.

AUTHORS' CONCLUSIONS

This second update found that laxatives were of similar effectiveness but the evidence remains limited due to insufficient data from a few small RCTs. None of the studies evaluated polyethylene glycol or any intervention given rectally. There is a need for more trials to evaluate the effectiveness of laxatives in palliative care populations. Extrapolating findings on the effectiveness of laxatives evaluated in other populations should proceed with caution. This is because of the differences inherent in people receiving palliative care that may impact, in a likely negative way, on the effect of a laxative.

Emerging therapies for patients with symptoms of opioid-induced bowel dysfunction

Opioid-induced bowel dysfunction (OIBD) comprises gastrointestinal (GI) symptoms, including dry mouth, nausea, vomiting, gastric stasis, bloating, abdominal pain, and opioid-induced constipation, which significantly impair patients’ quality of life and may lead to undertreatment of pain. Traditional laxatives are often prescribed for OIBD symptoms, although they display limited efficacy and exert adverse effects. Other strategies include prokinetics and change of opioids or their administration route. However, these approaches do not address underlying causes of OIBD associated with opioid effects on mostly peripheral opioid receptors located in the GI tract. Targeted management of OIBD comprises purely peripherally acting opioid receptor antagonists and a combination of opioid receptor agonist and antagonist. Methylnaltrexone induces laxation in 50%–60% of patients with advanced diseases and OIBD who do not respond to traditional oral laxatives without inducing opioid withdrawal symptoms with similar response (45%–50%) after an oral administration of naloxegol. A combination of prolonged-release oxycodone with prolonged-release naloxone (OXN) in one tablet (a ratio of 2:1) provides analgesia with limited negative effect on the bowel function, as oxycodone displays high oral bioavailability and naloxone demonstrates local antagonist effect on opioid receptors in the GI tract and is totally inactivated in the liver. OXN in daily doses of up to 80 mg/40 mg provides equally effective analgesia with improved bowel function compared to oxycodone administered alone in patients with chronic non-malignant and cancer-related pain. OIBD is a common complication of long-term opioid therapy and may lead to quality of life deterioration and undertreatment of pain. Thus, a complex assessment and management that addresses underlying causes and patomechanisms of OIBD is recommended. Newer strategies comprise methylnaltrexone or OXN administration in the management of OIBD, and OXN may be also considered as a preventive measure of OIBD development in patients who require opioid administration.

Advances in pharmacotherapy for opioid-induced constipation - a systematic review

INTRODUCTION

Opioid-induced constipation (OIC) is one of the most frequent and burdening adverse events (AE) of opioid therapy. This systematic review aimed to evaluate efficacy and safety of drugs in randomized controlled trials (RCTs) with adult OIC patients.

AREAS COVERED

Efficacy assessment focused on objective outcome measures (OOMs): bowel movement (BM) frequency, BM within 4 h and time to first BM. Twenty-one studies examining seven drugs were identified. Methylnaltrexone showed improvements in all three OOMs. RCTs in naloxone and alvimopan tended to be effective for BM frequency measures. Naloxegol (≥ 12.5 mg) improved all OOMs. Though effectiveness of lubiprostone was demonstrated for all OOMs, group differences were small to moderate. CB-5945 and prucalopride tended to increase BM frequency, especially for 0.1 mg twice daily and 4 mg daily, respectively. Besides nausea and diarrhea, abdominal pain was the most frequent AE for all drugs (risk ratio, range: 1.52 - 5.06) except for alvimopan. Treatment-related serious AEs were slightly higher for alvimopan (cardiac events) and prucalopride (severe abdominal pain, headache). Pain scores for placebo and intervention groups were similar for all drugs.

EXPERT OPINION

Finding a consensus definition and inclusion criteria for OIC plus a rational balance between efficacy and AEs of drugs remain future challenges.

Efficacy and tolerability of low-dose oral prolonged-release oxycodone/naloxone for chronic nononcological pain in older patients

Purpose

Chronic pain is highly prevalent in older adults. Increasing evidence indicates strong opioids as a valid option for chronic pain management in geriatrics. The aim of this study was to evaluate efficacy and safety of low-dose oral prolonged-release oxycodone–naloxone (OXN-PR) in patients aged ≥70 years.

Methods

This open-label prospective study assessed older patients naïve to strong opioids presenting with moderate-to-severe chronic pain. Patients were prescribed OXN-PR at an initial dose of 10/5 mg/day for 28 days. In case of insufficient analgesia, the initial daily dose could be increased gradually. The primary efficacy measure was change in pain intensity from baseline, assessed by a ten-point Numeric Rating Scale (NRS) at day 28 (T28). Changes in cognitive state, daily functioning, quality of life, constipation, and other adverse events were assessed.

Results

Of 53 patients enrolled (mean 81.7±6.2 years [range 70–92 years]), 52 (98.1%) completed the 28-day observation. At T28, the primary end point (≥30% reduction in mean pain from baseline in the absence of bowel function deterioration) was achieved in 38 patients (71.7%). OXN-PR significantly relieved pain (NRS score –3.26; P<0.0001), as well as daily need for rescue paracetamol (from 86.8% at baseline to 40.4% at T28; P<0.001), and reduced impact of pain on daily activities (Brief Pain Inventory Short Form from 6.2±1.5 to 3.4±2.1; P<0.0001). OXN-PR was also associated with significant improvement in daily functioning (Barthel Index from 53.3±14.1 to 61.3±14.3; P<0.01). No changes were observed in cognitive status and bowel function. OXN-PR was well tolerated; only one patient (1.9%) prematurely withdrew from treatment, due to drowsiness.

Conclusion

Findings from this open-label prospective study suggest that low-dose OXN-PR may be effective and well tolerated for treatment of moderate-to-severe chronic pain in older patients. Besides its effectiveness, these data indicate that low-dose OXN-PR may be considered a safe analgesic option in this fragile population and warrants further investigation in randomized controlled studies.

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 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.

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

BACKGROUND

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

PURPOSE

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

Standardized treatment of Chinese medicine decoction for cancer pain patients with opioid-induced constipation: a multi-center prospective randomized controlled study

OBJECTIVE

To observe the efficacy and the influence on quality of life (QOL) of syndrome differentiation treatment with Chinese medicine (CM) for opioid-induced constipation as well as the safety and influence on analgesic effect of opioids.

METHODS

Totally 406 cases enrolled from 53 collaborating medical centers were randomly assigned to a CM group and a control group. The CM group were treated with CM decoction based on syndrome differentiation, and the control group were treated with Phenolphthalein Tablet. Both groups were treated for 14 days. Cleveland constipation score (CCS), numerical rating scale (NRS) of pain and Chinese version of European Organisation for Research and Treatment of Cancer, Quality of Life Questionnaire-C30 V3.0 (EORTC QLQ-C30 V3.0) were used to evaluate the efficacy, pain controlled and QOL status.

RESULTS

The comparisons of CCS score reduction and QOL between the two groups after treatment suggested that the improvements of constipation and QOL in the CM group were better than that in the control group (P<0.05). The total efficiency of the CM group was better than the control group (93.5% vs. 86.4%, P<0.05). There was no significant difference in NRS scores between before and after treatment in both groups. There was no serious drug-related adverse event during the course of study.

CONCLUSION

CM decoction could effectively treat opioid-induced constipation and improve patients' QOL at the same time. It is safe and doesn't affect the analgesic effect of opioids when treating constipation.

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

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

Opioid-induced bowel dysfunction

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

Treatment of opioid-induced constipation: focus on the peripheral μ-opioid receptor antagonist methylnaltrexone

Most prescribed opioids exert their analgesic effects via activation of central μ-opioid receptors. However, μ-opioid receptors are also located in the gastrointestinal (GI) tract, and activation of these receptors by opioids can lead to GI-related adverse effects, in particular opioid-induced constipation (OIC). OIC has been associated with increased use of healthcare resources, increased healthcare costs, and decreased quality of life for patients. Nonpharmacologic (e.g., increased fiber uptake) and pharmacologic agents (e.g., laxatives) may be considered for the treatment and prevention of OIC. However, many interventions, such as laxatives alone, are generally insufficient to reverse OIC because they do not target the underlying cause of OIC, opioid activation of μ-opioid receptors in the GI tract. Therefore, there has been keen interest in antagonism of the μ-opioid receptor in the periphery to inhibit the effects of opioids in the GI tract. In this review, currently available pharmacologic therapies for the treatment and prevention of OIC are summarized briefly, with a primary focus on the administration of the peripheral μ-opioid receptor antagonist methylnaltrexone bromide in patients with OIC and advanced illness who are receiving palliative care. Also, clinical trial data of methylnaltrexone treatment in patients with OIC and other pain conditions (i.e., chronic noncancer pain and pain after orthopedic surgery) are reviewed. Data support that methylnaltrexone is efficacious for the treatment of OIC and has a favorable tolerability profile.

Cancer pain therapy with a fixed combination of prolonged-release oxycodone/naloxone: results from a non-interventional study

BACKGROUND

Strong opioids, including oxycodone, are the most effective analgesics used to combat moderate to severe cancer pain, but opioid-induced bowel dysfunction is a relevant problem associated with the therapy. Clinical studies have demonstrated equivalent analgesic efficacy and improved bowel function in treatment with a fixed combination of prolonged-release (PR) oxycodone and PR naloxone compared to oxycodone alone in patients with nonmalignant pain. Here, we report of a prospective, non-interventional study evaluating the effectiveness and safety of PR oxycodone/PR naloxone in a subgroup of patients with severe cancer pain.

PATIENTS AND METHODS

Within the non-interventional multicenter study, 1,178 cancer patients with severe chronic pain received PR oxycodone/PR naloxone, dosed according to pain intensity, for 4 weeks. Recorded variables included pain intensity, patient-reported bowel function (Bowel Function Index), and pain-related functional impairment as a measure of quality of life (QoL).

RESULTS

During treatment with PR oxycodone/PR naloxone, clinically relevant improvements in pain intensity were observed in opioid-naïve patients and in patients pretreated with weak or strong opioids, as reflected by reductions in pain scores of 51%, 53%, and 33%, respectively. Improvement in analgesia was paralleled by a significant reduction of opioid-induced bowel dysfunction in opioid-pretreated patients. The reductions in the mean Bowel Function Index of -20.5 and -36.5 in patients pretreated with weak and strong opioids, respectively, represent clinically relevant improvements in bowel function. Pain-related functional impairment decreased consistently across all seven domains, which is equivalent to a substantial improvement in QoL.

CONCLUSION

This subgroup analysis of cancer patients within a large non-interventional study demonstrates that treatment with PR oxycodone/PR naloxone provides effective analgesia with minimization of bowel dysfunction and improved QoL. These data extend our knowledge of the effectiveness and tolerability of PR oxycodone/PR naloxone to the population of patients with cancer under real-life conditions.

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

The place of oxycodone/naloxone in chronic pain management

Opioid analgesics are usually effective in the management of severe chronic pain. However, symptoms of opioid-induced bowel dysfunction (OIBD) are common during opioid therapy. Opioid-induced bowel dysfunction is often unsuccessfully managed due to limited effectiveness and numerous adverse effects of traditional laxatives. Newer treatment possibilities directed at the pathomechanism of OIBD comprise combined prolonged-release oxycodone with prolonged-release naloxone (oxycodone/naloxone) tablets. Oxycodone/naloxone provides effective analgesia with limited impact on bowel function as oxycodone displays high oral bioavailability and naloxone act as local antagonist on opioid receptors in the gastrointestinal tract due to nearly complete inactivation in the liver. Oxycodone/naloxone is administered to opioid-naive patients with severe pain and those unsuccessfully treated with weak opioids. Oxycodone/naloxone may be also administered to patients treated with strong opioids who experience intense symptoms of OIBD. Studies conducted to date indicate that oxycodone/naloxone is an important drug in chronic pain management, prevention and treatment of OIBD.

Oxycodone combined with opioid receptor antagonists: efficacy and safety

INTRODUCTION

A mu receptor antagonist combined with oxycodone (OXY) may improve pain control, reduce physical tolerance and withdrawal, minimizing opioid-related bowel dysfunction and act as an abuse deterrent.

AREAS COVERED

The authors cover the use of OXY plus ultra-low-dose naltrexone for analgesia and the use of sustained-release OXY plus sustained-release naloxone to reduce the opioid bowel syndrome. The authors briefly describe the use of sustained-release OXY and naltrexone pellets as a drug abuse deterrent formulation. Combinations of ultra-low-dose naltrexone plus OXY have been in separate trials involved in patients with chronic pain from osteoarthritis and idiopathic low back pain. High attrition and marginal differences between ultra-low-dose naltrexone plus OXY and OXY led to discontinuation of development. Prolonged-release (PR) naloxone combined with PR OXY demonstrates a consistent reduction in opioid-related bowel dysfunction in multiple randomized controlled trials. However, gastrointestinal side effects, including diarrhea, were increased in several trials with the combination compared with PR OXY alone. Analgesia appeared to be maintained although non-inferiority to PR OXY is not formally established. There were flaws to trial design and safety monitoring. Naltrexone has been combined with OXY in individual pellets encased in a capsule. This combination has been reported in a Phase II trial and is presently undergoing Phase III studies.

EXPERT OPINION

Due to the lack of efficacy the combination of altered low-dose naltrexone with oxycodone should cease in development. The combination of sustained release oxycodone plus naloxone reduces constipation with a consistent benefit. Safety has been suboptimally evaluated which is a concern. Although the drug is commercially available in several countries, ongoing safety monitoring particularly high doses would be important.

Design, synthesis, and biological evaluation of 17-cyclopropylmethyl-3,14β-dihydroxy-4,5α-epoxy-6β-[(4'-pyridyl)carboxamido]morphinan derivatives as peripheral selective μ opioid receptor Agents

Peripheral selective μ opioid receptor (MOR) antagonists could alleviate the symptoms of opioid-induced constipation (OIC) without compromising the analgesic effect of opioids. However, a variety of adverse effects were associated with them, partially due to their relatively low MOR selectivity. NAP, a 6β-N-4'-pyridyl substituted naltrexamine derivative, was identified previously as a potent and highly selective MOR antagonist mainly acting within the peripheral nervous system. The noticeable diarrhea associated with it prompted the design and synthesis of its analogues in order to study its structure-activity relationship. Among them, compound 8 showed improved pharmacological profiles compared to the original lead, acting mainly at peripheral while increasing the intestinal motility in morphine-pelleted mice (ED(50) = 0.03 mg/kg). The slight decrease of the ED(50) compared to the original lead was well compensated by the unobserved adverse effect. Hence, this compound seems to be a more promising lead to develop novel therapeutic agents toward OIC.

Methylnaltrexone in treatment of opioid-induced constipation in a pediatric patient

OBJECTIVES

Opioid-induced constipation persists as a challenge in the management of chronic pain treated with opioid therapy. Multiple opioid antagonists have been applied in attempt to combat the gastrointestinal side effects of opioid analgesia, however their lipid-soluble nature allows passage into the central nervous system and consequent antagonism of centrally mediated analgesia. In contrast, methylnaltrexone offers the advantage of peripheral receptor-specific opioid antagonism due to chemical alterations conferring greater polarity and less lipid solubility. We present use of enteral methylnatrexone to treat severe opioid-induced constipation in a young boy who had failed treatment with the non-specific opioid antagonist, naloxone. This case reports describes the safe transition from enteral naloxone to enteral methylnaltrexone and discusses the potential risk of relative opioid toxicity during the transition.

METHODS

Though methylnaltrexone has approved for subcutaneous use, the characteristics of the patient s disease required enteral administration which had not been described in pediatric dosing. Based on conservative extrapolation of data from adult dosing, a methylnaltrexone dosing regimen was selected and the naloxone was weaned over two days in an effort to avoid a relative opioid overdose.

RESULTS

The patient was successfully transitioned to methylnaltrexone from naloxone over two days. He did experience increased sedation during this time however no severe respiratory depression occurred due to the cessation of chronic central opioid antagonism causing a relative opioid toxicity. Following the institution of methylnaltrexone, his opioid requirement significantly decreased and his gastrointestinal symptoms improved.

DISCUSSION

Our case report demonstrates safe transition from enteral naloxone to enteral methylnaltrexone in a pediatric patient, avoiding the serious consequences of relative opioid toxicity. This patient experienced significant improvement of opioid-induced constipation and reduction in opioid requirements and it is possible that other patients would benefit as well. The role of enteral methylnaltrexone deserves further investigation.

The impact of opioid analgesics on the gastrointestinal tract function and the current management possibilities

Opioid-induced bowel dysfunction (OIBD) comprises gastrointestinal symptoms such as constipation, anorexia, nausea, vomiting, gastro-oesophageal reflux, delayed digestion, abdominal pain, bloating, hard stool and incomplete evacuation that significantly deteriorate patients' quality of life and compliance. Approximately one third of patients treated with opioids do not adhere to the opioid regimen or simply quit the treatment due to OIBD. Several strategies are undertaken to prevent or treat OIBD. Traditional oral laxatives are used but their effectiveness is limited and they display adverse effects. Other possibilities comprise opioid switch or changing the administration route. New therapies target opioid receptors in the gut that seem to be the main source of OIBD. One is a combination of an opioid and opioid antagonist (oxycodone/naloxone) in prolonged-release tablets, and another is a purely peripherally acting opioid receptor antagonist (methylnaltrexone) available in subcutaneous injections. The aim of this article is to review the pathomechanism and possible treatment strategies of OIBD.

Prolonged-release oxycodone/naloxone in the treatment of neuropathic pain - results from a large observational study

OBJECTIVES

Opioids have shown consistent efficacy in neuropathic pain, but opioid-induced bowel dysfunction is a relevant problem. In controlled clinical trials, a fixed-dose combination of prolonged-release (PR) oxycodone/PR naloxone was superior to oxycodone alone in bowel function, while providing effective analgesia. The present report is an analysis of its efficacy and safety in a subgroup of patients with severe chronic neuropathic pain who were treated in a large observational study under real-life conditions.

RESEARCH DESIGN AND METHODS

Dosed according to pain severity, 1488 patients with chronic severe neuropathic pain received PR oxycodone/PR naloxone for up to 4 weeks. Variables included pain severity, patient-reported bowel function (Bowel Function Index; BFI) and quality of life.

RESULTS

During treatment with PR oxycodone/PR naloxone, mean pain intensity decreased in opioid-naive and opioid-pretreated patients. After 4 weeks on treatment, mean BFI scores were reduced from 41.6 ± 31.6 at the initiation visit to 16.5 ± 19.6 (p < 0.001), reflecting normal bowel function. Quality of life was improved by 47%.

CONCLUSIONS

Treatment of severe neuropathic pain with PR oxycodone/PR naloxone provided effective analgesia with the added benefit of favorable effects on bowel function and quality of life.

Methylnaltrexone for opioid-induced constipation in patients with advanced illness: a 3-month open-label treatment extension study

Methylnaltrexone is a methylated form of the mu-opioid antagonist naltrexone that blocks peripheral effects of opioids without affecting centrally mediated analgesia. The authors conducted a 3-month open-label extension trial of methylnaltrexone in patients with advanced illness and opioid-induced constipation (OIC). Following completion of a 2-week double-blind (DB) trial, 82 patients with OIC who did not respond to laxatives received subcutaneous (SC) methylnaltrexone as needed for up to 3 months. Patients received 0.15 mg/kg as a first dose, adjusted to 0.3 mg/kg or 0.075 mg/kg as needed (maximum of one dose per 24 hours). Mean laxation response (rescue-free bowel movement within 4 hours) rates (DB phase, months 1, 2, 3 open-label phase) were 45.3%, 45.5%, 57.7%, and 57.3%, respectively, for patients treated with DB methylnaltrexone and 10.8%, 48.3%, 47.6%, and 52.1%, respectively, for patients treated with DB placebo. Median time to laxation among responders was 45 minutes (range 0-4 hours) for all doses. Approximately 50% of patients reported improvement in constipation distress. Patient and investigator global clinical impression of change scores also improved. There were minimal changes in pain scores and opioid withdrawal symptoms. Adverse events included abdominal pain and nausea, mostly mild or moderate in severity. SC methylnaltrexone administered PRN (as needed) for up to 3 months continued to rapidly induce laxation in advanced illness patients with OIC.

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.

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

BACKGROUND

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

DISCUSSION

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

Bowel function during pain therapy with oxycodone/naloxone prolonged-release tablets in patients with advanced cancer

BACKGROUND

The World Health Organization (WHO) step-III opioids are often required right from the start of pain therapy in order to achieve sufficient symptom control. Bowel dysfunction, particularly constipation, is one of the most frequent and persistent side effects of opioid therapy, and it is known to cause considerable distress in many patients. The aim of the study was to evaluate whether patients with advanced cancer and moderate to severe cancer pain will benefit from treatment with oxycodone/naloxone prolonged-release tablets (OXN), with particular regard to constipation.

MATERIAL AND METHODS

In this exploratory, non-randomised, open-label, mono-centre study we evaluated the bowel function in palliative care patients treated with OXN. During the treatment phase patients were titrated up to an adequate pain control. The Bristol Stool Form Scale (BSFS) (type 1-7) and Bowel Function Index (BFI) (0-100) were used to assess consistency and frequency of bowel movements. Global patient satisfaction was assessed with Patient Global Impression of Change Scale (PGIC) (1-7).

STATISTICS

mean ± SD, significance p<0.05.

RESULTS

Twenty-six patients [10 male patients (38.5%)] were included; mean age 70.6 ± 14.0 years, length of stay 22.6 ± 21.2 days. At admission all patients had opioid-induced constipation. During the observation period of 14 days the daily mean dose of OX was 36.2 ± 17.2 mg and of N 15.4 ± 5.3 mg. In five cancer patients pain control was not sufficient under the approved maximum total daily dose of 40/20 mg OXN; therefore switching to hydromorphone. BFI improved significantly in 21 patients (72.4 ± 17.0 vs. 36.8 ± 13.4) (p<0.0001); stool consistency (BSFS) improved from type 2.0 ± 0.7 to 4.9 ± 1.0 (p<0.0001). PGIC at discharge was 1.9 ± 0.8.

DISCUSSION

Patients with OXN treatment throughout the whole study phase showed a clinically relevant improvement in pain intensity and bowel function as well as increased satisfaction. Well-known disadvantages of laxative treatment might be spared or even circumvented under OXN treatment, if appropriate.

Resolution of opioid-induced postoperative ileus in a newborn infant after methylnaltrexone

Transient impairment of bowel function is a frequent and distressing problem in neonates on opioid-induced analgesia. Methylnaltrexone, a peripheral-acting μ-opioid receptor antagonist, has been studied in adults for the treatment of opioid-induced constipation in advanced illness and has been suggested as a promising therapeutic concept for reducing postoperative ileus. Here, we report on a newborn infant on fentanyl analgesia after major abdominal surgery with aggravated ileus. After 8 days of quiescent bowel, the patient's intestinal dysmotility resolved within 15 minutes after intravenous administration of methylnaltrexone (0.15 mg/kg body weight). Methylnatrexone was repeated daily until cessation of fentanyl administration. There were no signs of pain or opioid withdrawal.

Laxatives or methylnaltrexone for the management of constipation in palliative care patients

BACKGROUND

Constipation is common in palliative care; it can generate considerable suffering due to the unpleasant physical symptoms. In the first Cochrane Review on effectiveness of laxatives for the management of constipation in palliative care patients, published in 2006, no conclusions could be drawn because of the limited number of evaluations. This article describes the first update of this review.

OBJECTIVES

To determine the effectiveness of laxatives or methylnaltrexone for the management of constipation in palliative care patients.

SEARCH STRATEGY

We searched databases including MEDLINE and CENTRAL (The Cochrane Library) in 2005 and in the update to August 2010.

SELECTION CRITERIA

Randomised controlled trials (RCTs) evaluating laxatives for constipation in palliative care patients. In the update we also included RCTs on subcutaneous methylnaltrexone; an opioid-receptor antagonist that is now licensed for the treatment of opioid-induced constipation in palliative care when response to usual laxative therapy is insufficient.

DATA COLLECTION AND ANALYSIS

Two authors assessed trial quality and extracted data. The appropriateness of combining data from the studies depended upon clinical and outcome measure homogeneity.

MAIN RESULTS

We included seven studies involving 616 participants; all under-reported methodological features. In four studies the laxatives lactulose, senna, co-danthramer, misrakasneham, and magnesium hydroxide with liquid paraffin were evaluated. In three methylnaltrexone.In studies comparing the different laxatives evidence was inconclusive. Evidence on subcutaneous methylnaltrexone was clearer; in combined analysis (287 participants) methylnaltrexone, in comparison with a placebo, significantly induced laxation at 4 hours (odds ratio 6.95; 95% confidence interval 3.83 to 12.61). In combined analyses there was no difference in the proportion experiencing side effects, although participants on methylnaltrexone suffered more flatulence and dizziness. No evidence of opioid withdrawal was found. In one study severe adverse events, commonly abdominal pain, were reported that were possibly related to methylnaltrexone. A serious adverse event considered to be related to the methylnaltrexone also occurred; this involved a participant having severe diarrhoea, subsequent dehydration and cardiovascular collapse.

AUTHORS' CONCLUSIONS

The 2010 update found evidence on laxatives for management of constipation remains limited due to insufficient RCTs. However, the conclusions of this update have changed since the original review publication in that it now includes evidence on methylnaltrexone. Here it found that subcutaneous methylnaltrexone is effective in inducing laxation in palliative care patients with opioid-induced constipation and where conventional laxatives have failed. However, the safety of this product is not fully evaluated. Large, rigorous, independent trials are needed.

Role of oxycodone and oxycodone/naloxone in cancer pain management

Oxycodone is a valued opioid analgesic, which may be administered either as the first strong opioid or when other strong opioids are ineffective. In case of insufficient analgesia and/or intense adverse effects such as sedation, hallucinations and nausea/vomiting a switch from another opioid to oxycodone might be beneficial. Oxycodone is administered to opioid-naive patients with severe pain and to patients who were unsuccessfully treated with weak opioids, namely tramadol, codeine and dihydrocodeine. Oxycodone effective analgesia may be attributed to its affinity to μ and possibly κ opioid receptors, rapid penetration through the blood-brain barrier and higher concentrations in brain than in plasma. Oxycodone displays high bioavailability after oral administration and may be better than morphine in patients with renal impairment due to the decreased production of active metabolites. Recently an oral controlled-release oxycodone formulation was introduced in Poland. Another new product that was launched recently is a combination of prolonged-release oxycodone with prolonged-release naloxone (oxycodone/naloxone tablets). The aim of this review is to outline the pharmacodynamic and pharmacokinetic properties, drug interactions, dosing rules, adverse effects, equianalgesic dose ratio with other opioids and clinical studies of oxycodone in patients with cancer pain. The potential role of oxycodone/naloxone in chronic pain management and its impact on the bowel function is also discussed.

The role of opioid receptor antagonists in the treatment of opioid-induced constipation: a review

Opioid-induced constipation (OIC) is associated with negative impact of opioid analgesics on opioid receptors located in the gut wall. Until recently, OIC was treated symptomatically only, with different laxatives which did not target the pathophysiology of OIC. Recently, several opioid receptor antagonists have been introduced in the treatment of OIC. Methylnaltrexone (MNTX) is a peripheral mu-opioid receptor antagonist for subcutaneous administration, which does not evoke symptoms of opioid abstinence. MNTX is indicated for patients with OIC who are not amenable to therapy with oral laxatives. In clinical trials, the effectiveness of MNTX assessed as its ability to induce spontaneous bowel movement, is 50%-60% of treated patients; MNTX demonstrates significant superiority over placebo. Another product is combination of oral formulation of prolonged release oxycodone and prolonged release naloxone (PR oxycodone/PR naloxone), indicated for patients who require opioid administration for chronic pain and have already developed OIC, and for those who need opioid therapy and take the drug to prevent OIC. Naloxone administered orally displays local, antagonist effects on opioid receptors in the gut wall, negligible systemic bioavailability, and significantly reduces the oxycodone constipating effect. PR oxycodone/PR naloxone has similar analgesic efficacy, but causes less constipation and less laxative consumption in comparison with patients treated with oxycodone alone. Both products are expensive, therefore their administration should be carefully considered. On the other hand, uncontrolled OIC and the necessity to perform rectal invasive procedures (enema, manual evacuation) lead not only to increased health care costs, but most importantly, cause severe patient suffering.

Efficacy and safety of combined prolonged-release oxycodone and naloxone in the management of moderate/severe chronic non-malignant pain: results of a prospectively designed pooled analysis of two randomised, double-blind clinical trials

BACKGROUND

Two randomised 12-week, double-blind, parallel-group, multicenter studies comparing oxycodone PR/naloxone PR and oxycodone PR alone on symptoms of opioid-induced bowel dysfunction in patients with moderate/severe non-malignant pain have been conducted.

METHODS

These studies were prospectively designed to be pooled and the primary outcome measure of the pooled data analysis was to demonstrate non-inferiority in 12-week analgesic efficacy of oxycodone PR/naloxone PR versus oxycodone PR alone. Patients with opioid-induced constipation were switched to oxycodone PR and then randomised to fixed doses of oxycodone PR/naloxone PR (n = 292) or oxycodone PR (n = 295) for 12 weeks (20-80 mg/day).

RESULTS

No statistically significant differences in analgesic efficacy were observed for the two treatments (p = 0.3197; non-inferiority p < 0.0001; 95% CI -0.07, 0.23) and there was no statistically significant difference in frequency of analgesic rescue medication use. Improvements in Bowel Function Index score were observed for oxycodone PR/naloxone PR by Week 1 and at every subsequent time point (-15.1; p < 0.0001; 95% CI -17.3, -13.0). AE incidence was similar for both groups (61.0% and 57.3% of patients with oxycodone PR/naloxone PR and oxycodone PR alone, respectively).

CONCLUSIONS

Results of this pooled analysis confirm that oxycodone PR/naloxone PR provides effective analgesia and suggest that oxycodone PR/naloxone PR improves bowel function without compromising analgesic efficacy.

TRIAL REGISTRATION NUMBERS

ClinicalTrials.gov identifier: NCT00412100 and NCT00412152.

Fixed combination of oxycodone with naloxone: a new way to prevent and treat opioid-induced constipation

Morphine and other opioids increase tone and reduce propulsive motility in several segments of the gut, enhance absorption of fluids, and inhibit secretion. This opioid-induced bowel dysfunction may present as infrequent stools, hard stools, difficult defecation, bloating, and sense of incomplete emptying of the bowels, but also dry mouth, gastroesophageal reflux, epigastric fullness, and abdominal cramping. It afflicts about one-third of patients on opioid treatment. Lifestyle measures, such as regular toilet visits, physical activity, and fiber-rich diet, are very unlikely to be successful. Laxatives, such as bisacodyl, sodium picosulfate, sennosides, macrogols, and prucalopride, may relieve opioid-induced constipation (OIC) in a proportion of patients only. A new approach to counteract OIC is the coadministration of an opioid antagonist devoid of the potential to penetrate the brain. In the EU, an oxycodonenaloxone combination has been approved for this purpose. Both components are included in an oral extended-release preparation. Following its release, naloxone acts locally on the gut and antagonizes the inhibitory effect of the opioid. After being absorbed in parallel with oxycodone, naloxone is rapidly and completely inactivated by a high first-pass effect in the liver. In a 2:1 dose ratio it may improve OIC without interfering with the analgesic effect.

Rapid intradermal delivery of liquid formulations using a hollow microstructured array

Purpose

The purpose of this work is to demonstrate rapid intradermal delivery of up to 1.5 mL of formulation using a hollow microneedle delivery device designed for self-application.

Methods

3M’s hollow Microstructured Transdermal System (hMTS) was applied to domestic swine to demonstrate delivery of a variety of formulations including small molecule salts and proteins. Blood samples were collected after delivery and analyzed via HPLC or ELISA to provide a PK profile for the delivered drug. Site evaluations were conducted post delivery to determine skin tolerability.

Results

Up to 1.5 mL of formulation was infused into swine at a max rate of approximately 0.25 mL/min. A red blotch, the size of the hMTS array, was observed immediately after patch removal, but had faded so as to be almost indistinguishable 10 min post-patch removal. One-mL deliveries of commercial formulations of naloxone hydrochloride and human growth hormone and a formulation of equine anti-tetanus toxin were completed in swine. With few notable differences, the resulting PK profiles were similar to those achieved following subcutaneous injection of these formulations.

Conclusions

3M’s hMTS can provide rapid, intradermal delivery of 300–1,500 µL of liquid formulations of small molecules salts and proteins, compounds not typically compatible with passive transdermal delivery.

Critical illness, gastrointestinal complications, and medication therapy during enteral feeding in critically ill adult patients

Critically ill patients who are subjected to high stress or with severe injury can rapidly break down their body protein and energy stores. Unless adequate nutrition is provided, malnutrition and protein wasting may occur, which can negatively affect patient outcome. Enteral nutrition (EN) is the mainstay of nutrition support therapy in patients with a functional gastrointestinal (GI) tract who cannot take adequate oral nutrition. EN in critically ill patients provides the benefits of maintaining gut functionality, integrity, and immunity as well as decreasing infectious complications. However, the ability to provide timely and adequate EN to critically ill patients is often hindered by GI motility disorders and complications associated with EN. This paper reviews the GI complications and intolerances associated with EN in critically ill patients and provides recommendations for their prevention and treatment. It also addresses the role of commonly used medications in the intensive care unit and their impact on GI motility and EN delivery.

Long-term efficacy and safety of combined prolonged-release oxycodone and naloxone in the management of non-cancer chronic pain

OBJECTIVE

The aim of this study was to assess safety and efficacy of fixed combination oxycodone prolonged release (PR)/naloxone PR in terms of both analgesia and improving opioid-induced bowel dysfunction (OIBD) and associated symptoms, such as opioid-induced constipation (OIC), in adults with chronic non-cancer pain.

STUDY DESIGN

These were open-label extension studies in which patients who had previously completed a 12-week, double-blind study received oxycodone PR/naloxone PR for up to 52 weeks. The analgesia study assessed pain using the modified Brief Pain Inventory-Short Form (BPI-SF). The bowel function study assessed improvements in constipation using the Bowel Function Index (BFI).

RESULTS

At open-label baseline in the analgesia study (n = 379), mean score [+/- standard deviation (SD)] for the BPI-SF item 'average pain over the last 24 h' was 3.9 +/- 1.52, and this remained low at 6 months (3.7 +/- 1.59) and 12 months (3.8 +/- 1.72). Mean scores for BPI-SF item 'sleep interference', and the BPI-SF 'pain' and 'interference with activities' subscales also remained low throughout the 52-week study. In the bowel function study (n = 258), mean BFI score (+/- SD) decreased from 35.6 +/- 27.74 at the start of the extension study to 20.6 +/- 24.01 after 12 months of treatment with oxycodone PR/naloxone PR. Pain scores also remained low and stable during this study. Adverse events in both extension phases were consistent with those associated with opioid therapy; no additional safety concerns were observed.

CONCLUSION

Results from these two open-label extension studies demonstrate the long-term efficacy and tolerability of fixed combination oxycodone PR/naloxone PR in the treatment of chronic pain. Patients experienced clinically relevant improvements in OIBD while receiving effective analgesic therapy.

[Methylnaltrexone. A new approach for therapy of opioid-induced obstipation]

Chronic pain patients using opioids frequently suffer from constipation which compromises well-being. Such an opioid-induced gastro-intestinal complication can occur regularly in patients in palliative care as well as in analgesic sedated intensive care patients or during prolonged perioperative pain therapy. Discomfort and distress in the affected patients can be so severely pronounced that they would rather suffer from the pain than from the side effect of constipation. Conventional therapy can be insufficient in providing satisfactory relief of constipation, mostly because this opioid-induced bowel hypomotility can be laxative-resistant. Moreover, constipation does not decrease during the course of therapy as do other side effects. It is well known that opioid-induced constipation is mediated via activation of micro-opioid receptors in the gastrointestinal tract. Selective peripheral micro-receptor antagonists (such as methylnaltrexone, Relistor) can effectively treat opioid-induced constipation. An interference with central analgesia does not occur as the molecules cannot pass the blood-brain barrier due to their charged states. A reduction of opioid therapy or the development of withdrawal symptoms can be avoided. Studies have shown that methylnaltrexone is not only safe and efficient for chronically constipated palliative care patients but offers promising therapeutic options for further patient collectives.