New Formulation of Sustained Release Naloxone Can Reverse Opioid Induced Constipation Without Compromising the Desired Opioid Effects

Constipation in Cancer Patients - an Update of Clinical Evidence

OPINION STATEMENT

Constipation is one of the most frequent problems in cancer patients, and its etiology is multifactorial. It leads to decreased quality of life and impedes optimal pain treatment. Despite the high prevalence, constipation is frequently underdiagnosed mainly because of lack of validated diagnostic criteria or widely accepted definition of constipation in cancer patients. All cancer patients should be evaluated regularly for constipation, and concomitant causes and risk factors were assessed. Opioids are responsible for a much of the secondary constipation in cancer patients. The management of constipation in cancer patients should be multifaceted, addressing dietary and behavioral issues and optimizing pharmacological interventions. Prevention of opioid-induced constipation (OIC) is pivotal, as treatment is often unsatisfactory or inefficient. Dietary and behavioral interventions should be considered. Non-pharmacological measures include hydration and nutrition, ensuring privacy during defecation, using a commode or footstool, and the availability of a caregiver. Abdominal massage may be of value. Traditional laxatives are recommended in prevention but not in the treatment of OIC. Peripherally acting mu-opioid receptor antagonists (PAMORA) appear the first choice in the treatment and an alternative to laxatives in some recent clinical practice guidelines in preventing OIC. Naldemedine, naloxegol, and methylnaltrexone are supported by quality evidence for OIC management. Naloxone or naltrexone, taken orally in combined formulations with opioids, may be valuable in preventing or reducing OIC symptoms.

Efficacy and Safety of Peripherally Acting Mu-Opioid Receptor Antagonists for the Treatment of Opioid-Induced Constipation: A Bayesian Network Meta-analysis

OBJECTIVE

To assess the efficacy and safety of peripherally acting mu-opioid receptor antagonists (PAMORAs) for the treatment of opioid-induced constipation (OIC).

METHODS

Randomized controlled trials (RCTs) were searched for OIC therapy comparing PAMORAs with placebo. Both a pairwise and network meta-analysis were performed. The surface under the cumulative ranking area (SUCRA) was used to determine the efficacy and safety of OIC treatment using different PAMORAs.

RESULTS

The primary target outcome was a response that achieves an average of three or more bowel movements (BMs) per week. In the network meta-analysis, four PAMORAs (naldemedine, naloxone, methylnaltrexone, and alvimopan) showed a better BM response than the placebo. Naldemedine was ranked first (odds ratio [OR] = 2.8, 95% credible interval [CrI] = 2-4.5, SUCRA = 89.42%), followed by naloxone (OR = 2.9, 95% CrI = 1.6-5.3, SUCRA = 87.44%), alvimopan (OR = 2.2, 95% CrI = 1.3-3.5, SUCRA = 68.02%), and methylnaltrexone (OR = 1.7, 95% CrI = 1.0-2.8, SUCRA = 46.09%). There were no significant differences in safety found between the PAMORAs and the placebo.

CONCLUSIONS

We found that PAMORAs are effective and can be safely used for the treatment of OIC. In network meta-analysis, naldemedine and naloxone appear to be the most effective PAMORAs for the treatment of OIC.

Systematic review with meta-analysis: efficacy and safety of treatments for opioid-induced constipation

BACKGROUND

When opioid-induced constipation is treated with centrally acting opioid antagonists, there may be opioid withdrawal or aggravation of pain due to inhibition of μ-opioid analgesia. This led to the development of peripherally acting μ-opioid receptor antagonists (PAMORAs).

AIM

To evaluate the efficacy of available PAMORAs and other approved or experimental treatments for relieving constipation in patients with opioid-induced constipation, based on a systematic review and meta-analysis of published studies.

METHODS

A search of MEDLINE, EMBASE and EBM Reviews Cochrane Central Register of Controlled Trials was completed in July 2019 for randomised trials compared to placebo. FDA approved doses or highest studied dose was evaluated. Efficacy was based on diverse endpoints, including continuous variables (the bowel function index, number of spontaneous bowel movements and stool consistency based on Bristol Stool Form Scale), or responder analysis (combination of >3 spontaneous bowel movements or complete spontaneous bowel movements plus 1 spontaneous bowel movement or complete spontaneous bowel movements, respectively, over baseline [so-called FDA endpoints]). Adverse effects evaluated included central opioid withdrawal, serious adverse events, abdominal pain and diarrhoea.

RESULTS

We included 35 trials at low risk of bias enrolling 13 566 patients. All PAMORAs demonstrated efficacy on diverse patient response endpoints. There was greater efficacy with approved doses of the PAMORAs (methylnaltrexone, naloxegol and naldemidine), with lower efficacy or lower efficacy and greater adverse effects with combination oxycodone with naloxone, lubiprostone and linaclotide.

CONCLUSIONS

Therapeutic response in opioid-induced constipation is best achieved with the PAMORAs, methylnaltrexone, naloxegol and naldemidine, which are associated with low risk of serious adverse events.

Novel Oral Nanoparticle Formulation of Sustained Release Naloxone with Mild Withdrawal Symptoms in Mice

Chronic use of opioids can lead to tolerance, dependence, abuse, and addiction. This in turn can result in dose escalation and opioid overdose. Opioid overdose can be fatal due to severe opioid-induced respiratory depression (OIRD). Naloxone, a nonspecific antagonist of the mu-opioid receptors, is used for the reversal of OIRD. However, one of the major challenges of using naloxone is its short elimination half-life, which is significantly shorter compared to many opioid analgesics. Thus, renarcotization and rapid return to full respiratory depression might occur, specifically in individuals who have taken large doses or long-acting opioid formulations. Additionally, because of the very low oral bioavailability of naloxone, an oral formulation is not currently available. This study examines in mice a novel oral formulation of naloxone based on polymer nanoparticles (NP-naloxone). A single dose of 1 or 5 mg/kg NP-naloxone was highly effective at inhibiting the activating effects of repeated administration of 10 mg/kg morphine for at least up to 24 h. Onset of action was approximately 5 min. Reversal of morphine-induced locomotion was already detected within 1 min and a full effect of returning to baseline activity levels was observed within 5 min. Importantly, at 1 mg/kg, NP-naloxone precipitated very minimal withdrawal behaviors. At the 5 mg/kg dose, NP-naloxone precipitated approximately 40% of the jumping withdrawal behaviors of injectable naloxone. Thus, this study demonstrates that orally administered naloxone based on polymer nanoparticles has high potential to be developed to circumvent OIRD and withdrawal symptoms.

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

OBJECTIVE

Opioids are increasingly prescribed in the West and have deleterious GI consequences. Pharmacological therapies to treat opioid-induced constipation (OIC) are available, but their relative efficacy is unclear. We performed a systematic review and network meta-analysis to address this deficit in current knowledge.

DESIGN

We searched MEDLINE, EMBASE, EMBASE Classic and the Cochrane central register of controlled trials through to December 2017 to identify randomised controlled trials (RCTs) of pharmacological therapies in the treatment of adults with OIC. Trials had to report a dichotomous assessment of overall response to therapy, and data were pooled using a random effects model. Efficacy and safety of pharmacological therapies was reported as a pooled relative risk (RR) with 95% CIs to summarise the effect of each comparison tested and ranked treatments according to their P-score.

RESULTS

Twenty-seven eligible RCTs of pharmacological therapies, containing 9149 patients, were identified. In our primary analysis, using failure to achieve an average of ≥3 bowel movements (BMs) per week with an increase of ≥1 BM per week over baseline or an average of ≥3 BMs per week, to define non-response, the network meta-analysis ranked naloxone first in terms of efficacy (RR=0.65; 95% CI 0.52 to 0.80, P-score=0.84), and it was also the safest drug. When non-response to therapy was defined using failure to achieve an average of ≥3 BMs per week, with an increase of ≥1 BM per week over baseline, naldemedinewas ranked first (RR=0.66; 95% CI 0.56 to 0.77, P score=0.91) and alvimopan second (RR=0.74; 95% CI 0.57 to 0.94, P-score=0.71).

CONCLUSION

In network meta-analysis, naloxone and naldemedine appear to be the most efficacious treatments for OIC. Naloxone was the safest of these agents.

Pharmacological Treatment of Opioid-Induced Constipation Is Effective but Choice of Endpoints Affects the Therapeutic Gain

BACKGROUND

Widespread opioid use has led to increase in opioid-related adverse effects like constipation. We examined the impact of study endpoints on reported treatment benefits.

METHODS

Using MEDLINE, EMBASE, and ClinicalTrials.gov, we searched for randomized control trials targeting chronic opioid-induced constipation (OIC) and subjected them to meta-analysis. Data are given with 95% confidence intervals.

RESULTS

Thirty trials met our inclusion criteria. Combining all dichotomous definitions of responders, active drugs were consistently more effective than placebo, with an odds ratio (OR): 2.30 [2.01-2.63; 15 studies], independent of the underlying drug mechanism. The choice of endpoints significantly affected the therapeutic gain. When time from drug administration to defecation was used, the OR decreased from 4.74 [2.71-4.74] at 6 h or less to 2.46 [1.80-3.30] at 24 h (P < 0.05). Using other response definitions, the relative benefit over placebo was 2.10 [1.77-2.50; 12 studies] for weekly bowel frequency, 2.03 [1.39-2.95; 9 studies] for symptom scores, 2.21 [1.25-3.90; 4 studies] for global assessment scales, and 1.27 [0.79-2.03; 7 studies] for rescue laxative use.

CONCLUSION

While treatment of OIC with active drugs is more effective than placebo, the relative gain depends on the choice of endpoints. The commonly used time-dependent response definition is associated with the highest response rate but is of questionable relevance in a chronic disorder. The limited data do not clearly demonstrate a unique advantage of the peripherally restricted opioid antagonists, suggesting that treatment with often cheaper agents should be optimized before shifting to these novel expensive agents.

Efficacy of Treatments for Opioid-Induced Constipation: Systematic Review and Meta-analysis

BACKGROUND & AIMS

Opioid-induced constipation (OIC) is a common problem in patients on chronic opioid therapy for cancer-related and non-cancer-related pain. Approved treatments for OIC are methylnaltrexone, naloxone, naloxegol, alvimopan, naldemedine, and lubiprostone. Since a meta-analysis performed in 2014, 2 new agents have been approved by the Food and Drug Administration for treatment of OIC (naloxegol and naldemedine).

METHODS

We conducted a search of the medical literature following the protocol outlined in the Cochrane Handbook for systematic review. We searched MEDLINE, EMBASE, EMBASE Classic, Web of Science, and the Cochrane Central Register of Controlled Trials until March 2017 to identify randomized controlled trials of peripheral μ-opioid-receptor antagonists (methylnaltrexone, naloxone, naloxegol, alvimopan, axelopran, or naldemedine), lubiprostone, or prucalopride. Response to therapy was extracted in a dichotomous assessment as an overall response to therapy. The effect of pharmacologic therapies was pooled and reported as a relative risk (RR) of failure to respond to the treatment drug, with 95% CIs.

RESULTS

We included 27 placebo-controlled trials in our meta-analysis (23 trials evaluated μ-opioid-receptor antagonists, 3 trials evaluated lubiprostone, and 1 trial evaluated prucalopride). In these trials, 5390 patients received a drug and 3491 received a placebo. Overall, μ-opioid-receptor antagonists, lubiprostone, and prucalopride were superior to placebo for the treatment of OIC, with a RR of failure to respond to therapy of 0.70 (95% CI, 0.64-0.75) and an overall number needed to treat of 5 (95% CI, 4-7). When restricted to only Food and Drug Administration-approved medications for OIC, the RR of failure to respond to therapy was 0.69 (95% CI, 0.62-0.77), with a number needed to treat of 5 (95% CI, 4-7). Sensitivity analyses and meta-regression performed to account for heterogeneity showed that treatment was more likely to be effective in study populations taking higher doses of opiates at baseline or refractory to laxatives. Study duration and prespecified primary outcome did not affect the RR of failure. Participants who received μ-opioid-receptor antagonists were significantly more likely to have diarrhea, abdominal pain, nausea, or vomiting than patients who received placebo.

CONCLUSIONS

In a systematic review and meta-analysis, we found μ-opioid-receptor antagonists to be safe and effective for the treatment of OIC. Prescription-strength laxatives (prucalopride, lubiprostone) are slightly better than placebo in reducing OIC.

Reduction in pain: Is it worth the gain? The effect of opioids on the GI tract

The use of opioid medications for acute and chronic pain has increased significantly in the past 20 years in the United States. Given the high density of opioid receptors in the gastrointestinal tract, side effects are common in these patients including constipation, dysphagia, bloating, nausea, and vomiting. These side effects, which are experienced by most patients who take opioids, can lead to significant impairment in quality of life. Unlike other side effects from opioids, gastrointestinal side effects do not diminish with continued use, often leading patients to reduce or discontinue their opioid treatment to relieve these side effects. Therefore, physicians must be aware and anticipate potential side effects in patients receiving opioids to ensure appropriate pain management.

Drugs for Treating Opioid-Induced Constipation: A Mixed Treatment Comparison Network Meta-analysis of Randomized Controlled Clinical Trials

CONTEXT

Opioid-induced constipation is a common problem associated with chronic use of opioid analgesics.

OBJECTIVES

The objective of this study was to compare available interventions for the treatment of opioid-induced constipation, using principles of network meta-analysis.

METHODS

Electronic databases were searched for randomized controlled clinical trials evaluating drugs used in opioid-induced constipation. Number of patients with rescue-free bowel movements (RFBM) was the primary outcome, and time for achieving RFBM, adverse events, and changes in the analgesic activity of the opioid analgesics were the secondary outcomes. Inverse variance heterogeneity model was used for direct and mixed treatment comparison analysis. Odds ratio for categorical outcomes and weighted mean difference for numerical outcomes were the effect estimates.

RESULTS

We included a total of 23 studies in the systematic review and 21 in the network meta-analysis. Lubriprostone, prucalopride, naldemedine, naloxegol, alvimopan, subcutaneous, and oral methyl naltrexone were observed to perform better than placebo in terms of RFBM. Additionally, subcutaneous methyl naltrexone was significantly better than lubiprostone, naloxegol, oral methyl naltrexone, and prucalopride. Lubiprostone and naldemedine were associated with increased risks of adverse events. Subcutaneous methyl naltrexone did not significantly affect the analgesia due to background opioid use. Quality of evidence for the comparisons is either low or very low.

CONCLUSION

Subcutaneous methyl naltrexone was found to perform better than other interventions for managing opioid-induced constipation.

Efficacy and safety of multimodal analgesic techniques for preventing chronic postsurgery pain under different surgical categories: a meta-analysis

The purpose of this meta-analysis was to compare the efficacy and safety of regional anesthesia to manage chronic postsurgery pain. A systematic search of PubMed, EmBase, and the Cochrane Central Register of Controlled Trials was performed to identify randomized controlled trials that focused on chronic pain frequency, analgesic consumption, and adverse effects under different surgical categories. We collected 21 trials assessing 1,980 patients for our meta-analysis. The summary of relative risks (RRs) and standard mean differences (SMDs) were calculated to measure the treatment effect of regional anesthesia. Results indicated that regional anesthesia significantly reduced the frequency of postsurgery pain (RR, 0.69; 95% confidence interval [CI], 0.56–0.85; p < 0.001). The results showed significant differences in overall patient satisfaction between applications with and without regional anesthesia (SMD, 1.95; 95%CI, 0.83–3.06; p = 0.001); however in other results, there were no significant differences between the two groups. Subgroup analysis suggested that regional anesthesia treatment might differ according to country. In conclusion, our study indicated that regional anesthesia was effective and safe in reducing the frequency of postsurgery pain and improved overall patient satisfaction; however, studies on the long-term efficacy and safety of regional anesthesia are still required to further confirm these findings.

Endogenous Opiates and Behavior: 2015

This paper is the thirty-eighth consecutive installment of the annual review of research concerning the endogenous opioid system. It summarizes papers published during 2015 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, drug abuse and alcohol, 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.

Peripherally acting μ-opioid receptor antagonists as treatment options for constipation in noncancer pain patients on chronic opioid therapy

Opioid-induced constipation (OIC), a prevalent and distressing side effect of opioid therapy, does not reliably respond to treatment with conventional laxatives. OIC can be a treatment-limiting adverse event. Recent advances in medications with peripherally acting μ-opioid receptor antagonists, such as methylnaltrexone, naloxegol, and alvimopan, hold promise for treating OIC and thus extending the benefits of opioid analgesia to more chronic pain patients. Peripherally acting μ-opioid receptor antagonists have been clinically tested to improve bowel symptoms without compromise to pain relief, although there are associated side effects, including abdominal pain. Other treatment options include fixed-dose combination products of oxycodone analgesic together with naloxone.

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.

Novel Oral Therapies for Opioid-induced Bowel Dysfunction in Patients with Chronic Noncancer Pain

Opioid analgesics are frequently prescribed and play an important role in chronic pain management. Opioid-induced bowel dysfunction, which includes constipation, hardened stool, incomplete evacuation, gas, and nausea and vomiting, is the most common adverse event associated with opioid use. Mu-opioid receptors are specifically responsible for opioid-induced bowel dysfunction, resulting in reduced peristaltic and secretory actions. Agents that reverse these actions in the bowel without reversing pain control in the central nervous system may be preferred over traditional laxatives. The efficacy and safety of these agents in chronic noncancer pain were assessed from publications identified through Ovid and PubMed database searches. Trials that evaluated the safety and efficacy of oral agents for opioid-induced constipation or opioid-induced bowel dysfunction, excluding laxatives, were reviewed. Lubiprostone and naloxegol are approved in the United States by the Food and Drug Administration for use in opioid-induced constipation. Axelopran (TD-1211) and sustained-release naloxone have undergone phase 2 and phase 1 studies, respectively, for the same indication. Naloxegol and axelopran are peripherally acting μ-opioid receptor antagonists. Naloxone essentially functions as a peripherally acting μ-opioid receptor antagonist when administered orally in a sustained-release formulation. Lubiprostone is a locally acting chloride channel (CIC-2) activator that increases secretions and peristalsis. All agents increase spontaneous bowel movements and reduce other bowel symptoms compared with placebo in patients with noncancer pain who are chronic opioid users. The most common adverse events were gastrointestinal in nature, and none of the drugs were associated with severe adverse or cardiovascular events. Investigations comparing these agents to regimens using standard laxative and combination therapy and trials in special populations and patients with active cancer are needed to further define their role in therapy.