Managing opioid-induced constipation in advanced illness: focus on methylnaltrexone bromide

Long-Term Safety and Efficacy of Subcutaneous Methylnaltrexone in Patients with Opioid-Induced Constipation and Chronic Noncancer Pain: A Phase 3, Open-Label Trial

Objective. Methylnaltrexone, a peripherally acting µ-opioid receptor antagonist, alleviates opioid-induced constipation. Understanding its long-term safety and efficacy profile in patients with chronic noncancer pain is warranted given the persistence of opioid-induced constipation.

Methods. In this phase 3, multicenter, open-label trial, adults with chronic noncancer pain (N = 1034) received subcutaneous methylnaltrexone 12 mg once daily for 48 weeks.

Results. The most common adverse events were gastrointestinal related (e.g., abdominal pain, diarrhea, nausea) and were mild to moderate in intensity. Only 15.2% of patients discontinued because of an adverse event. Serious cardiac-related adverse events occurred in nine patients. Of the seven instances of major adverse coronary events reported, three were adjudicated after external review; all instances occurred in patients with cardiovascular risk factors. Methylnaltrexone elicited a bowel movement within four hours in 34.1% of the injections throughout the 48-week treatment period.

Conclusions. Change from baseline in mean weekly bowel movement rate, Bowel Movement Straining Scale score, Bristol Stool Scale score, and mean percentage of patients with complete evacuation from baseline to week 48 were significantly improved (P < 0.001 for all). Long-term subcutaneous methylnaltrexone was well tolerated, with no new safety concerns, and provided consistent opioid-induced constipation relief in patients with chronic noncancer pain.

Efficacy and Safety of Methylnaltrexone for Opioid-Induced Constipation in Patients With Chronic Noncancer Pain: A Placebo Crossover Analysis

In patients with chronic noncancer pain, subcutaneous methylnaltrexone for opioid-induced constipation (OIC) was examined in a randomized controlled trial (RCT) followed by an open-label extension (OLE). This study examined the reproducibility of RCT findings by analyzing data from placebo-treated patients who crossed over to methylnaltrexone.

Concomitant Opioid and Laxative Use in Older Adults in Hospice Care in the United States: 2007

OBJECTIVES

To examine laxative use by individuals in hospice who were taking opioids during the last week of life.

DESIGN

Retrospective cross-sectional.

SETTING

2007 National Home and Hospice Care Survey.

PARTICIPANTS

Individuals in hospice aged 65 and older who were taking opioids during the last week of life (N = 2,825).

MEASUREMENTS

Hospice staff were asked the names of all medications and drugs that participants were taking 7 days before and on the day of death while in hospice, including any standing, routine, or as-needed medications." Medications "used" included medications taken and as-needed medications provided in case a symptom developed. Opioids included all opioid-combination drugs. Laxatives included fibers, lubricants, stimulants, and suppositories.

RESULTS

Forty-one percent of participants had cancer as the primary hospice diagnosis, 13% heart disease, 12% debility, 11% dementia, 8% lung disease, and 15% other. Overall, 52% of opioid users used a laxative in the last week of life; the proportions of opioid and laxative users did not differ according to diagnosis. Racial minorities taking opioids had lower odds than white participants (odds ratio (OR) = 0.57, 95% confidence interval (CI) = 0.33-0.99) of using laxatives. Participants taking opioids enrolled in hospice for 7 days or less had lower odds of using laxatives than those enrolled for more than 7 days (OR = 0.65, 95% CI = 0.37-0.95), as did those in hospice inpatient, hospital, or other settings (OR = 0.45, 95% CI = 0.43-0.93) than those in long-term care settings. Participants using five or fewer medications had lower odds of using laxatives than those using six to 10 (OR = 6.01, 95% CI = 3.88-9.32) or 11 to 25 medications (OR = 13.80, 95% CI = 8.74-21.80).

CONCLUSION

In 2007, slightly more than half of older adults in hospice who were taking opioids used laxatives during the last week of life. Recent quality indicators from the Centers for Medicare and Medicaid Services recommend laxative treatment when opioid therapy is initiated to prevent opioid-induced constipation and are intended to improve laxative use in individuals in hospice treated with opioids.

Cost-effectiveness analysis of oxycodone with naloxone versus oxycodone alone for the management of moderate-to-severe pain in patients with opioid-induced constipation in Canada

BACKGROUND

Approximately 20-30% of Canadians suffer from chronic pain. Guidelines for the management of chronic pain support the use of controlled-release (CR) opioids to treat chronic pain. Although effective in managing chronic pain, oxycodone is associated with high rates of opioid-induced constipation (OIC). The cost-effectiveness of a combination of oxycodone for the management of pain and naloxone for the relief of OIC has not previously been evaluated for Canada.

METHODS

A decision analytic model was developed to estimate the cost-utility of combination oxycodone/naloxone compared to oxycodone alone in four populations. Drug costs for managing pain and healthcare costs related to managing OIC were included in the analysis and the primary measure of effectiveness was quality adjusted life years (QALYs) derived from OIC rates observed in clinical trials. The analysis was conducted from a healthcare system perspective, used a 1-year time horizon, and results were expressed in 2015 Canadian dollars.

RESULTS

In all four patient populations, there was a trade-off between slightly higher total expected costs for Targin treated patients compared to oxycodone treated patients, but also improved clinical benefits in terms of reduced OIC, which resulted in higher QALYs for patients. Although analgesic costs were found to be slightly higher for Targin treated patients, Targin also resulted in cost offsets to the healthcare system in terms of less rescue laxative drug use and other resources required for the management of OIC. The resulting 1-year cost-utility of Targin compared to oxycodone ranged from $2178-$7732 per QALY gained in the base case analysis, and it was found that these cost-utility results remained robust and at low values throughout a series of one-way deterministic analyses of uncertainty.

CONCLUSION

The clinical effectiveness of oxycodone/naloxone in managing pain and OIC compared to CR oxycodone alone resulted in low cost-utility estimates.

Analysis of opioid-mediated analgesia in Phase III studies of methylnaltrexone for opioid-induced constipation in patients with chronic noncancer pain

Background

Subcutaneous methylnaltrexone is efficacious and well tolerated for opioid-induced constipation (OIC) but may theoretically disrupt opioid-mediated analgesia.

Methods

Opioid use, pain intensity, and opioid withdrawal (Objective Opioid Withdrawal Scale [OOWS] and Subjective Opiate Withdrawal Scale [SOWS] scores) were reported in a randomized, double-blind trial with an open-label extension (RCT) and an open-label trial (OLT) evaluating safety in adults with chronic noncancer pain. In the RCT, patients taking ≥50 mg of oral morphine equivalents daily with <3 rescue-free bowel movements weekly received methyl naltrexone 12 mg once daily (n=150), every other day (n=148), or placebo (n=162) for 4 weeks, followed by open-label methylnaltrexone 12 mg (as needed [prn]; n=364) for 8 weeks. In the OLT, patients (n=1,034) on stable opioid doses with OIC received methylnaltrexone 12 mg prn for up to 48 weeks.

Results

Minimal fluctuations of median morphine equivalent dose from baseline (BL) were observed in the RCT double-blind period (BL, 154.8–161.0 mg/d; range, 137.1–168.0 mg/d), RCT open-label period (BL, 156.3–174.6; range, 144.0–180.0) and OLT (BL, 120 mg/d; range, 117.3–121.1 mg/d). No significant change from BL in pain intensity score occurred in any group at weeks 2 or 4 (both P≥0.1) of the RCT double-blind period, and scores remained stable during the open-label period and in the OLT (mean change, −0.2 to 0.1). Changes from BL in OOWS and SOWS scores during the double-blind period were not significantly impacted by methylnaltrexone exposure at weeks 2 or 4 (P>0.05 for all).

Conclusion

Methylnaltrexone did not affect opioid-mediated analgesia in patients with chronic noncancer pain and OIC.

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.

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.

Managing constipation: a focus on care and treatment in the palliative setting

Constipation can cause unnecessary discomfort and suffering for patients, and there appears to be a lack of awareness among nurses and doctors about its cause, impact and management. A large proportion of the evidence for the assessment and management of constipation in the context of palliative care is derived from the perspective of advanced cancer and from guidelines developed at a European level. Although constipation remains a problem for palliative care patients, early intervention combined with continuous and impeccable assessment can assist in its management and improve patient comfort at the end of life.

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.

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

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

SUMMARY

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