Impact of Patient Subgroups on the Efficacy and Safety of Methylnaltrexone for Opioid-Induced Constipation in Patients with Advanced Illness.

Purpose: We evaluated the impact of baseline patient characteristics on safety and efficacy of methylnaltrexone, a peripherally acting µ-opioid receptor antagonist, in patients with advanced illness with opioid-induced constipation (OIC). Patients and Methods: This analysis pooled data from 2 randomized, double-blind, placebo-controlled studies (study 302: NCT00402038; study 4000: NCT00672477) in patients with advanced illness, including cancer, and OIC. Patients were randomized to receive subcutaneous methylnaltrexone (study 302: 0.15 mg/kg; study 4000: 8 or 12 mg based on weight) or placebo every other day for 2 weeks. The proportions of patients achieving rescue-free laxation within 4 or 24 hours after the first dose of study drug were assessed in patient subgroups stratified by baseline age, Eastern Cooperative Oncology Group (ECOG) performance status, cancer status, laxative type, and opioid requirement. Treatment-emergent adverse events (TEAEs) were evaluated. Results: Overall, 363 patients were included in this analysis (methylnaltrexone, 178; placebo, 185). Mean (SD) age was 66.3 (13.7) years and 48.5% were men overall. A significantly greater proportion of patients receiving methylnaltrexone versus placebo achieved rescue-free laxation within 4 hours (111/178 [62.4%] vs 31/185 [16.8%]; P<0.0001) and 24 hours (135/178 [75.8%] vs 81/185 [43.8%]; P<0.0001) of the first dose. These trends were consistent across all subgroups. Most patients experienced ≥1 TEAE in the overall population (methylnaltrexone, 82.1%; placebo, 76.2%), which remained consistent when stratified by baseline characteristics. More than half of TEAEs were gastrointestinal in nature. Abdominal pain was more common in patients receiving methylnaltrexone than placebo across baseline characteristic subgroups. Conclusion: Methylnaltrexone treatment was superior to placebo in achieving rescue-free laxation within 4 and 24 hours after the first dose, irrespective of patients' cancer status, baseline ECOG performance status, or baseline opioid or laxative use. The methylnaltrexone safety profile remained consistent across baseline characteristic subgroups.

Methylnaltrexone Treatment for Opioid-Induced Constipation in Patients with and without Cancer: Effect of Initial Dose.

Purpose: Opioid-induced constipation (OIC) is a common side effect of opioid therapy. Methylnaltrexone (MNTX) is a selective, peripherally acting µ-opioid receptor antagonist, with demonstrated efficacy in treating OIC. We pooled results from MNTX clinical trials to compare responses to an initial dose in patients with chronic cancer and noncancer pain. Patients and Methods: This post hoc analysis used pooled data from 3 randomized, placebo-controlled studies of MNTX in patients with advanced illness with OIC. Assessments included the proportions of patients achieving rescue-free laxation (RFL) within 4 and 24 hours of the first study drug dose, time to RFL, current and worst pain intensity, and adverse events, stratified by the presence/absence of cancer. Results: A total of 355 patients with cancer (MNTX n = 198, placebo n = 157) and 163 without active cancer (MNTX n = 83; placebo n = 80) were included. More patients treated with MNTX compared with those who received placebo achieved an RFL within 4 (cancer: MNTX, 61.1% vs placebo,15.3%, p<0.0001; noncancer: MNTX, 62.2% vs placebo, 17.5%, p<0.0001) and 24 hours (cancer: MNTX, 71.2% vs placebo, 41.4%, p<0.0001; noncancer: MNTX, 74.4% vs placebo, 37.5%, p<0.0001) of the initial dose. Cumulative RFL response rates within 4 hours of the first, second, or third dose of study drug were also higher in MNTX-treated patients. The estimated time to RFL was shorter among those who received MNTX and similar in cancer and noncancer patients. Mean pain scores declined similarly in all groups. The most common adverse events in both cancer and noncancer patients were abdominal pain, flatulence, and nausea. Conclusion: After the first dose, MNTX rapidly induced a laxation response in the majority of both cancer and noncancer patients with advanced illness. Opioid-induced analgesia was not compromised, and adverse events were primarily gastrointestinal in nature. Methylnaltrexone is a well-tolerated and effective treatment for OIC in both cancer and noncancer patients.

Cumulative Laxation Response with Methylnaltrexone: Implications for Hospitalized Patients with Advanced Illness and Opioid-Induced Constipation.

Background: Opioid-induced constipation (OIC) may increase the risk of fecal impaction and mortality in patients with advanced illness. Methylnaltrexone (MNTX) is efficacious for OIC. Objective: The purpose of this analysis was to evaluate cumulative rescue-free laxation response with repeat MNTX dosing in patients with advanced illness who were refractory to current laxative regimens and to assess the influence, if any, of poor functional status on response to MNTX treatment. Methods: This analysis included pooled data from patients with advanced illness and established OIC who were on a stable opioid regimen in a pivotal, randomized, placebo (PBO)-controlled clinical trial (study 302 [NCT00402038]) or a randomized, PBO-controlled Food and Drug Administration-required postmarketing study (study 4000 [NCT00672477]). Patients in study 302 received subcutaneous MNTX 0.15 mg/kg or PBO every other day, whereas those in study 4000 received MNTX 8 mg (body weight ≥38 to <62 kg), MNTX 12 mg (body weight ≥62 kg), or PBO every other day. Outcomes included cumulative rescue-free laxation rates at 4- and 24-hours postdose for the first 3 doses of study drug and time to rescue-free laxation. To assess if functional status influenced treatment outcomes, we performed a secondary analysis on the outcomes stratified by baseline World Health Organization/Eastern Cooperative Oncology Group performance status, pain scores, and safety. Results: One hundred eighty-five patients received PBO and 179 patients received MNTX. The median age was 66.0 years, 51.5% were women, 56.5% had a baseline World Health Organization/Eastern Cooperative Oncology Group performance status score >2, and 63.4% had a primary diagnosis of cancer. Cumulative rescue-free laxation rates were significantly higher with MNTX than PBO 4- and 24-hours after doses 1, 2, and 3 (P < 0.0001), and between-treatment comparisons remained significant (P < 0.0001) regardless of performance status. The estimated time to first rescue-free laxation was shorter for patients receiving MNTX versus PBO. No new safety signals were identified. Conclusions: Repeated use of MNTX represents a safe and effective treatment for OIC in patients with advanced illness regardless of baseline performance status. ClinicalTrials.gov identifier: NCT00672477. (Curr Ther Res Clin Exp. 2023; 84:XXX-XXX)© 2023 Elsevier HS Journals, Inc.

A Randomized, Double-Blind, Parallel Design Thorough QT Study With a Nested Crossover to Compare the Cardiac Safety of Amiselimod With Placebo and Positive Control in Healthy Volunteers.

This double-blind study evaluated the cardiac safety of amiselimod. Healthy adults (n = 190) were randomized (2:1:1) to receive (1) oral placebo (day -1), followed by oral amiselimod (days 1-26), which was upwardly titrated from 0.4 to 1.6 mg once daily to achieve steady-state concentrations comparable with 0.4 (therapeutic) and 0.8 mg (supratherapeutic) once daily, and placebo (day 27); (2) placebo (day -1), oral moxifloxacin 400 mg (day 1; positive control), followed by placebo (days 1-27); or (3) placebo (days -1 to 26), followed by moxifloxacin 400 mg (day 27). No participant had a corrected QT interval by Fredericia (QTcF) >500 milliseconds or a change from baseline (dQTcF) >60 milliseconds. The upper limits of the 90%CIs for the differences in least-squares mean difference in dQTcF between amiselimod and placebo on days 13 and 26 were <10 milliseconds. Area under the concentration-time curve from 0 to 23.5 hours after dosing and maximum plasma concentration of amiselimod and amiselimod-P (active metabolite) at steady-state concentrations for the 0.8-mg dose on day 26 were approximately double that observed with the 0.4-mg dose on day 13. All adverse events were mild to moderate in severity, and no deaths occurred. Amiselimod did not have any clinically relevant effect on the QTcF interval.

Reductions in All-Cause Mortality Associated with the Use of Methylnaltrexone for Opioid-Induced Bowel Disorders: A Pooled Analysis.

OBJECTIVE: Preclinical and clinical studies suggest that activation of the µ-opioid receptor may reduce overall survival and increase the risk for all-cause mortality in patients with cancer and noncancer pain. Methylnaltrexone, a selective, peripherally acting µ-opioid receptor antagonist, has demonstrated efficacy for the treatment of opioid-induced constipation. This retrospective analysis of 12 randomized, double-blind, placebo-controlled studies of methylnaltrexone evaluated the treatment of opioid-induced bowel disorders in patients with advanced illness or noncancer pain. METHODS: The risk of all-cause mortality within 30 days after the last dose of study medication during the double-blind phase was compared between methylnaltrexone and placebo groups. The data were further stratified by cancer vs noncancer, age, gender, and acute vs chronic diagnoses. RESULTS: Pooled data included 2,526 methylnaltrexone-treated patients of which 33 died, and 1,192 placebo-treated patients of which 35 died. The mortality rate was 17.8 deaths/100 person-years of exposure in the methylnaltrexone group and 49.5 deaths/100 person-years of exposure for the placebo group. The all-cause mortality risk was significantly lower among patients receiving methylnaltrexone compared with placebo (hazard ratio: 0.399, 95% confidence interval: 0.25, 0.64; P = .0002), corresponding to a 60% risk reduction. Significant risk reductions were observed for those receiving methylnaltrexone who had cancer or chronic diagnoses. Methylnaltrexone-treated patients had a significantly reduced mortality risk compared with placebo regardless of age or gender. CONCLUSIONS: Methylnaltrexone reduced all-cause mortality vs placebo treatment across multiple trials, suggesting methylnaltrexone may confer survival benefits in patients with opioid-induced bowel disorders taking opioids for cancer-related or chronic noncancer pain.

First-Dose Efficacy of Methylnaltrexone in Patients with Severe Medical Illness and Opioid-Induced Constipation: A Pooled Analysis.

BACKGROUND: Opioid-induced constipation (OIC) is a frequent consequence of opioid analgesia that may increase patient risk for emergency department visits and hospitalization. Methylnaltrexone is a peripherally acting µ-opioid receptor antagonist indicated for the treatment of OIC. OBJECTIVE: To assess the safety and efficacy of a single methylnaltrexone dose. METHODS: Results were pooled from three randomized, placebo-controlled methylnaltrexone (MNTX) studies in opioid-treated patients with advanced illness and OIC, despite treatment with conventional laxatives. Baseline assessments included demographics, disease/treatment characteristics, and functional levels. Efficacy endpoints included rescue-free laxation (RFL) rates within 4 and 24 h, time to first RFL, pain score change, and adverse events (AEs) after a single MNTX dose or placebo. RESULTS: The analysis included 281 patients receiving MNTX and 237 receiving placebo. Mean age was 66.2 years for MNTX and 65.8 for placebo; ∼50% were men. The most frequent primary diagnosis was cancer (MNTX = 70.5%; placebo = 66.2%) and most (∼98%) were receiving at least one laxative at baseline. RFL occurred in 61.4% vs. 16.0%, and 72.1% vs. 40.1% MNTX vs. placebo patients, within 4 and 24 h of the initial dose, respectively. Relative to placebo, MNTX use reduced the time to first RFL, with most MNTX-treated patients achieving RFL within 2 h. Baseline and posttreatment pain scores were similar (p = 0.9556 vs. placebo for current and worst pain change from baseline), demonstrating that MNTX did not negatively affect opioid analgesia. Most AEs were gastrointestinal related and dissipated by the second dose. CONCLUSIONS: Methylnaltrexone provides early RFL without compromising analgesia in patients receiving chronic opioid therapy.

Subcutaneous Methylnaltrexone for Treatment of Opioid-Induced Constipation in Cancer versus Noncancer Patients: An Analysis of Efficacy and Safety Variables from Two Studies.

PURPOSE: Methylnaltrexone inhibits opioid-induced constipation (OIC) by binding to peripheral µ-opioid receptors without impacting central opioid receptor mediated analgesia. This analysis compared methylnaltrexone efficacy and safety among advanced illness patients with and without active cancer and OIC. PATIENTS AND METHODS: This post hoc analysis included two multicenter, randomized, double-blind, placebo-controlled studies in adults with advanced illness and OIC who received subcutaneous methylnaltrexone. Efficacy endpoints included the proportion of patients achieving rescue-free laxation (RFL), time to RFL, weekly laxations within 24 hours after dosing, rescue laxative use, and pain scores. Adverse events were monitored for safety. RESULTS: After pooling, 178 patients received methylnaltrexone (n = 116 with cancer) and 185 received placebo (n = 114 with cancer). Median baseline daily opioid morphine equivalents (mg/d) were higher in cancer (methylnaltrexone: 180; placebo: 188) versus noncancer patients (methylnaltrexone: 120; placebo: 80). The proportions of patients achieving RFL within 4 hours after ≥2 of the first 4 doses were significantly greater with methylnaltrexone (cancer: 56.9%; noncancer: 58.1%) versus placebo (cancer: 5.3%; noncancer: 11.3%; P < 0.0001). The median time to laxation within 24 hours after the first methylnaltrexone dose was significantly shorter in cancer and noncancer patients versus placebo (cancer: 0.96 vs 22.53 hours, P < 0.0001; noncancer: 1.25 vs >24 hours, P = 0.0002). The mean number of weekly laxations within 24 hours after dosing by week 2 was significantly higher in methylnaltrexone- vs placebo-treated cancer and noncancer patients (cancer: 7.9 vs 4.9, P < 0.0001; noncancer: 8.4 vs 5.0, P < 0.0001). Methylnaltrexone reduced rescue laxative use without impacting pain scores. Consistent with previous data, methylnaltrexone was well tolerated in cancer and noncancer patients, and the AE profile did not suggest symptoms of opioid withdrawal. CONCLUSION: Methylnaltrexone reduced RFL time in advanced-illness patients with and without active cancer, while maintaining pain control with opioid treatment despite higher baseline opioid use among cancer patients.

The Influence of Age on Central Effects of Methylnaltrexone in Patients with Opioid-Induced Constipation.

BACKGROUND: Methylnaltrexone, a peripherally acting µ-opioid receptor antagonist approved for the treatment of opioid-induced constipation (OIC), has restricted diffusion across the blood-brain barrier (BBB) and has not been demonstrated to impact opioid-induced central analgesia. Age-related changes in BBB permeability may compromise methylnaltrexone's restricted diffusion and alter opioid-induced central analgesic effects. OBJECTIVE: This analysis evaluated whether opioid analgesia is compromised in older adults receiving methylnaltrexone for OIC. METHODS: The analysis included adults diagnosed with OIC who received opioids for pain management and who had a terminal illness or chronic nonmalignant pain. Data were pooled from four randomized, double-blind trials and stratified by age (< 65 years and ≥ 65 years). Endpoints included pain intensity scores, symptoms of opioid withdrawal, treatment-related adverse events (TRAEs), and rescue-free laxation (RFL) within 4 h of treatment. RESULTS: Overall, 1323 patients were < 65 years of age (n = 908, methylnaltrexone; n = 415, placebo) and 304 patients were ≥ 65 years of age (n = 171, methylnaltrexone; n = 133, placebo). Nonsignificant pain intensity score reductions were observed in all groups. In the older cohort, measures of opioid withdrawal did not show statistical differences from baseline in either the methylnaltrexone or placebo groups. The most frequently reported TRAEs were abdominal pain, flatulence, and nausea. Relative to the first dose, gastrointestinal TRAEs potentially related to opioid withdrawal declined with the second dose and were comparable with placebo, regardless of age. RFL response within 4 h of methylnaltrexone treatment increased significantly in both age cohorts relative to placebo. CONCLUSIONS: Methylnaltrexone use did not adversely affect pain control, opioid withdrawal effects, or AEs while providing effective RFL, regardless of age. These results suggest that age does not appear to influence the safety and efficacy of methylnaltrexone for OIC. Further research is needed to assess the impact of other factors that alter BBB permeability, such as dementia, stroke, or drug interactions, on the safety and efficacy of methylnaltrexone. CLINICAL TRIAL REGISTRATION NUMBERS: Study 302, NCT00402038; study 3200K1-4000, NCT00672477; study 3200K1-3356, NCT00529087; study 3201, NCT01186770.

The influence of brain metastases on the central nervous system effects of methylnaltrexone: a post hoc analysis of 3 randomized, double-blind studies.

PURPOSE: Peripherally acting µ-opioid receptor antagonists such as methylnaltrexone (MNTX, Relistor®) are indicated for the treatment of opioid-induced constipation (OIC). The structural properties unique to MNTX restrict it from traversing the blood-brain barrier (BBB); however, the BBB may become more permeable in patients with brain metastases. We investigated whether the presence of brain metastases in cancer patients compromises the central effects of opioids among patients receiving MNTX for OIC. METHODS: This post hoc analysis of pooled data from 3 randomized, placebo-controlled trials included cancer patients with OIC who received MNTX or placebo. Endpoints included changes from baseline in pain scores, rescue-free laxation (RFL) within 4 or 24 h of the first dose, and treatment-emergent adverse events (TEAEs), including those potentially related to opioid withdrawal symptoms. RESULTS: Among 356 cancer patients in the pooled population, 47 (MNTX n = 27; placebo n = 20) had brain metastases and 309 (MNTX n = 172; placebo n = 137) did not have brain metastases. No significant differences in current pain, worst pain, or change in pain scores from baseline were observed between patients treated with MNTX or placebo. Among patients with brain metastases, a significantly greater proportion of patients who received MNTX versus placebo achieved an RFL within 4 h after the first dose (70.4% vs 15.0%, respectively, p = 0.0002). TEAEs were similar between treatment groups and were generally gastrointestinal in nature and not related to opioid withdrawal. CONCLUSION: Focal disruptions of the BBB caused by brain metastases did not appear to alter central nervous system penetrance of MNTX.

Attrition of methylnaltrexone treatment-emergent adverse events in patients with chronic noncancer pain and opioid-induced constipation: a post hoc pooled analysis of two clinical trials.

Background: Opioids prescribed for the management of chronic noncancer pain are associated with nausea, vomiting, and constipation. Methylnaltrexone, a peripherally acting µ-opioid receptor antagonist, has demonstrated robust efficacy and was well-tolerated in treating opioid-induced constipation without affecting central analgesia. Our objective was to assess changes in the frequency of treatment-emergent adverse events (TEAEs) after the first or second dose of methylnaltrexone or placebo. Methods: This post hoc analysis pooled data from two randomized, placebo-controlled clinical trials assessing methylnaltrexone for opioid-induced constipation in the outpatient setting. Patients received subcutaneous methylnaltrexone (12 mg once daily or 12 mg once every other day), oral methylnaltrexone (150, 300, or 450 mg daily), or placebo. TEAEs, opioid withdrawal symptoms, pain intensity, and rescue-free bowel movements (RFBMs) within 4 hours of the first dose (i.e., RFBM responders) were assessed. Associations between TEAE frequencies and RFBM response were also evaluated. Results: The analysis included 1263 adult patients with chronic noncancer pain. TEAE rates declined from treatment day 1 to 2 (methylnaltrexone: 16.2%-5.3%; placebo: 6.6%-5.4%). Among methylnaltrexone-treated patients, significantly greater proportions of RFBM responders versus nonresponders reported gastrointestinal TEAEs on day 1. No associations between RFBM response and the frequency of TEAEs were observed in the placebo group. No meaningful changes in opioid withdrawal symptoms or pain intensity were observed. Conclusions: Early-onset TEAEs following methylnaltrexone treatment, particularly gastrointestinal TEAEs, are at least partially due to laxation. Methylnaltrexone treatment effectively relieves opioid-induced constipation without affecting the central analgesic effects of opioids.

Subcutaneous methylnaltrexone for opioid-induced constipation in advanced-illness patients with or without active cancer.

Aim: To evaluate methylnaltrexone for opioid-induced constipation in patients with and without cancer. Methods: This post hoc analysis comprises two Phase III, multicenter, double-blind, randomized studies of advanced-illness patients who received methylnaltrexone subcutaneous injection or placebo. Results: Significantly more patients treated with methylnaltrexone than placebo experienced laxation within 4 (cancer = 55.5 vs 15.5%; noncancer = 55.6 vs 12.8%) and 24 (cancer = 64.7 vs 29.8%; noncancer = 64.4 vs 30.8%) h after the first dose (p < 0.01 vs placebo). Regardless of cancer status, methylnaltrexone reduced median time to laxation and improved constipation relief without impacting opioid analgesia or withdrawal symptoms. Conclusion: Methylnaltrexone provided significant improvements in opioid-induced constipation over placebo in advanced-illness patients with and without cancer. Clinical trial registration numbers: study 301: NCT00401362; study 302: NCT00402038.

Safety of oral methylnaltrexone for opioid-induced constipation in patients with chronic noncancer pain.

PURPOSE: Oral methylnaltrexone was shown to be effective in treating opioid-induced constipation (OIC) in patients with chronic noncancer pain in a Phase III randomized controlled trial. This report provides a detailed safety analysis from that study. METHODS: Adults (n=803) with chronic noncancer pain for ≥2 months and confirmed OIC while receiving opioid doses ≥50 mg morphine equivalent per day for ≥14 days were randomized 1:1:1:1 to oral methylnaltrexone (150, 300, or 450 mg) or placebo once daily for 4 weeks, followed by as-needed use for 8 weeks. Safety was evaluated by examining treatment-emergent adverse events (TEAEs), clinical laboratory parameters, vital signs, electrocardiography, rescue-laxative and opioid use, Objective Opioid Withdrawal Scale (OOWS) and Subjective Opioid Withdrawal Scale (SOWS), and pain-intensity scores. RESULTS: TEAEs occurred at a similar incidence in the methylnaltrexone groups (59.0%) and placebo group (63.0%). The most common TEAEs with methylnaltrexone were abdominal pain (8.0% vs 8.5% with placebo), nausea (6.8% vs 9.0%), and diarrhea (6.0% vs 3.5%). Cardiac-related TEAEs occurred in 1.8% and 1.0% of patients, respectively, and no major adverse cardiovascular events were reported. No patient had a cluster of TEAEs associated with opioid withdrawal after excluding gastrointestinal TEAEs. Changes in laboratory parameters, vital signs, and electrocardiography were generally small and similar across treatment groups. Rescue-laxative use was more common with placebo than methylnaltrexone 450 mg (6.20% vs 4.27% of study days, P=0.024). Changes in opioid dose, OOWS and SOWS scores, and pain-intensity scores during treatment were minimal. CONCLUSION: Oral methylnaltrexone had a safety profile comparable with placebo in the treatment of OIC in patients with chronic noncancer pain, with no evidence of cardiac toxicity or opioid withdrawal.

Randomized, Double-Blind Trial of Oral Methylnaltrexone for the Treatment of Opioid-Induced Constipation in Patients with Chronic Noncancer Pain.

BACKGROUND: Subcutaneous methylnaltrexone, a peripherally acting µ-opioid receptor antagonist, improves opioid-induced constipation (OIC) in patients with chronic noncancer pain. An oral methylnaltrexone formulation has been developed. METHODS: In this phase 3, double-blind trial, adults with chronic noncancer pain receiving opioid doses of ≥ 50 mg/day oral morphine equivalents with OIC were randomly assigned to oral methylnaltrexone (150, 300, or 450 mg) or placebo once daily (QD) for 4 weeks followed by as-needed dosing for 8 weeks. Patients who had ≥ 3 rescue-free bowel movements (RFBMs)/week, with an increase of ≥ 1 RFBM/week from baseline for ≥ 3 of 4 weeks during the QD period, were responders. RESULTS: Overall, 803 patients were included in the analyses. A significantly greater percentage of patients had an increase in mean percentage of dosing days resulting in an RFBM within 4 hours of dosing during weeks 1 through 4 (QD period; primary endpoint) with methylnaltrexone (300 mg/day [24.6%; P = 0.002] and 450 mg/day [27.4%; P < 0.0001]) vs. placebo (18.2%). The percentage of responders (49.3% for 300 mg [P = 0.03] and 51.5% for 450 mg [P = 0.005] vs. 38.3% with placebo) and change from baseline in mean number of weekly RFBMs (difference vs. placebo, 0.5 for 300 mg [P = 0.03] and 0.5 for 450 mg [P = 0.02]) was significantly greater with methylnaltrexone 300 and 450 mg/day vs. placebo during the QD period. All dosages of oral methylnaltrexone were well tolerated. CONCLUSIONS: Oral methylnaltrexone was efficacious and well tolerated for OIC in patients with chronic noncancer pain, particularly the 450-mg dose.

Efficacy and Tolerability of Subcutaneous Methylnaltrexone in Patients with Advanced Illness and Opioid-Induced Constipation: A Responder Analysis of 2 Randomized, Placebo-Controlled Trials.

BACKGROUND: Subcutaneous methylnaltrexone is efficacious and well tolerated in inducing bowel movements in patients with advanced illness and opioid-induced constipation (OIC); factors determining optimal responsiveness to OIC treatment, however, have not been elucidated. This post hoc responder analysis examined the influence of demographic and baseline characteristics on methylnaltrexone efficacy and tolerability in this population. METHODS: Data were pooled from 2 randomized, double-blind, placebo-controlled, phase 3 studies of subcutaneous methylnaltrexone (0.15 and 0.30 mg/kg) [ClinicalTrials.gov identifiers: Study 301 - NCT00401362; Study 302 - NCT00402038]. Subgroup analyses of the primary outcome, percentage of patients with rescue medication-free bowel movements (RFBM) within 4 hours of first dose, were conducted for age, sex, primary diagnosis, baseline constipation-related distress score, and baseline oral morphine equivalent dose. RESULTS: More than 50% of 165 patients treated with either methylnaltrexone dose experienced a RFBM within 4 hours vs. 14.6% of 123 placebo-treated patients (P < 0.0001 for both methylnaltrexone doses vs. placebo). Methylnaltrexone response was significantly greater than placebo response in all subgroups (P < 0.01). The largest differences vs. placebo were observed for patients taking methylnaltrexone 0.30 mg/kg with a noncancer primary diagnosis (70.0% [methylnaltrexone] vs. 12.8% [placebo]; P < 0.001) and for patients taking methylnaltrexone 0.30 mg/kg maintained on ≥ 150 mg/day baseline morphine equivalent doses (73.3% vs. 16.7%; P < 0.0001). Common adverse events were abdominal pain (pooled methylnaltrexone: 27.9%, placebo: 9.8%), flatulence (13.3%, 5.7%), and nausea (10.9%, 4.9%). Tolerability was comparable across subgroups. CONCLUSION: Subcutaneous methylnaltrexone provides a rapid, robust, and consistent RFBM response in patients with advanced illness and OIC. Methylnaltrexone 0.30 mg/kg may elicit particularly favorable responses in select patient populations.

Characterization of abdominal pain during methylnaltrexone treatment of opioid-induced constipation in advanced illness: a post hoc analysis of two clinical trials.

CONTEXT: Methylnaltrexone is a selective peripherally acting mu-opioid receptor antagonist that decreases the constipating effects of opioids without affecting centrally mediated analgesia. In two double-blind, placebo-controlled, Phase III studies of methylnaltrexone for opioid-induced constipation in patients with advanced illness, abdominal pain was the most common adverse event (AE) reported. OBJECTIVES: This analysis sought to further characterize the Medical Dictionary for Regulatory Activities-defined abdominal pain AEs experienced in these studies. METHODS: A post hoc analysis of verbatim descriptions was used to further assess AEs characterized as abdominal pain in both trials. Descriptive summary statistics were used to assess severity of abdominal pain, effect of abdominal pain on global pain scores, and other characteristics. Logistic regression analysis was used to determine the association of baseline characteristics with abdominal pain. RESULTS: Most verbatim descriptions of abdominal pain referred to "abdominal cramps" or "cramping." Abdominal pain AEs were mostly mild to moderate in severity and did not affect patients' global evaluation of pain. The incidence of abdominal pain AEs in methylnaltrexone-treated patients was greatest after the first dose and decreased with subsequent doses. No association between abdominal pain AEs and most baseline patient characteristics was noted. CONCLUSION: Abdominal pain AEs in methylnaltrexone-treated patients in clinical trials are usually described as "cramps" or "cramping," are mostly mild to moderate in severity, and decrease in incidence with subsequent dosing.

Long-term tolerability and effectiveness of oxymorphone extended release in patients with cancer.

OBJECTIVE: To evaluate the long-term safety, tolerability, and effectiveness of oxymorphone extended release (ER) in patients with cancer-related pain. DESIGN: Post hoc analysis of two-1-year open-label extension studies. SETTING: Multiple US cancer treatment facilities. PATIENTS: Patients with cancer pain who had participated in two short-term crossover comparator trials of oxymorphone ER: one open-label and one double-blind randomized. INTERVENTIONS: Patients who had been taking oxymorphone ER continued the dose established in the previous study. Patients who had been taking a comparator opioid were switched to an equianalgesic dose of oxymorphone ER. All patients underwent individualized oxymorphone ER dose titration to optimize effectiveness and tolerability. ASSESSMENTS: Current, average, worst, and least pain scores were normalized to a 100-point scale. Patients rated treatment on a five-point global assessment of study medication (Poor = 1 to Excellent = 5). All adverse events (AEs) were recorded. RESULTS: Of the 80 patients who entered the extension trials, 26 completed 52 weeks, 7 discontinued owing to loss of effectiveness, and 20 discontinued owing to AEs, most of which were unrelated to study drug. No significant increase in mean (standard deviation [SDD average pain intensity was observed from baseline (30.5 [19.6], 100-point scale) to final visit (35.9 [21.1], p = 0.37). The most common AEs were concomitant disease progression (28.8 percent, n=23), nausea (22.5 percent, n=18), dyspnea (16.3 percent, n=13), fatigue (16.3 percent, n=13), and edema of the lower limb (15 percent, n=12). CONCLUSIONS: In these patients with pain related to cancer, oxymorphone ER was generally well tolerated and provided stable long-term pain control.

Consistent and clinically relevant effects with fentanyl buccal tablet in the treatment of patients receiving maintenance opioid therapy and experiencing cancer-related breakthrough pain.

Fentanyl buccal tablet (FBT) has shown efficacy and tolerability in patients with cancer-related persistent pain treated with maintenance opioids. We conducted a combined analysis of two similarly designed, randomized, placebo-controlled studies to further evaluate the consistency and clinical relevance of analgesia outcomes. Of the 252 patients enrolled, 150 fulfilled the criteria for efficacy analysis and experienced 1,417 breakthrough pain episodes. A consistently greater effect was noted with FBT vs. placebo on the following measures: improvements from baseline of >or=33% and >or=50% in pain intensity (PI), a >or=2-point reduction in PI, and a score of >or=2 for pain relief. Improvements in these clinically meaningful efficacy measures were seen with FBT at 15 minutes (earliest common evaluation) and remained evident at 60 minutes (final common evaluation). They were also reflected in a more favorable global medication performance assessment for FBT over placebo. FBT was generally well tolerated; most adverse events were typical of potent opioid use in a cancer population. Application-site (buccal) abnormalities were infrequent and led to withdrawal of three patients. There were no serious adverse events or deaths attributable to FBT. This analysis suggests that FBT provides an analgesic effect that is consistent across multiple clinically relevant efficacy measures.

Opioid switching and rotation in primary care: implementation and clinical utility.

BACKGROUND: Opioid therapy is the standard treatment for moderate-to-severe cancer pain and is becoming a more frequent treatment for moderate-to-severe chronic noncancer pain. Response to opioids varies significantly between patients and even within the individual patient at different stages of treatment. Finding an opioid at a dose that provides adequate long-term analgesia with minimal adverse effects can be difficult. Opioid switching and opioid rotation, at different stages of therapy, represent two clinical strategies used to optimize opioid response for patients with moderate-to-severe pain. OBJECTIVES: Review the theoretical and clinical evidence supporting the concepts of opioid switching and rotation, outline the conditions under which these practices should be considered, and briefly suggest practical steps for their implementation. SCOPE: Clinical literature, clinical practice and guideline databases, and professional society websites were searched for articles or reports describing opioid switching or opioid rotation in chronic pain therapy; variability in patient response to opioid therapy; physiologic, pharmacologic, and genetic factors that affect clinical response to opioids; and practical approaches to maximizing analgesia and minimizing adverse effects in opioid therapy. It is outside the scope of this review to evaluate the pharmacoeconomic aspects that affect changes in opioid therapy. FINDINGS: The variability in de novo clinical response to opioids likely represents the interaction of the varying properties of the individual opioids with the variability in individual patient biology. This interaction forms the rationale for opioid switching and explains its clinical utility. As with opioid switching, success with opioid rotation is related to the myriad of factors determining an individual patient's response to a specific opioid. However, the benefits of opioid rotation also derive from a partial reversal of tolerance at the mu-opioid receptor and the response of different micro-opioid receptor subtypes to the different opioids.

Palliative care and pain: new strategies for managing opioid bowel dysfunction.

Opioid analgesics are a cornerstone of pain therapy in the hospice and palliative care population. However, opioid-induced bowel dysfunction (OBD) is a commonly associated condition that frequently compromises the usefulness of these agents. Although its most common and debilitating symptom is constipation, the impact of OBD extends beyond constipation to encompass a myriad of gastrointestinal (GI) signs and symptoms, ranging from decreased gastric emptying and reflux to abdominal pain, cramping, bloating, nausea, and vomiting. Even after aggressive therapies to improve bowel function have been implemented, many patients continue to experience symptoms of OBD. To avoid these unwanted effects, some even choose to decrease or discontinue therapy with opioid analgesics, and experience inadequate pain control. The net result of OBD is a seriously negative impact on quality of life (QOL). For these reasons, it is important that palliative care practitioners have an adequate understanding of normal GI function and the underlying mechanisms responsible for OBD, the burden of OBD in the context of appropriate and effective pain management, and the benefits provided by effective pharmacotherapy. Several real-world cases are discussed to illustrate the application of optimal symptom management and the use of strategies that minimize the effects of OBD and improve patient QOL.