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

Authors Rauck RL, Slatkin NE, Stambler N, Israel RJ

Received 4 April 2018

Accepted for publication 21 September 2018

Published 24 December 2018 Volume 2019:12 Pages 139—150


Checked for plagiarism Yes

Review by Single anonymous peer review

Peer reviewer comments 6

Editor who approved publication: Dr E Alfonso Romero-Sandoval

Richard L Rauck,1 Neal E Slatkin,2,3 Nancy Stambler,4 Robert J Israel3

1Carolinas Pain Institute, Winston-Salem, NC, USA; 2School of Medicine, University of California Riverside, Riverside, CA, USA; 3Medical Affairs, Salix Pharmaceuticals, Bridgewater, NJ, USA; 4Clinical Research, Progenics Pharmaceuticals, New York, NY, USA

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.

Keywords: analgesia, µ-opioid-receptor antagonist, nonmalignant, safety

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