Subcutaneous methylnaltrexone eases opioid-induced constipation without opioid dose reduction

  • Chamberlain BH & al.
  • Pain Manag
  • 17 Jan 2020

  • curated by Kelli Whitlock Burton
  • Clinical Essentials
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Takeaway

  • Methylnaltrexone by subcutaneous injection is significantly more effective than placebo at reducing opioid-induced constipation (OIC) in patients with and without cancer, with no opioid withdrawal symptoms.
  • Treatment-related adverse events (AEs) were more common in patients who received methylnaltrexone compared with placebo and most common among those with cancer.

Why this matters

  • Methylnaltrexone is effective at reducing OIC without the need to reduce the opioid dose.

Study design

  • Post-hoc analysis of 2 phase 3, multicenter, double-blind, randomized studies.
    • Of 123 patients receiving placebo, 84 had cancer. 
    • Of 164 patients receiving subcutaneous methylnaltrexone injection, 119 had cancer.
  • Funding: Salix Pharmaceuticals.

Key results

  • More patients treated with methylnaltrexone vs placebo experienced laxation (P<.01 style="list-style-type:circle;">
  •  Within 4 hours of the first dose:
    • Patients with cancer: 55.5% vs 15.5%.
    • Patients without cancer: 55.6% vs 12.8%.
  • Within 24 hours of the first dose:
    • Cancer: 64.7% vs 29.8%.
    • Noncancer: 64.4% vs 30.8%.
  • Methylnaltrexone reduced median time to laxation (1.5-2.2 hours), regardless of cancer status.
  • Opioid withdrawal symptoms were not evident in patients receiving methylnaltrexone.
  • Treatment-emergent AEs were more common in patients receiving methylnaltrexone, especially in those with cancer.
  • Limitations

    • Patients with/without cancer were not prespecified populations in the studies.
    • Limited generalizability of findings.

    Co-authored with Chitra Ravi, MPharm