Newswise — Despite the side effects associated with opioid treatment for pain, management of moderate to severe cancer pain often includes opioid therapy. Opioid-induced constipation (OIC) is a common side effect of opioid treatment for cancer pain, affecting approximately 60% of patients. Prolonged use of opioids in cancer patients increases the likelihood that OIC may occur, which can compromise pain relief and increase symptom burden.

Methylnaltrexone, available as an oral tablet or a subcutaneous (SC) injection, is a medication approved to treat OIC in adults with chronic pain not caused by active cancer. The SC formulation of methylnaltrexone is also approved for the treatment of OIC in adults with advanced illness or pain caused by active cancer.

Researchers from multiple institutions looked at the response to SC methylnaltrexone in patients with advanced illness who had OIC. They examined data from two double-blind, placebo-controlled studies and looked at results for patients with and without cancer who did not respond to previous treatment for OIC. In both studies, they found that about 50%–70% of cancer patients treated with methylnaltrexone had a bowel movement within 4 hours without the use of additional treatments for their constipation, compared with 15% of placebo-treated patients. In addition, more patients treated with methylnaltrexone maintained a response at 24 hours after dosing compared with patients treated with placebo.

The most common side effects reported for methylnaltrexone were gastrointestinal effects (such as abdominal pain, diarrhea, and nausea). Importantly, methylnaltrexone treatment did not diminish pain relief from the opioid therapy. Results from these studies thus show that SC methylnaltrexone provided safe, effective, and rapid relief of OIC in patients with cancer, without disrupting opioid pain management.

The report received a Best of Meeting Abstract Award from the American Society of Regional Anesthesia and Pain Medicine (ASRA) for its 19th Annual Pain Medicine Meeting, being held virtually November 20-22, 2020. Lead author Eric D. Shah, MD, will present Abstract #1347, “Subcutaneous Methylnaltrexone in Cancer and Noncancer Patients for Rapid Relief of Opioid-Induced Constipation” on Saturday, November 21, at 12 pm ET.

ASRA is a professional member organization of more than 5,000 physicians and healthcare providers across the United States and the world. The vision of ASRA is to relieve the global burden of pain. ASRA is dedicated to advancing the science and practice of regional anesthesia and pain medicine to improve patient outcomes through research, education, and advocacy. Learn more at