A new study reports that Methylnaltrexone (MNTX), prescribed to address opioid-induced constipation (OIC), a common side effect of chronic opioid therapy, may be associated with slowing tumor growth and improving survival rates in patients with advanced cancer. The study is described as the first human-based research, and involves a combination of results from 2 randomized, placebo-controlled trials. Patients who responded to MNTX had significantly fewer reports of tumor progression (7.6 percent) compared to those who didn’t respond (22 percent) or who took the placebo (25.4 percent), based on physician reporting of adverse events. The results were presented at the ANESTHESIOLOGY® 2015 annual meeting.
The study examined 229 patients with advanced cancer, including lung, prostate, breast or pancreatic, who received palliative care and were being treated for opioid-induced constipation, but did not respond to conventional laxatives. Of these, 117 were given MNTX, while 112 were given a placebo. Of the results, Filip Janku, MD, co-author of the studies and assistant professor of investigational cancer therapeutics at The University of Texas MD Anderson Cancer Center, Houston commented “We’re not precisely sure why MNTX was associated with fewer reports of tumor progression and longer survival in our patients – proving what causes this response is very difficult – but it could be that MNTX influences several side effects of opioids unrelated to pain relief. The findings are consistent with what was seen in the lab.” MNTX received approval in 2008, and has since been prescribed to over 800,000 patients, according to a news story. MNTX is marketed by Salix Pharmaceuticals. Read more about the study findings here.