Relistor (methylnaltrexone bromide) helps to keep opioids from attaching to mu-opioid receptors in the gut. Relistor (methylnaltrexone bromide) works differently from over-the-counter (OTC) laxatives—it is specifically designed to target the effect opioids have in the gut without impacting opioid pain relief in the central nervous system. Tell your doctor if you experience any changes in your pain relief.