Background: Methylnaltrexone (MNTX) is a peripherally acting µ-opioid receptor antagonist indicated for opioid-induced constipation (OIC), which can be a serious consequence of opioid analgesia. We evaluated whether baseline osmotic agent (eg, milk of magnesia, polyethylene glycol, lactulose, sorbitol) or stimulant (eg, senna, bisacodyl) use affects the efficacy and safety of MNTX among a subgroup of [...]