van Malderen K, et al. - The clinicians performed this work to assess the peripherally acting mu-opioid receptor antagonists (PAMORAs) dose required for opioid-naïve subjects to achieve similar beneficial effects on symptoms or valid surrogates to those observed in chronic opioid users. Compared to chronic opioid users, opioid-naïve subjects required a higher dose of PAMORA to achieve μ-opioid antagonist effect.