Methylnaltrexone for Opioid-Induced Constipation in Advanced Illness

This study investigated the safety and efficacy of subcutaneous methylnaltrexone, a μ-opioid–receptor antagonist, for treating opioid-induced constipation in patients with advanced illness. Methylnaltrexone rapidly induced laxation without affecting central analgesia or precipitating withdrawal. This study investigated the safety and efficacy of subcutaneous methylnaltrexone for treating opioid-induced constipation in patients with advanced illness. Methylnaltrexone rapidly induced laxation without affecting central analgesia or precipitating withdrawal. Clinicians often use opioids to treat moderate-to-severe pain; however, opioids frequently induce or aggravate constipation. Empirically, laxative therapy may be burdensome and ineffective and result in temporally unpredictable responses. In addition, severe opioid-induced constipation may limit opioid therapy, worsening analgesia. These drawbacks can substantially compromise the quality of life, especially in patients with advanced illness. Opioid-induced constipation is predominantly mediated by gastrointestinal μ-opioid receptors. 1 , 2 Selective blockade of these peripheral receptors might relieve constipation without compromising centrally mediated effects of opioid analgesia or precipitating withdrawal. N-methylation of the uncharged systemic opioid antagonist, naltrexone, 3 results in a charged derivative, methylnaltrexone, which . . .