Methylnaltrexone in the treatment of opioid-induced constipation

Beverley Greenwood-Van Meerveld1, Kelly M Standifer21Veterans Affairs Medical Center, Oklahoma Center for Neuroscience, Department of Physiology, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USA; 2Department of Pharmaceutical Sciences, Oklahoma Center for Neuroscience, University of Oklahoma Health Sciences Center, Oklahoma City, OK, USAAbstract: Constipation is a significant problem related to opioid medications used to manage pain. This review attempts to outline the latest findings related to the therapeutic usefulness of a μ opioid receptor antagonist, methylnaltrexone in the treatment of opioid-induced constipation. The review highlights methylnaltrexone bromide (RelistorTM; Progenics/Wyeth) a quaternary derivative of naltrexone, which was recently approved in the United States, Europe and Canada. The Food and Drug Administration in the United States approved a subcutaneous injection for the treatment of opioid bowel dysfunction in patients with advanced illness who are receiving palliative care and when laxative therapy has been insufficient. Methylnaltrexone is a peripherally restricted, μ opioid receptor antagonist that accelerates oral–cecal transit in patients with opioidinduced constipation without reversing the analgesic effects of morphine or inducing symptoms of opioid withdrawal. An analysis of the mechanism of action and the potential benefits of using methylnaltrexone is based on data from published basic research and recent clinical studies.Keywords: methylnaltrexone, constipation, opioid