Study of Methylnaltrexone in Opioid-Induced Constipation Patients

Methylnaltrexone is a quaternary derivative of the pure opioid antagonists naltrexone. It is fairly lipid soluble and readily cross the blood-brain barrier. This property provides methylnaltrexone with the potential to block the undesired side-effects of opioid pain medications predominantly mediated by receptors located peripherally while sparing opioid effects mediated at receptors in the central nervous system, most importantly analgesia. This is a multicenter, randomized, double-blind , placebo-controlled trail to investigate the safety and efficacy of subcutaneous methylnaltrexone for treating opioid-induced constipation in patients with advanced illness. The randomization schedule was used to assign patients in a 2:1 ratio to multicenter or an equal volume of placebo administered subcutaneously on alternate days for 2 weeks. The clinical trail was estimated to enroll 180 patients totally.