Opioid side effects--mechanism-based therapy.

Opioid analgesics generate numerous side effects that complicate their use in postoperative care,1 in the treatment of sickle cell vaso-occlusive episodes, and in the treatment of pain associated with advanced cancer and other life-shortening illnesses.2 These side effects include sedation, respiratory depression, impaired cognition, nausea and vomiting, loss of appetite, pruritus, urinary retention, impaired orthostatic tolerance, and (perhaps most commonly of all) ileus and constipation. The therapies that are typically used for opioid side effects are rarely evidence-based and are often ineffective.2 In this issue of the Journal, Thomas et al.3 describe the results of a multicenter trial of methylnaltrexone . . .