• Frank Porreca and Michael H Ossipov.
• Department of Pharmacology, University of Arizona, Tuscon, Arizona 85724, USA. frankp@u.arizona.edu
• Pain Med. 2009 May 1; 10 (4): 654-62.

ObjectivesGastrointestinal (GI) side effects such as nausea and vomiting are common following opioid analgesia and represent a significant cause of patient discomfort and treatment dissatisfaction. This review examines the mechanisms that produce these side effects, their impact on treatment outcomes in chronic pain patients, and counteractive strategies.ResultsA number of mechanisms by which opioids produce nausea and vomiting have been identified. These involve both central and peripheral sites including the vomiting center, chemoreceptor trigger zones, cerebral cortex, and the vestibular apparatus of the brain, as well as the GI tract itself. Nausea and vomiting have a negative impact on treatment efficacy and successful patient management because they limit the effective analgesic dosage that can be achieved and are frequently reported as the reason for discontinuation of opioid pain medication or missed doses. While various strategies such as antiemetic agents or opioid switching can be employed to control these side effects, neither option is ideal because they are not always effective and incur additional costs and inconvenience. Opioid-sparing analgesic agents may provide a further alternative to avoid nausea and vomiting due to their reduced reliance on mu-opioid signalling pathways to induce analgesia.ConclusionsNausea and vomiting side effects limit the analgesic efficiency of current opioid therapies. There is a clear need for the development of improved opioid-based analgesics that mitigate these intolerable effects.

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