What are opioids? What role do they play in cancer treatment?

Cancers treated: Various

Subclasses of this group: Phenanthrenes, phenylpiperidines, diphenylheptanes, benzomorphans

Delivery routes: Oral administration is preferred because it is the least invasive and least costly route. If a patient has difficulty swallowing or suffers from nausea or vomiting, then other options may include rectal, transdermal, and transmucosal administration or injection under the skin or into the vein or spinal area. Patient-controlled access pumps that deliver opioids to these areas are also available. Opioids are produced in both long-acting and immediate-release forms and are often used with other pain medications for enhanced analgesia.

How these drugs work: Opioids mimic the body’s natural painkillers (for example, endorphins) by binding to receptors on the surfaces of cells in the central nervous system and gastrointestinal tract. Full agonists, the largest group of opioids, stimulate the receptors, blocking the release of neurotransmitters and interfering with the transmission of pain signals to the brain. They also alter the perception of pain. Partial agonists produce weaker effects and may also block the analgesic action of other opioids.

Side effects: Adverse events are common across opioids and include sedation, nausea and vomiting, constipation, respiratory depression, dry mouth, itching, sexual dysfunction, and urinary retention. Because of the wealth of opioid receptor sites in the central nervous system, cognitive effects such as hallucinations, euphoria, and depression may also occur. Tolerance and physical dependence may develop, although psychological addiction is rarely associated with opioid use by cancer patients.

Bibliography

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Amer. Soc. of Clinical Oncology. "Pain: Treating Pain with Medication." Cancer.Net. ASCO, Feb. 2013. Web. 22 Aug. 2014.

Davis, Mellar P. Opioids in Cancer Pain. 2d ed. Oxford: Oxford UP, 2009. eBook Collection (EBSCOhost). Web. 22 Aug. 2014.

Natl. Insts. of Health and Friends of the Natl. Lib. of Medicine. "Opioids and Chronic Pain." NIH MedlinePlus: The Magazine 6.1 (2011): 9. NLM.NIH.gov. Web. 22 Aug. 2014.

Portenoy, Russell K., and Eduardo Bruera. Cancer Pain: Assessment and Management. 2d ed. Cambridge: Cambridge UP, 2010. eBook Collection (EBSCOhost). Web. 22 Aug. 2014.