​Opioid-induced hallucination (OIH), while uncommon and underreported, is a significant adverse side effect of treating patients with opioids, according to a literature review published in the October 2016 issue of Anesthesia and Analgesia. OIH tends to go underreported because the hallucinations are often attributed instead to underlying psychiatric or personality disorders, and also because patients may be reluctant to divulge their experience of hallucinations for fear of judgment. To better assess the magnitude of the problem, the authors conducted a search using MEDLINE/PubMed (using MeSH terms), Cochrane Review, and Google Scholar for the words "opioid" and "hallucination," along with other terms such as "neurotoxic," "delirium," and several commonly prescribed opioids. They discovered "numerous reports" of hallucinations attributed to opioids, "which have typically been described as auditory, visual, or rarely tactile hallucinations." The majority of cases in the literature occurred during end-of-life care or treatment for cancer pain. Morphine, likely because of its long history and widespread use, was the opioid most frequently associated with hallucination. The authors outlined several methods of diagnosis and treatment for OIH. The first step is to rule out other possible causes for the hallucination, such as psychiatric disease, substance abuse, drug withdrawal, or electrolyte disorder. One significant challenge to diagnosis is the presence of neuropsychiatric disease. For instance, the authors said, some reports place the incidence of hallucination among those with Parkinson disease as high as 39.8%. Ultimately, the authors said, OIH should be diagnosed based on clinical judgment rather than any specific test result. Several treatment options exist, the simplest of which is discontinuing the opioid treatment. If this is not an option, providers can consider decreasing the dosage, rotating the opioids, altering the route of administration, or treating the patient with an opioid antagonist. The article also includes an infographic that outlined other adverse effects of opioids. In 2013, the infographic said, 16,235 opioid-related deaths occurred, accounting for 71% of all pharmaceutical deaths. An accompanying editorial noted that another hurdle to measuring the true impact of OIH is that some patients seek out opioids for their hallucinatory effects. It is currently difficult to discern the risk factors for OIH, the authors noted, but they posited that anonymous surveys could add to understanding of the problem. Providers should be aware that the potential hallucinatory effects could be a reason for misuse and abuse of opioids, the authors said, and clinical judgment should be exercised.

HRC Recommends: Opioids are high-alert medications with a heightened risk of causing significant harm if used in error, and even appropriate prescribing carries risks. In addition, prescription opioid abuse poses a high risk for addiction, diversion, and subsequent heroin use. Healthcare organizations may wish to consider adopting standardized tools and approaches for opioid prescribing and monitoring.