EDMONTON, Alberta-Vigorous worldwide pain education efforts emphasizing undertreatment have resulted in a "very healthy increase" in the use of opioids around the world, including increases in dose and length of exposure, Eduardo Bruera, MD, of the University of Alberta and Edmonton General Hospital, said at a plenary session of the 8th World Congress on Pain.
As a result of this increased usage, along with more and better neuro-psychiatric assessments, a spectrum of neuropsychiatric toxicities of opioids in cancer patients is emerging.
"It is no longer acceptable for patients on opioids to be lying in bed, often confused. Clinicians are looking to improve cognitive and physical performance, and are more likely to identify neuropsychiatric effects than before," Dr. Bruera said.
The patient population likely to receive massive opioid doses for long periods-patients with advanced cancer who may have low circulating albumin levels, low glomerular filtration rates, and profound physical and mental fatigue-also helps to explain the increase in reports of opioid neurotoxicity.
Delirium, myoclonus, grand mal seizures, and hyperalgesia have all been reported in patients receiving strong opioids. Myoclonus has been seen in association with renal failure in patients receiving high opioid doses for prolonged periods, and may improve with opioid rotation, he said.
Delirium occurs more often in those on prolonged high-dose therapy who also have neuropathic pain, renal failure, and dehydration, and are using other psychoactive drugs.