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.