Although opioid-related side effects are common among cancer patients treated for pain, wide heterogeneity among study outcome measures precludes formulation of specific drug profiles, according to a systematic review published in the October issue of Journal of Pain.1
Analyzing data from 25 studies of opioid-naïve patients, researchers found that rates of nausea ranged from 3% to 85%, constipation from 5% to 97%, vomiting from 4% to 50%, drowsiness from 3% to 88%, and dry mouth from 1% to 94%, respectively.
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According to the authors, the study is the first to provide an overview of side effects after starting treatment with morphine, oxycodone, fentanyl, or methadone for cancer-related pain.
Very little has been known about specific opioid-related events in this population. Our research shows that adverse events vary immensely, and highlights the need for researchers to standardize how they report side effects so true comparisons can be made, lead study author and medical oncologist Astrid Oosten, MD, from Erasmus MC Cancer Institute in Rotterdam, the Netherlands, told Clinical Pain Advisor.
“We have to conclude [that] the true incidence of side effects of opiates [remains] unknown. There are no good data available,” Dr. Oosten said. “We hoped we could create a good overview, and find differences in rates of adverse events [that] would help with the choice for specific types of opiates. We have to conclude [that] we really have insufficient data. There has to be better research done, and I’m afraid the findings from this review do not help the clinician at all to make a choice for specific types of opiates.”
Cancer: A Confounding Factor
Pain for cancer patients is most often caused by the disease itself — from a tumor pressing on bones, nerves or body organs, according to the American Cancer Society.2 Opiates are commonly used to treat moderate to severe pain.
What the review findings mean is that for now, clinical practice will remain the same.