As the opioid crisis unfolded, prescriptions for the narcotic alternative saw a two-fold increase despite unclear evidence of benefit for pain. Between 2005 and 2015, as the opioid crisis in the US came into focus, prescriptions for gabapentinoid medications – gabapentin and pregabalin – to adults with cancer saw a two-fold increase, a University of Michigan Rogel Cancer Centre study has found.
Gabapentin, which affects voltage-gated calcium channels in the brain, was originally approved as an anti-seizure medication and later for treating nerve pain. Today, up to 95% of its use may be "off-label," researchers have found – a highlighting a lack of rigorous study of its mechanisms and efficacy for treating pain more broadly, as well as other conditions it's commonly prescribed for, like migraines and fibromyalgia.
The U-M study, which examined federal Medical Expenditure Panel Survey data, presents the first evidence and measurement of a steep upward trend in gabapentinoid prescriptions among adults with cancer, says lead author Alex Fauer, a doctoral student at the U-M School of Nursing. The findings dovetail with broader, national trends.
"Cancer is a disease of ageing, so we were surprised to find that adults 18-44 were the largest age group getting these prescriptions," Fauer says. "This may indicate doctors are increasingly prescribing gabapentinoids as an alternative to opioids for treating cancer pain in younger adult patients. It may additionally point to a growing incidence of nerve pain caused by chemotherapy in cancer survivors."
The study found the number of adults with cancer who were prescribed gabapentinoids grew from 3.3% in 2005 to 8.3% in 2015, with the total number of prescriptions growing from 1.2m to 3.5m over that decade.
More recent data wasn't available, but likely shows a continuation of the trend, Fauer says. The data also doesn't include inpatient treatment, excluding many of the sickest patients.
Use of gabapentinoids to treat the complex pain syndromes of cancer patients is problematic for a couple of reasons, says senior study author Dr Christopher Friese, the Elizabeth Tone Hosmer professor of nursing and a professor of health management and policy at the U-M School of Public Health.
"The medications' mechanisms of action and efficacy for pain control and other off-label conditions need further study," he says. "Additionally, evidence indicates the healthcare profession may have been underestimating the risks associated with gabapentinoids – including the potential for abuse and physical dependence, and dangers when taken in combination with opioids and other medications."
More investigation of the effectiveness of gabapentinoids for cancer pain is needed to inform clinical practice, Fauer adds, along with deeper understanding of potential risks. "The whole goal is treating patients' pain while keeping them safe," he says.
Background: Gabapentinoid use for long-term cancer pain control may be problematic, given unclear mechanisms of action and increased concerns for physical dependence. The purpose of this report is to examine trends of gabapentinoid use among US adults with cancer from 2005 to 2015.
Methods: We conducted a serial, cross-sectional study using data from the Medical Expenditure Panel Survey (MEPS). We performed multiple logistic regression to examine the annual percentages of gabapentinoid users, which were adjusted for age, sex, and US region of residence. The amount of gabapentinoid prescriptions filled in 2015 was also estimated.
Results: The adjusted percentage of gabapentinoid users in 2015 was 5.60% (3.79%, 7.41%), 2.39 times greater than the percentage in 2005 (p < .001). By 2015, the number of gabapentinoid prescriptions had grown to approximately 3.52 million (2.40 million, 4.65 million).
Conclusion: We observed greater than a twofold increase in the trend of gabapentinoid medication use among US adults with cancer. Investigations on the long-term efficacy of gabapentinoids for complex pain syndromes, and mitigation of risks, is essential to guide informed clinical management and keep patients safe.
Alex J Fauer, Matthew A Davis, Sung Won Choi, Lauren P Wallner, Christopher R Friese
[link url="https://labblog.uofmhealth.org/lab-report/gabapentinoids-appear-increasingly-to-be-prescribed-off-label-for-cancer-pain"]Michigan Medicine – University of Michigan[/link]
[link url="https://link.springer.com/article/10.1007%2Fs00520-019-05100-9"]Supportive Care in Cancer abstract[/link]