Injection drug use among people receiving chronic prescription opioid treatment for noncancer pain was infrequent overall (3% to 4% within five years) but about eight times higher than among opioid-naive patients, a study found.
To assess the association between long-term prescription opioids for noncancer pain and the initiation of injection drug use among patients without a history of substance use, researchers used data from an administrative database of 1.7 million individuals tested for hepatitis C virus or HIV in British Columbia, Canada, that was linked to administrative health databases, including prescriptions from community pharmacies.
Patients ages 11 to 65 years without a history of substance use except alcohol were analyzed for prescription opioid use for noncancer pain based on drugs dispensed between 2000 and 2015. Episodes were classified by the length and intensity of opioid use: acute (<90 episode days), episodic (lasting ≥90 episode days, with <90 days' drug supply and/or <50% episode intensity), and chronic (lasting ≥90 episode days, with ≥90 days' drug supply and ≥50% episode intensity). People with a chronic episode were matched 1:1:1:1 on socioeconomic variables to those with episodic or acute episodes and to those who were opioid-naive. Results were published Nov. 18 by The BMJ.
Overall, 59,804 participants (14,951 people from each opioid use category) were included in the matched cohort with a median follow-up of 5.8 years. There were 1,149 participants who began using injection drugs. Cumulative probability of injection drug use initiation at five years was highest for participants with chronic opioid use (4.0%), followed by those with episodic use (1.3%), those with acute use (0.7%), and those who were opioid-naive (0.4%). Risk of starting injection drug use was 8.4 times (95% CI, 6.4 to 10.9 times) higher in those with chronic opioid use compared to those who were opioid-naive. A sensitivity analysis limited to individuals with a history of chronic pain showed that their cumulative risk with chronic use (3.4% within five years) was lower than the primary results, but the relative risk was not (hazard ratio, 9.7; 95% CI, 6.5 to 14.5).
The researchers noted that the database-driven study was unable to determine the underlying reasons for starting injection drug use or whether they were causally related to opioid treatment. These findings should not be used as a reason to support involuntary tapering or discontinuation of long-term prescription opioid treatment, the authors noted.
In related news, the CDC released updated drug overdose death counts. Trends since 2015 have shown a steady increase, and data from April 2021 revealed a 28.5% increase over the previous 12 months.