Physical pain is common and associated with nonmedical prescription opioid use among people who inject drugs

Background: People who inject drugs (PWID) often have poor health and lack access to health care. The aim of this study was to examine whether PWID engage in self-treatment through nonmedical prescription opioid use (NMPOU). We describe the prevalence and features of self-reported physical pain and its association with NMPOU. Methods: PWID (N = 702) in San Francisco, California (age 18+) were recruited to complete interviewer administered surveys between 2011 and 2013. Multivariate logistic regression analysis was conducted to examine the associations among self-reported pain dimensions (past 24-h average pain, pain interference with functional domains) and NMPOU, controlling for age, sex, psychiatric illness, opioid substitution treatment, homelessness, street heroin use and unmet healthcare needs. Results: Almost half of the sample reported pain, based on self-reported measures in the 24 h before their interview. The most common pain locations were to their back and lower extremities. Past 24-h NMPOU was common (14.7%) and associated with past 24 h average pain intensity on a 10 point self-rating scale (adjusted odds ratio [AOR] = 2.15, 95% confidence interval [CI] 1.21-3.80), and past 24 h pain interference with general activity (AOR 1.82 [95% CI 1.04-3.21]), walking ability (AOR 2.52 [95% CI 1.37-4.63]), physical ability (AOR 2.01 [95% CI 1.16-3.45]), sleep (AOR 1.98 [95% CI 1.13-3.48]) and enjoyment of life (AOR 1.79 [95% CI 1.02-3.15]). Conclusion: Both pain and NMPOU are common among PWID, and highly correlated in this study. These findings suggest that greater efforts are needed to direct preventive health and services toward this population.