The risk of infective endocarditis among people who inject drugs: a retrospective, population-based time series analysis

Background — Infective endocarditis is an important and increasingly common complication among people who inject drugs. We conducted this study to determine if the increasing risk associates with changes in the opioids injected. Specifically, we hypothesized that the removal of tradition controlled-release oxycodone from the Canadian market at the end of 2011 would associate with an increased use of hydromorphone and an increased risk of infective endocarditis.

Methods — We conducted a retrospective, population-based time series analysis using the linked health administrative databases of Ontario, Canada. We measured the quarterly risk of admissions for injection drug use-related infective endocarditis and changes in opioid prescription rates from 2006 to 2015. We set the intervention point at the fourth quarter of 2011, when tradition controlled-release oxycodone was removed from the Canadian market.

Results — We observed an increase in the risk of admissions for injection drug use-related infective endocarditis over the study period. Prior to the intervention point we observed a mean of 13.4 admissions per quarter, and after, a mean of 35.1 admissions per quarter. However, no significant change in this risk occurred at the intervention point. Rather, the risk of infectious endocarditis appeared to have increased earlier and in parallel with the rise in hydromorphone prescriptions. Hydromorphone represented 16% of all opioid prescriptions at the start of the observation period and 53% by the end.

Interpretation — The risk of injection drug use-related infective endocarditis is increasing and is temporally associated with increasing prescriptions for hydromorphone. This relationship warrants further exploration.