Assessing the impact of a temporary class drug order on ethylphenidate-related infections among people who inject drugs in Lothian, Scotland: an interrupted time-series analysis.

BACKGROUND AND AIMS: In April 2015, the UK government enacted a temporary class drug order (TCDO) on ethylphenidate in response to reported harms associated with its use, in particular an outbreak of infections among people who inject drugs (PWID) in Lothian, Scotland. This study assesses the effect that the TCDO had on reducing the most common infections identified during the outbreak: Streptococcus pyogenes and Staphylococcus aureus.

DESIGN: The outbreak was split into a pre-intervention period (35 weeks) and a post-intervention period (26 weeks) based around the date of the TCDO. Segmented negative binomial regression models were used to compare trends in weekly counts of infections between the pre- and post-intervention periods.

SETTING AND PARTICIPANTS: PWID in the Lothian region of Scotland.

MEASUREMENTS: Cases of S. pyogenes and S. aureus infections reported within the National Health Service, Lothian.

FINDINGS: There were 251 S. pyogenes and/or S. aureus infections recorded among 211 PWID between February 2014 and December 2015: 171 infections in the pre-intervention period and 51 in the post-intervention period. Significant trend changes in weekly S. pyogenes and/or S. aureus infections following the TCDO were found [relative risk (RR) = 0.88, 95% confidence interval (CI) = 0.82-0.94]. PWID who self-reported using novel psychoactive substances (NPS) were at higher risk of acquiring these infections (RR = 1.81, 95% CI = 1.12-2.93), particularly when comparing the risk of infection with NPS use for a specific strain, S. pyogenes emm76.0, against the risk of infection with NPS use for S. pyogenes (emm types other than emm76.0) (RR = 3.49, 95% CI = 1.32-9.21).

CONCLUSIONS: The UK government's 2015 temporary class drug order on ethylphenidate was effective in reducing infections among people who inject drugs during an outbreak situation in Lothian, Scotland.