BACKGROUND: Opioid overdose has a high mortality, but is often reversible with 
appropriate overdose management and naloxone (opioid antagonist). Training in 
these skills has been successfully trialled internationally with opioid users 
themselves. Healthcare professionals working in substance misuse are in a prime 
position to deliver overdose prevention training to drug users and may 
themselves witness opioid overdoses. The best method of training dissemination 
has not been identified. The study assessed post-training change in clinician 
knowledge for managing an opioid overdose and administering naloxone, evaluated 
the 'cascade method' for disseminating training, and identified barriers to 
implementation.
METHODS: A repeated-measures design evaluated knowledge pre-and-post training. A 
sub-set of clinicians were interviewed to identify barriers to implementation. 
Clinicians from addiction services across England received training. 
Participants self-completed a structured questionnaire recording overdose 
knowledge, confidence and barriers to implementation.
RESULTS: One hundred clinicians were trained initially, who trained a further 
119 clinicians (n=219) and thereafter trained 239 drug users. The mean composite 
score for opioid overdose risk signs and actions to be taken was 18.3/26 (±3.8) 
which increased to 21.2/26 (±4.1) after training, demonstrating a significant 
improvement in knowledge (Z=9.2, p<0.001). The proportion of clinicians willing 
to use naloxone in an opioid overdose rose from 77% to 99% after training. 
Barriers to implementing training were clinician time and confidence, service 
resources, client willingness and naloxone formulation.
CONCLUSIONS: Training clinicians how to manage an opioid overdose and administer 
naloxone was effective. However the 'cascade method' was only modestly 
successful for disseminating training to a large clinician workforce, with a 
range of clinician and service perceived obstacles. Drug policy changes and 
improvements to educational programmes for drug services would be important to 
ensure successful implementation of overdose training internationally.