How confident can we be that take-home naloxone programmes are effective without the ‘gold standard’ randomised trial? Judged against nine criteria for establishing the presumption of causality, evidence that the provision of naloxone reduces overdose-related deaths among opioid users.

Key points from summary and commentary

• The featured review assessed the impact of take-home naloxone programmes using the nine Bradford Hill criteria – a well-established method for establishing the likelihood of a ‘cause and effect’ relationship between an intervention and an outcome where it is not possible to allocate participants at random to an intervention versus a comparator.
• This method demonstrated that provision of the overdose antidote naloxone to people who are not healthcare workers is likely to be an effective way of preventing overdose-related deaths.
• Take-home naloxone has led to improved survival rates among programme participants and reduced heroin overdose mortality rates in the community, and is accompanied by only a low rate of adverse events.