Naloxone opioid overdose training. The training teaches participants to recognise an opioid overdose and how to administer the antidote naloxone. Naloxone can be administered as either an injection or a nasal spray. Opioids, such as heroin, depress the nervous and respiratory systems. When administered naloxone binds to opioid receptors in the central nervous system, competing with and replacing the opioid drug. This reduces the harmful effects of the opioid. Photographed in Detroit, Michigan, USA.