Naloxone is an opiate antagonist that can reverse the effects of an opioid overdose in just minutes. Naloxone is a nasal spray; it is given through the nose. It's so easy to deliver that some forms can even be given by friends and family. Opioids need to get into opioid receptors in order to work. During an overdose, they can slow down bodily functions like breathing until they stop. Naloxone blocks opioid receptors so that other opioids can't get in.