Naloxone is a medication that binds to and blocks opioid receptors in the brain. If someone overdoses on heroin, the narcotic binds to these opioid receptors, triggering potentially life-threatening respiratory depression. Naloxone can reverse the effects of respiratory depression by binding to the same opioid receptors and disrupting the effects of heroin. This should cause normal breathing to be restored. Naloxone works within a few minutes. The opioid overdose agent can be administered by nasal spray or by injection.