Narcan (naloxone) begins to take effect almost immediately or typically within two to three minutes. It is administered intranasally through spraying into the nose, but can also be taken by mouth or injected.
Narcan is a brand-name medication containing an opioid antagonist called naloxone that turns off opioid receptors. Naloxone binds more strongly and quickly to the opioid receptors in our brain than opioid agonists. It can quickly reverse the effects of an opioid that is leading to an overdose, particularly sedation and respiratory depression. This makes Narcan (naloxone) a very powerful reversal agent in acute overdose.