Opioid antagonists

Opioid antagonists block opioid receptors and displace opioids already bound there. Naloxone rapidly reverses opioid overdose and can be given by injection or as a nasal spray. Its effect can wear off before a long-acting opioid's does, so breathing is watched closely and doses are repeated as needed. In people who are dependent on opioids, reversal can trigger sudden withdrawal and severe pain.

• NaloxoneKnown brand names include Narcan, Rextovy, and Zimhi.