Naloxone: general

Naloxone is a synthetic opioid antagonist, chemically related to oxymorphone but with an allyl group in place of the methyl group on the nitrogen atom [1][2]. It was first synthesized in 1960 [3], patented in 1966 [3], and approved by the FDA for injectable use in 1971 [3]. It has been used to reverse opioid overdose for more than 50 years [4].

It works by attaching to opioid receptors and blocking or displacing opioids already there [5][6]. It is a pure, competitive antagonist — it has no opioid effects of its own [1][4][2]. In an overdose, it rapidly reverses slowed or stopped breathing, reduced consciousness, and constricted pupils caused by opioids [3][5]. As with opioid antagonists generally, it produces essentially no effect in someone who hasn't taken opioids, does not produce a high [7][8].

Two things matter most before using it. First, as with opioid antagonists generally, their effects last only about an hour, shorter than many opioids stay active in the body — heroin and other opioids can outlast them [8]. Watch the person, don't assume one dose is the end of the emergency. Second, as with opioid antagonists generally, it can bring on sudden opioid withdrawal in someone who is physically dependent [9] — unpleasant, not typically what makes an overdose dangerous, but expect it.

Naloxone comes in two FDA-approved forms, injectable and prepackaged nasal spray [5], and can be obtained without a prescription in 43 states [4]. It can be given by emergency medical personnel and law enforcement officials [4].

References

1. Naloxone | C19H21NO4 | CID 5284596 - PubChem — National Center for Biotechnology Information
2. DailyMed - NALOXONE HYDROCHLORIDE injection, solution — National Library of Medicine
3. Clinical Pharmacokinetics and Pharmacodynamics of Naloxone - PMC — Springer / PubMed Central
4. Naloxone - StatPearls - NCBI Bookshelf — StatPearls Publishing / NCBI
5. Naloxone DrugFacts | National Institute on Drug Abuse (NIDA) — National Institute on Drug Abuse
6. Naloxone | Description, Actions, Uses, & Side Effects | Britannica — Encyclopædia Britannica
7. Opioid overdose — World Health Organization
8. Opioid medicines - side effects, withdrawal symptoms, dependency — Australian Government Department of Health and Aged Care
9. Opioid Overdose Management — Ontario Poison Centre