Naloxone can restart breathing after an opioid overdose within minutes
Patented in 1961, naloxone knocks opioids off their receptors and can bring back breathing in two minutes when injected into a vein. Once a hospital drug, it now comes as a pocket nasal spray sold over the counter, and handing it to people likely to witness an overdose has been shown to cut deaths.
Naloxone, best known by the brand Narcan, is an opioid antagonist: it blocks the drugs rather than mimicking them. Speed depends on the route. Given into a vein it acts within about two minutes, into a muscle within roughly five, and as a nasal spray within around ten, though some estimates put the nasal onset at three to seven minutes. It was approved for overdose in the United States in 1971 and sits on the World Health Organization's List of Essential Medicines.
The nasal route has a practical history. In 2001 paramedics in Denver tested it as an alternative to intravenous doses, and over one month 91% of patients who responded to naloxone did so with the spray alone. Narcan nasal spray won US approval in 2015. Because rescuers often needed several 4 mg doses, the FDA approved an 8 mg spray, Kloxxado, in 2021. Pocket-sized auto-injectors designed for family members and other non-specialists also exist.
There are catches. Many opioids outlast naloxone, which works for roughly 45 minutes intravenously, so breathing can fail again once it wears off, and patients may need repeat doses and observation. In someone dependent on opioids it can trigger abrupt withdrawal, with agitation, vomiting, sweating and a racing heart, which is why clinicians may give small doses every few minutes instead of one large dose. Whether it helps in cardiac arrest caused by an overdose is unclear.
It also has a clever supporting role. Swallowed or dissolved under the tongue, naloxone is barely absorbed, so manufacturers add it to tablets and strips such as buprenorphine: taken as intended, only the partner drug works, while injecting the mixture is meant to be blunted. Researchers have also explored it for shock, constipation caused by opioids and dissociative disorders, with no firm conclusions.
Source: Naloxone
