The standard first dose of naloxone is one spray into one nostril, which delivers 4 mg in the most widely available nasal spray (Narcan). If the person doesn’t respond within 2 to 3 minutes, give a second dose in the opposite nostril. There is no strict upper limit on how many doses you can give, and naloxone has an excellent safety profile even at very high amounts, so the guiding principle is simple: keep dosing every 2 to 3 minutes until the person starts breathing normally or emergency help arrives.
Nasal Spray Doses by Product
Several naloxone nasal sprays are available, and each device is pre-loaded with a fixed dose. You don’t need to measure anything. One full squeeze of the device equals one dose.
- Narcan: 4 mg per spray
- Kloxxado: 8 mg per spray
- Rezenopy: 10 mg per spray
- Generic nasal naloxone: 3 mg per spray
Regardless of which product you have, the instructions are the same. Give one spray into one nostril. Wait 2 to 3 minutes. If normal breathing hasn’t returned, use a new device and spray into the other nostril. Continue alternating nostrils with a fresh device each time. You cannot reuse a device once it has been sprayed.
Injectable Naloxone Doses
Injectable naloxone, given into the muscle (typically the outer thigh), uses a lower milligram dose because the drug enters the bloodstream more directly. The standard starting dose is 0.4 mg, though some kits contain pre-filled syringes with up to 2 mg. As with the nasal spray, a second injection can be given after 2 to 3 minutes if the person hasn’t responded. Auto-injectors, where available, deliver a fixed dose and talk you through the steps with audio instructions.
Why Fentanyl May Require More Doses
Naloxone works by knocking opioid molecules off the receptors in the brain that control breathing. With potent synthetic opioids like fentanyl and its analogues, more of those receptors are occupied, and more naloxone is needed to compete for binding sites. Animal and human studies both support this: doses that reliably reverse a heroin or prescription painkiller overdose sometimes fall short against fentanyl.
In practice, this means you may need to give multiple rounds of naloxone before the person starts breathing again. Because most street drugs now contain fentanyl or its analogues, higher-dose products like Kloxxado (8 mg) and Rezenopy (10 mg) were developed specifically for this reality. If you only have a 4 mg spray, just keep giving additional doses every 2 to 3 minutes. The drug is safe at cumulative levels far above what bystanders typically administer. In clinical testing, healthy volunteers received doses as high as 24 mg with no adverse effects, and even extremely high intravenous doses in non-opioid-dependent people have shown no toxicity.
When to Give It
Naloxone should be given to anyone showing signs of an opioid overdose, or whenever an overdose is suspected. You don’t need to be certain. The key signs to look for are slow, shallow, or stopped breathing; unconsciousness or an inability to wake the person; very small, pinpoint pupils; limp arms and legs; pale or bluish skin, especially around the lips and fingertips; and a faint or absent heartbeat. If someone is unresponsive and you know or suspect opioids are involved, give naloxone. It will not harm someone who hasn’t taken opioids.
Children and Infants
Nasal naloxone sprays are approved for both adults and children at the same dose per device. A child receives the same single spray as an adult. This applies across all available nasal products. The pre-filled devices are not adjustable, so a 4 mg spray delivers 4 mg whether the patient is an adult or a toddler. The same 2 to 3 minute interval between doses applies.
The Risk of Wearing Off Too Soon
Naloxone’s effects last roughly 30 to 90 minutes, which is often shorter than the opioid still circulating in the person’s body. This means someone who wakes up after naloxone can slip back into overdose once the naloxone wears off. This is called re-sedation, and it’s the reason emergency medical care is still necessary even after a person responds. Stay with them, keep them on their side to prevent choking, and be prepared to give another dose if their breathing slows again.
Using Expired Naloxone
If the only naloxone available is past its expiration date, use it. A study testing expired naloxone products, some stored for nearly 30 years, found that most still contained more than 90% of their labeled dose. Degradation was slow, and no significant harmful byproducts were detected. An expired dose that’s slightly less potent is far better than no dose at all.