Naloxone is given in three main ways: as a nasal spray, as an injection into a muscle, or as an injection under the skin. The nasal spray is the most common form used by bystanders because it requires no medical training. All forms work by knocking opioids off the brain’s receptors, rapidly reversing the effects of an overdose, though the speed varies by route. Intravenous naloxone, given in hospitals, acts fastest, but the forms available to the public are designed to be used by anyone, anywhere.
Recognizing When Naloxone Is Needed
Before reaching for naloxone, you need to recognize what an opioid overdose looks like. The key signs are slow or shallow breathing (or no breathing at all), very small “pinpoint” pupils, unconsciousness or an inability to speak, and limp arms and legs. Skin may appear pale, and lips or fingernails can turn purple or blue. Vomiting and a faint heartbeat are also common. If someone shows these signs after using opioids, or if you’re unsure what they took but suspect an overdose, giving naloxone is the right call. It won’t cause harm if opioids aren’t involved.
Nasal Spray: The Most Common Method
The standard nasal spray (sold as Narcan) delivers 4 mg of naloxone in a single burst into one nostril. A higher-dose version called Kloxxado delivers 8 mg. Both come as single-use, pre-loaded devices that require no assembly or priming.
To use it, remove the device from the box and peel back the tab to open the package. Hold the spray with your thumb on the bottom of the plunger and your first and middle fingers on either side of the nozzle. Lay the person on their back, support their neck with one hand, and let the head tilt slightly back. Insert the nozzle tip gently into one nostril until your fingers touch the base of their nose, then press the plunger firmly. That’s the entire dose.
If the person doesn’t respond within 2 to 3 minutes, give a second spray in the other nostril. You can keep alternating nostrils every 2 to 3 minutes until they respond or emergency help arrives. Each device contains only one dose, so you’ll need a fresh one for each spray.
Nasal naloxone takes roughly 15 to 30 minutes to reach its peak concentration in the blood, which is slower than injection. But it begins working well before that peak, and the simplicity of the device makes it the preferred option for people without medical training.
Injection Into a Muscle or Under the Skin
Injectable naloxone comes in two forms: pre-filled devices and vials that require drawing up the medication with a syringe.
The Zimhi pre-filled syringe delivers a 5 mg dose and is injected into a muscle or under the skin, typically into the outer thigh. It works through clothing, so there’s no need to remove pants or roll up fabric in an emergency. You remove the safety guard, press the device against the thigh, and push down. Printed instructions on the device label walk you through it.
The Evzio auto-injector, available in 0.4 mg and 2 mg doses, goes a step further: it has a built-in speaker that provides voice-guided instructions as you use it, similar to an automated defibrillator. It’s also injected into the outer thigh.
For vial-and-syringe kits, the process involves a couple more steps. You remove the cap from the vial, insert the needle through the rubber stopper, and pull back the plunger to draw all the liquid into the syringe. Then inject straight into the muscle of the outer thigh or the shoulder (the same spot where you’d get a flu shot). You can inject through clothing, which saves critical seconds.
Intramuscular injection generally produces a faster response than nasal spray, since the drug enters the bloodstream more directly. If there’s no improvement after 2 to 5 minutes, a second dose can be given.
How Long the Effects Last
Naloxone’s effects last about 2 hours when given intravenously, and possibly somewhat longer when given by injection into muscle or by nasal spray. This is a critical detail, because many opioids last longer than naloxone does. Once naloxone wears off, the person can slip back into overdose. That’s why calling emergency services is essential even if the person wakes up and seems fine. They need to be monitored well beyond that initial recovery window.
What Happens After Naloxone Works
When naloxone kicks in and reverses the opioid effects, the person may experience sudden withdrawal symptoms. These aren’t dangerous but can be intense and disorienting. Common signs include watery eyes, runny nose, yawning, sweating, and hot flashes. Pupils will dilate noticeably. The person may feel agitated, nauseated, or confused.
These reactions happen because naloxone strips opioids from the brain’s receptors all at once, and the body, which had adjusted to the opioid’s presence, is suddenly without it. The discomfort is temporary, and the alternative (not breathing) is far worse. It helps to calmly explain to the person what happened when they come to, since they may not remember the events leading up to the overdose.
Using Naloxone on Children
The nasal spray can be used on children at the same 4 mg dose as adults. For injectable forms, children receive the same devices, with one modification: for infants under 1 year old, you should pinch the thigh muscle while giving the injection to ensure the needle reaches the muscle tissue. Dosing in newborns is more nuanced. The American Academy of Pediatrics has historically recommended against giving naloxone to babies born to opioid-dependent mothers, because it can trigger acute withdrawal and seizures in infants who were exposed to opioids throughout pregnancy.
Storing Naloxone So It Works When You Need It
Naloxone should ideally be stored between 15 and 30°C (roughly 59 to 86°F) and kept out of direct light. But real-world testing shows it’s more durable than those guidelines suggest. Studies have found naloxone remains stable after being frozen and thawed between -20 and 4°C, and it holds up even at temperatures as high as 80°C (176°F). This means carrying a kit in your bag, keeping one in a car’s glove compartment, or storing one at home are all reasonable, even if conditions aren’t perfectly controlled. Check the expiration date periodically, but don’t worry that imperfect storage has ruined it.