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Does Narcan expire, and does it have side effects?

Medically reviewed by Asia, RN, BSN

Written by Justin Alcalde, AHA and American Red Cross instructor, CPR West Covina

Price and class details checked October 19, 2026.

Yes, Narcan expires: replace it before the date on the box. In someone who is physically dependent on opioids it can bring on sudden withdrawal, and the Drug Facts label warns of shaking, sweating, nausea or feeling angry on waking, which it says is to be expected. Otherwise, CDC and SAMHSA say naloxone does not harm someone who is not having an opioid overdose. It works on fentanyl, and FDA approved Narcan 4 mg nasal spray for sale without a prescription on March 29, 2023.

If you have more questions, the SOS First Aid app has an AI assistant you can ask about compression rates, AED use, drug dosing and more, with answers based on the AHA 2025 guidelines.

Side effects

Naloxone works by blocking the effects of opioids. In a person who is physically dependent on opioids, that can set off withdrawal quickly. The Narcan Drug Facts label warns that some people may have shaking, sweating, nausea or feel angry when they wake up, and says this is to be expected.

CDC FDA label

Who	What the sources list
People physically dependent on opioids	Withdrawal: body aches, diarrhea, fast heartbeat, fever, runny nose, sneezing, goose bumps, sweating, yawning, nausea or vomiting, nervousness, restlessness or irritability, shivering or trembling, stomach cramps, weakness and higher blood pressure (FDA label). CDC lists fever, anxiety, irritability, rapid heart rate, sweating, nausea, vomiting and tremors.
Healthy adults in a study	In a study of 30 healthy adult volunteers, the most common reactions were higher blood pressure, constipation, toothache, muscle spasms, muscle and bone pain, headache, dry skin, and a dry, swollen, stuffy, inflamed or sore nose (FDA prescribing information).
Newborns	In babies under 4 weeks old who have been receiving opioids regularly, sudden withdrawal may be life threatening if it is not treated the right way. Signs include seizures, crying more than usual and increased reflexes (FDA label).
Rare, serious reactions	The prescribing information lists rare heart and lung problems after naloxone, reported mostly after surgery in patients who had heart disease or took certain other medicines.

FDA label CDC

SAMHSA says withdrawal symptoms are uncomfortable and can be quite miserable, but are generally not life threatening.

SAMHSA

Does Narcan expire?

Yes. Each box has an expiration date, and the Narcan label says to replace it before that date. FDA says the shelf life of Narcan 4 mg nasal spray was extended from 2 years to 3 years in August 2020, and from 3 years to 4 years for products made after its January 17, 2024 announcement. Boxes made before then keep the date printed on them, and FDA advises everyone to go by the expiration date on each package.

FDA label FDA

What to do with expired Narcan

Replace it.
Get a new one before the date passes. Our guide to free or low cost Narcan near West Covina lists where.
FDA label
If an expired one is all you have in an emergency, use it.
SAMHSA says that in an overdose you should give any naloxone you have. It says studies show naloxone stays at a usable standard after years of storage, that it may become less effective over time, and that research shows it does not cause harm when used past its expiration date.
SAMHSA
Once you have a new one, dispose of the old one.
FDA says the best way to get rid of unused or expired medicine is a drug take back location, such as some pharmacies or police stations, or a prepaid mail back envelope. FDA also says some sprays have their own disposal instructions, so check the package or ask a pharmacist.
FDA

How to store it

The Drug Facts label says to store Narcan at room temperature or in the refrigerator, between 36°F and 77°F, not to freeze it, to avoid heat above 104°F, and to protect it from light. Do not use it if the blister is open or torn, or if the device looks damaged. The prescribing information says a frozen device will not spray: if it is frozen when you need it, do not wait for it to thaw, get emergency help right away. A device that has thawed at room temperature for 15 minutes can still be used.

FDA label

How fast it works and how long it lasts

Question	What the sources say
How fast does it work?	CDC says naloxone can restore normal breathing within 2 to 3 minutes. FDA says that when it is given soon after an overdose starts, the person will usually wake up within one to three minutes.
How long does it last?	SAMHSA says naloxone wears off after 30 to 90 minutes and overdose symptoms may return. The Narcan prescribing information says most opioids can last longer in the body than naloxone does.
How long should someone stay with them?	CDC says until emergency help arrives or for at least four hours. SAMHSA says at least 4 hours from the last dose.

CDC FDA SAMHSA FDA label

Does it work on fentanyl and other drugs?

Fentanyl: yes. CDC says naloxone can reverse an overdose from opioids including fentanyl, and SAMHSA says all opioid overdose reversal medications work on overdoses caused by fentanyl.
Buprenorphine: the Narcan label says reversal may be incomplete for some opioids, such as buprenorphine, and larger or repeat doses may be needed.
Other sedating drugs: SAMHSA says naloxone may be less effective when several drugs are involved, especially sedating ones such as alcohol or benzodiazepines. CDC says naloxone will not reverse xylazine but should still be given.
Stimulants: SAMHSA says no medication reverses a stimulant overdose the way naloxone reverses an opioid overdose. CDC says fentanyl is often mixed into cocaine and methamphetamine, and SAMHSA says to use naloxone even if you are not sure what someone took.

CDC SAMHSA FDA label

Can it hurt someone who is not overdosing?

CDC says naloxone will not harm someone who is overdosing on drugs other than opioids, so it is best to use it if you think someone is overdosing. FDA says that in an emergency other than an opioid overdose, such as a diabetic coma or cardiac arrest, naloxone will generally have no effect and cause no additional harm. What it can cause, in a person who is physically dependent on opioids, is the withdrawal described above. FDA also says naloxone is not addictive, has no abuse potential and is not a controlled substance.

CDC FDA

Is Narcan over the counter?

Yes. On March 29, 2023, FDA approved Narcan 4 mg nasal spray for use without a prescription, the first naloxone product approved that way, and FDA has since approved other over the counter naloxone nasal sprays. In California, CDPH says anyone can buy naloxone over the counter from a pharmacy or an online retailer, and the state's CalRx program sells naloxone nasal spray for $19 per twin pack. CDPH says injectable naloxone still needs a prescription or a standing order.

FDA CDPH CalRx

Where sources differ

Using expired naloxone. FDA advises going by the expiration date printed on each package, and the Narcan label says to replace it before that date. SAMHSA says that in an emergency any naloxone is better than none, and that expired naloxone may be less effective but does not cause harm. Replace it on time, and if an expired device is all you have during an overdose, SAMHSA says to use it.

How serious withdrawal is. The Narcan prescribing information calls it severe opioid withdrawal and warns it can be life threatening in newborns. SAMHSA says withdrawal is uncomfortable and can be quite miserable, but is generally not life threatening.

Extra doses and fentanyl. CDC says more than one dose may be required when stronger opioids like fentanyl are involved. SAMHSA says more than one dose may not be necessary for a known fentanyl overdose. See how to use Narcan for the label's dosing steps.

Learn it before you need it

Our SOS First Aid app sets out the BLS response to opioid emergencies as clear numbered steps, next to adult, child and infant CPR and choking relief, so you can study it ahead of time. In person, choose Heartsaver First Aid CPR AED ($98), Red Cross BLS ($69) for healthcare work, or the 45 minute Red Cross Naloxone Skill Boost for $75.

Questions people ask

Can you use Narcan after it expires?

Replace it before the date. If an expired device is the only naloxone you have during an overdose, SAMHSA says to use it: any naloxone is better than none, and research shows it does not cause harm past its date, though it may be less effective.

Is Narcan addictive?

No. FDA says naloxone is not addictive, has no abuse potential and is not a controlled substance.

Can Narcan be given to a baby?

FDA says naloxone can be used for a suspected overdose in people of all ages, including infants. The Narcan label warns that in babies under 4 weeks old who have been receiving opioids regularly, sudden withdrawal may be life threatening if not treated, so call 911 right away.

Can I take Narcan before using to prevent an overdose?

No. CDC says naloxone cannot be taken before using drugs to prevent an overdose. It has to be given by someone else during an overdose.

Do I need a prescription for Narcan in California?

No. CDPH says anyone can buy naloxone over the counter from a pharmacy or an online retailer. See where to get free or low cost Narcan near West Covina.

Sources

This page is education, not medical or legal advice. In an emergency, call 911 first.