Key takeaways

  • Common mild side effects of Narcan include nasal dryness or stuffiness, headache, and muscle or bone pain.
  • Severe opioid withdrawal symptoms can occur as a serious side effect of Narcan, but these are typically seen in people who have taken opioids before.
  • It’s safe to administer Narcan to someone if you suspect an opioid overdose, even if you’re unsure. It won’t have negative effects on people who do not have opioids in their system.

Narcan (naloxone) is an over-the-counter (OTC) nasal spray that treats opioid overdose in adults and children. It can be purchased from a pharmacy without a prescription.

An opioid overdose occurs when someone accidentally or intentionally takes more opioids than their body can safely process. (Opioids are very strong pain medications, such as oxycodone or morphine.) Opioid overdose is a medical emergency that causes slow, weak breathing and loss of consciousness. This can be fatal if not treated.

Narcan works by temporarily reversing the effects of an opioid overdose. If you experience an opioid overdose, you won’t be able to give Narcan to yourself. It’s meant to be given by someone else.

It’s important to note that Narcan is not a substitute for medical treatment. After giving Narcan to someone, call 911 or your local emergency number right away, even if the person wakes up. Narcan works quickly, but its effects may wear off before the opioids are out of the body. This means symptoms like slow breathing can come back, so it’s important to get emergency medical help even if the person wakes up.

Keep reading to learn about the common, mild, and serious side effects Narcan can cause.

Narcan can cause certain side effects, some more common than others. These side effects may be temporary, lasting a few hours. Talk with your medical emergency team or doctor if side effects do not go away, get worse, or become too difficult to tolerate.

Examples of side effects most commonly reported with Narcan include:

To learn more about these side effects, see the “Side effects explained” section.

Mild side effects that have been reported with Narcan include:

  • increased blood pressure
  • muscle spasms
  • toothache
  • dry skin
  • mild opioid withdrawal symptoms in people who are physically dependent on opioids*
  • stuffy nose*
  • dryness or pain in the nose*
  • headache*
  • pain in the muscles or bones*

It’s important to note that, except for dryness or pain in the nose, the above side effects would only occur in someone who’s taken opioids before receiving Narcan. (Dryness or pain in the nose can occur in anyone receiving Narcan because the drug is given through the nose.)

In most cases, mild side effects should be temporary. And some may be easily managed, too. But if you have any symptoms that are ongoing or that bother you, talk with your doctor or pharmacist.

Narcan may cause mild side effects other than the ones listed above. To learn more, see Narcan’s prescribing information.

* To learn more about this side effect, see the “Side effects explained” section.

Some people may experience serious side effects after using Narcan.

A serious side effect that has been reported with Narcan is severe opioid withdrawal symptoms in people who are physically dependent on opioids. This side effect would only occur in someone who’s used opioids before receiving Narcan. To learn more, see the “Side effects explained” section.

If you develop serious side effects after receiving Narcan, call your doctor right away. If the side effects seem life threatening or if you think you’re having a medical emergency, immediately call 911 or your local emergency number.

Note: After the Food and Drug Administration (FDA) approves a drug, it tracks and reviews side effects of the medication. Sharing your experience helps make medication safer for everyone by giving doctors and researchers more information about how the drug works in real life. If you develop a side effect while receiving Narcan and want to tell the FDA about it, visit MedWatch or call 800-FDA-1088.

Allergic reaction

Like most drugs, Narcan can cause an allergic reaction in some people. However, it’s not clear whether this side effect occurred in studies of the drug.

Symptoms of an allergic reaction can be mild or serious and may include:

  • skin rash
  • itchiness
  • flushing (temporary warmth, redness, or deepening of skin color)
  • swelling under your skin, typically in your eyelids, lips, hands, or feet
  • swelling of your mouth, tongue, or throat, which can make it hard to breathe

Serious allergic reactions, such as swelling or trouble breathing, could be life threatening and require immediate medical care.

What might help

If you’ve given someone Narcan, call 911 or your local emergency number right away. After treating the person’s overdose, the emergency medical team can treat an allergic reaction if needed.

If your doctor confirms you had an allergic reaction to Narcan, they’ll decide if you can be given this drug in the future.

Below you can find answers to some frequently asked questions about Narcan’s side effects.

Does Narcan cause any long-term side effects?

No, Narcan is not known to cause any long-term side effects. It’s a quick-acting medication for opioid overdose, and side effects from Narcan typically go away within a couple of hours.

If you have questions about how long potential side effects from this drug may last, talk with your doctor or pharmacist.

What effect does Narcan have on someone who doesn’t need it?

Narcan won’t have any effect on someone who doesn’t need it (someone who does not have opioids in their body). So it’s safe to give someone Narcan if you think they may have overdosed on opioids, but aren’t sure.

If you have questions about who to give Narcan to, talk with a doctor or pharmacist.

How long does Narcan stay in your system?

Narcan stays in your system for about 2 hours. If you have questions about how your body eliminates Narcan, talk with your doctor or pharmacist.

The possible side effects of Narcan in children who have ingested opioids are similar to those seen in adults. However, Narcan may cause more severe opioid withdrawal symptoms in newborns than in older children or adults given the medication. They can be life threatening for newborns if they’re not treated right away by medical professionals.

Opioid withdrawal symptoms in newborns can include:

  • seizures
  • crying more than usual
  • increased reflexes, which may cause twitching or shakiness
  • very fast breathing
  • vomiting

If a newborn ingests Narcan, call 911 or your local emergency number right away. The emergency medical team will give the newborn the appropriate treatment to help them recover from opioid withdrawal symptoms. The child will then need to be monitored in the hospital for at least 24 hours after receiving Narcan.

To learn about opioid withdrawal symptoms that both adults and children of all ages can experience, see the “Side effects explained” section.

Below, you can learn more about some of the side effects Narcan may cause.

It’s important to note that although Narcan may cause side effects in some people, an opioid overdose can be fatal. Using Narcan can save someone’s life. You shouldn’t delay giving Narcan to treat an opioid overdose because of concerns about side effects.

And keep in mind that the active drug in Narcan doesn’t affect people who haven’t used opioids. So you can safely give Narcan to someone if you think they may have overdosed on opioids but aren’t sure.

Opioid withdrawal symptoms

Sudden opioid withdrawal symptoms can occur right after someone is treated with Narcan. This is because Narcan blocks and reverses the effects of opioids in the body.

Narcan commonly causes opioid withdrawal symptoms in people who are physically dependent on opioids. With physical dependence, your body needs a substance to function like usual.

Physical dependence can develop in someone who’s been taking opioids regularly for a long time. In this situation, if opioids are stopped or their effects are blocked by Narcan, it causes withdrawal symptoms.

Opioid withdrawal symptoms caused by Narcan can be mild or severe. They can include:

  • nausea and vomiting
  • diarrhea
  • body aches or cramps
  • shivering or goosebumps
  • runny nose or sneezing
  • fever or sweating
  • increased blood pressure
  • fast heart rate
  • feeling irritable or nervous
  • aggressive behavior

Serious heart problems, such as heart rhythm problems or heart attack, can also be opioid withdrawal symptoms. These have typically occurred in people with heart disease who received Narcan after an operation or procedure. They’ve also occurred in people who receive Narcan and are also taking other drugs that can affect the heart. If you’re concerned about heart problems with Narcan, talk with your doctor or pharmacist.

What might help

If you’ve given someone Narcan, call 911 or your local emergency number right away. When the emergency medical team arrives, they can give the person treatment to help them recover from opioid withdrawal symptoms if needed.

Opioid withdrawal symptoms can sometimes lead someone who is physically dependent on opioids to take more opioids. This can be very dangerous and lead to another overdose. After an opioid overdose has been treated, it’s also important that the person receives advice about treatments for opioid use disorder.

Nasal dryness, pain, or stuffy nose

Receiving Narcan may cause dryness or pain in the nose. It may also cause a stuffy nose. These side effects have been reported in people using the drug, although it isn’t clear whether they’re common or how often they happen.

What might help

Nose-related side effects will typically wear off within a few hours after receiving Narcan. However, if these side effects are bothersome to you, talk with a healthcare professional. They can suggest ways to help relieve these side effects.

Headache or pain in your muscles or bones

Someone who’s received Narcan may experience pain, such as a headache or pain in their muscles or bones. These types of pain have been reported in people who received Narcan, although it isn’t clear how often or whether they’re common.

Narcan blocks and reverses all the effects of opioids, including the pain relief these drugs provide. Therefore, any pain someone had before using opioids may quickly come back after they’re given Narcan.

What might help

If you’ve given someone Narcan, call 911 or your local emergency number right away. After the emergency medical team has treated the person’s overdose, they can treat their pain if needed.

The person who received Narcan shouldn’t take opioids for pain after receiving Narcan. This can cause them to overdose again.

If you experience an opioid overdose, your doctor can determine what the best treatment plan is for you.

Narcan may not be right for you if you have certain medical conditions or other factors that affect your health. Talk with your doctor or pharmacist about your health history before you take Narcan. Be sure to talk with your doctor if any of the following apply to you:

Alcohol and Narcan

Narcan can be used to treat an opioid overdose in someone who has also consumed alcohol. Alcohol doesn’t affect the way Narcan works.

However, Narcan won’t reverse the effects of alcohol. If you or someone else has overdosed on alcohol, call 911 or your local emergency number right away.

Using Narcan in someone who is pregnant or breastfeeding

It’s not known whether Narcan is safe to use during pregnancy. Studies in animals didn’t find harmful effects when naloxone (the active ingredient in Narcan) was given to pregnant animals. However, animal studies don’t always reflect what will happen in humans.

If given to someone who’s pregnant, Narcan could cause side effects, such as opioid withdrawal symptoms in a fetus. However, an opioid overdose can result in the death of the pregnant person or pregnancy loss. Therefore, the American College of Obstetricians and Gynecologists recommends Narcan as an option for treating opioid overdose in someone who’s pregnant.

It’s not known if Narcan passes into breast milk or if it can cause side effects in a child who is breastfed. But because an opioid overdose can be fatal, Narcan can be used to save the life of someone who is breastfeeding if they’ve overdosed on opioids.

If you’ve received Narcan while pregnant or breastfeeding, contact your doctor right away. They can determine if you or your child needs any extra monitoring or treatment.

If you have any questions about the safety of using Narcan in someone who’s pregnant or breastfeeding, talk with a doctor a pharmacist.

Disclaimer: Healthline has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.