What is naloxone?

Naloxone is an FDA approved medicine used to quickly reverse an opioid overdose. Naloxone is a opioid antagonist that works by attaching to opioid receptors and therefore reverses and blocks the effects of other opioids.

Naloxone should be used as soon as possible to treat a known or suspected opioid overdose emergency if there are signs of slowed breathing, severe sleepiness or the person is not able to respond (loss of consciousness). Once naloxone has been given the patient must receive emergency medical care straight away, even if they wake up.

Naloxone is not a controlled substance, according to the US Drug Enforcement Administration (DEA).

Naloxone is available as a nasal spray (Narcan 4mg, Rezenopy 10 mg, Kloxxado 8mg) or an injection (Zimhi 5 mg/0.5 mL).

Narcan nasal spray became approved by the FDA on March 29, 2023 as is an over-the-counter (OTC) medicine that is available without a prescription. Other naloxone products are still prescription medicines, but in many states, these products are available from a pharmacist without a prescription from your doctor, under state Naloxone Access Laws or alternate arrangements.

Opioids are sometimes called a narcotic. Examples of opioids are buprenorphine, codeine, fentanyl, oxycodone (Oxycontin), heroin, hydrocodone (Vicodin, Lortab), hydromorphone, meperidine, morphine, methadone, oxymorphone, and tramadol.

What is Naloxone used for?

Naloxone is used to treat a known or suspected opioid overdose emergency in children or adults. Signs of an opioid overdose may include:

• slowed breathing, or no breathing;
• very small or pinpoint pupils in the eyes;
• slow heartbeats; or
• extreme drowsiness, especially if you cannot wake the person from sleep.

Even if you are not sure an opioid overdose has occurred, if the person is not breathing or is unresponsive, give the naloxone right away and then seek emergency medical care.

Naloxone has different uses when used in multi-ingredient medications including buprenorphine with naloxone (Suboxone, Zubsolv, Bunavail) which is used to treat opioid addiction, and naloxone with oxycodone (Targiniq ER) which is used for pain.

Warnings

In an emergency situation it may not be possible before you are treated to tell your caregivers about your health conditions or if you are pregnant or breast feeding. Make sure any doctor caring for you afterward knows that you have received this medicine.
A person caring for you can give the naloxone if you stop breathing or don’t wake up. Make sure any person caring for you knows where you keep this medicine and how to use it.

Your caregiver must get emergency help after giving you this medicine. You may need another injection every 2 to 3 minutes until emergency help arrives.

Drinking alcohol can increase certain side effects of naloxone.

Naloxone may impair your thinking or reactions. Be careful if you drive or do anything that requires you to be alert.

If you are using any narcotic pain medication, the pain-relieving effects of the narcotic will be reversed while you are also receiving this medicine.

Before taking this medicine

You should not be treated with this medicine if you are allergic to naloxone or any inactive ingredients in the injection or nasal spray.

If possible, before you receive naloxone, tell your doctor if:

• you have heart problems; or
• you are pregnant or breastfeeding.

Using naloxone while you are pregnant may cause opioid withdrawal effects in your unborn baby. However, having an opioid overdose can be fatal to both mother and baby. It is much more important to treat an overdose in the mother. You must get emergency medical help after using this medicine. Be sure all emergency medical caregivers know that you are pregnant.

If you use opioid medicine while you are pregnant, your baby could become dependent on the drug. This can cause life-threatening withdrawal symptoms in the baby after it is born. Babies born dependent on opioids may need medical treatment for several weeks.

In an emergency, you may not be able to tell caregivers if you are pregnant or breastfeeding. Make sure any doctor caring for your pregnancy or your baby knows you received this medicine.

How is naloxone given?

Use naloxone exactly as prescribed by your doctor. Follow all directions on your prescription label and read all medication guides or instruction sheets.

If you are a caregiver or family member, read all instructions when you first get this medicine so you will know how to use it in an emergency. Ask your doctor or pharmacist if you have any questions.

Naloxone injection instructions

• Each naloxone injection contains only one dose of medicine and cannot be reused.
• Place the patient on their back and when you are ready to inject, pull off cap to expose needle.
• Do not put your finger on top of the device. For a child under the age of 1 years old, pinch the thigh muscle while administering the dose.
• Hold naloxone injection by finger grips only and slowly insert the needle into the thigh.
• After needle is in thigh you should push the plunger all the way down until it clicks and then hold for 2 seconds.
• Right after the injection, using one hand with fingers behind the needle, slide the safety guard over the needle. You should not use two hands to activate the safety guard. Put the used syringe into the blue case and close the case.

Naloxone nasal spray instructions

• Each naloxone nasal spray contains only one dose of medicine and cannot be reused.
• Lay the person on their back. Support their neck with your hand and allow the head to tilt back before giving the nasal spray.
• Remove the nasal spray from the box. Peel back the tab to open the nasal spray blister.
• Hold the nasal spray with your thumb on the bottom of the plunger and your first and middle fingers on either side of the nozzle. Do not apply any pressure until you are ready to give the dose.
• Gently insert the tip of the nozzle into one nostril until your fingers on either side of the nozzle are against the bottom of the person’s nose.
• Press the plunger firmly to give the dose of nasal spray, then after giving the dose, remove the nasal spray from the nostril.

After giving a dose of naloxone

• You need to get emergency medical help as soon as you have been given the injection or nasal spray.
• Tell the healthcare provider that you have given a dose of this medicine.
• Turn the patient on their side to place them in the recovery position after giving them the naloxone.
• If symptoms continue or return after using this medicine, an additional dose may be needed.
• If you are giving additional doses, use a new nasal spray or new injection every 2 to 3 minutes and continue to watch the person closely until emergency help has arrived closely.
• You may need to perform CPR (cardiopulmonary resuscitation) on the person while you are waiting for emergency help to arrive.
• Using naloxone does not take the place of emergency medical care.

Dosing information

Usual Adult Dose for Opioid Overdose

Initial dose:

• 0.4 mg to 2 mg IV; alternatively, may give IM or subcutaneously
• If the desired response is not obtained, doses should be repeated at 2 to 3 minute intervals
• If no response is observed with a total dose of 10 mg, the diagnosis of opioid-induced or partial opioid-induced toxicity should be questioned

Auto-injector:

• Administer 0.4 mg (1 actuation) IM or subcutaneously into the anterolateral aspect of the thigh (through clothing if necessary)
• If the desired response is not achieved, a second dose may be administered after 2 or 3 minutes; additional doses may be administered every 2 to 3 minutes until emergency medical assistance arrives

Nasal Spray:

• Administer 1 spray intranasally into 1 nostril
• If the desired response is not achieved after 2 or 3 minutes, give a second dose intranasally into alternate nostril; additional doses may be administered every 2 to 3 minutes in alternating nostrils until emergency medical assistance arrives

Comments:

• IV route is recommended in emergency situations since it has the most rapid onset of action.
• The duration of action of some opioids exceed that of this drug, therefore, repeat doses may be needed; the need for repeat doses will depend on the amount, type, and route of administration of the opioid being antagonized.

Usual Adult Dose for Reversal of Opioid Sedation

Initial dose:

• 0.1 to 0.2 mg IV at 2 to 3 minute intervals to the desired degree of reversal
• Supplemental doses administered IM have been shown to produce a longer-lasting effect

Intravenous Infusion:

• A concentration of 0.004 mg/mL may be administered by IV infusion; titrate in accordance with patient’s response

Comments:

• For the partial reversal of opioid depression following the use of opioids during surgery, smaller doses of naloxone are usually sufficient; larger than necessary doses may result in significant reversal of analgesia and increases in blood pressure.

Usual Pediatric Dose for Opioid Overdose

Neonates:

• Initial dose: 0.01 mg/kg IV, IM, or subcutaneously; repeat dose every 2 to 3 minutes as needed

Children:

• Initial dose: 0.01 mg/kg IV; if the desired response is not obtained, may give 0.1 mg/kg IV
• If the IV route is not available may give IM or subcutaneously in divided doses.
• Administer 0.4 mg (1 actuation) IM or subcutaneously into the anterolateral aspect of the thigh (through clothing if necessary); if the desired response is not achieved, a second dose may be administered after 2 or 3 minutes; additional doses may be administered every 2 to 3 minutes until emergency medical assistance arrives
• Under 1 year of age: Thigh muscle should be pinched while administering injection

Comments:

• Neonatal opioid withdrawal syndrome may be life-threatening and should be treated according to protocols developed by neonatology experts.
• To avoid precipitating opioid withdrawal symptoms, consider use of a naloxone product that can be dosed according to weight and titrated to effect.
• The duration of action of some opioids will exceed that of this drug, therefore, repeat doses may be needed; the need for repeat doses will depend on the amount, type, and route of administration of the opioid being antagonized.
• Patients should remain under continued surveillance; if a patients responds and relapses back into respiratory depression, additional doses should be given.
• Additional supportive and/or resuscitative measures may be helpful while awaiting emergency medical assistance.

Usual Pediatric Dose for Reversal of Opioid Sedation

Neonates:

• Initial dose: 0.01 mg/kg IV, IM or subcutaneously at 2 to 3 minute intervals to the desired degree of reversal

Children:

• 0.005 mg to 0.01 mg IV at 2 to 3 minute intervals to the desired degree of reversal

Intravenous Infusion:

• A concentration of 0.004 mg/mL may be administered by IV infusion; titrate in accordance with patient’s response

Comments:

• For the partial reversal of opioid depression following the use of opioids during surgery, smaller doses of naloxone are usually sufficient; larger than necessary doses may result in significant reversal of analgesia and increases in blood pressure.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line .

What should I avoid while using naloxone?

Avoid leaving a person alone after giving him or her a naloxone dose. An overdose can impair a person’s thinking or reactions.

Naloxone side effects

Get emergency medical help if you have signs of an allergic reaction to naloxone: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Because naloxone reverses opioid effects, the administration may cause sudden withdrawal symptoms such as:

• nausea, vomiting, diarrhea, stomach pain;
• fever, sweating, body aches, weakness;
• tremors or shivering, fast heart rate, pounding heartbeats, increased blood pressure;
• goose bumps, shivering;
• runny nose, yawning; or
• feeling nervous, restless, or irritable.

Sudden withdrawal symptoms in a baby younger than 4 weeks old may be life-threatening if not treated the right way. Symptoms include crying, stiffness, overactive reflexes, and seizures. Call your doctor or get emergency medical help if you are unsure how to properly give this medicine to a baby.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA .

What other drugs will affect naloxone?

Other drugs may interact with naloxone, including prescription and over-the-counter medicines, vitamins, and herbal products. Tell your doctor about all your current medicines and any medicine you start or stop using.

Ingredients

Kloxxado nasal spray
Active ingredient: naloxone hydrochloride
Inactive ingredients: dehydrated alcohol (20% (w/w)), edetate disodium dihydrate, propylene glycol, purified water, and sodium hydroxide and hydrochloric acid to adjust pH. The pH range is from 4.0 to 5.5.

Narcan nasal spray
Active ingredient: naloxone hydrochloride
nactive ingredients: benzalkonium chloride (preservative), disodium ethylenediaminetetraacetate (stabilizer), sodium chloride, hydrochloric acid to adjust pH and sterile water.

Narcan is not made with natural rubber latex.

Rezenopy nasal spray
Active ingredient: naloxone hydrochloride
Inactive ingredients: glycerin, trisodium citrate dihydrate, hydrochloric acid, and sodium hydroxide to adjust pH, and purified water.

Rezenopy nasal spray is not made with natural rubber latex.

Zimhi injection
Active ingredient: naloxone hydrochloride
Inactive ingredients: sodium chloride, hydrochloric acid to adjust pH, and water for injection.
Zimhi is not made with natural rubber latex.

Storage

Kloxxado

• Store at room temperature 68ºF to 77ºF (20°C to 25°C).
• Do not freeze. Do not expose to temperatures below 41°F (5°C) or above 104°F (40°C).
• Keep Kloxxado nasal spray in its box until ready to use. Protect from light.

Narcan

• Store below 77°F (25°C) with excursions permitted up to 104°F (40°C).
• Do not freeze Narcan or expose it to excessive heat above 104°F (40°C).
• Keep Narcan in its box until ready to use. Protect from light.
• Replace Narcan before the expiration date on the box.
• Keep this medicine and all medicines out of the reach of children.

Rezenopy

• Store Rezenopy nasal spray either in the refrigerator or at room temperature between 2°C to 25°C (36°F to 77°F).
• Do not freeze. Do not expose to excessive heat above 40°C (104°F). Keep it in its box until ready to use. Protect from light.
• Replace the nasal spray before the expiration date on the box.
• Keep out of the reach of children.

Zimhi

• Store between 68°F to 77°F (20°C to 25°C). Do not expose to extreme cold or heat. For example, do not store in your vehicle’s glove box and do not store in the refrigerator or freezer.
• Store the Zimhi syringe in its closed plastic case to protect from light.
• Check Your Stored Zimhi Often – The solution should be clear when viewed through the window on the device. If the solution is discolored (yellowish or brown color), cloudy or contains particles, replace Zimhi with a new one.

What is naltrexone?

Naltrexone is a prescription medication used to treat alcohol use disorder (AUD) and opioid use disorder (OUD) to reduce cravings and help control physiological dependence. Naltrexone works by blocking the effects of alcohol and opioid medications, preventing the euphoria and intoxication (the “buzz”) these substances cause, and it also helps reduce the urge or cravings to use alcohol or opioids. 

For alcohol use disorder, naltrexone helps people lessen their drinking behaviors and avoid relapses, and over time, cravings for alcohol will decrease. For opioid use disorder, naltrexone prevents euphoria and reduces physiological dependence on opioids such as heroin, morphine, and codeine to help people avoid relapses and remain opioid-free.

Low dose naltrexone (LDN) is used for conditions such as fibromyalgia, Crohn’s disease, multiple sclerosis, and complex regional pain syndrome, as it may work as an anti-inflammatory agent in the central nervous system. Use of low dose naltrexone is an off-label use and is not FDA-approved for these conditions.

Naltrexone is available as an intramuscular injection (Vivitrol) and as oral tablets. The branded tablets (Revia, Depade) have been discontinued, but generic versions are available.

Naltrexone is an opioid antagonist. Its mechanism of action (MOA) is blocking the mu opioid receptor. This medicine also modifies how the hypothalamus, pituitary gland, and adrenal gland (hypothalamic-pituitary-adrenal axis, HPA axis) interact to suppress the amount of alcohol consumed.

What is naltrexone used for?

Naltrexone to is a prescription medication that is FDA-approved: 

• to treat alcohol dependence
• for the blockade of the effects of exogenously administered opioids. To prevent relapse to opioid dependence after opioid detoxification.

You should stop drinking alcohol or using opioids before starting this medicine. To avoid precipitated opioid withdrawal, it is recommended you should have an opioid-free interval of a minimum of 7 to 10 days if previously dependent on short-acting opioids. Patients transitioning from buprenorphine or methadone may be vulnerable to precipitation of withdrawal symptoms for as long as two weeks.

Low dose naltrexone (LDN) use is not FDA approved.

This medicine should not be used in children and adolescents under 18 years.

Naltrexone side effects

Common naltrexone side effects

Common side effects of naltrexone may include nausea, vomiting, loss of appetite, joint pain, muscle cramps, headache, dizziness, drowsiness, sleep problems (insomnia), tooth pain or cold symptoms such as stuffy nose, sneezing, sore throat, feeling, anxious or nervous.

Serious naltrexone side effects

Get emergency medical help if you have signs of an allergic reaction: hives, difficulty breathing, swelling of your face, lips, tongue, or throat.

Using opioid medicine while you are receiving this medicine could stimulate opioid withdrawal symptoms. Common withdrawal symptoms are craving for opioids, sweating, yawning, fever, stomach pain, vomiting, diarrhea, watery eyes, runny or stuffy nose, tingling, goose bumps, body aches, shaking, muscle twitching, trouble sleeping, feeling anxious, depressed, fearful, restless or uneasy.

Naltrexone may cause other serious side effects. Call your doctor at once if you have:

• weak or shallow breathing;
• cough that does not go away;
• new or worsening cough, wheezing, trouble breathing;
• severe nausea, vomiting, or diarrhea;
• severe pain, swelling, blistering, skin changes, a dark scab, or a hard lump where the medicine was injected;
• liver problems – stomach pain (upper right side), dark urine, tiredness, vomiting, loss of appetite, clay-colored stools, jaundice (yellowing of the skin or eyes); or
• symptoms of depression – unusual mood or behavior changes, loss of interest in things you once enjoyed, crying, new sleep problems, thoughts about hurting yourself.

You may feel nauseated the first time you receive an injection of this medicine. You may also have a headache, tiredness, joint and muscle pain, loss of appetite, and vomiting.

Tell your healthcare provider if you have any side effect that bothers you, or that does not go away.

This is not a complete list of side effects, and others may occur. Call your doctor for medical advice about side effects. You may report side effects to the FDA.

Before taking this medicine

You should not be treated with  this medicine if you are allergic to it, or if:

• you are currently addicted to opioids;
• you are having withdrawal symptoms from opioid addiction;
• you are using any opioid pain medicine (including fentanyl, Vicodin, OxyContin, and many others);
• you have failed the naloxone challenge test or have a positive urine screen for opioids or
• you have used any opioid medicine such as methadone, buprenorphine, tramadol, and other opioids within 7 to 14 days.

Also, tell your doctor if you have or have ever had:

• bleeding problems such as hemophilia; or
• liver or kidney disease.
• have alcohol dependence and use opioids.

Pregnancy 

Tell your doctor if you are pregnant or plan to become pregnant. It is not known if this medicine will harm your unborn baby. This medication should only be used during pregnancy if the potential benefits justify the potential risk to the fetus.

Breastfeeding

Tell your doctor if you are breastfeeding. It is not known if this medicine passes into your milk when it is administered by IM injection, and it is not known if it can harm your baby. Naltrexone from tablets passes into breast milk. Talk to your healthcare provider about whether you will breastfeed or take this medication. You should not do both.

Important information

This medicine can cause serious side effects, including:

Risk of opioid overdose.

You can accidentally overdose in two ways.

• Naltrexone blocks the effects of opioid drugs. Do not take large amounts of opioids, including opioid-containing medicines, such as heroin or prescription pain pills, to try to overcome the opioid-blocking effects of this medication. This can lead to serious injury, coma, or death.
• After you receive a dose of the extended-release injection form of this medication, its blocking effect slowly decreases and completely goes away over time. If you have used opioid street drugs or opioid-containing medicines in the past, using opioids in amounts that you used before treatment can lead to overdose and death. You may also be more sensitive to the effects of lower amounts of opioids:
  • after you have gone through detoxification
  • when your next injection is due
  • if you miss a dose of this medication
  • after you stop treatment with this medicine

It is important that you tell your family and the people closest to you of this increased sensitivity to opioids and the risk of overdose.

You or someone close to you should call 911 or get emergency medical help right away if you:

• have trouble breathing
• become very drowsy with slowed breathing
• have slow, shallow breathing (little chest movement with breathing)
• feel faint, very dizzy, confused, or have unusual symptoms

Talk to your healthcare provider about naloxone, a medicine that is available to patients for the emergency treatment of an opioid overdose.

Call 911 or get emergency medical help right away in all cases of known or suspected opioid overdose, even if naloxone is administered.

Severe reactions at the site of the naltrexone injection (injection site reactions).

Some people have had severe injection site reactions, including tissue death (necrosis), while receiving injections. Some of these injection site reactions have required surgery. This medication must be injected by a healthcare provider. Call your healthcare provider right away if you notice any of the following at any of your injection sites:

• intense pain
• the area feels hard
• large area of swelling
• lumps
• blisters
• an open wound
• a dark scab

Tell your healthcare provider about any reaction at an injection site that concerns you, gets worse over time, or does not get better by two weeks after the injection.

Sudden opioid withdrawal

Anyone who receives naltrexone must not use any type of opioid (must be opioid-free), including street drugs, prescription pain medicines, cough, cold, or diarrhea medicines that contain opioids, or opioid dependence treatments, buprenorphine or methadone, for at least 7 to 14 days before starting this medication. Using opioids in the 7 to 14 days before you start receiving treatment may cause you to suddenly have symptoms of opioid withdrawal when you receive treatment. Sudden opioid withdrawal can be severe, and you may need to go to the hospital.

You must be opioid-free before receiving naltrexone unless your healthcare provider decides that you don’t need to go through detox first. Instead, your doctor may decide to give this medication in a medical facility that can treat you for sudden opioid withdrawal.

Liver damage or hepatitis.

This medicine can cause liver damage or hepatitis.

Tell your healthcare provider if you have any of the following symptoms of liver problems during treatment with this medication:

• stomach area pain lasting more than a few days
• dark urine
• yellowing of the whites of your eyes
• tiredness

Your healthcare provider may need to stop treating you with this medication if you get signs or symptoms of a serious liver problem.

You must inform every doctor who treats you that you are taking Naltrexone. Non-opiate based anesthetics should be used if you require an anesthetic in an emergency situation. If you have to use opiate-containing anesthetics, you may need higher doses than usual. You may also be more sensitive to the side-effects (breathing difficulties and circulatory problems).

How should I use this medicine?

Using opioids in the 7 to 14 days before you start receiving naltrexone may cause you to suddenly have symptoms of opioid withdrawal. To avoid this, you should not use short-acting opioids for a minimum of 7-10 days before starting treatment with this medicine.

How to take naltrexone tablets

• Always take this medicine exactly as your doctor has told you. Check with your doctor or pharmacist if you are not sure.
• Take this medication once a day by mouth as your doctor tells you to.
• The amount of time you should take this medication will be decided by your doctor. In certain cases, a longer period of treatment may be beneficial.

How you will receive a naltrexone injection

• Your injection will be given by a healthcare provider every 4 weeks or once a month.
• Get your injection regularly to get the most benefit. Inform your doctor when you received the last injection.
• Do not attempt to inject yourself with this medication. Serious reactions, some that may require hospitalization, might happen.
• This medicine is given as an injection into a muscle in your buttocks using a special needle that comes with it.
• You may notice pain, redness, itching, bruising, swelling, or a hard lump where the medicine was injected. Call your doctor if you have this type of reaction, especially if it gets worse or does not clear up within 2 weeks.
• After this medication is injected, it lasts for a month, and it cannot be removed from the body.

General dosing information

Naltrexone is only part of a complete treatment program that may also include additional forms of counseling and/or monitoring. Follow your doctor’s instructions very carefully.

After taking this medicine, your body will be more sensitive to opioids. If you use an opioid medicine in the future, you will need to use less than before the naltrexone treatment. Using the same amount of opioids you used before could lead to overdose or death.

Whenever you need medical treatment, be sure to tell the treating healthcare provider that you are receiving this medication and mention when you got your last dose. This is important because naltrexone can also block the effects of opioid-containing medicines that might be prescribed for you for pain, cough or colds, or diarrhea.

Carry written information with you at all times to alert healthcare providers that you are taking this medication so that they can treat you properly in an emergency. Ask your healthcare provider how you can get a wallet card to carry with you.

Naltrexone Dosing information

Naltrexone dose tablets:

• Alcohol dependence: The recommended dose is 1 tablet (50 mg) once a day.
• Opioid use disorder: Start with half a tablet (25 mg), and if no withdrawal signs occur, increase the dose to 1 tablet (50 mg) a day from then on.

Naltrexone dose intramuscular injection:

• Alcohol dependence and opioid use disorder: The recommended dose is naltrexone 380 mg delivered intramuscularly (IM) as a gluteal injection every 4 weeks or once a month, alternating buttocks for each subsequent.

Comments:

• There is no data specifically addressing switching from buprenorphine or methadone to naltrexone; however, some patients have reported severe manifestations of precipitated
• Patients switching from buprenorphine or methadone may be vulnerable to precipitated withdrawal for up to 2 weeks.
• Be prepared to manage withdrawal symptomatically with non-opioid medications.
• This drug is of value only as a part of a comprehensive management plan that includes measures to ensure the patient takes this medication.

For more detailed dosing information, click on the link below.

What happens if I miss a dose?

If you forget to take your tablet, take it as soon as possible. However, if it is almost time for your next dose, skip the missed dose and go back to your regular dosing schedule. Do not take a double dose to make up for a forgotten dose.

If you miss your appointment for your naltrexone injection, schedule another appointment as soon as possible.

What happens if I overdose?

If you take more naltrexone tablets than you should, tell your Doctor or Pharmacist or contact your nearest hospital emergency department immediately.

What should I avoid while using this medicine?

Do not drive a car, operate machinery, or do other dangerous activities until you know how this medication affects you. This medicine may make you feel dizzy and sleepy.

What is Narcan?

Narcan (naloxone) nasal spray is an over-the-counter medicine used to treat an opioid overdose emergency, Narcan works by rapidly reversing the opioid’s effects. Naran should be given as soon as possible when an opioid overdose is suspected, and then the patient should also receive emergency medical care immediately, even if they wake up.

Narcan nasal spray became FDA-approved on March 29, 2023, as an over-the-counter (OTC) medicine without the need for a prescription, however, it is unknown when the OTC Narcan nasal spray product will be available. Until the OTC nasal spray becomes available, the nasal spray with the prescription label will still be available from a pharmacist without a prescription from your doctor under state Naloxone Access Laws or alternate arrangements.

Narcan nasal spray can be used for adults and children for known or suspected opioid overdose if there are signs of slowed breathing, severe sleepiness, or the person is not able to respond (loss of consciousness).

Narcan works to block the opioid effect as it is an opioid antagonist as it competes for the opiate receptors in the brain and other areas of the body to help reverse the dangerous effects of the opioid so that the patient’s breathing improves and they become more awake, and their blood pressure normalizes.

Examples of opioids are codeine, oxycodone (Oxycontin), heroin morphine, hydrocodone (Vicodin, Lortab), fentanyl, methadone, oxymorphone, meperidine, tramadol, buprenorphine, and hydromorphone.

Narcan was originally available as an njection, which has since been discontinued. The Narcan nasal spray is available as an over-the-counter medicine, so a prescription is NOT needed. 

Important information

Narcan is used to reverse the effects of opioid medicines temporarily, it will have no effect in people who are not taking opioid medicines. Always carry a nasal spray with you in case of an opioid overdose emergency.

Use Narcan as soon as possible if you or your caregiver think there are signs or symptoms of an opioid emergency, even if you are not sure because an opioid emergency can cause severe injury or death. Signs and symptoms of an opioid emergency may include:

• unusual sleepiness and you are not able to wake the person up with a loud voice or by rubbing firmly on the middle of their chest (sternum)
• breathing problems including slow or shallow breathing in a person who is difficult to wake up or who looks like they are not breathing
• the pupil (black circle in the center of the colored part of the eye) is very small, sometimes called “pinpoint pupils,” in someone difficult to awaken.

You should know where the nasal spray is stored and how to give the nasal spray before an opioid emergency happens. This is important if you have family members, caregivers, or other people who are at risk of opioid overdose and may need to have Narcan administered in an opioid emergency.

After giving the first dose of this medicine, you need to get emergency medical help right away, even if the person wakes up. Rescue breathing or CPR (cardiopulmonary resuscitation) may be given while waiting for emergency medical help

The signs and symptoms of an opioid emergency can return after this medicine is given. If this happens, give another dose after 2 to 3 minutes using a new nasal spray device and watch the person closely until emergency help is received.

Before taking this medicine

You should not be treated with Narcan if you are allergic to naloxone or any of the ingredients in this nasal spray. See below for a full list of Narcan ingredients.

If possible before you receive Narcan, tell your doctor if:

• you have heart problems; or
• you are pregnant or breastfeeding.

If you use opioid medicine during pregnancy, your baby could be born with life-threatening withdrawal symptoms, and may need medical treatment for several weeks.

Using Narcan while you are pregnant may also cause opioid withdrawal effects in your unborn baby. However, having an opioid overdose can be fatal to both mother and baby. It is much more important to treat an overdose in the mother. You must get emergency medical help after using this medicine. Be sure all emergency medical caregivers know that you are pregnant.

If you use opioid medicine while you are pregnant, your baby could become dependent on the drug. This can cause life-threatening withdrawal symptoms in the baby after it is born. Babies born dependent on opioids may need medical treatment for several weeks.

In an emergency, you may not be able to tell caregivers if you are pregnant or breastfeeding. Make sure any doctor caring for your pregnancy or your baby knows you received Narcan.

How should I use Narcan?

Use this medicine exactly as prescribed by your healthcare provider.

• Each nasal spray device contains only one dose of medicine and cannot be reused.
• Narcan is available in 2 mg and 4 mg strength. Your healthcare provider will prescribe the strength that is right for you.
• Remove the nasal spray device from the box. Peel back the tab with the circle to open the nasal spray.
• Do not prime Narcan nasal spray.
• Lay the person on their back with their neck supported with your hand and allow the head to tilt back before giving the nasal spray.
• Hold the nasal spray with your thumb on the bottom of the red plunger and your first and middle fingers on either side of the nozzle.
• Gently insert the tip of the nozzle into one nostril until your fingers on either side of the nozzle are against the bottom of the person’s nose.
• Press the red plunger firmly to administer the dose of Narcan.
• Remove the Narcan from the nostril after giving the dose.
• You must get emergency help immediately after giving this medicine.
• After giving this medicine, stay with the person and watch for continued signs of overdose. You may need to give another dose every 2 to 3 minutes until emergency help arrives. If another dose is needed, give Narcan in the other nostril from a new Narcan nasal spray.
• Do not assume that an overdose episode has ended if symptoms improve. You may need to perform CPR (cardiopulmonary resuscitation) on the person while you are waiting for emergency help to arrive.

Dosing information

Usual Adult and Pediatric Dose for Opioid Overdose:

Administer 1 spray intranasally into 1 nostril

If desired response is not achieved after 2 or 3 minutes, give a second dose from a new nasal spray device, intranasally into alternate nostrils; additional doses may be administered every 2 to 3 minutes in alternating nostrils until emergency medical assistance arrives.

Comments:

• IV route is recommended in emergency situations since it has the most rapid onset of action.
• The duration of action of some opioids exceed that of this drug, therefore, repeat doses may be needed; the need for repeat doses will depend on the amount, type, and route of administration of the opioid being antagonized.
• Patients should remain under continued surveillance; if a patients responds and relapses back into respiratory depression, additional doses should be given.
• Additional supportive and/or resuscitative measures may be helpful while awaiting emergency medical assistance.

What should I avoid while taking Narcan?

Avoid leaving a person alone after giving him or her a dose of this medicine. An overdose of naloxone can impair a person’s thinking or reactions.

Narcan side effects

Get emergency medical help if you have signs of an allergic reaction to Narcan: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Because Narcan reverses opioid effects, its use may cause sudden withdrawal symptoms such as:

• nausea, vomiting, diarrhea, stomach pain;
• fever, sweating, body aches, weakness;
• tremors or shivering, fast heart rate, pounding heartbeats, increased blood pressure;
• goose bumps, shivering;
• runny nose, yawning; or
• feeling nervous, restless, or irritable.

What is methylene blue?

Methylene blue is an oxidation-reduction agent used to treat methemoglobinemia, a condition where hemoglobin is oxidized, impairing its ability to carry oxygen. Methylene blue works by reducing the oxidized hemoglobin, converting it back to hemoglobin so that it can carry oxygen properly again. Methemoglobinemia can lead to symptoms like cyanosis, fatigue, and shortness of breath.

When used for methemoglobinemia, methylene blue is given as an injection by your healthcare provider in a hospital or clinic.

Methylene blue  FDA approval was granted on April 8, 2016, for treating methemoglobinemia under the brand name Provayblue.

This medicine does not reverse methemoglobinemia in patients with glucose-6-phosphate dehydrogenase (G-6-PD) deficiency, and it may induce or worsen hemolysis in these patients.

Methylene blue is also called methylthioninium chloride.

Methylene blue has also been used as a diagnostic dye, for malaria, shock, cystitis, urethritis, cyanide and carbon monoxide poisoning, and ifosfamide-induced encephalopathy off-label.

Methylene blue off-label uses

Diagnostic Applications

Surgeons may use methylene blue as a dye to identify sentinel lymph nodes during cancer surgeries, such as lumpectomies or mastectomies. It’s also used to evaluate or indicate lesions and other conditions during procedures.

Malaria Treatment

In the past, methylene blue has been used to treat malaria in areas with chloroquine-resistant Plasmodium falciparum strains.  

Vasoplegic Syndrome

Methylene blue has been used off-label for vasoplegic syndrome, a severe drop in blood pressure due to vasodilation that can occur during coronary artery bypass grafting. It may be used when epinephrine has not worked to stabilize blood pressure.

Ifosfamide-Induced Encephalopathy

Cancer patients undergoing chemotherapy with ifosfamide may develop neurotoxicity, leading to confusion, hallucinations, or even coma. Methylene blue may be beneficial in treating this condition, but it is ineffective when used as a preventative treatment.

Low-dose Methylene blue for Alzheimer’s disease 

Methylene blue for Alzheimer’s disease is gaining attention as a potential therapy to slow cognitive decline. Researchers are studying a low-dose form known as hydromethylthionine, a specially modified version of methylene blue designed for better absorption and enhanced brain penetration when taken orally.

Clinical studies have shown that taking 4 mg of hydromethylthionine twice daily can significantly slow the progression of Alzheimer’s symptoms and reduce brain atrophy (shrinkage). This low-dose approach appears promising compared to traditional treatments.

Scientists believe that methylene blue works for Alzheimer’s disease by inhibiting the buildup of tau protein, an abnormal protein that forms tangles inside brain cells and may contribute to cognitive decline.

Hydromethylthionine is also known as LMTM (Leuco-Methylthioninium Bis(Hydromethanesulphonate)) or methylthioninium moiety. This form has been the focus of clinical trials aiming to develop new, more effective therapies for Alzheimer’s disease.

Early results suggest that low-dose methylene blue may offer a novel way to protect brain function and slow disease progression, but further large-scale studies are still needed to confirm its benefits.

Methylene Blue and Skin Aging

Researchers are exploring methylene blue as a possible ingredient in anti-aging skincare. One major cause of skin aging is oxidative damage, which can slow down collagen production and speed up its breakdown, leading to wrinkles, uneven pigmentation, and thinner skin.

Because methylene blue has antioxidant properties, scientists hope that methylene blue skin products could help protect the skin, improve its appearance, and even support wound healing. Some early clinical trials have been conducted, but this research is still in the experimental stage, and more studies are needed to confirm if or how well it works.

Methylene blue side effects

Get emergency medical help if you have signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Tell your caregivers right away if you have:

• confusion or weakness;
• pale or yellowed skin;
• dark colored urine;
• fever; or
• high levels of serotonin in the body – agitation, hallucinations, fever, fast heart rate, overactive reflexes, nausea, vomiting, diarrhea, loss of coordination, fainting.

Common side effects of methylene blue may include:

• pain in your arms or legs;
• blue or green urine;
• altered sense of taste;
• headache, dizziness;
• sweating, skin discoloration;
• nausea; or
• feeling hot.

This is not a complete list of side effects, and others may occur. Call your doctor for medical advice about side effects. You may report side effects to the FDA 

Warnings

You should not be treated with methylene blue if you have glucose-6-phosphate dehydrogenase (G6PD) deficiency or a severe hypersensitivity to methylene blue.

Many drugs can interact with methylene blue. Tell your doctor about all your current medicines and any you recently stopped using, especially an antidepressant.

Before taking this medicine

You should not be treated with methylene blue if you are allergic to it, or if you have:

• a genetic enzyme deficiency called glucose-6-phosphate dehydrogenase (G6PD) deficiency.

Many drugs can interact with methylene blue. Tell your doctor about all your current medicines and any you recently stopped using, especially:

• alfentanil, fentanyl;
• buspirone;
• digoxin, digitalis;
• dihydroergotamine, ergotamine;
• phenytoin;
• pimozide;
• quinidine;
• warfarin (Coumadin, Jantoven);
• an MAO inhibitor – isocarboxazid, linezolid, phenelzine, rasagiline, selegiline, tranylcypromine, and others;
• an “SSRI” antidepressant – citalopram, escitalopram, fluoxetine, paroxetine, sertraline, Prozac, Paxil, Zoloft, and others;
• an “SNRI” antidepressant – desvenlafaxine, duloxetine, levomilnacipran, milnacipran, venlafaxine, Effexor, Cymbalta, Pristiq, and others;
• other antidepressants – bupropion, clomipramine, mirtazapine; or
• medicine to prevent organ transplant rejection – cyclosporine, sirolimus, tacrolimus.

To make sure methylene blue is safe for you, tell your doctor if you have:

• liver disease; or
• kidney disease.

Using methylene blue during pregnancy could harm the unborn baby. Tell your doctor if you are pregnant.

How is methylene blue given?

When methylene blue is used for methemoglobinemia, it is given as an IV injection. A healthcare provider will give you this injection. The IV infusion can take up to 30 minutes to complete.

Your breathing, blood pressure, oxygen levels, kidney function, and other vital signs will be watched closely while you are receiving methylene blue. Your blood will also need to be tested to help your doctor determine that the medicine is working.

You may only need to receive one dose of methylene blue. If you do need a second dose, it can be given 1 hour after your first dose.

Methylene blue will most likely cause your urine or stools to appear blue or green in color. This is a normal side effect of the medication and will not cause any harm. However, this effect may cause unusual results with certain urine tests.

 The approved intravenous dosage is 1 mg/kg administered over 5 to 30 minutes.

The recommended dosage in patients with moderate or severe renal impairment (eGFR 15-59 mL/min/1.73 m2 is a single dose of 1 mg/kg.

What happens if I miss a dose?

Because you will receive methylene blue in a clinical setting, you are not likely to miss a dose.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line .

Overdose symptoms may include vomiting, stomach pain, chest pain or tightness, wheezing, trouble breathing, feeling like you might pass out, fast heart rate, anxiety, confusion, tremor, dilated pupils, blue-colored skin or lips, numbness, or tingling.

What should I avoid while receiving methylene blue?

Methylene blue may cause blurred vision and may impair your thinking or reactions. Be careful if you drive or do anything that requires you to be alert and able to see clearly.

For at least 24 hours after treatment with methylene blue, avoid exposure to sunlight or tanning beds. This medicine can make you sunburn more easily. Wear protective clothing and use sunscreen (SPF 30 or higher) when you are outdoors.

What is acetylcysteine?

Acetylcysteine is used to help prevent or lessen liver damage caused by taking large quantities of acetaminophen (Tylenol).

There are other brands and forms of acetylcysteine available, and some can be purchased over the counter. Not all forms of acetylcysteine are effective as an acetaminophen antidote. Do not attempt to treat an acetaminophen overdose without medical advice.

Acetylcysteine may also be used for purposes not listed in this medication guide.

Acetylcysteine side effects

Get emergency medical help if you have signs of an allergic reaction: hives; difficult breathing; swelling of your face, lips, tongue, or throat.

Acetylcysteine may cause serious side effects. Call your doctor at once if you have:

• severe or ongoing vomiting;
• coughing up blood or vomit that looks like coffee grounds; or
• signs that the medicine may not be working–upper stomach pain, loss of appetite, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes).

Common side effects of acetylcysteine may include:

• nausea, vomiting, upset stomach;
• rash; or
• fever.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Acetylcysteine side effects (more detail)

Warnings

In an emergency, you may not be able to tell caregivers about your health conditions. Make sure any doctor caring for you afterward knows you received acetylcysteine.

Before taking this medicine

You should not use acetylcysteine if you are allergic to it.

If possible before you receive acetylcysteine, tell your caregivers if you have ever had:

• a stomach ulcer;
• stomach bleeding or bleeding in your esophagus (esophageal varices);
• high blood pressure, or if you are on a low-salt diet;
• congestive heart failure; or
• kidney disease.

Ask a doctor before using this medicine if you are pregnant or breastfeeding.

In an emergency, you may not be able to tell caregivers if you are pregnant or breast feeding. Make sure any doctor caring for your pregnancy or your baby knows you received this medicine.

How should I take acetylcysteine?

Use exactly as directed on the label, or as prescribed by your doctor.

Do not take acetylcysteine at home if you don’t understand all instructions.

If you are in an emergency medical setting: Before you take acetylcysteine, your caregivers will perform a blood test to measure the level of acetaminophen in your body. This test is most effective when performed within 4 to 8 hours after an acetaminophen overdose. If you cannot remember when you last took acetaminophen or how much you took, you will most likely be given the first dose of acetylcysteine right away.

Your doctor will determine how long to treat you with acetylcysteine. Do not stop taking acetylcysteine until your doctor tells you to.

If you vomit within 1 hour after taking acetylcysteine, you may need to take another dose.

Store at room temperature away from moisture and heat.

Detailed Acetylcysteine dosage information

What happens if I miss a dose?

Take the medicine as soon as you can, but skip the missed dose if it is almost time for your next dose. Do not take two doses at one time.

What happens if I overdose?

Seek emergency medical attention or call the Poison Help line .

What should I avoid while taking acetylcysteine?

Follow your doctor’s instructions about any restrictions on food, beverages, or activity.

What other drugs will affect acetylcysteine?

Other drugs may affect acetylcysteine, including prescription and over-the-counter medicines, vitamins, and herbal products. Tell your doctor about all your current medicines and any medicine you start or stop using.

Does acetylcysteine interact with my other drugs?

Enter medications to view a detailed interaction report using our Drug Interaction Checker.Drug nameAdd a drug to check interactionsAdd

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