Naloxone
Pronunciation: (nah-LOX-own).
- Generic name
- Naloxone
- Brand names
- Evzio, Nalsave, Naloxone Hydrochloride, Nyxoid, Narcan, Prenoxad
- Drug class
- Opioid Antagonist
Availability and supply rules vary by country
Trade names by country: United States · Canada
Australia: · Full directory
What Naloxone is and how it works
Uses, formulations, monitoring, and supply rules can differ by patient, product, and country. Follow the exact local product information and professional advice.
Mechanism of action: how Naloxone works
Naloxone is classified as Opioid Antagonist. See the how-to-take, warnings, and interactions sections for the redistributed clinician-authored dosing and safety detail formerly held in this field. (2)
What Naloxone is used for
Emergency reversal of opioid overdose (to restore normal breathing when it has slowed or stopped due to opioids such as heroin, morphine, oxycodone, or fentanyl)
Emergency reversal of opioid overdose (to restore normal breathing when it has slowed or stopped due to opioids such as heroin, morphine, oxycodone, or fentanyl) (1) (3)
Before taking Naloxone
Do not take / not appropriate for
- Naloxone has only one contraindication: a known hypersensitivity (serious allergic reaction) to naloxone hydrochloride or to any of the other ingredients in the product. Apart from that, there is no medical condition, no age, no pregnancy status, and no other medicine that makes naloxone unsafe to give in a suspected opioid overdose. (all countries) (3)
- Do not delay or withhold naloxone because you are unsure whether opioids are involved. Naloxone is given in a suspected opioid overdose, and an untreated opioid overdose is fatal. If opioids turn out not to be the cause, naloxone will simply have no effect. (all countries) (3) (1)
Tell your clinician about
- Always call emergency services as well as giving naloxone — naloxone wears off sooner than most opioids, and breathing can stop again after the person first wakes up.
- Tell the emergency team if the person is known to be opioid-dependent or pregnant, because naloxone can trigger sudden opioid withdrawal — this is a reason for close monitoring and follow-up care, not a reason to withhold the dose.
- After the emergency, tell the treating clinician about any known allergy to naloxone, all opioid medicines the person takes, and any heart or lung condition, so that ongoing care can be planned.
How to take Naloxone
- In a suspected opioid overdose, call emergency services immediately and give naloxone as soon as possible — these two actions go together, not one after the other. It can be given by injection (into muscle, under the skin, or into a vein) or as a nasal spray. Follow the instructions provided with your specific product. Inject into the outer thigh or upper arm, or spray into one nostril. If there is no response after 2-3 minutes, another dose may be given while waiting for emergency services to arrive.
- This page does not provide a dose calculator. Dosing must follow the prescriber, pharmacist, or product label.
Procedures and treatment changes
Tell the treating team before surgery, procedures, or any medicine change. Do not alter treatment without the responsible clinician. (1) (3)
Missed dose
Naloxone is not taken on a schedule — it is given only in a suspected opioid overdose emergency, so the usual concept of a "missed dose" does not apply. If someone is carrying naloxone for future emergency use and has a question about their specific product's routine (e.g., replacing an expired device), that is a question for the prescribing clinician or pharmacist, not an emergency-response question.
Overdose
If you suspect a naloxone overdose or experience severe side effects, seek emergency medical help immediately or contact a poison control center. The clinician-authored database record for this medicine (not independently verified against a professional label in this research pass) describes naloxone overdose as unlikely to be dangerous in most cases, though excessive doses may cause severe opioid-withdrawal symptoms in people who are opioid-dependent. (1) (3)
Side effects
Side effects and their urgency vary; report severe, persistent, or concerning symptoms to a healthcare professional.
Pain, burning, or redness at the injection site
Incidence: Reported as a common side effect by MedlinePlus (NIH/NLM)
Hot flashes or flushing
Incidence: Reported as a common side effect by MedlinePlus (NIH/NLM)
Chest pain, severe shortness of breath, persistent vomiting, seizures, or signs of a severe allergic reaction such as swelling of the face, lips, tongue, or throat
Incidence: Reported in the clinician-authored database; seek immediate medical attention if this occurs (in addition to calling emergency services for the overdose itself)
Rapid, pounding, or irregular heartbeat, hallucinations, loss of consciousness, or signs of opioid withdrawal (body aches, diarrhea, fever, vomiting)
Incidence: Reported by MedlinePlus (NIH/NLM); seek emergency treatment if this occurs
Serious warnings
Naloxone is given in a suspected life-threatening opioid overdose regardless of other medical history — serious
Symptoms: Naloxone is given in a suspected life-threatening opioid overdose regardless of other medical history; a known allergy to naloxone should still be raised with a clinician or emergency responder afterward, and with the prescriber if naloxone is being carried for future use.
Action: Follow the urgency stated and seek prompt or emergency care when indicated. (1) (3)
May cause acute opioid withdrawal symptoms — serious
Symptoms: May cause acute opioid withdrawal symptoms.
Action: Follow the urgency stated and seek prompt or emergency care when indicated. (1) (3)
Effects may wear off before opioids leave the body—monitor closely — serious
Symptoms: Effects may wear off before opioids leave the body—monitor closely.
Action: Follow the urgency stated and seek prompt or emergency care when indicated. (1) (3)
Not effective for non-opioid overdoses — serious
Symptoms: Not effective for non-opioid overdoses.
Action: Follow the urgency stated and seek prompt or emergency care when indicated. (1) (3)
For anyone carrying naloxone for future emergency use (not during an active overdose), heart, kidney, or liver disease should be disclosed to the prescriber — serious
Symptoms: For anyone carrying naloxone for future emergency use (not during an active overdose), heart, kidney, or liver disease should be disclosed to the prescriber.
Action: Follow the urgency stated and seek prompt or emergency care when indicated. (2) (1)
Repeated dosing may be required for potent synthetic opioids — serious
Symptoms: Repeated dosing may be required for potent synthetic opioids.
Action: Follow the urgency stated and seek prompt or emergency care when indicated. (1) (3)
Interactions
| Medicine or test | Effect | Action |
|---|---|---|
| General | Naloxone has no significant drug-drug interactions, but it may precipitate withdrawal in people dependent on opioids. Naloxone may not fully reverse the effects of certain opioids such as buprenorphine and pentazocine, so higher or repeated doses may be needed. | (2) (1) |
Pregnancy, breastfeeding, kidney/liver function, age
Pregnancy
Inform the doctor if pregnant or planning pregnancy when naloxone is prescribed in advance; in an actual overdose emergency, give naloxone regardless — fetal monitoring may be needed afterward. (1) (3)
Breastfeeding
Inform the doctor if breastfeeding when naloxone is prescribed in advance; in an actual overdose emergency, give naloxone regardless of breastfeeding status. (1) (3)
Children
In a suspected pediatric opioid overdose, give naloxone and call emergency services immediately using whatever naloxone product is available (follow the product's instructions). The FDA label for naloxone hydrochloride injection confirms the clinician database's weight-based figure: an initial pediatric dose of 0.01 mg/kg IV (IM or subcutaneous in divided doses if IV is not possible); if clinical improvement is not achieved, a subsequent dose of 0.1 mg/kg may be given. The same 0.01 mg/kg IV/IM/SC figure applies to neonatal opioid-induced depression. Exact dosing in an emergency should still be confirmed with emergency responders or a clinician, not calculated by the reader. (1) (3)
Renal_impairment
The FDA label for naloxone hydrochloride injection states that safety and effectiveness in patients with renal insufficiency/failure, or in patients with liver disease, have not been established in well-controlled clinical trials, and that caution should be exercised when naloxone is administered to these patient populations. In an actual overdose emergency, this does not change the decision to give naloxone — it is a note for the clinician team managing follow-up care. (1) (3)
Hepatic_impairment
The FDA label for naloxone hydrochloride injection states that safety and effectiveness in patients with renal insufficiency/failure, or in patients with liver disease, have not been established in well-controlled clinical trials, and that caution should be exercised when naloxone is administered to these patient populations. In an actual overdose emergency, this does not change the decision to give naloxone — it is a note for the clinician team managing follow-up care. (1) (3)
Monitoring
(1) (3)Storage
Store at room temperature, away from light and moisture. Do not freeze. Keep out of reach of children.
Professional information
Clinician-facing context only. This section does not replace current product labeling.
General
Indication: Emergency reversal of opioid overdose
Dose summary: Now independently verified against FDA prescribing information: adult initial dose 0.4 mg to 2 mg IV (IM or subcutaneous also acceptable) for naloxone hydrochloride injection, or one 4 mg intranasal spray (one nostril) for naloxone nasal spray products (e.g. Narcan); may be repeated every 2-3 minutes as needed until the person responds or emergency help arrives. For injection, if no response is seen after a cumulative 10 mg, the diagnosis of opioid-induced toxicity should be questioned. Higher or repeated doses may be required for potent synthetic opioids. Not enabled as a self-service dosing tool.
Renal context: The FDA label states safety and effectiveness in patients with renal insufficiency/failure have not been established in well-controlled clinical trials; caution should be exercised when naloxone is administered to this population. This does not change the decision to give naloxone in an active overdose emergency. (2) (3)
Hepatic guidance
The FDA label states safety and effectiveness in patients with liver disease have not been established in well-controlled clinical trials; caution should be exercised when naloxone is administered to this population. This does not change the decision to give naloxone in an active overdose emergency.
Frequently asked questions
How quickly does naloxone work?
Naloxone usually works within 2 to 5 minutes after administration. If there is no response, a second dose should be given after 2-3 minutes.
Can naloxone be used more than once?
Yes. Multiple doses may be needed, especially with strong opioids like fentanyl. Always seek emergency help after use.
Is naloxone safe for children?
In a suspected pediatric opioid overdose, give naloxone and call emergency services immediately — this is a life-threatening emergency where naloxone should still be given. The clinician-authored database record's specific weight-based pediatric dosing figure has not been independently verified against a primary product label in this research pass; let emergency responders or a clinician confirm exact dosing.
Does naloxone have any effect if no opioids are present?
No. Naloxone has no effect if opioids are not present in the body.
Can naloxone cause withdrawal symptoms?
Yes. In people dependent on opioids, naloxone can cause sudden withdrawal symptoms such as agitation, nausea, vomiting, sweating, and rapid heart rate.
Do I still need to call emergency services after giving naloxone?
Yes. Always call emergency services after administering naloxone, as further medical care may be needed and the effects of naloxone may wear off before the opioids leave the body.
How should naloxone be stored?
Store naloxone at room temperature, away from light and moisture. Do not freeze. Keep out of reach of children.
What is the mechanism of action of Naloxone?
Naloxone is classified as Opioid Antagonist. See the how-to-take, warnings, and interactions sections for the redistributed clinician-authored dosing and safety detail formerly held in this field. (2)
What is the generic name of Naloxone?
The generic name is Naloxone. It is sold under brand names including Evzio, Nalsave, Naloxone Hydrochloride, Nyxoid, Narcan, Prenoxad.
What class of drug is Naloxone?
Naloxone is classed as: Opioid Antagonist.
References
- Naloxone Injection: MedlinePlus Drug InformationMedlinePlus, U.S. National Library of Medicine · United States · accessed 2026-08-06 · source 1
- Clinician-authored medicine record (naloxone) from MedGuideGlobal databaseMedGuideGlobal · null · accessed 2026-08-06 · source 2
- Naloxone Hydrochloride Injection, USP — FDA prescribing information, DailyMed; cross-checked with NARCAN (naloxone hydrochloride) nasal spray FDA prescribing informationUS FDA (prescribing information via DailyMed) · United States · accessed 2026-08-07 · source 3
- BUPRENORPHINE AND NALOXONE TABLET [HIKMA PHARMACEUTICALS USA INC.] — US prescribing information (DailyMed SPL)U.S. National Library of Medicine (DailyMed) · US · accessed 2026-08-14 · source 4
- PENTAZOCINE HYDROCHLORIDE AND NALOXONE HYDROCHLORIDE — FDA approval record (Drugs@FDA ANDA075735)U.S. Food and Drug Administration · US · accessed 2026-08-14 · source 5
- Naloxone — RxNorm normalized drug concept (RXCUI 203192)U.S. National Library of Medicine (RxNorm) · US · accessed 2026-08-14 · source 6
Brand names by country
Single-ingredient Naloxone names are shown separately by country. Product availability, strengths, and supply rules can change; combination products are not included here.
Priority countries
United States
- Narcan4 mg/.1mL · emergent devices inc.
- REZENOPY10 mg/.11mL · scienture llc
- REXTOVY4 mg/.25mL · international medication systems, ltd.
- ZIMHI5 mg/.5mL · zmi pharma inc.
- NARCAN NALOXONE HCI4 mg/.1mL · hf acquisition co llc, dba healthfirst
- RiVive3 mg/.1mL · harm reduction therapeutics, inc.
- Narcan Naloxone HCL4 mg/.1mL · hf acquisition co llc, dba healthfirst
- NALOXONE HCI.4 mg/mL · hf acquisition co. llc, dba health first
- KLOXXADO8 mg/.1mL · hikma specialty usa inc.
Canada
- NALOXONE HYDROCHLORIDE INJECTION SDZ PRESERVATIVE FREE
- S.O.S. NALOXONE HYDROCHLORIDE