Definition and research guide
This page combines a MeSH definition, publication statistics and selected research abstracts. It is a starting point for reading the literature, not a medical textbook or a systematic evidence review.
Content available: 4 complete abstracts (910 words), 10 references. Full article text is not stored or reproduced here; follow the PMID, DOI or PMC links to read the original sources and their access terms.
Definition
A specific opiate antagonist that has no agonist activity. It is a competitive antagonist at mu, delta, and kappa opioid receptors.
Definition: NLM Medical Subject Headings (MeSH) scope note (Public domain (U.S. National Library of Medicine); attribution requested). View the MeSH record.
Also known as: Narcan; Narcanti; Naloxone Hydrobromide; Hydrobromide, Naloxone; Naloxone Hydrochloride; Hydrochloride, Naloxone; Naloxone Hydrochloride Dihydride; Dihydride, Naloxone Hydrochloride.
Where it fits in the MeSH classification
- Broader topics
- Morphinans
- Narrower topics
- Buprenorphine, Naloxone Drug Combination; Naltrexone
Research landscape
PubMed indexes 29,138 records tagged with the MeSH heading “Naloxone” (counts retrieved 2026-10-31). 3,706 of them (12.7%) were published from 2020 onward, and the busiest period so far is through 1999 with 15,661 records.
Reviews account for 1,705 records (5.9%) and meta-analyses for 171. Randomized controlled trials number 1,863 (6.4%) as a share of all records on the topic.
Show the data
| Period | Records |
|---|---|
| through 1999 | 15,661 |
| 2000-2009 | 4,696 |
| 2010-2019 | 5,075 |
| 2020 onward | 3,706 |
Publication-type chart data
| Type | Records | Share |
|---|---|---|
| Reviews | 1,705 | 5.9% |
| Meta-analyses | 171 | 0.6% |
| Randomized controlled trials | 1,863 | 6.4% |
Method: PubMed query "Naloxone"[MeSH Terms] with publication-type and date filters, retrieved 2026-10-31.
Reading the evidence in drugs and chemicals
Studies of a chemical or drug can answer very different questions: what it is and how it behaves in cells and animals, how the body handles it, and whether it changes outcomes in people. Laboratory and animal findings often do not carry over to patients, and observational studies of exposures are confounded by who uses a substance and why. Nothing on this page is a recommendation to use, avoid, start or stop any substance or medicine; talk to a qualified clinician or pharmacist about your own situation. Check the dose, the species, the comparison group and whether a patient-relevant outcome was measured.
Evidence from open-access studies
These open-access studies come from PubMed’s best-match results for this heading (papers whose main topic it is), ranked here by citation count, with one recent addition. Each abstract is reproduced in full under its recorded open licence so that you can read the authors’ own words. They illustrate the literature; they are not a systematic summary of it. Citation counts measure attention, not reliability or clinical benefit.
Naloxone Availability and Cost After Transition to an Over-the-Counter Product [1]
Abstract reading summary — source excerpts
- Opening excerpt
- ImportanceThe US Food and Drug Administration approved Narcan, a nasal spray formulation of naloxone, for sale as an over-the-counter (OTC) medication in March 2023.
- Closing excerpt
- Cost was higher at independent pharmacies compared with chain pharmacies and lower in urban pharmacies compared with suburban and rural pharmacies.
- Interpretation limits
- Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (255 words)
ImportanceThe US Food and Drug Administration approved Narcan, a nasal spray formulation of naloxone, for sale as an over-the-counter (OTC) medication in March 2023. The purpose of OTC approval was to improve naloxone accessibility to reduce opioid overdoses; however, research has not yet evaluated whether naloxone's availability and cost changed since this policy was implemented.ObjectiveTo evaluate whether the accessibility and cost of naloxone at North Carolina community pharmacies changed after OTC naloxone became available and whether cost and availability varied by pharmacy type and urbanicity.Design, setting, and participantsThis longitudinal telephone-based secret shopper survey study included a stratified sample of 202 North Carolina community pharmacies, including health department, independent, and chain pharmacies. There were 2 separate data collection efforts from March to April 2023 (before OTC naloxone could be sold at pharmacies) and November 2023 to January 2024 (after OTC naloxone was sold at pharmacies).ExposureOTC naloxone first became available for sale at community pharmacies in September 2023.Main outcomes and measuresThe main outcomes were same-day availability of naloxone without a clinician-issued prescription and the quoted out-of-pocket cost for cash-paying patients.ResultsData were collected from 192 pharmacies. Same-day naloxone availability increased from 42.2% (81 of 192) before OTC naloxone availability to 57.8% (111 of 192) after (P Conclusions and relevanceThe Food and Drug Administration's approval of OTC naloxone nasal spray contributed to an increase in pharmacy-based availability of naloxone and a reduction of its cost for cash-paying patients. Cost was higher at independent pharmacies compared with chain pharmacies and lower in urban pharmacies compared with suburban and rural pharmacies.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 39058509 · DOI · PMC11282446
Effect of naltrexone pretreatment on ketamine-induced glutamatergic activity and symptoms of depression: a randomized crossover study [2]
Abstract reading summary — source excerpts
- Opening excerpt
- We investigated the potential role of the opioid system in modulating glutamatergic effects of ketamine administration in major depressive disorder.
- Closing excerpt
- gov registration: NCT04977674 .
- Interpretation limits
- Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (160 words)
We investigated the potential role of the opioid system in modulating glutamatergic effects of ketamine administration in major depressive disorder. Twenty-six adults with major depressive disorder participated in a double-blind crossover study, receiving oral placebo or 50 mg naltrexone before an intravenous infusion of 0.5 mg per kg ketamine. Brain glutamatergic activity in the anterior cingulate cortex was measured using functional magnetic resonance spectroscopy and depressive symptoms were assessed with the Montgomery-Åsberg Depression Rating Scale. Naltrexone attenuated the increase in glutamate + glutamine to total N-acetylaspartate ratio during ketamine infusion compared to placebo (F1,253 = 4.83, P = 0.029) and also attenuated the reduction in Montgomery-Åsberg Depression Rating Scale scores on day 1 (condition-by-time interaction, F1,74 = 5.39, P = 0.023). These findings demonstrate that the opioid system modulates the acute response to ketamine and subsequent antidepressant effects. Interactions between the glutamate and opioid systems may have implications for the development of new depression treatment strategies. ClinicalTrials.gov registration: NCT04977674 .
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 40707608 · DOI · PMC12443602
Effectiveness of naloxone distribution in community settings to reduce opioid overdose deaths among people who use drugs: a systematic review and meta-analysis [3]
Abstract reading summary — source excerpts
- Opening excerpt
- BackgroundIt is estimated that over 111,000 people in the U.
- Closing excerpt
- The very high survival rates provide clear evidence for public health to continue efforts to expand channels for naloxone distribution in community settings.
- Interpretation limits
- Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (305 words)
BackgroundIt is estimated that over 111,000 people in the U.S. died from a drug overdose in the twelve-month period ending in July 2023. More than three-quarters of those deaths were attributed to opioids. Naloxone has long been available in healthcare facilities to reverse opioid overdose rapidly and safely but is not universally accessible for use in community settings where overdoses occur. We conducted a systematic literature review and meta-analysis to assess the effectiveness of overdose education and naloxone distribution (OEND) programs in three types of community settings to reduce overdose deaths among people who use opioids nonmedically.MethodsWe systematically searched electronic databases, including Medline (OVID), Embase (OVID), Psycinfo (OVID), and Global Health (OVID), for peer-reviewed studies of OEND programs published during 2003-2018 (Group 1) that reported overdose outcomes individual level survivals or deaths immediately following naloxone administration. The PRISMA checklist guided screening, quality assessment, and data abstraction. We later identified studies published during 2018-2022 (Group 2), when drug usage and fentanyl-related overdose deaths notably increased, differed from earlier ones. We conducted meta-analyses on both Groups using random effects models to estimate summary survival proportions.ResultsAmong the 44 Group 1 studies published during 2003-2018, survival did not differ by time (year), location, naloxone dose, or route of administration, but studies of OEND programs serving people who use drugs reported 98.3% (95% CI: 97.5-98.8) survival; those serving family of people who use drugs or other community members reported 95.0% (95% CI: 91.4-97.1) survival; and those for police reported 92.4% (95% CI: 88.9-94.8) survival (p ConclusionsCommunity-based naloxone distribution programs can be effective in preventing opioid overdose deaths. The paper demonstrates that in the face of increasing overdose deaths over time, survival after naloxone administration has been sustained. The very high survival rates provide clear evidence for public health to continue efforts to expand channels for naloxone distribution in community settings.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 40133970 · DOI · PMC11934755
Breaking barriers: evaluating access models for harm reduction vending machines [4]
Abstract reading summary — source excerpts
- Opening excerpt
- The opioid epidemic continues to claim lives at alarming rates, disproportionately affecting marginalized communities, with structural barriers preventing equitable access to lifesaving interventions such as naloxone.
- Closing excerpt
- Further research is needed to evaluate the long-term impacts of unrestricted HRVM access models on overdose prevention and other health outcomes.
- Interpretation limits
- Verbatim excerpts from the authors’ abstract; the closing excerpt may describe a finding, limitation or recommendation. Design, population, effect size and uncertainty have not been independently extracted or appraised. Read the complete abstract and linked paper before interpreting the findings.
Read complete abstract (190 words)
The opioid epidemic continues to claim lives at alarming rates, disproportionately affecting marginalized communities, with structural barriers preventing equitable access to lifesaving interventions such as naloxone. Harm reduction vending machines (HRVMs) offer a promising solution to this issue, providing low-barrier access to naloxone and other harm reduction supplies. This study examines the impact of different HRVM access models on product utilization, specifically focusing on an outdoor HRVM, Project HOPE, located in Bakersfield, California. Initially, the machine required participant registration and imposed product limits; however, these restrictions were removed in August 2023 to improve access. An interrupted time series analysis of data from June to October 2023 reveal a significant increase in product utilization following the shift to unrestricted access, with increases in demand for naloxone kits, safer injection kits, wound care kits, and other basic needs supplies. The findings suggest that removing barriers to HRVM access, including registration requirements and product limits, can significantly improve the utilization of harm reduction supplies, potentially reducing opioid-related fatalities and promoting health equity. Further research is needed to evaluate the long-term impacts of unrestricted HRVM access models on overdose prevention and other health outcomes.
Abstract reproduced from the open-access article under the recorded cc by licence; © the authors. PMID 41343981 · DOI · PMC13331765
Key reviews and meta-analyses
The most cited review-type papers among PubMed’s best-match results for this heading, listed with bibliographic details only. Follow the links for the full text and access terms.
- Research article Management of opioid analgesic overdose [5]
- Research article A systematic review of community opioid overdose prevention and naloxone distribution programs [6]
- Research article Are take-home naloxone programmes effective? Systematic review utilizing application of the Bradford Hill criteria [7]
- Research article Management of opioid use disorders: a national clinical practice guideline [8]
- Research article Efficacy of naltrexone and acamprosate for alcoholism treatment: a meta-analysis [9]
- Research article Pharmacotherapy of addictions [10]
References
- Marley GT, Annis IE, Egan KL, Delamater P, Carpenter DM. Naloxone Availability and Cost After Transition to an Over-the-Counter Product. . 2024. PMID 39058509 · DOI · PMC11282446
- Jelen LA, Lythgoe DJ, Stone JM, Young AH, Mehta MA. Effect of naltrexone pretreatment on ketamine-induced glutamatergic activity and symptoms of depression: a randomized crossover study. . 2025. PMID 40707608 · DOI · PMC12443602
- Fischer LS, Asher A, Stein R, Becasen J, Doreson A, Mermin J, et al.. Effectiveness of naloxone distribution in community settings to reduce opioid overdose deaths among people who use drugs: a systematic review and meta-analysis. . 2025. PMID 40133970 · DOI · PMC11934755
- Herrera A, Conner B, Beshirs P, Bluthenthal R. Breaking barriers: evaluating access models for harm reduction vending machines. . 2026. PMID 41343981 · DOI · PMC13331765
- Boyer EW. Management of opioid analgesic overdose. N Engl J Med. 2012. PMID 22784117 · DOI · PMC3739053
- Clark AK, Wilder CM, Winstanley EL. A systematic review of community opioid overdose prevention and naloxone distribution programs. J Addict Med. 2014. PMID 24874759 · DOI
- McDonald R, Strang J. Are take-home naloxone programmes effective? Systematic review utilizing application of the Bradford Hill criteria. Addiction. 2016. PMID 27028542 · DOI · PMC5071734
- Bruneau J, Ahamad K, Goyer MÈ, Poulin G, Selby P, Fischer B, et al.. Management of opioid use disorders: a national clinical practice guideline. CMAJ. 2018. PMID 29507156 · DOI · PMC5837873
- Kranzler HR, Van Kirk J. Efficacy of naltrexone and acamprosate for alcoholism treatment: a meta-analysis. Alcohol Clin Exp Res. 2001. PMID 11584154 · DOI
- Kreek MJ, LaForge KS, Butelman E. Pharmacotherapy of addictions. Nat Rev Drug Discov. 2002. PMID 12209151 · DOI
About this article
- Sources
- NLM Medical Subject Headings (definition, synonyms); NCBI PubMed (counts, identifiers); Europe PMC (open-access abstracts and citation counts).
- Verification
- Every reference was resolved against PubMed on 2026-10-31; title, year and DOI matched.
- Review state
- automated source verified; no human expert review has been recorded yet.
- Version
- 1, last updated 2026-10-31.
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Evidence strength
EvidenceHelix's computed view of the study designs behind this topic: how common meta-analyses, randomized trials and reviews are, how recent the literature is, and a plain-language reading. It describes the design mix of the literature. It is not a quality appraisal of any study, and it is not medical advice.