Naloxone is an opioid antagonist medication used to block or reverse the effects of opioid drugs, particularly within the setting of drug overdoses which are rapidly becoming a leading cause of death worldwide. More specifically, naloxone has a high affinity for μ-opioid receptors, where it acts as an inverse agonist, causing the rapid removal of any other drugs bound to these receptors. When taken in large quantities, opioid medications such as [morphine], [hydromorphone], [methadone], [heroin], or [fentanyl] are capable of causing life-threatening symptoms such as respiratory depression, reduced heart rate, slurred speech, drowsiness, and constricted pupils. If untreated, this can progress to vomiting, absent pulse and breathing, loss of consciousness, and even death. Naloxone is indicated for the rapid reversal of these symptoms of central nervous system depression in opioid overdose. It’s important to note that naloxone only works on opioid receptors within the body, and is therefore not capable of reversing the effects of non-opioid medications such as stimulants like [methamphetamine] or [cocaine], or benzodiazepines like [lorazepam] or [diazepam]. Also known as the brand name product Narcan, naloxone is currently available by intramuscular (IM) or subcutaneous (SubQ) injection, nasal spray, or intravenous (IV) infusion. Naloxone IM injections are commonly available in the form of “kits”, which is ideal for making overdose treatment accessible and readily available for administration by minimally trained individuals within the community. Kits commonly include the supplies necessary to treat an overdose in a non-medical setting such as alcohol swabs, syringes, a rescue breathing mask, and instructions for use. Frequently also carried by medical and emergency personnel and at events known to be associated with heavy drug use like music festivals, naloxone kits are considered a key component of harm reduction strategies. There are over-the-counter nasal sprays available. When injected intramuscularly (IM), naloxone acts within three to five minutes. Administration of naloxone is associated with very few side effects. Notably, if injected into a person not currently using opioid medications, there would be no noticeable effects at all. However, for individuals using opioid medications or experiencing an overdose, IM injection of naloxone rapidly reverses opioid effects and can cause the injected individual to immediately experience withdrawal symptoms. Common symptoms of opioid withdrawal include nausea, vomiting, sweating, runny nose, aches, and diarrhea. Although certainly physically uncomfortable, opioid withdrawal symptoms are not life-threatening; administration of naloxone is, therefore, appropriate for any person appearing to have any symptoms of an opioid overdose. Due to its short duration of action, persons injected with naloxone should be monitored for responsiveness and potentially injected a second time or taken to the hospital. Naloxone is also available within the combination product Suboxone with the opioid medication [buprenorphine]. Suboxone is used for the maintenance treatment of opioid dependence and addiction. When taken orally, naloxone has no pharmacological effect and does not reduce the effectiveness of the opioid effect of buprenorphine. The primary purpose of including naloxone within Suboxone is to act as a deterrent to injection, as injected naloxone would rapidly reverse the effects of buprenorphine. Naloxone was granted FDA approval on 13 April 1971.
Science-backed ERA derivation by certified toxicologists with ex-agency experts -
Naloxone
Drug Overview
What is Naloxone?
Masuu Global provides end-to-end Environmental Risk Assessment (ERA) support for pharmaceutical and healthcare products, covering Phase I environmental exposure assessment, Phase II environmental fate and effects assessment, data-gap analysis, testing strategy, laboratory coordination and final regulatory-ready reporting.
Request Your Assessment
Add this compound to your inquiry list and our team will follow up with full documentation, pricing, and licensing terms.
View Inquiry List →ERA Phase I Evaluation, ERA Phase II Evaluation, Consortium Testing Support (OECD Ecotoxicology Study)
Regulatory Framework
Assessment Methodology
Masuu Global follows a science-based, tiered and risk-based ERA methodology, aligned with applicable international regulatory requirements. For human medicinal products, our approach is primarily guided by the EMA Guideline EMEA/CHMP/SWP/4447/00 Rev. 1, effective 1 September 2024, together with relevant OECD Test Guidelines and regional regulatory requirements.
EMA — Environmental Risk Assessment
Assessment of potential environmental exposure associated with the use, manufacture and disposal of medicinal products, with a structured approach to determine whether further environmental assessment is required.
Phase I — Environmental Exposure Assessment
Initial screening to determine potential environmental exposure, covering PEC calculation, physicochemical properties, usage and dosage data, environmental entry pathways, and persistence and fate considerations.
Phase II — Environmental Fate & Effects Assessment
Where Phase I indicates further assessment is required, Phase II provides detailed evaluation of environmental fate, persistence and ecological effects — including biodegradation, bioaccumulation, aquatic toxicity, PNEC derivation and PEC/PNEC risk characterisation.
OECD & International Testing Principles
Where laboratory studies are required, testing strategies are designed with consideration of relevant OECD Test Guidelines, GLP expectations and applicable regulatory requirements.
Risk-Based Environmental Assessment
Integration of physicochemical data, environmental fate information, ecotoxicological data, existing literature, published studies, regulatory databases, usage data, and environmental monitoring data.
Weight-of-Evidence (WoE) Approach
A scientifically justified WoE approach integrates existing data and avoids unnecessary testing wherever scientifically and regulatorily justified.
ERA Assessment Pathway
Phase I → Phase II → Risk Characterization
Each phase builds on the prior tier — screening first, escalating only when the evidence demands it.
Environmental Exposure Assessment
Initial screening to determine whether the substance requires progression to Phase II.
- Product and substance information review
- Indication, dose and usage assessment
- PEC calculation and environmental exposure estimation
- Physicochemical property review
- Initial environmental risk screening
- Determination of Phase II requirement
Environmental Fate & Effects
Detailed evaluation when Phase I triggers further assessment.
- Biodegradation, hydrolysis & photolysis
- Adsorption/desorption behaviour
- Bioaccumulation potential
- Algal, Daphnia and fish toxicity
- Chronic ecotoxicity, where required
- PEC/PNEC risk characterisation
Laboratory Coordination & Study Execution
When regulatory testing is mandatory, Masuu coordinates with qualified GLP/appropriate testing laboratories and specialized scientific partners — giving clients a single point of contact across the full testing lifecycle.
Final ERA Report — Contents
- Executive summary
- Substance & product information
- Environmental exposure assessment
- Phase I evaluation
- Phase II assessment (where applicable)
- Environmental fate assessment
- Ecotoxicological assessment
- PEC/PNEC calculations
- Risk characterisation
- Data gap evaluation
- Testing rationale
- Risk mitigation considerations
- References and supporting scientific evidence
How We Work
Report Preparation Process
Every ERA follows a structured, tiered workflow designed to deliver scientifically defensible and regulator-ready assessments.
Comprehensive Data Collection
Product, substance, usage, physicochemical, toxicological, environmental and regulatory information collected and reviewed.
Phase I Environmental Screening
Environmental exposure assessment and determination of whether the assessment can conclude at Phase I or requires progression.
Phase II Evaluation
Detailed environmental fate and ecotoxicological assessment when Phase II is triggered.
Data Gap & Testing Strategy
Missing information identified and available alternatives evaluated before recommending additional testing.
Consortium Testing Support
Where testing is mandatory, Masuu coordinates with qualified testing partners through its Consortium Model.
Scientific & Regulatory Review
Integration and critical review of generated and existing data by experienced scientific and regulatory experts.
Final ERA Delivery
Comprehensive ERA report with transparent methodology, scientific rationale, calculations, conclusions and regulatory recommendations.
Ex-Agency Advantage
Why Masuu Global?
Our experienced regulatory and scientific experts bring a practical regulatory perspective — helping clients understand not only what data are required, but why they are required and how regulators may evaluate them.
Ready to request your assessment?
Add this compound to your inquiry list, or browse our full database of 7,000+ molecules.