Naloxone Half-Life And How Long It Stays In One’s System?

Last Updated: December 18, 2019

Authored by Nena Messina, Ph.D.

Naloxone is a famously fast-acting medication, which leads many to believe it does not remain in the system for long. Anyone who takes the medication needs to understand the naloxone half-life, as well as how the body processes the medication. Here is what users should know about how long naloxone stays in the system.

Naloxone Half-Life

Naloxone hydrochloride both acts fast on the body and is quickly removed from it. The naloxone half-life—or how long it takes for the concentration of the drug in the plasma to be reduced by 50%—is in the range of just one to two hours, depending on the method of ingestion. In some cases, it may be beneficial to look at the alpha half-life versus the beta half-life. The alpha Narcan half-life is just four minutes. The beta half-life comes in at right about 60 minutes.

How Long Does Naloxone Stay In One’s System?

While the half-life of Narcan is short, the medication remains in the body much longer. How long Narcan stays in the system varies depending on many factors, from age to liver health to weight. The method of ingestion can also determine how quickly the drug clears the body.

When Narcan is taken orally or intravenously, up to 40 percent of the metabolites will be excreted within six hours. Within 24 hours of taking the drug, 50 percent will have been excreted, reaching 70 percent within 72 hours. This means that within a week or less, all metabolites should clear the body, making the time for how long Narcan stays in the system less than seven days.

Naloxone Pharmacology

The pharmacology of the drug is key to how Narcan works. This extends beyond the half-life of naloxone and gets into how the body processes the medication. The pharmacology of Narcan can be examined in terms of five things: absorption, the volume of distribution, protein binding, naloxone metabolism, and route of elimination.

naloxone metabolism


Drug absorption rates quantify how long it takes for the medication, in this case Narcan, to enter the bloodstream system. This impacts how quickly it can generate the desired effects. Indirectly, it affects how long naloxone stays in the system as well. For Narcan, the absorption rate is from 1-2 mins to about 5 mins depending on the route of administration.

Volume Of Distribution

The volume of distribution is used to determine how much Narcan is needed to generate the desired effects in an individual’s system. Because Narcan acts so quickly, it is rapidly distributed in the body, keeping the volume of distribution very low.

Protein Binding

Protein binding describes the degree to which Narcan binds to proteins present in the blood system. Narcan does bind to proteins in the plasma, but this binding is weak compared to most drugs. Narcan primarily binds to plasma albumin but can attach to others as well.


Naloxone metabolism describes how the body processes the drug. It undergoes hepatic metabolism, which means it is processed by the liver rather than the kidneys. In the liver, it undergoes glucuronidation to create the metabolite naloxone-3-glucuronide. Once metabolized, the body can eliminate the drug from the system.

Route Of Elimination

Naloxone can be eliminated from the body system through urine, feces, and sweat. However, the primary route of elimination for the drug is the urine. This makes it the one place where testing is likely to pick up the presence of the drug before Narcan comes out.

naloxone drug test

Naloxone And Positive Drug Tests

For many users, there is a fear that using naloxone can cause a positive drug test. On a scientific level, this fear makes sense. The metabolites produced by the body when processing naloxone are similar in structure to those that emerge after taking opiates. However, naloxone will not produce a positive result when testing for opioids.

This does not mean that someone who takes naloxone is guaranteed to have a negative test result, though. The time Narcan stays in the system, metabolites included, is lesser than opioids are. If a person takes Narcan to counteract the effects of opioids, they may be saved from an overdose, but they will not be saved from a positive drug test.

Recovering From Opiate Abuse

Narcan is an important safeguard for those who abuse opiates, ensuring that they do not die from an overdose. However, the safest route to take is to stop the use of opiates completely, eliminating the possibility of an overdose occurring. To safely discontinue using opiates and to learn how to stay clean, users should turn to drug rehabilitation centers. There, the proper substance abuse treatment is provided to prevent relapse, as well as ensure longstanding recovery.

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Published on: June 19th, 2019

Updated on: December 18th, 2019

About Author

Nena Messina, Ph.D.

Nena Messina is a specialist in drug-related domestic violence. She devoted her life to the study of the connection between crime, mental health, and substance abuse. Apart from her work as management at addiction center, Nena regularly takes part in the educational program as a lecturer.


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