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Fentanyl is one of the most powerful synthetic opioids used in modern medicine - up to 100 times stronger than morphine. Initially developed in the 1960s to treat severe pain in surgical and cancer patients, it has since become both an important tool in pain management and a major contributor to the opioid crisis. In its illicit form, fentanyl is now a leading cause of overdose deaths across North America.
In this article, we examine how long fentanyl stays in the body and why. Keep reading to learn more.
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What is Fentanyl?
Fentanyl is a synthetic opioid that operates with staggering intensity - approximately 50-100 times more potent than morphine1. Originally developed for medical use, it’s legitimately prescribed to manage severe breakthrough pain in cancer patients and those with chronic conditions unresponsive to other painkillers.
However, illegally manufactured fentanyl is often mixed with heroin or pressed into counterfeit pills2, frequently without the user’s knowledge. And this can be very dangerous, leading to overdose deaths and serious medical emergencies.
So, why is fentanyl so potent? Fentanyl’s molecular structure allows it to bind effectively to opioid receptors in the brain, even more so than traditional opioids3. This property not only makes fentanyl highly effective for pain relief but also means that even small amounts can trigger an overdose.
Additionally, this potency affects detection - the body metabolizes it quickly, but sensitive tests can identify its distinctive metabolites for significantly longer periods4.
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How Is Fentanyl Eliminated From the Body?
Once fentanyl enters the body, it’s primarily processed by the liver5. There, an enzyme called CYP3A4 breaks it down into norfentanyl6, its main byproduct. Unlike fentanyl, norfentanyl does not have strong effects on the brain or body. But it stays in the system longer and is often used in drug testing to detect fentanyl use. Most of this byproduct is removed from the body through urine, with a smaller amount eliminated in feces.
The speed at which fentanyl leaves the body depends largely on how it was taken. For example:
- Intravenous (IV) fentanyl has a short half-life of about two to four hours, meaning it is cleared relatively quickly.
- Transdermal patches release the drug slowly over time, so it stays in the body much longer—even up to several days after the patch is removed.
- Lozenges and sublingual tablets, which dissolve in the mouth, fall somewhere in between, with moderate absorption and elimination rates.
Several other factors—such as a person’s liver function, age, weight, and overall health—can also affect how long fentanyl and its byproducts stay in the body.
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How Long Is Fentanyl Positive For?
Drug tests for fentanyl are designed to detect both the drug itself and its main byproduct, norfentanyl. The length of time fentanyl remains detectable depends on the type of test used, the amount and frequency of use, and individual differences in metabolism. Here’s a breakdown of what that means:
- Urine tests are the most common method and typically detect fentanyl for 1 to 3 days after use. In some cases, especially with high doses or frequent use, it may be detected for up to 72 hours or longer.
- Blood tests have a much shorter detection window, usually up to 12 hours after the last dose. Because of this, they’re mostly used in emergency or clinical settings to identify recent use.
- Saliva tests can detect fentanyl for approximately one to two days and are gaining popularity due to being non-invasive and harder to tamper with than urine tests.
- Hair tests can show fentanyl use over the past 90 days or more, offering a long-term view of substance use history. However, they are more expensive and less commonly used due to cost and complexity.
It’s important to note that standard drug panels (like the basic five or ten-panel tests) often do not include fentanyl. Unless a test is specifically designed to detect synthetic opioids, fentanyl use may go unnoticed, even if recent.
Detection windows can also vary from person to person. As previously touched on above, factors that may extend how long fentanyl stays in the system include heavy or long-term use, slower metabolism, liver or kidney problems, older age, and interactions with other medications that affect how fentanyl is processed.
Are you struggling with a fentanyl addiction? At Freedom Recovery Centers (FRC), we’re here to help. You don’t have to do this alone. Call us at 804-635-3746 or fill out our online form.
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