Fentanyl is a potent opioid that can linger in your body for hours or days, depending on both the dosage form and the body part being tested.

Fentanyl is a potent opioid that can be used for both illicit and legitimate medical purposes. The drug’s pain-relieving effects can be extremely helpful in treating severe pain. However, fentanyl can also be used illicitly and sometimes laced into other illicit drugs. How long fentanyl lasts in your system can vary depending on multiple factors. If you or a loved one take fentanyl, it is important to know how long the drug is expected to stay in your system.

What Is Fentanyl?

Fentanyl is a Schedule II controlled substance and opioid often prescribed to treat severe pain, like pain from cancer. As a potent narcotic, its use is strictly controlled by the Drug Enforcement Administration. Fentanyl is also available illicitly from drug dealers, some of which secretly mix the substance into other drugs to make them more addictive.

How Long Does It Take for Fentanyl to Kick In?

Fentanyl can take different amounts of time to kick in, depending on the dosage form. Some dosage forms have a quicker onset than others.

Fentanyl Dosage Form	Onset of Action
Injectable (administered only in hospitals)	Rapid, within minutes
Lozenge	Within 10 minutes
Intrabuccal tablet	Within 10 minutes
Sublingual tablet	Within 10 minutes
Sublingual spray	Within 10 minutes
Nasal spray	Within 10 minutes
Transdermal skin patch	Within 12–24 hours

How Long Does Fentanyl Last?

Fentanyl lasts different amounts of time depending on the dosage form. It is important to know how long the drug is expected to last because this can directly impact how often you should take fentanyl.

Fentanyl Dosage Form	Duration of Effect
Injectable (administered only in hospitals)	30–60 minutes
Lozenge	4 hours
Intrabuccal tablet	4 hours
Sublingual tablet	2 hours
Sublingual spray	4 hours
Nasal spray	2 hours
Transdermal skin patch	72–96 hours

Effects of Fentanyl

As an analgesic, fentanyl provides pain relief from severe, debilitating pain. However, the drug also carries a risk of side effects, including:

• Nausea or vomiting
• Sleepiness
• Dizziness
• Trouble sleeping
• Constipation
• Sweating
• Fatigue
• Feeling cold
• Appetite loss
• Headache

As an opioid, fentanyl can also cause an overdose. Fentanyl overdose symptoms include:

• Unresponsiveness
• Slowed breathing
• Pinpoint pupils

If you suspect someone is overdosing on fentanyl, give them the opioid reversal agent Narcan (naloxone) and then call 911 immediately. Even if the person takes fentanyl illicitly, you will not get in trouble for saving a life.

Fentanyl Half-life

The half-life of a drug refers to how long it takes your body to eliminate one-half of it from your system. This has a direct impact on how long fentanyl stays in your system. Fentanyl’s half-life varies alongside the dosage form, with some chemically formulated to last in your body much longer than other forms.

Fentanyl Dosage Form	Half-Life
Lozenge	Up to 6.4 hours
Intrabuccal tablet	Up to 11.7 hours
Sublingual tablet	Up to 13.5 hours
Sublingual spray	Up to 12 hours
Nasal spray	Up to 25 hours
Transdermal skin patch	Up to 27 hours

How Long Does Fentanyl Stay In Your System?

Fentanyl can be detected in your system for different amounts depending on the body part tested. However, not all dosage forms of fentanyl have been extensively tested for how long they stay in your system, so the following information should be treated as only a general rule of thumb.

How Long Does Fentanyl Stay In Your Urine?

Both fentanyl and its breakdown product norfentanyl can be found in urine for up to three days following the last dose you take.

How Long Does Fentanyl Stay In Your Hair?

A 1.5-inch sample of hair can detect fentanyl use within the previous 90 days.

How Long Does Fentanyl Stay In Your Blood?

Fentanyl can be found in both blood and plasma (the liquid part of the blood) for up to 12 hours after the last dose. Fentanyl’s breakdown product norfentanyl can also be found in blood and plasma for a slightly shorter period, up to 10 hours.

How Long Does Fentanyl Stay In Your Saliva?

Fentanyl can be found in saliva for up to two days after the last dose.

Factors That Influence How Long Fentanyl Stays in Your System

Many factors can impact fentanyl’s detection time. These factors can vary between people, meaning fentanyl may be detectable in some people for shorter or longer periods than others. Some factors influencing fentanyl detection times include:

• Dose of fentanyl: A higher fentanyl dose may stay in the body longer than a smaller dose.
• How often you take fentanyl: More frequent fentanyl use may mean the drug stays detectable in your system for longer than if you take it sporadically.
• Fentanyl formulation: Some long-acting fentanyl dosage forms like transdermal fentanyl have a long half-life, which may keep the drug detectable in your system for much longer than a dosage form with a shorter half-life.
• Age: Younger people often eliminate fentanyl from their bodies more quickly than older people.
• Kidney function: People with kidney impairment often take longer to clear fentanyl from their bodies than people with healthier kidneys.
• Drug interactions: Other substances that impact the activity of CYP3A4, the enzyme that processes fentanyl, can make fentanyl last longer or shorter than expected.

False Positive for Fentanyl

Studies found several different substances caused false positives for fentanyl. For example, in some urine tests, methamphetamine can cause false positives for fentanyl.

In addition, some people use fentanyl test strips to try to test illicit substances for fentanyl before taking them. However, some test strips can show false positives for fentanyl, specifically when testing methamphetamine, MDMA (ecstasy) or diphenhydramine.

How Is Fentanyl Metabolized in the Body?

The liver enzymes in your body metabolize or break down fentanyl. The main liver enzyme responsible for breaking down fentanyl is CYP3A4. This enzyme works both in your liver and intestines to rid your body of fentanyl. To a lesser extent, a chemical process called hydrolysis breaks down fentanyl, where water molecules chemically split fentanyl and break its atomic bonds.

How to Get Fentanyl Out of Your System

Because liver enzymes break down fentanyl, there is no way to speed up how long it takes to get fentanyl out of your system. Once the drug is in your body, you need to wait for your liver enzymes to process and remove it from your body. You cannot speed up the activity of these enzymes, as the liver naturally produces them.

Drinking water, exercising, sweating or taking herbal concoctions will not work at speeding up how long it takes to get fentanyl out of your body, as none of these things will speed up the liver enzymes responsible for processing fentanyl.

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