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How Long Does Fentanyl Stay in Your System?

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By Johnny Bevers

Fentanyl is a powerful synthetic opiate that is considered even more potent than morphine.  This opiate analgesic is only used to treat patients with severe pain or to help patient’s manage their pain post-surgery when other methods of pain relief are not effective.  People who grow tolerant to pain meds and opiates (usually those suffering from chronic pain conditions) may be prescribed fentanyl as well to help them manage their pain levels.  Fentanyl is considered a schedule two prescription medication and it is heavily regulated by the FDA and DEA. Fentanyl is also something that should only be used as it is prescribed.  Not only can patients easily become addicted to the drug, but too much in a person’s system could cause adverse side effects and even lead to death.

What is Fentanyl?

Fentanyl is for severe pain and pain management.  In some cases, it may be used to help patients who are suffering from breakthrough pain — a severe pain that comes and goes in patients who suffer from chronic or severe pain.  There are many names for fentanyl and when prescribed, it can go by Duragesic, Sublimaze and Actiq.  When bought and/or sold on the street, it can go by numerous names, including Goodfella, Jackpot, Apache, China Girl, and China White.


Like other opioids (such as morphine or heroin), fentanyl binds with the body’s opiate receptors — highly concentrated centers in the brain that control a person’s emotions and pain.  Once bound, these receptors drive up the amount of dopamine, which produces a state of relaxation and euphoria.

Fentanyl is a prescribed medication.  It is typically administered through an injection, transdermal patch, or it can be administered in a lozenge.  Fentanyl is usually prescribed after traditional opioids are no longer effective, including morphine and oxycodone.  It is commonly prescribed to patients suffering from cancer who are on other forms of pain medication, but need help controlling severe or breakthrough pain episodes.

fentanyl ampule

Sometimes fentanyl does not work right away.  Because it must first bind with the brain’s pain receptors, there are instances where it can take three to six days for the drug to become effective.  Patients who are taking fentanyl are urged to not increase their dose, even if it does not appear to be working.  This situation is one of the common reasons patients accidentally overdose on their medication.  Patients with severe pain are often prescribed short-acting pain medications to help control the pain while fentanyl starts working and until it starts providing its full effect.  Transdermal patches must build their levels up in the skin before they can start to affect pain receptors in the brain.   Patients are typically given the lowest dose, then must wait 24 to 48 hours for the drug to absorb and then physicians can adjust the levels.  In some cases physicians may need to adjust in slow increments, waiting days in between, until they know the full effect of the drug.

Common Side Effects Associated with Fentanyl

There are a lot of side effects associated with fentanyl, even when it is taken properly.  Some common side effects include:

  • Drowsiness
  • Lightheadedness
  • Euphoria
  • Fatigue or weakness
  • Dry mouth
  • Difficulty urinating or breathing
  • Constipation (especially after long-term use)
  • Hives
  • Slow and/or fast heartbeat

Another common side effect is dependency.  Patients who use fentanyl frequently report their body requiring the use of the drug daily in order to avoid severe withdrawal symptoms.  Dependency is not the same as addiction and patients that do become dependent must be slowly weaned off the prescription to avoid any adverse side effects.  Even if a patient is not dependent on the drug, it cannot be stopped abruptly.  If stopped quickly, withdrawal symptoms may occur and some of which can be severe — if not life threatening.  Some withdrawal symptoms include runny nose, shakes, anxiety, faster heart rate, fast breathing, poor appetite, etc.  Even when a fentanyl patch is removed, some of the medication remains on the skin and continues to absorb into the body, which can make it difficult for physicians and caretakers to determine when the next patch should be applied.  Patients who take fentanyl cannot drive or operate machinery. Also, because fatigue and weakness are very common side effects, patients often cannot walk or may need to be assisted while walking to avoid any trips or falls. Because it can labor a person’s breathing, most physicians will only administer fentanyl when they can monitor a patient’s oxygen saturation, blood pressure and heart.

actavis fentanyl pain patch

How Long Does Fentanyl Stay in the System?

Fentanyl is a powerful pain medication and therefore, it should be used responsibly. Patients who are taking fentanyl should be warned about the possible dependency, but also understand how other medications, foods and even lifestyles can affect the levels of this drug in their system. Because fentanyl is an easy drug to overdose accidentally on, patients should meet with their physicians regularly and be tested to ensure their fentanyl levels are within therapeutic range.


If you are taking a drug test and you are concerned about the levels of fentanyl, the levels will vary depending on the testing method.  For example, urine can detect fentanyl eight to 24 hours after use.  Blood tests can only accurately test up to 12 hours, while saliva can detect levels of fentanyl for up to two days.  Hair follicle tests, however, can detect the use of fentanyl for up to 90 days, because the drug may have cleared your system, but will still be present in your hairs for three months.

fentanyl pop

  • The amount of time it takes for a drug to leave your system is based on the half-life of the drug.  Every time your body is able to reduce the drug by 50 percent, you have reached a half-life.  It takes five to six half-life cycles to remove fentanyl from the body. Patches, for example, typically take 9.5 to 12.4 hours until they no longer last, but that still could take up to 74 hours for the drug to fully clear your system.  Most patches that are prescribed to patients last about 72 hours — though some patients report the drugs only being effective for 36 to 40 hours.
  • Patients that use the transdermal patch have to be very cautious about their fentanyl levels.  Being too close to heat can actually cause the body to absorb the drug faster — increasing levels and leading to accidental overdose.
  • Research has also shown that certain foods can raise the level of this medication in a person’s system — regardless of how much of the original dose they were given.  Foods, such as grapefruit, can actually increase the levels of fentanyl in a person’s system and increase the side effects.  Also, beverages that contain alcohol can increase the severity of the side effects.
  • Many variables can determine how long fentanyl stays in a person’s system.  These variables can include a person’s weight, how often they are given the drug, how fast their body metabolizes it and the type of drug test being used to measure fentanyl levels.  Also, how well hydrated a patient is at the time the drug is administered is important.  The more hydrated the body is, the faster the body flushes the drug from the system.

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