Fentanyl False Positives

How Is Fentanyl Presence Checked?

The presence of fentanyl can be detected using lab tests or test strips. Lab tests are typically administered in clinical settings. Test strips may or may not be available based on the state in which you are located. In many states, they remain illegal as they are considered drug paraphernalia. However, in January 2023, lawmakers in Florida “filed legislation that would add Florida to a growing list of states that have moved to decriminalize or legalize fentanyl test strips.” (1)

Urine samples are the most common method of detecting fentanyl and other drugs. (2) However, in some cases, clinical tests use blood or hair samples, or saliva can be obtained using a mouth swab.

Fentanyl test strips are small paper strips designed to identify the presence of fentanyl in a substance, such as heroin. (3) They are used as a harm reduction method for people who misuse drugs, particularly those who use opioids, to determine if their drug supply is tainted with fentanyl.

How Do False Positives Occur When Testing?

Although many types of drug tests tend to be very accurate, false positives can occur for many reasons, including contamination or improper administration.

Reasons for False Positives Include:

• Contamination—Urine samples can be contaminated by environmental factors or substances that can interfere with test results. For example, if the person taking the test was exposed to fentanyl in the environment or handled a fentanyl-contaminated substance, it may lead to a false positive result.
• Improper Test Administration—Urine drug tests must be administered correctly to ensure accurate results. Failure to follow the proper collection, storage, and handling procedures can produce false positive results.
• Cross-Reactivity—Urine drug tests use antibodies that bind to specific drugs or metabolites. (4) Sometimes, these antibodies cross-react with other substances, producing a false positive. For example, some medications, such as antidepressants or antipsychotics, can cross-react with fentanyl drug tests and render a positive result, even when fentanyl is absent.

Medications Reported to Cause False Positives for Fentanyl Include:

• Codeine, an opiate and common pain reliever.
• Tramadol, an opioid pain reliever.
• Diphenhydramine, an antihistamine often used to treat allergies.
• Methadone, a medication used to treat opioid addiction.
• Poppy seeds, which can contain trace amounts of opiate alkaloids from which fentanyl is derived.

Can Standard Urine Drug Screens Detect Fentanyl?

Most standard urine drug screens do not specifically test for fentanyl. However, some urine drug screens may detect the presence of opiates or opioids in general (including fentanyl), depending on the specific panel used.

Traditional urine drug screens typically test for common drugs such as marijuana, cocaine, amphetamines, opioids (such as morphine and codeine), and benzodiazepines. Fentanyl is a synthetic opioid and may not be detected by the standard opioid panel.

What Metabolites Do Drug Screens Look For?

Fentanyl drug screens typically look for fentanyl’s metabolites, the drug’s breakdown products produced by the body after ingestion. The most common of these detected in drug screens include norfentanyl, despropionyl fentanyl, and hydroxy fentanyl. Metabolites are easier to detect and have longer half-lives than the parent drug. This allows for an extended detection window to help identify recent drug use.