What Is Para-Fluorofentanyl (pFF)? The Fentanyl Analog Reappearing in the U.S. Drug Supply

Para-fluorofentanyl, often abbreviated pFF and also called 4-fluorofentanyl or p-fluorofentanyl, is a synthetic opioid closely related to fentanyl. Although it is not a new substance, pFF has reemerged in the illicit drug supply and has been identified alongside fentanyl, counterfeit pills, heroin, stimulants, and other emerging substances.

The issue has become particularly relevant again in 2026. In September, the White House Office of National Drug Control Policy (ONDCP) identified fluorofentanyl among the fentanyl analogs presenting a heightened national threat. ONDCP wastewater monitoring also detected para-fluorofentanyl specifically across all four U.S. Census regions during 2026. ONDCP

For people using illicit opioids, this does not necessarily mean they are intentionally seeking out a new drug called pFF. Historically, para-fluorofentanyl has frequently been detected with fentanyl rather than by itself, making it another example of how the unregulated opioid supply can change without the person using it knowing what has changed. CDC

Key Points About Para-Fluorofentanyl

Para-fluorofentanyl (pFF) is a synthetic opioid and fentanyl analog also known as 4-fluorofentanyl or p-fluorofentanyl.
pFF is not an approved medication in the United States and has been controlled as a Schedule I substance since 1986. CDC
The substance is not entirely new. It appeared in the illicit market decades ago before reemerging prominently beginning around 2020.
CDC documented 1,658 overdose deaths involving pFF across 43 reporting jurisdictions from July 2020 through June 2021, and Tennessee was one of six states reporting more than 100 pFF-involved deaths during that period. CDC
pFF remains relevant in 2026. ONDCP has detected para-fluorofentanyl in wastewater across all four Census regions of the United States. ONDCP
The exact potency of para-fluorofentanyl should not be reduced to a single definitive comparison with fentanyl. Published sources have reported differing estimates, and the concentration of an illicit product can vary significantly.
Like fentanyl and other potent opioids, pFF can cause profound sedation, slowed or stopped breathing, unconsciousness, and fatal overdose.
Naloxone should be given when an opioid overdose is suspected, followed by emergency medical care. If normal breathing does not return after the first dose, CDC recommends giving another dose after approximately two to three minutes. CDC
How Brooks helps: Brooks Healing Center provides medical opioid detox, residential addiction treatment, medication assessment and support for opioid use disorder when clinically appropriate, evidence-based therapy, PHP, structured recovery support, and continuing-care planning.

What Is Para-Fluorofentanyl?

Para-fluorofentanyl belongs to a group of substances sometimes called fentanyl analogs or “fentalogs.” These compounds have chemical structures related to fentanyl but may differ in potency, duration, metabolism, and how readily routine toxicology testing identifies them.

pFF was originally synthesized during pharmaceutical research in the 1960s but never became an approved medication. It appeared in the illicit opioid supply during the late 1970s and early 1980s before largely disappearing from routine detection. The United States classified para-fluorofentanyl as a Schedule I controlled substance in 1986. CDC

Decades later, laboratories began identifying it again. CDC documented its return in postmortem toxicology beginning around 2020, including cases in Tennessee.

That history matters because para-fluorofentanyl is sometimes described as though it were a completely new designer drug. It is more accurate to describe it as an older fentanyl analog that has reemerged as the illicit opioid market continues to change.

Is Para-Fluorofentanyl Stronger Than Fentanyl?

There is no responsible reason to give someone a single number and say para-fluorofentanyl is exactly “X times stronger” than fentanyl.

Earlier CDC analysis stated that the limited available evidence suggested pFF was similar to or slightly less potent than illegally manufactured fentanyl, while other reports and more recent federal threat assessments have described fluorofentanyl compounds more broadly as comparable to or potentially more potent than fentanyl. CDC; ONDCP

These statements are not necessarily equivalent because “fluorofentanyl” can encompass more than one structural form, while para-fluorofentanyl refers to a particular isomer. Laboratory potency also does not tell someone how concentrated an illicit powder or pill will be.

The clinically important point is simpler: pFF is a highly potent opioid capable of causing fatal respiratory depression, and illicit products containing it do not have standardized concentrations.

A person cannot look at a powder, pill, or bag and determine whether it contains fentanyl, pFF, another fentanyl analog, a nitazene, or multiple substances together.

Para-Fluorofentanyl Has Already Been Found in Tennessee

Para-fluorofentanyl is not merely a problem occurring somewhere else in the country.

The Knox County Regional Forensic Center first identified pFF in overdose toxicology in November 2020. During November 2020 through August 2021, investigators reported 770 unintentional overdose deaths in Knoxville and surrounding Tennessee counties. Para-fluorofentanyl was detected in 48 of those cases. CDC

National CDC analysis covering July 2020 through June 2021 subsequently identified pFF involvement in 1,658 overdose deaths among 43 participating jurisdictions. Tennessee was among six states reporting more than 100 deaths involving the substance. CDC

The trend did not simply disappear after those early reports. A September 15, 2026 ONDCP threat notice reported para-fluorofentanyl in wastewater samples spanning all four Census regions of the country. The same notice reported widespread laboratory detection of the broader fluorofentanyl category during 2025. ONDCP

This is one reason the modern opioid crisis cannot be understood as a fentanyl-only problem. Fentanyl remains central to overdose risk, but analogs and additional adulterants continue changing the composition of the supply.

Why Is pFF Being Mixed With Fentanyl?

The exact reasons illicit manufacturers use para-fluorofentanyl cannot be assumed from a toxicology result alone. It may appear as an intentionally produced opioid, as part of a fentanyl mixture, or because manufacturers change chemicals and precursor materials as the illicit market evolves.

What researchers do know is that pFF has very frequently appeared alongside fentanyl.

In CDC’s national analysis, more than 90% of pFF-involved overdose deaths during the studied months also involved illegally manufactured fentanyl. Researchers specifically cautioned that the available data could not determine whether pFF represented a separate product or increasing diversification of fentanyl mixtures. CDC

That distinction matters. Someone who believes they are using ordinary street fentanyl may have no way of knowing that pFF or another opioid is present as well.

The same uncertainty applies beyond opioids. Counterfeit prescription pills, cocaine, methamphetamine, and heroin may also contain fentanyl or related synthetic opioids without being advertised that way. CDC continues to warn that fentanyl cannot reliably be identified by sight, smell, or taste. CDC

What Does a Para-Fluorofentanyl Overdose Look Like?

Because pFF acts as an opioid, a para-fluorofentanyl overdose can resemble an overdose involving fentanyl, heroin, or another potent opioid.

Warning signs can include:

Very slow, shallow, irregular, or stopped breathing
Inability to wake the person
Extreme sleepiness or loss of consciousness
Pinpoint pupils
Blue, gray, or unusually pale lips or skin
Limpness
Choking, gurgling, or unusual snoring sounds
Reduced responsiveness
Coma

Do not wait to determine exactly which opioid was taken before responding.

If someone cannot be awakened or is breathing abnormally, call 911 and administer naloxone if it is available. CDC recommends giving one dose, monitoring the person’s breathing, and administering another dose after approximately two to three minutes if normal breathing has not returned. Follow the 911 dispatcher’s instructions for rescue breathing or CPR as appropriate. If the person is breathing but unconscious, place them on their side. Remain with them until emergency help arrives. CDC; SAMHSA

Naloxone reverses opioid effects, so it remains appropriate when pFF or another fentanyl analog may be involved.

However, today’s illicit supply can contain additional non-opioid sedatives. If substances such as medetomidine, xylazine, or benzodiazepines are also present, naloxone will not reverse those drugs themselves. Breathing may improve while the person remains heavily sedated, which is another reason emergency medical evaluation remains necessary.

Can Narcan Reverse Para-Fluorofentanyl?

Yes. Naloxone, commonly sold as Narcan, is an opioid antagonist and should be used in a suspected overdose involving para-fluorofentanyl.

The presence of a particularly potent opioid does not make naloxone pointless. The priority is restoring adequate breathing.

If the first dose does not restore normal breathing within two to three minutes, CDC advises administering another dose while continuing emergency response efforts. Naloxone may also wear off before some opioids do, so someone who initially wakes up can become unresponsive again. CDC

Calling 911 remains important even when the person appears to recover.

Will Para-Fluorofentanyl Show Up on a Drug Test?

Not necessarily, and this is one of the more important issues surrounding emerging fentanyl analogs.

Standard hospital opioid urine screens are not designed to identify every fentanyl analog. ONDCP warned in September 2026 that standard opioid screens do not detect fentanyl analogs and that even fentanyl-specific screens may detect particular analogs differently depending on the test being used. Definitive identification can require specialized laboratory testing. ONDCP

This is also why a routine drug test cannot be treated as a complete inventory of everything someone has been exposed to.

Consumer fentanyl test strips are still an important harm-reduction tool, particularly because ordinary fentanyl is so prevalent in the illicit supply. However, CDC cautions that a negative fentanyl test strip does not guarantee that a substance is free from every fentanyl-like drug. CDC

Does pFF Cause Addiction and Withdrawal?

Para-fluorofentanyl is an opioid, so repeated exposure can contribute to the same broad cycle of tolerance, physical dependence, withdrawal, cravings, compulsive opioid use, and opioid use disorder associated with fentanyl and other opioids.

Someone using what they believe is fentanyl may never know that pFF has been part of their supply. Treatment therefore does not depend on someone arriving with a laboratory-confirmed diagnosis of “para-fluorofentanyl addiction.”

Clinical assessment looks at the larger pattern: what substances are believed to be used, frequency of use, withdrawal symptoms, overdose history, possible polysubstance exposure, previous treatment, medical needs, mental-health symptoms, and whether medications for opioid use disorder may be appropriate.

Withdrawal management is only the beginning. Detox can address immediate physical dependence and stabilization, but opioid use disorder generally requires continuing treatment rather than detoxification alone.

Treatment for Fentanyl and Para-Fluorofentanyl Use in Tennessee

Brooks Healing Center provides opioid addiction treatment from its clinical campus in Normandy, Tennessee, between Nashville and Chattanooga.

Someone entering treatment after using fentanyl, counterfeit pills, heroin, or an uncertain street opioid supply may need care that accounts for much more than the drug name they were given. The modern supply can involve fentanyl analogs, stimulants, benzodiazepine-like substances, veterinary sedatives, nitazenes, and other compounds that may affect stabilization and treatment planning.

Depending on clinical need, treatment at Brooks may include:

Medical detox and opioid withdrawal management
Residential addiction treatment
Assessment for medications for opioid use disorder
Buprenorphine-based treatment when clinically appropriate
Individual and group therapy
Treatment for appropriate co-occurring mental-health concerns
Relapse and overdose-prevention planning
Partial Hospitalization Program
Structured recovery housing
Sober living
Continuing-care planning

Brooks does not operate an opioid treatment program or dispense methadone for opioid use disorder. When clinically appropriate, care involving methadone can be coordinated with an outside qualified provider. Brooks’ existing fentanyl treatment program also supports appropriate buprenorphine-based options as part of a broader treatment plan. Brooks Healing Center

The Larger Issue Is an Unpredictable Opioid Supply

Para-fluorofentanyl is important, but the larger lesson is not that everyone should begin trying to identify one more street drug.

The larger issue is that the contents of the illicit opioid supply can change faster than people using it, families, treatment providers, and routine drug screens can identify those changes.

Fentanyl may be accompanied by pFF. Another sample may contain a nitazene. Another may include medetomidine or another sedative. Counterfeit pills may resemble legitimate oxycodone or another medication while containing none of the expected pharmaceutical ingredient.

That unpredictability is one reason a person’s previous tolerance to a particular bag, pill, powder, or supplier cannot guarantee what will happen with the next exposure.

For someone repeatedly using fentanyl or another illicit opioid, surviving the last dose does not establish that the next one will be equivalent.

Get Help for Fentanyl or Synthetic Opioid Addiction in Tennessee

A person does not need to know whether their supply contains para-fluorofentanyl before asking for help.

Repeated opioid withdrawal, increasing tolerance, using primarily to avoid becoming sick, counterfeit-pill use, unsuccessful attempts to stop, previous overdose, or continuing to use despite serious consequences are all reasons to consider professional assessment.

Brooks Healing Center provides a connected path from medical opioid detox and residential treatment into continued clinical care and recovery support. For someone exposed to today’s changing fentanyl supply, treatment can address both immediate physical dependence and the underlying opioid use disorder rather than waiting for another unknown batch or another overdose.

Call Brooks Healing Center Admissions 24/7. CALL NOW: 931-486-8824

Frequently Asked Questions About Para-Fluorofentanyl

What is another name for para-fluorofentanyl?

Para-fluorofentanyl may be abbreviated pFF and is also called 4-fluorofentanyl or p-fluorofentanyl. It is one particular fluorinated fentanyl analog.

Is para-fluorofentanyl the same as fentanyl?

No. It is chemically related to fentanyl but is a distinct fentanyl analog. In the illicit supply, the two substances are frequently detected together.

Is para-fluorofentanyl stronger than fentanyl?

The exact relative potency of pFF is not settled well enough to responsibly give a universal numerical comparison. CDC previously described limited evidence suggesting potency similar to or somewhat below fentanyl, while newer federal information describes fluorofentanyl compounds more broadly as comparable to or potentially more potent. Regardless of the exact laboratory comparison, pFF is a potent opioid capable of causing fatal respiratory depression. CDC; ONDCP

Is para-fluorofentanyl in Tennessee?

It has been documented in Tennessee. CDC and Tennessee-area forensic data identified pFF in overdose deaths beginning in 2020, and Tennessee was among the states with more than 100 pFF-involved deaths in CDC’s July 2020–June 2021 analysis. More recently, federal wastewater surveillance detected pFF across all four U.S. Census regions during 2026. CDC; ONDCP

Does naloxone work on pFF?

Yes. pFF is an opioid, and naloxone should be administered when an overdose is suspected. Call 911 even if the person begins responding to naloxone.

Can a fentanyl test strip detect para-fluorofentanyl?

A fentanyl test strip should not be treated as a definitive pFF test. Test strips are useful for identifying fentanyl in many drug samples, but CDC cautions that they may not detect every fentanyl-like substance. A negative result does not prove an illicit drug is safe. CDC

Does Brooks treat people who have been using para-fluorofentanyl?

Brooks treats opioid use disorder and opioid dependence rather than requiring a person to know the precise fentanyl analog in their supply. Clinically appropriate patients may receive medical detox, residential care, medication assessment, therapy, PHP, and continued recovery support.

Related Resources

Related Treatment Pages

Sources

Bitting, J., O’Donnell, J., & Mattson, C. L. (2022). Notes from the field: Overdose deaths involving para-fluorofentanyl—United States, July 2020–June 2021. Morbidity and Mortality Weekly Report, 71(39), 1239–1240. https://www.cdc.gov/mmwr/volumes/71/wr/mm7139a3.htm

Centers for Disease Control and Prevention. (2024, April 2). Naloxone frequently asked questions. https://www.cdc.gov/stop-overdose/naloxone-faq/

Centers for Disease Control and Prevention. (2025, June 9). Fentanyl. https://www.cdc.gov/overdose-prevention/about/fentanyl.html

Michigan Department of Health and Human Services. (2022). Emerging trend: Para-fluorofentanyl (pFF) increase in Michigan, 2018–2022 year-to-date. https://www.michigan.gov/opioids/-/media/Project/Websites/opioids/documents/Para-fluorofentanyl_Edited.pdf

Office of National Drug Control Policy. (2026, September 15). Drug threat notice: Key fentanyl analogues, involved in at least 12,500 deaths since 2023, pose heightened threat to nation. https://www.whitehouse.gov/wp-content/uploads/2026/09/Drug-Threat-fentanyl-analogues-1.pdf

Substance Abuse and Mental Health Services Administration. (2024). Overdose prevention and response toolkit. https://www.cdc.gov/overdose-prevention/media/pdfs/2024/04/SAMHSA-overdose-prevention-response-toolkit.pdf

Trecki, J., Gerona, R. R., Ellison, R., Thomas, C., & Mileusnic-Polchan, D. (2022). Notes from the field: Increased incidence of fentanyl-related deaths involving para-fluorofentanyl or metonitazene—Knox County, Tennessee, November 2020–August 2021. Morbidity and Mortality Weekly Report, 71(4), 153–155. https://www.cdc.gov/mmwr/volumes/71/wr/mm7104a3.htm