Fentanyl
Extremely potent synthetic opioid, 50-100x stronger than morphine. Used medically for severe pain. Major contributor to overdose crisis due to presence in illicit drug supply.
Important information
This information is for educational purposes only. Always research thoroughly, test your substances, understand legal implications, and consult healthcare professionals. Never use substances alone or in unsafe environments.
Dosage information
Medical: micrograms only. Street doses impossible to measure accurately - EXTREME DANGER.
Dosage ranges are reference values from published literature, not recommendations. Potency varies by source, body weight, and individual sensitivity — harm-reduction practice starts well below the ranges listed.
Before any number: set, setting, purity, dose · LD50 · microdosing
On this page: known interactions · harm reduction
Duration
30 minutes - 2 hours (IV) | Varies by preparation
IV: 30min-2 hours. EXTREME overdose risk — dosing is in micrograms.
Transdermal patch: 48-72 hours. Medical use only.
Known interactions
Dangerous Fentanyl + Heroin (Diacetylmorphine)
Combining opioids dramatically increases overdose risk. Fentanyl's extreme potency makes any combination with other opioids potentially lethal.
Risks: Fatal respiratory depression · Overdose death · Loss of consciousness · Cardiac arrest
Mechanism: Additive mu-opioid receptor activation causes severe respiratory depression. Fentanyl's potency (50-100x morphine) makes dosing unpredictable.
What reduces the risk
- NEVER combine opioids
- Always have naloxone/Narcan available
- Never use alone
- Call 911 immediately if overdose suspected
Sources: CDC: Fentanyl Facts · NIDA: Overdose Death Rates · TripSit Interaction Chart
Dangerous Fentanyl + Alprazolam (Xanax)
Opioid + benzodiazepine is one of the most common fatal drug combinations. Both suppress breathing through different mechanisms.
Risks: Fatal respiratory depression · Profound sedation · Coma · Death — even at normal doses of each
Mechanism: Opioids depress brainstem respiratory centers via mu-receptors. Benzodiazepines enhance GABA inhibition. Combined effect on respiratory drive is synergistic, not just additive.
What reduces the risk
- NEVER combine opioids with benzodiazepines
- FDA Black Box Warning exists for this combination
- Have naloxone available
- Seek medical supervision if prescribed both
Sources: FDA Drug Safety Communication: Opioid-Benzodiazepine Interactions (2016) · Park TW et al. Benzodiazepine prescribing patterns and deaths from drug overdose. BMJ. 2015 · TripSit Interaction Chart
Dangerous Fentanyl + Cocaine
Cocaine does not cancel out fentanyl. It masks the sedation that would otherwise signal a rising opioid dose, so the opioid is often repeated, and it wears off first — leaving the respiratory depression unopposed.
Risks: Fatal respiratory depression after the stimulant wears off · Opioid dose repeated because sedation is masked · Cardiac strain from raised oxygen demand against suppressed breathing · Overdose recognised too late
Mechanism: Opposing effects on different systems, with different durations. The stimulant raises arousal, heart rate and oxygen demand while the mu-opioid agonist suppresses the respiratory drive. When the stimulant clears, the opioid effect remains.
What reduces the risk
- Avoid the combination
- Risk continues for hours after the stimulant fades, not only at the peak
- Keep naloxone within reach and do not dose alone
- Fentanyl test strips miss some analogues, so a negative result settles nothing
Sources: CDC: stimulant-involved opioid overdose deaths (National Vital Statistics System) · NIDA Research Topics: Polysubstance Use
Dangerous Fentanyl + Methamphetamine
Methamphetamine does not cancel out fentanyl. It masks the sedation that would otherwise signal a rising opioid dose, so the opioid is often repeated, and it wears off first — leaving the respiratory depression unopposed.
Risks: Fatal respiratory depression after the stimulant wears off · Opioid dose repeated because sedation is masked · Cardiac strain from raised oxygen demand against suppressed breathing · Overdose recognised too late
Mechanism: Opposing effects on different systems, with different durations. The stimulant raises arousal, heart rate and oxygen demand while the mu-opioid agonist suppresses the respiratory drive. When the stimulant clears, the opioid effect remains.
What reduces the risk
- Avoid the combination
- Risk continues for hours after the stimulant fades, not only at the peak
- Keep naloxone within reach and do not dose alone
- Fentanyl test strips miss some analogues, so a negative result settles nothing
Sources: CDC: stimulant-involved opioid overdose deaths (National Vital Statistics System) · NIDA Research Topics: Polysubstance Use
Dangerous Fentanyl + Adderall (Amphetamine)
Adderall does not cancel out fentanyl. It masks the sedation that would otherwise signal a rising opioid dose, so the opioid is often repeated, and it wears off first — leaving the respiratory depression unopposed.
Risks: Fatal respiratory depression after the stimulant wears off · Opioid dose repeated because sedation is masked · Cardiac strain from raised oxygen demand against suppressed breathing · Overdose recognised too late
Mechanism: Opposing effects on different systems, with different durations. The stimulant raises arousal, heart rate and oxygen demand while the mu-opioid agonist suppresses the respiratory drive. When the stimulant clears, the opioid effect remains.
What reduces the risk
- Avoid the combination
- Risk continues for hours after the stimulant fades, not only at the peak
- Keep naloxone within reach and do not dose alone
- Fentanyl test strips miss some analogues, so a negative result settles nothing
Sources: CDC: stimulant-involved opioid overdose deaths (National Vital Statistics System) · NIDA Research Topics: Polysubstance Use
Dangerous Fentanyl + Alcohol (Ethanol)
Alcohol dramatically increases opioid overdose risk. Even small amounts of alcohol with fentanyl can be fatal.
Risks: Fatal respiratory depression · Overdose · Aspiration of vomit · Cardiac depression
Mechanism: Both substances depress CNS and respiratory function. Alcohol enhances opioid absorption and impairs metabolism.
What reduces the risk
- NEVER combine alcohol with any opioid
- Even small amounts of alcohol increase overdose risk
- Have naloxone available
- Never use alone
Sources: NIAAA: Harmful Interactions with Alcohol · TripSit Interaction Chart · FDA Drug Interaction Warnings
Dangerous Fentanyl + Kratom (Mitragyna speciosa)
Kratom activates opioid receptors. Combining with fentanyl creates additive respiratory depression risk.
Risks: Respiratory depression · Overdose · Profound sedation · Death
Mechanism: Both act on mu-opioid receptors. Kratom's partial agonism combined with fentanyl's full agonism can cause respiratory failure.
What reduces the risk
- NEVER combine kratom with opioids
- If using kratom for opioid reduction, do so under medical supervision
- Have naloxone available
Sources: FDA: Kratom and Opioid Interaction Warnings · TripSit Interaction Chart · Prozialeck WC et al. Pharmacology of Kratom. J Am Osteopath Assoc. 2012
Dangerous Fentanyl + Ibogaine
Ibogaine causes QT prolongation. Combined with opioids, risk of fatal cardiac arrhythmia and respiratory depression is extreme.
Risks: Fatal cardiac arrhythmia · QT prolongation leading to Torsades de Pointes · Respiratory failure · Death
Mechanism: Ibogaine blocks hERG potassium channels (QT prolongation) + opioid respiratory depression = cardiac arrest risk.
What reduces the risk
- Ibogaine requires full medical screening before use
- All opioids must be cleared from the system first
- Only use ibogaine in a medical facility with cardiac monitoring
- EKG screening mandatory
Sources: Koenig X, Hilber K. The anti-addiction drug ibogaine and the heart. Molecules. 2015 · MAPS: Ibogaine Therapy Guidelines · TripSit Interaction Chart
Dangerous Fentanyl + Ketamine
Despite some medical co-administration, unsupervised combination of ketamine and opioids creates severe respiratory depression risk.
Risks: Respiratory depression · Loss of consciousness · Inability to detect overdose symptoms · Death
Mechanism: Ketamine's dissociative sedation masks opioid overdose signs. Combined respiratory depression can be fatal.
What reduces the risk
- Never combine without medical supervision
- Have naloxone available
- Never use alone
Sources: TripSit Interaction Chart · PsychonautWiki: Ketamine Interactions
Caution Fentanyl + Caffeine
Caffeine is a far weaker stimulant than cocaine or amphetamine, and this is not the same risk as those combinations. It still shifts how sedated a person feels without changing what fentanyl does to breathing.
Risks: Sedation judged by how alert someone feels rather than by the dose taken · No protection against respiratory depression · Disrupted sleep across a long opioid offset
Mechanism: Raised alertness can make an opioid feel less sedating than it is. The masking is much weaker than with a potent stimulant, and it offers no protection against respiratory depression.
What reduces the risk
- Do not read alertness as a sign the opioid has worn off
- Never use a stimulant to counteract opioid sedation
- Keep naloxone within reach and do not dose alone
Sources: NIDA Research Topics: Polysubstance Use
Caution Fentanyl + Nicotine
Nicotine is a far weaker stimulant than cocaine or amphetamine, and this is not the same risk as those combinations. It still shifts how sedated a person feels without changing what fentanyl does to breathing.
Risks: Sedation judged by how alert someone feels rather than by the dose taken · No protection against respiratory depression · Disrupted sleep across a long opioid offset
Mechanism: Raised alertness can make an opioid feel less sedating than it is. The masking is much weaker than with a potent stimulant, and it offers no protection against respiratory depression.
What reduces the risk
- Do not read alertness as a sign the opioid has worn off
- Never use a stimulant to counteract opioid sedation
- Keep naloxone within reach and do not dose alone
Sources: NIDA Research Topics: Polysubstance Use
Absence of a listed interaction never implies safety. Check any combination in the app's 23×23 interaction matrix.
Harm reduction
- NEVER use alone
- Fentanyl test strips essential
- Naloxone/Narcan on hand always
- Start with tiny amount if testing
- Never mix with alcohol or benzos
- Call 911 immediately if overdose
- Supervised consumption sites
- Don't assume tolerance
Risks & side effects
- EXTREMELY HIGH overdose risk
- Respiratory failure
- Death
- Highly addictive
- Severe withdrawal
- Often in other drugs unknowingly
Effects
- Extreme pain relief
- Euphoria
- Sedation
- Relaxation
- Respiratory depression
- Nausea
Legal status
Schedule II. Prescription medication. Illicit analogues are Schedule I.
Pharmacology
Mu-opioid receptor agonist. Extremely high potency and lipophilicity.
Therapeutic research
- FDA-approved: Intravenous fentanyl for surgical anesthesia and acute pain management
- FDA-approved: Transdermal patches for chronic pain in opioid-tolerant patients
- FDA-approved: Transmucosal forms (Actiq, Fentora) for breakthrough cancer pain
- WHO Essential Medicine for pain management and anesthesia
- Research into abuse-deterrent formulations and safer opioid alternatives
- Focus of public health research on harm reduction: naloxone distribution, fentanyl test strips, drug checking services
Clinical studies 5
Overdose Deaths Involving Fentanyl and Fentanyl Analogs — New York City, 2000–2017
Colon-Berezin et al. 2019 CDC MMWR. Epidemiological analysis of fentanyl overdose deaths showing dramatic increase from 2 to 57% of overdose deaths.
Testing the test strips: laboratory performance of fentanyl test strips
Halifax et al. 2024 Harm Reduction Journal. Laboratory evaluation of fentanyl test strip accuracy for harm reduction applications.
O'Donnell et al. 2018 CDC MMWR. Epidemiological report on carfentanil-involved overdose deaths across 10 states, documenting lethal doses and forensic findings.
Walter 2023 JAMA. Clinical overview of fentanyl overdose presentation, treatment with naloxone, and harm reduction strategies.
Zibbell et al. 2019 JAMA Network Open. Analysis correlating carfentanil/fentanyl seizures with overdose mortality, establishing dose-lethality relationships.
History & culture
Fentanyl was first synthesized by Paul Janssen of Janssen Pharmaceutica in 1960 as part of a search for more potent analgesics. It was introduced for medical use in 1968 as an intravenous anesthetic (Sublimaze). Transdermal patches (Duragesic) were approved in 1990 for chronic pain management. Illicitly manufactured fentanyl (IMF) began appearing in the US drug supply around 2013, primarily produced in clandestine labs in China and Mexico. By 2021, synthetic opioids (primarily fentanyl) surpassed all other drugs as the leading cause of overdose death in the US, killing over 70,000 Americans annually. The ongoing fentanyl crisis represents the deadliest phase of the opioid epidemic.
Natural origins
Fentanyl is entirely synthetic — it has no natural precursors in the traditional sense. It is a 4-anilidopiperidine, structurally unrelated to morphine and other opium-derived opioids. Despite binding the same mu-opioid receptors as natural opioids, fentanyl was designed from scratch. Its extreme potency (50–100x morphine) comes from high lipophilicity and strong receptor binding affinity. The illicit fentanyl supply has spawned numerous analogues (carfentanil, acetylfentanyl, fluorofentanyl) — some even more potent than fentanyl itself.
Molecular family: Opioids
Opioids are alkaloids and semisynthetic compounds that activate opioid receptors (mu, delta, kappa). Natural opioids derive from the opium poppy, producing morphine, codeine, and papaverine. Heroin is a semisynthetic modification of morphine, while fentanyl is a fully synthetic compound. These substances differ fundamentally from psychedelics and dissociatives—producing pain relief, euphoria, and respiratory depression through endogenous opioid system activation. Key characteristics: - Primarily mu-opioid receptor agonists - Natural alkaloids from opium poppy or fully synthetic - Include morphine, codeine, heroin, fentanyl, buprenorphine - Produce analgesia, sedation, and euphoria - Activate endogenous opioid system - High abuse and addiction potential Unlike psychedelics that enhance perception or dissociatives that disconnect it, opioids modulate pain and affect regulation through a different neurochemical system. The structural diversity within opioids—from poppy alkaloids to laboratory synthesis—produces a spectrum of effects balancing therapeutic benefit against addiction risk.
Structurally related to Endogenous opioid peptides (beta-endorphin, enkephalins)
