This page shows what was measured, who it was measured in, and what that does not settle.
What Fentanyl does in the body
Hospital anaesthesia and severe chronic pain, with a separate deadly illicit supply.
Fentanyl is a µ-opioid agonist about a hundred times more potent than morphine by weight, and far more fat-soluble, so it crosses into the brain within seconds. Outside that setting the same properties are what kill. Doses that matter are measured in micrograms, so an uneven mixture is a lethal one, and the effect arrives before anyone can intervene. There is a second mechanism as well: fentanyl produces rigidity of the diaphragm, chest wall and upper airway within a very narrow dose range, by pathways that are not purely opioid — which is part of why naloxone works less reliably here than against heroin.
What happened in people
In one year, synthetic opioids led by illicit fentanyl were involved in 64 in 100 United States overdose deaths.
✓ Reviewed first-read answer
Where this came from
A person wrote this and a reviewer approved it against this exact record. It carries no effect size.
A reviewer approved this against this record. The reviewed-claim record carrying the exact population and effect size does not exist yet.
No source is stored against this line.
The limit that matters most
A carefully measured hospital dose and an unknown street dose are not comparable exposures.
Where it acts
µ-opioid receptors in the brainstem respiratory centres and the spinal dorsal horn; the rigidity syndrome involves brainstem noradrenergic and cholinergic pathways as well
Kind of result
The kind of result is not recorded
Supervision
Professional supervision is normally required. A regulator classifies this substance in a way that restricts how it is supplied.
What the registries record it as
The substance registry classes this as chemical.
FDA substance registry · UF599785JZ · read 2026-08-29
Its recorded molecular formula is C22H28N2O, weighing 336.5 g/mol.
US prescribing information · bf02ffd0-cc5d-446b-b648-378f6885052f · read 2026-08-30
Where each sentence above came from
The recorded explanation names an amount, so it does not open this page. The page opens with what it is taken for instead, and the recorded explanation follows below.
Shown as the opening line on this page.
The limit a reviewer approved as the one that matters most here.
The four opening statements run to 136 words.
Words this page uses
Four words worth knowing first
Chosen from what this page shows, with each one explained before the word it depends on.
Stand-in result
A stand-in result is a number measured because the real result takes too long.
A picture of it, and where the picture fails
It is like judging a journey by the speedometer rather than by arriving.
Where that stops being true. Speed does predict arrival. Many stand-in results do not predict the real one.
What people get wrong. A stand-in result is often reported as the result itself.
A surrogate endpoint substituted for a clinical endpoint, valid only where the substitution has been shown to hold.
Enzyme
An enzyme is a protein that speeds up one chemical change.
A picture of it, and where the picture fails
An enzyme is like a machine on a production line doing one cut.
Where that stops being true. A machine is switched on and off by a person. Enzymes are controlled by the cell.
What people get wrong. Enzymes are thought to be used up. They are not; they work again and again.
A catalytic protein that lowers the activation energy of a specific reaction.
Receptor
A receptor is a part of a cell that a signal fits into.
A picture of it, and where the picture fails
A receptor is like a lock waiting for one key.
Where that stops being true. A lock either opens or does not. A receptor can be half-triggered, or worn out.
What people get wrong. Fitting a receptor is read as causing a benefit. It causes a step, and nothing more.
A protein that binds a specific ligand and converts that binding into a cellular response.
Pathway
A pathway is a chain of steps inside a cell, each one setting off the next.
A picture of it, and where the picture fails
A pathway is like a row of dominoes.
Where that stops being true. Dominoes fall one way. Pathways loop back and can switch themselves off.
What people get wrong. Changing one step is read as changing the outcome. Other steps often absorb it.
An ordered series of molecular interactions producing a defined cellular change.
What happened in people◇Read from sources, not yet reviewed
What was measured, goal by goal
One row for each goal a registered study measured something for. One column for each kind of thing that could be measured.
Registered studies list 40 outcome measures that RNAWiki could read. A registered study says what someone planned to measure. It does not say what they found. 0 of the matched studies tested this substance, and 0 posted a result.
There is no single score. A strong test result and a weak life result are different facts.
Goals down the side, kinds of measurement across the top. Each cell says what kind of thing was registered, not what was found.
Goal
Life outcome
What a body can do
How a person feels
A test result
A step in the body
Harms
How long
Who was studied
Pain
∅Nothing in the sources checkedNo registered study lists a life outcome for this goal.
∅Nothing in the sources checkedNo registered study lists a performance measure for this goal.
…Waiting for a reviewer10 registered symptom measure.
∅Nothing in the sources checkedNo registered study lists a test result for this goal.
∅Nothing in the sources checkedNo registered study lists a body-step measure for this goal.
—Not recordedHarms were not a registered measure for this goal.
—Not recordedNo finished study window is recorded.
…Waiting for a reviewerWho was studied is listed further down the page.
Sleep
∅Nothing in the sources checkedNo registered study lists a life outcome for this goal.
∅Nothing in the sources checkedNo registered study lists a performance measure for this goal.
∅Nothing in the sources checkedNo registered study lists a symptom measure for this goal.
∅Nothing in the sources checkedNo registered study lists a test result for this goal.
∅Nothing in the sources checkedNo registered study lists a body-step measure for this goal.
—Not recordedHarms were not a registered measure for this goal.
—Not recordedNo finished study window is recorded.
…Waiting for a reviewerWho was studied is listed further down the page.
Endurance
∅Nothing in the sources checkedNo registered study lists a life outcome for this goal.
…Waiting for a reviewer1 registered performance measure of this kind.
∅Nothing in the sources checkedNo registered study lists a symptom measure for this goal.
∅Nothing in the sources checkedNo registered study lists a test result for this goal.
∅Nothing in the sources checkedNo registered study lists a body-step measure for this goal.
—Not recordedHarms were not a registered measure for this goal.
—Not recordedNo finished study window is recorded.
…Waiting for a reviewerWho was studied is listed further down the page.
Recovery
∅Nothing in the sources checkedNo registered study lists a life outcome for this goal.
∅Nothing in the sources checkedNo registered study lists a performance measure for this goal.
∅Nothing in the sources checkedNo registered study lists a symptom measure for this goal.
∅Nothing in the sources checkedNo registered study lists a test result for this goal.
∅Nothing in the sources checkedNo registered study lists a body-step measure for this goal.
—Not recordedHarms were not a registered measure for this goal.
—Not recordedNo finished study window is recorded.
…Waiting for a reviewerWho was studied is listed further down the page.
Which registered measures put each goal on this table
Pain
pain; pain at rest; pain relief; incidence of pain; time to analgesia; pain reduction; pain visual analogue scale; postoperative pain
Sleep
quality of sleep
Endurance
endurance time
Recovery
recovery time
Sorted by fixed word lists, version v1. A name the rules do not recognise stays unsorted rather than moving to the nearest column.
What each mark on this table means
∅ Nothing in the sources checked
No registered study lists a life outcome for this goal.
… Waiting for a reviewer
10 registered symptom measure.
— Not recorded
Harms were not a registered measure for this goal.
What happened in people◇Read from sources, not yet reviewed
What happened in people
Each card is one study: the exact question it asked, who was in it, and whether it showed what it set out to show.
Whether the TIRF REMS prevented prescribing to opioid-nontolerant patients and for non-approved indications
✗ The study did not show it
Who was studied
Rollman et al. 2019 FDA TIRF REMS document analysis
How many people
4877
Study design
Qualitative analysis of regulatory documents, 2012-2017
Compared against
Not recorded for this study
Kind of result
A number that stands in for health
What was found
At 60 months, 34.6% to 55.4% of TIRF-prescribed patients were opioid-nontolerant; 34.2% of prescribers reported prescribing for chronic non-cancer pain at 48 months
Repeated elsewhere
Unreplicated
What this does not prove. A study that did not show an effect does not show that no effect exists anywhere.
The limits of this study, and where it came from
Main limit. No prescriber was reported as disenrolled for inappropriate prescribing despite a noncompliance plan, and few substantive changes were made to the programme over the 60 months examined.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Intravenous, transdermal patch, transmucosal lozenge or spray — and, illicitly, powder and counterfeit tablets
Interval reported. Not recorded in this summary
Written into the record, not signed off as a reviewed claim.
Trends in and characteristics of overdose deaths involving illicitly manufactured fentanyls
✓ The study showed what it set out to show
Who was studied
O'Donnell et al. 2021 SUDORS analysis of IMF-involved deaths
How many people
0
Study design
National surveillance analysis, July 2019-December 2020
Compared against
Not recorded for this study
Kind of result
Living longer, or avoiding a major event
What was found
IMF-involved deaths rose 33.1% in midwestern, 64.7% in southern and 93.9% in western jurisdictions; stimulant co-involvement in approximately 4 in 10
Repeated elsewhere
Replicated
What this does not prove. Meeting one endpoint in one population does not carry to other goals or other people.
The limits of this study, and where it came from
Main limit. 56.1% of decedents had no pulse when first responders arrived, which places a hard ceiling on what any reversal agent can achieve at the population level.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Intravenous, transdermal patch, transmucosal lozenge or spray — and, illicitly, powder and counterfeit tablets
Interval reported. Not recorded in this summary
Written into the record, not signed off as a reviewed claim.
Trends in and characteristics of overdose deaths with evidence of counterfeit pill use
✓ The study showed what it set out to show
Who was studied
O'Donnell et al. 2023 counterfeit pill analysis
How many people
0
Study design
National surveillance analysis, July 2019-December 2021
Compared against
Not recorded for this study
Kind of result
Living longer, or avoiding a major event
What was found
Quarterly percentage rose from 2.0% to 4.7% nationally and from 4.7% to 14.7% in western jurisdictions; IMFs the only drugs involved in 41.4% of such deaths
Repeated elsewhere
Replicated
What this does not prove. Meeting one endpoint in one population does not carry to other goals or other people.
The limits of this study, and where it came from
Main limit. Evidence of counterfeit pill use depends on scene investigation and is likely undercounted. Decedents were substantially younger than in other overdose deaths, 57.1% under 35.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Intravenous, transdermal patch, transmucosal lozenge or spray — and, illicitly, powder and counterfeit tablets
Interval reported. Not recorded in this summary
Written into the record, not signed off as a reviewed claim.
RNAWiki holds 3 written-up human studies for this substance, each with the question it asked.
How we know it
Each card names the study, the number of people and what the study set out to measure.
What this does not prove
These summaries were written by a person and have not been signed off as reviewed claims.
Why it matters
A study that failed is as informative as one that worked, and both are here.
What we still do not know
No reviewed claim exists, so no exact population, effect size or interval is published yet.
What happened in people◇Read from sources, not yet reviewed
How close this is to real life
The top step is something a person would feel or care about. The bottom is a guess from software. Filled steps are where evidence exists for this substance.
□Living longer, or avoiding a major eventNo evidence recorded. Death, a heart attack, a stroke, a hospital stay.No registered study measures this.
■What a body can do day to dayEvidence recorded. Walking, dressing, breathing, recovering.1 registered measure of this kind.
■Measured performanceEvidence recorded. How much was lifted, how far was run, how fast.1 registered measure of this kind.
■Symptoms and quality of lifeEvidence recorded. Pain, tiredness, mood, sleep, as the person rated it.10 registered measures of this kind.
■A number that stands in for healthEvidence recorded. Cholesterol, blood sugar, bone density. A stand-in, not the thing itself.2 registered measures of this kind.
■A step measured inside a personEvidence recorded. Something measured in human tissue or human cells.A human record sits on the stored organism ladder.
■AnimalsEvidence recorded. Mice, rats, dogs. Useful for ideas, not proof about people.Stored records in Mouse, Rat, Dog. A result in animals says what to test next. It does not say what happens in people.
■Cells in a dishEvidence recorded. Cells or chemistry on a bench, far from a whole body.Stored mechanism abstracts describe steps measured in cells or tissue.
□A guess from softwareNo evidence recorded. Nobody measured it. RNAWiki never publishes one as a finding.RNAWiki stores no prediction for this record. Software can suggest a link. RNAWiki does not publish one as a finding.
Higher on these steps means closer to something a person would feel. It does not mean better done.
What it changes in the body◇Read from sources, not yet reviewed
The path through the body
From what a person takes to what changes. A solid line is a step measured in people. A dashed line is a step nobody has measured that way.
Start
Fentanyl
What a person takes: Intravenous, transdermal patch, transmucosal lozenge or spray — and, illicitly, powder and counterfeit tablets.
The measurement behind this step
Every approved delivery system exists to control the rate of exposure: an intravenous bolus titrated by an anaesthetist with the airway secured, a transdermal patch releasing tens of micrograms an hour, a transmucosal unit for breakthrough pain in an already tolerant patient. The illicit delivery system has no rate control at all. Counterfeit tablets pressed to resemble oxycodone or alprazolam are the fastest-growing route, and they deliver fentanyl to people who believe they are taking a pharmaceutical.
Getting in
Given in micrograms — or in an unmeasured amount
In hospital, a syringe or a patch delivering tens of micrograms an hour. Illicitly, a fraction of a milligram somewhere in a powder or a pressed tablet.
╌╌Described, with no measurement named. No measurement is named for this step, so it is drawn as an unconfirmed link.
The measurement behind this step
Intravenous, transdermal or transmucosal administration in the approved products, all at microgram dosing. In the illicit supply, blended powder or counterfeit tablets with no assay and no assurance of homogeneity — the variance between tablets from one batch is the determinant of outcome.
It is far more fat-soluble than morphine, so it crosses into the brain almost immediately rather than over many minutes.
╌╌Described, with no measurement named. No measurement is named for this step, so it is drawn as an unconfirmed link.
The measurement behind this step
High lipophilicity gives rapid blood-brain equilibration and fast onset, the property that made it valuable in anaesthesia. Metabolised by CYP3A4 to norfentanyl, the analytical marker used alongside the parent compound in casework.
The same receptor as morphine, at roughly a hundredth of the weight for the same effect.
╌╌Described, with no measurement named. No measurement is named for this step, so it is drawn as an unconfirmed link.
The measurement behind this step
Potent µ-opioid agonism on an anilidopiperidine scaffold, giving analgesia with hemodynamic stability — the combination that revolutionised surgical anaesthesia in the 1970s and the reason the drug remains in routine use.
And, within a narrow dose range, locks the chest rigid
The diaphragm, chest wall and upper airway can become rigid. This is a separate effect from ordinary opioid respiratory depression and it comes on very fast.
╌╌Described, with no measurement named. No measurement is named for this step, so it is drawn as an unconfirmed link.
The measurement behind this step
Wooden chest syndrome, involving α-adrenergic and cholinergic mechanisms as well as opioid ones, producing mechanical failure of respiration and airway closure. Almost routinely fatal without expert airway management, and distinct from the slower respiratory depression of morphine-derived alkaloids.
Naloxone works on the opioid receptor and should always be given. It may not address the rigidity, which is why airway management matters.
╌╌Described, with no measurement named. No measurement is named for this step, so it is drawn as an unconfirmed link.
The measurement behind this step
Competitive µ-opioid antagonism reverses the opioid component. The review literature argues naloxone may be ineffective against the centrally mediated noradrenergic and cholinergic effects manifesting as rigidity and airway closure — one reason 56.1% of IMF decedents had no pulse when first responders arrived.
No suggested links are held for this record, so nothing is hidden from this path.
What we know
The record describes 5 steps from taking it to an effect in a person.
How we know it
Each step names the study behind it in the technical detail beside it.
What this does not prove
A change inside the body is a reason to look. It is not a result in a person.
Why it matters
A reader can see exactly where the chain stops being measured in people.
What we still do not know
No reviewed claim binds any of these steps to a named population.
What it would be like to take◇Read from sources, not yet reviewed
Felt, measured, or meaningful
Three different things that get called the same word. Registered studies measured all three, and mixing them is how a blood test becomes a health claim.
Felt
Things a person could notice without a test.
pain
pain at rest
pain relief
incidence of pain
pain reduction
pain visual analogue scale
postoperative pain
visual analogue scale pain intensity
pain level
pain numeric rating scale
Measured
Things only a test, a scale or a device shows.
plasma potassium concentration
endurance time
time to reach the maximum drug concentration in plasma
Meaningful
Things that change how a life goes, not only a number.
No registered study measured anything of this kind.
A registered study says what someone planned to measure. It does not say what they found. A number moving is not the same as a life going better. The two are shown apart here.
Felt, but not shown to help. A person notices a change. No study showed it leads anywhere good.
Measured, but not felt. A number moves. The person notices nothing. Both can be true.
Measured, but not shown to matter. A number moves in the good direction. Nobody showed that lives went better.
Matters, but takes years. The result that counts may take longer than anyone would keep watching.
Names that fit none of the three (27)
primary
safety and tolerability
intraoperative signs of inadequate anesthesia
postoperative recall of events
mlaep parameters
duration of hospital stay
time to analgesia
onset time of brachial plexus anesthesia
adverse events
onset time of brachial plexus sensory block
quality of sleep
bioequivalence according to us fda guidelines
rate and extend of absorption
intracranial pressure
vital signs
decreased minute ventilation
total midazolam
duration of block
time to first requirement of analgesic supplement
postoperative analgesic requirements
These are harms, study-process measures, or names the rules did not recognise. They are shown rather than dropped.
What it would be like to take◇Read from sources, not yet reviewed
How long anything takes
Nine different lengths of time that get confused with each other. None of them is worked out from another.
Before anything is noticed.RNAWiki does not store this separately, and never works it out from another figure on this page.
Before a test result moves.RNAWiki does not store this separately, and never works it out from another figure on this page.
Before performance moves.RNAWiki does not store this separately, and never works it out from another figure on this page.
How long the result was watched.No finished study window is recorded for a study that tested this substance.
How long people took it.How long people actually took it is not stored. The study window is not the same thing.
How long people were followed.Follow-up length is not stored separately. It is never read off the study window, which would be a different thing.
How fast the body clears it. 34 hours hours
Read from the label, which states: “A study conducted with the fentanyl transdermal system patch in elderly patients demonstrated that fentanyl pharmacokinetics did not differ significantly from young adult subjects, although peak serum concentrations tended to be lower and mean half-life values were prolonged to approximately 34 hours.”
How long effects linger.RNAWiki does not store this separately, and never works it out from another figure on this page.
Beyond the studies. Nothing is recorded about the long term.
The longest finished study sets the edge of what anyone measured.
A study window is not how long people took it, and neither is how long they were followed. Where RNAWiki holds only one of the three, it shows one.
What is missing or unclear◇Read from sources, not yet reviewed
Were people like you studied?
RNAWiki cannot tell whether a study fits you. It can show who was in it, and where the result stops carrying.
Who was studied
People similar to this profile were included.
Surgical patients under anaesthesia, patients with severe chronic or cancer pain, and — in the illicit supply — people who mostly did not choose it, with counterfeit-pill deaths concentrated in the under-35 age group.
Who is missing from the studies
Which groups were under-represented in the studies has not been recorded for this substance. Pregnancy, breastfeeding, children, older adults, and people with liver or kidney conditions are commonly excluded from trials; nothing here says whether they were.
What the label states about particular groups
On pediatric, the label states: “The safety of fentanyl transdermal system was evaluated in three open-label trials in 289 pediatric patients with chronic pain, 2 years of age through 18 years of age.”
US prescribing information · bf02ffd0-cc5d-446b-b648-378f6885052f · read 2026-08-30
On older people, the label states: “Clinical studies of fentanyl transdermal system did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects.”
US prescribing information · bf02ffd0-cc5d-446b-b648-378f6885052f · read 2026-08-30
On people who are pregnant, the label states: “Risk Summary Use of opioid analgesics for an extended period of time during pregnancy may cause neonatal opioid withdrawal syndrome [see Warnings and Precautions ( 5.5 )] .”
US prescribing information · bf02ffd0-cc5d-446b-b648-378f6885052f · read 2026-08-30
On people who are breastfeeding, the label states: “Risk Summary Fentanyl is excreted in human milk; therefore, fentanyl transdermal system is not recommended for use in nursing women because of the possibility of effects in their infants.”
US prescribing information · bf02ffd0-cc5d-446b-b648-378f6885052f · read 2026-08-30
On people with reduced liver function, the label states: “The effect of hepatic impairment on the pharmacokinetics of fentanyl transdermal system has not been fully evaluated.”
US prescribing information · bf02ffd0-cc5d-446b-b648-378f6885052f · read 2026-08-30
On people with reduced kidney function, the label states: “The effect of renal impairment on the pharmacokinetics of fentanyl transdermal system has not been fully evaluated.”
US prescribing information · bf02ffd0-cc5d-446b-b648-378f6885052f · read 2026-08-30
Where the result stopped carrying
The TIRF REMS failed on its central measure across 60 months, with no prescriber reported disenrolled and few substantive programme changes
Harm-reduction services built around injection reach only part of the population: 27.1% of IMF decedents had evidence of snorting, smoking or ingestion without injection
This is a scope explorer, not a diagnosis engine.
It shows who was studied so you can see whether people similar to you were included.
RNAWiki cannot tell whether a study fits you. It can show who was in it.
What it would be like to take◇Read from sources, not yet reviewed
Why it might seem to do nothing
A real effect and a noticed effect are different things. These are the recorded reasons the two come apart.
It was studied for a different goal
The studies measured something else entirely.
On this record: Some registered studies measured things that match no goal on this page.
It was studied in different people
The people in the studies were not much like the reader.
On this record: Which groups were under-represented in the studies has not been recorded for this substance. Pregnancy, breastfeeding, children, older adults, and people with liver or kidney conditions are commonly excluded from trials; nothing here says whether they were.
The evidence may simply be wrong
Small early studies often do not hold up.
On this record: RNAWiki has not yet published a reviewed conclusion for this use.
Other reasons RNAWiki checked and found nothing for (10)
A different form was studied
The studied form is not the form on the shelf. Nothing in this record points to this reason.
There was nothing to correct
Where a level is already normal, topping it up may change nothing. Nothing in this record points to this reason.
Something else had to happen too
In the studies it was paired with training, a diet or another treatment. Nothing in this record points to this reason.
The change is too small to feel
A real change can still sit below what a person notices. Nothing in this record points to this reason.
Day-to-day swing hides it
Sleep, food, stress and time of day move most numbers more than this would. Nothing in this record points to this reason.
Not enough time yet
The studies ran longer than the person has waited. Nothing in this record points to this reason.
It was not taken as studied
Missed days change the result, and studies count them. Nothing in this record points to this reason.
Something else changed at the same time
Two changes at once cannot be told apart afterwards. Nothing in this record points to this reason.
The product may not be what it says
Contents of a sold product are not always what the label states. Nothing in this record points to this reason.
No recorded reason
RNAWiki has nothing stored that would explain it. Nothing in this record points to this reason.
None of these is a reason to take more. Taking more is not a step this page ever suggests.
What it would be like to take◇Read from sources, not yet reviewed
What taking it involves
The recorded facts about getting hold of it and using it. Nothing here is a suggestion about what you should do.
How it is supplied
Given by a clinician
❝ Quoted from a source
Where this came from
Copied from a source RNAWiki stored, with the source named.
Read from the recorded approval status.
No source is stored against this line.
Form and route
Intravenous, transdermal patch, transmucosal lozenge or spray — and, illicitly, powder and counterfeit tablets
✎ Source-linked record
Where this came from
A person wrote this into the record with the study named beside it. No reviewer has signed it off.
The form and route recorded on this substance.
No source is stored against this line.
Who oversees it
Professional supervision is normally required. A regulator classifies this substance in a way that restricts how it is supplied.
❝ Quoted from a source
Where this came from
Copied from a source RNAWiki stored, with the source named.
Suppression classes recorded: S1, S2, S5, S6.
No source is stored against this line.
What is in the pack
Every approved delivery system exists to control the rate of exposure: an intravenous bolus titrated by an anaesthetist with the airway secured, a transdermal patch releasing tens of micrograms an hour, a transmucosal unit for breakthrough pain in an already tolerant patient.
✎ Source-linked record
Where this came from
A person wrote this into the record with the study named beside it. No reviewer has signed it off.
Recorded notes on how this is sold. The rest of the recorded wording: The illicit delivery system has no rate control at all. Counterfeit tablets pressed to resemble oxycodone or alprazolam are the fastest-growing route, and they deliver fentanyl to people who believe they are taking a pharmaceutical.
No source is stored against this line.
Where it is registered
Regulatory records are listed in the technical disclosure at the foot of this page.
# Counted from records
Where this came from
A count of rows RNAWiki holds. It describes our records, not your body.
Register entries are stored per jurisdiction and shown with their dates.
No source is stored against this line.
Why people stop
Not recorded.
∅ Nothing recorded
Where this came from
RNAWiki holds nothing here and says so rather than guessing.
No record of why people stopped taking it is stored for this substance.
No source is stored against this line.
What it would be like to take◇Read from sources, not yet reviewed
What can go wrong
Sorted by where each line came from. A regulator's label and a report somebody sent in are not the same kind of fact.
·Worth asking a clinician aboutWritten into the record from the studies named on this page
Respiratory depression is the dose-limiting effect and the mechanism of death. Wooden chest syndrome — rigidity of diaphragm, chest wall and upper airway within a very narrow dose range — is a distinct and faster mechanism, involves non-opioid pathways, and is almost routinely fatal without expert airway management. Naloxone reverses the opioid component and should always be given; it may not address the rigidity. Transdermal patches carry additional hazards from heat exposure, from damaged or chewed patches, and from residual drug after removal. In the illicit supply the dominant hazard is dose variance, compounded by frequent co-presence of stimulants and of xylazine, which has no antidote. In the SUDORS series 56.1% of decedents had no pulse when first responders arrived.
Nobody counted how many people took this and were fine, so this cannot be turned into a rate.
These are reports people sent to a regulator. They do not show the medicine caused the reaction.
Nobody counted how many people took the medicine and reported nothing.
The same event can be reported more than once, and many reports are incomplete.
News coverage, lawsuits and new warnings change how often people report.
A count is not a rate and not a risk.
Fentanyl appears in spontaneous reports to regulators. Across the 6 most-reported reaction terms, 52 reaction mentions were counted. One report can name several reactions.
The recorded terms (6)
application site erythema — 15 reaction mentions
application site vesicles — 12 reaction mentions
application site burn — 9 reaction mentions
application site irritation — 6 reaction mentions
application site pruritus — 5 reaction mentions
application site rash — 5 reaction mentions
open-targets-adr · recorded 2026-06-24 · a recorded source, not a stored snapshot
Over a long time. No completed tested study window is recorded, so long-term effects are not established by the registry record.
Groups the studies covered thinly. Which groups were under-represented in the studies has not been recorded for this substance. Pregnancy, breastfeeding, children, older adults, and people with liver or kidney conditions are commonly excluded from trials; nothing here says whether they were.
What is missing or unclear◇Read from sources, not yet reviewed
Does the exact form matter?
Evidence belongs to the exact thing that was tested. A different salt, a different mixture or a different preparation is a different question.
The form that was studied
Intravenous, transdermal patch, transmucosal lozenge or spray — and, illicitly, powder and counterfeit tablets
✎ Source-linked record
Where this came from
A person wrote this into the record with the study named beside it. No reviewer has signed it off.
The form used in the studies cited on this page.
No source is stored against this line.
What is sold
The illicit delivery system has no rate control at all. Counterfeit tablets pressed to resemble oxycodone or alprazolam are the fastest-growing route, and they deliver fentanyl to people who believe they are taking a pharmaceutical.
✎ Source-linked record
Where this came from
A person wrote this into the record with the study named beside it. No reviewer has signed it off.
Recorded notes on which forms are sold and how they compare.
No source is stored against this line.
What is recorded as being sold
86 products list this as an active ingredient in the United States drug directory. 86 of them contain it and nothing else.
FDA National Drug Code directory · 0406-1205 · read 2026-08-29
They are sold as crystal, injection, injection, solution, lozenge, patch and patch, extended release, taken intramuscular, intravenous, oral and transdermal.
FDA National Drug Code directory · 0406-1205 · read 2026-08-29
The regulator's established pharmacologic class for it is full opioid agonists [moa] and opioid agonist [epc].
FDA National Drug Code directory · 0406-1205 · read 2026-08-29
14 published labels name it as an active ingredient. 14 of them describe this substance alone, which is where its own label text on this page comes from.
US prescribing information · bf02ffd0-cc5d-446b-b648-378f6885052f · read 2026-08-29
Those labels are classed as human prescription drug.
US prescribing information · bf02ffd0-cc5d-446b-b648-378f6885052f · read 2026-08-29
FENTANYL is transdermal at 3 DOSAGE FORMS AND STRENGTHS Transdermal system: Fentanyl Transdermal System 12 mcg/hour * (system size 5.35 cm 2 ) Fentanyl Transdermal System 25 mcg/hour (system size 10.7 cm 2 ) Fentanyl Transdermal System 37.5 mcg/h…, recorded as fda label in effect 2026-04-07 in the United States.
US prescribing information · bf02ffd0-cc5d-446b-b648-378f6885052f · read 2026-08-30
Recorded price in US: 1.7269 USD per one millilitre, across 11 priced products whose strengths and pack forms differ, as of 2026-08-26, paid by retail pharmacies buying the product, as surveyed by the Centers for Medicare & Medicaid Services. It is not a list price, an insurance price, or what anyone pays at a counter..
Recorded source · 2026-08-26 · read 2026-08-28
Recorded price in US: 5.82577–57.686 USD per one unit as the pricing file counts it — a tablet, capsule, patch or single item, across 45 priced products whose strengths and pack forms differ, as of 2026-08-26, paid by retail pharmacies buying the product, as surveyed by the Centers for Medicare & Medicaid Services. It is not a list price, an insurance price, or what anyone pays at a counter..
Recorded source · 2026-08-26 · read 2026-08-28
Evidence carries across two names for one substance. It does not carry across a salt, a mirror form or a mixture.
What it would be like to take◇Read from sources, not yet reviewed
What you could measure
This one is decided with a clinician, so this section holds questions to ask rather than a plan to run.
Self-experiment planning is not offered for a prescription or clinician-supervised medicine. The questions below are for a clinician or pharmacist.
Questions worth asking
Which of the trials of Fentanyl studied people like me?
What was measured, and for how long?
Was the result a laboratory value or a health outcome?
What would we watch for, and when would we stop?
Tracking can show whether something changed for you. It cannot show what caused it.
RNAWiki records evidence. It does not say whether this substance is right for you.
What is missing or unclear◇Read from sources, not yet reviewed
Claims that go past the evidence
Things said about this substance that sound reasonable, and the exact step that is missing between the evidence and the claim.
✗Goes past the evidence
That the 100-fold morphine potency ratio describes per-dose risk independently of dose control
Why it sounds right. It follows from something real on this page: a body step, an animal result or a related finding.
The missing step. Nobody measured this in people for this use, or the study that did measure it did not show it.
What would change this
A study in people, for this exact use, measuring this exact thing, that a reviewer signs off.
RNAWiki has not yet published a reviewed conclusion for this use.
✗Goes past the evidence
That restricting fentanyl prescribing addresses a mortality driven by an illicitly manufactured supply
Why it sounds right. It follows from something real on this page: a body step, an animal result or a related finding.
The missing step. Nobody measured this in people for this use, or the study that did measure it did not show it.
What would change this
A study in people, for this exact use, measuring this exact thing, that a reviewer signs off.
RNAWiki has not yet published a reviewed conclusion for this use.
✗Goes past the evidence
That naloxone addresses the whole of a fentanyl overdose; the rigidity component is argued to be non-opioid
Why it sounds right. It follows from something real on this page: a body step, an animal result or a related finding.
The missing step. Nobody measured this in people for this use, or the study that did measure it did not show it.
What would change this
A study in people, for this exact use, measuring this exact thing, that a reviewer signs off.
RNAWiki has not yet published a reviewed conclusion for this use.
✗Goes past the evidence
That a postmortem fentanyl concentration establishes cause of death in a tolerant person, where therapeutic and fatal ranges overlap
Why it sounds right. It follows from something real on this page: a body step, an animal result or a related finding.
The missing step. Nobody measured this in people for this use, or the study that did measure it did not show it.
What would change this
A study in people, for this exact use, measuring this exact thing, that a reviewer signs off.
RNAWiki has not yet published a reviewed conclusion for this use.
What is missing or unclear◇Read from sources, not yet reviewed
What nobody knows yet
Open questions, each with why it is open and what would close it.
Missing populations
Which groups were under-represented in the studies has not been recorded.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
Missing long-term data
No completed tested study window is recorded.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
No reviewed conclusion
RNAWiki has not yet published a reviewed conclusion for this use.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
Missing interaction studies
No interaction was found in the registers checked. Not finding one is not the same as showing there is none.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
Formulation uncertainty
Several salts, forms or products of Fentanyl are recorded. Results from one form may not transfer to another.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
Mechanism not reviewed
No reviewed mechanism story exists for this substance.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
What happened in people◇Read from sources, not yet reviewed
Check any of this yourself
Every line above traced back to the study it came from. This is the technical layer, and the vocabulary changes here.
Every line above can be traced to the study named beside it. Follow the link and read it.
Two thirds of a hundred thousand deaths a year
In plain words
In the twelve months to April 2021, US overdose deaths passed 100,000 for the first time, and 64% involved synthetic opioids other than methadone — mainly illicitly manufactured fentanyl.
What was measured
Regional increases in IMF-involved overdose deaths, stimulant co-involvement, route of use and pulse status on first-responder arrival
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
O'Donnell et al. reported that during May 2020 to April 2021 the estimated number of US drug overdose deaths exceeded 100,000 over a 12-month period for the first time, with 64.0% involving synthetic opioids other than methadone, mainly illicitly manufactured fentanyls. Using CDC's State Unintentional Drug Overdose Reporting System for July 2019 to December 2020, IMF-involved deaths rose sharply in midwestern (33.1%), southern (64.7%) and western (93.9%) jurisdictions. Approximately four in ten IMF-involved deaths also involved a stimulant. 56.1% of decedents had no pulse when first responders arrived. Injection was the most frequently reported single route at 24.5%, but 27.1% had evidence of snorting, smoking or ingestion without injection — a distribution that matters because harm-reduction services designed around injection reach only part of the affected population.
Written into the record, not signed off as a reviewed claim
Wooden chest: rigidity within an extremely narrow dose range
In plain words
Anaesthetists learned in the 1970s that fentanyl can lock the diaphragm, chest wall and upper airway rigid within a very small dose window. That effect is not purely opioid, and naloxone does not reliably reverse it.
What was measured
Clinical and preclinical characterisation of fentanyl-induced chest-wall and airway rigidity and its receptor mechanisms
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
Torralva and Janowsky review the human clinical pharmacology and animal data on fentanyl-induced wooden chest syndrome: profound rigidity of the diaphragm, chest wall and upper airway developing within an extremely narrow dosing range, almost routinely fatal without expert airway management, and familiar to anaesthesiologists since fentanyl entered US practice in the early 1970s but largely unknown outside anaesthesia. They argue that the mechanism involves α-adrenergic and cholinergic receptor-mediated mechanical failure of the respiratory and cardiovascular systems, and that naloxone may therefore be ineffective against these centrally mediated components. They contrast this with morphine and heroin, which produce at most mild abdominal rigidity at high doses and a slower onset of respiratory depression. The clinical consequence is that fentanyl overdose is not simply a faster version of heroin overdose, and that reversal strategies designed around opioid receptor antagonism address only part of it.
Written into the record, not signed off as a reviewed claim
A REMS that did not stop half the prescriptions going to the wrong patients
In plain words
Transmucosal fentanyl products are approved only for breakthrough cancer pain in patients already tolerant to opioids. FDA's own data showed between 34.6% and 55.4% of patients prescribed them were not opioid-tolerant — and the programme was not substantially changed.
What was measured
Proportion of TIRF-prescribed patients who were opioid-nontolerant, and prescriber and patient knowledge, across 60 months of REMS assessments
Effect estimate
No reviewed effect estimate exists for this record.
Limits
This entry records a failure.
From the source
Rollman et al. analysed 4,877 pages of FDA documents obtained by Freedom of Information Act request, covering six annual REMS assessment reports from 2012 to 2017 for transmucosal immediate-release fentanyls. Twelve months in, 7.9% of pharmacists, 11.6% of prescribers and 2.6% of patients incorrectly reported that TIRFs can be prescribed to opioid-nontolerant patients, and similar misunderstanding persisted in later reports. At 60 months, product-specific claims analyses showed between 34.6% and 55.4% of patients prescribed TIRFs were opioid-nontolerant — the single contraindication the programme existed to prevent. At 48 months, 34.2% of prescribers reported prescribing TIRFs for opioid-tolerant patients with chronic non-cancer pain; at 60 months, 18.4% of prescribers and 47.7% of patients erroneously believed TIRFs were approved for that. Over the 60 months examined, few substantive changes were made to the REMS, and although a noncompliance plan existed, there was no report of any prescriber being disenrolled for inappropriate prescribing.
Written into the record, not signed off as a reviewed claim
Counterfeit pills: deaths doubled, and tripled in the West
In plain words
Overdose deaths with evidence of counterfeit pill use more than doubled between 2019 and 2021, and more than tripled in western states. The people dying were much younger than in other overdose deaths.
What was measured
Quarterly percentage of overdose deaths with evidence of counterfeit pill use, with decedent characteristics and drug involvement
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
O'Donnell et al. analysed SUDORS data for July 2019 to December 2021 across 29 states and DC. The quarterly percentage of overdose deaths with evidence of counterfeit pill use more than doubled, from 2.0% in July-September 2019 to 4.7% in October-December 2021, and more than tripled in western jurisdictions, from 4.7% to 14.7%. Illicitly manufactured fentanyls were the only drugs involved in 41.4% of deaths with evidence of counterfeit pill use, against 19.5% of deaths without — meaning counterfeit-pill deaths were far more often single-substance fentanyl deaths. Decedents with counterfeit pill evidence were younger (57.1% versus 28.1% aged under 35), more often Hispanic or Latino (18.7% versus 9.4%), and more often had a history of prescription drug misuse (27.0% versus 9.4%). Smoking was the commonest non-ingestion route at 39.5%. A counterfeit tablet is the delivery mechanism by which fentanyl reaches people who believe they are taking a pharmaceutical.
Written into the record, not signed off as a reviewed claim
The approved product and the illicit supply are not the same thing
In plain words
Fentanyl has been an approved anaesthetic since 1968 and a pain patch since 1990. The fentanyl in the overdose data is manufactured illicitly and does not come from those products.
What was measured
Approval dates of the pharmaceutical products against CDC's definition and tracking of illicitly manufactured fentanyls
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
Sublimaze was approved on 19 February 1968 (NDA 016619), Duragesic on 7 August 1990 (NDA 019813) and Actiq on 4 November 1998 (NDA 020747). CDC's surveillance terminology is deliberate: "illicitly manufactured fentanyls", covering fentanyl and illicit fentanyl analogues, introduced primarily as adulterants in or replacements for white powder heroin east of the Mississippi and now widespread, increasingly pressed into counterfeit pills resembling oxycodone or alprazolam, and expanding into western markets. That is a separate manufacturing and distribution system from the pharmaceutical one, and conflating them produces two errors in opposite directions: it implies that restricting prescriptions addresses the overdose crisis, and it implies that a hospital anaesthetic carries the mortality of the street supply. This record separates them because the surveillance literature does.
Written into the record, not signed off as a reviewed claim
Four in ten deaths also involve a stimulant
In plain words
Fentanyl deaths are usually not fentanyl-only. About 40% also involve a stimulant such as methamphetamine or cocaine, which changes both the risk and the treatment.
What was measured
Proportion of IMF-involved overdose deaths with a co-involved stimulant
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
Approximately four in ten illicitly-manufactured-fentanyl-involved deaths also involved a stimulant in the 2019-2020 SUDORS analysis. That co-involvement matters for three reasons the surveillance authors state: it raises overdose risk, it complicates treatment for substance use disorder, and it means that interventions built solely around opioid pharmacology address part of the exposure. It also interacts with the xylazine finding on this site — xylazine was co-present with illicitly manufactured fentanyls in 98.4% of xylazine-positive deaths — so a single fatal exposure now routinely involves an opioid, a sedative with no antidote and often a stimulant, none of which the others' antidotes address.
Written into the record, not signed off as a reviewed claim
Potency comparisons describe weight, not risk per dose
In plain words
"A hundred times stronger than morphine" is a statement about milligrams, not about how dangerous a given dose is. A titrated anaesthetic dose and an unmeasured street dose of the same drug are not comparable exposures.
What was measured
That a per-weight potency ratio to morphine describes the per-dose risk of a fentanyl exposure independently of how the dose was measured
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
The 100-fold morphine potency ratio is a per-weight comparison and is well established. The inference commonly drawn from it — that fentanyl is intrinsically a hundred times more dangerous — does not follow, because risk depends on dose control rather than on potency. Fentanyl is used millions of times a year in operating theatres precisely because it is titratable, with the airway already secured and the dose measured in micrograms. What makes the illicit supply lethal is that potency and absent dose control appear together: a drug active in micrograms, blended into a powder or pressed into a tablet by a process with no quality control, produces variance the user cannot detect. The measured finding underneath is the one from the counterfeit-pill analysis, where fentanyl was the only drug involved in 41.4% of those deaths.
This order is fixed in code and does not count clicks or time on the page.
What is not here
3 questions this page could not answer
These sections were prepared and left out because there was nothing to put in them. They are listed rather than hidden, so the gaps in this record are visible.
What it may clash with — found nothing in the sources checked.
Other ways to the same goal — found nothing in the sources checked.
What changed on this page — found nothing in the sources checked.
The record as stored
The full record, for auditing
Everything above is built from what is below. This layer keeps the technical vocabulary, record identifiers and every stored row, so a reader who wants to check the page can.
The older medicine-wide conclusion held in this record
Written for a clinical reader, and about the medicine as a whole rather than about one indication, population and set of trials. RNAWiki does not treat it as a programme conclusion and no reviewer has signed it off in that form. It is here word for word because it is what the record holds.
The same molecule underpins one of anaesthesia's most controllable analgesics and the deadliest drug in the American supply — and the difference is entirely dose control, because at anaesthetic concentrations fentanyl also produces a chest-wall rigidity that develops within an extremely narrow dosing range and that naloxone does not reliably reverse.
Recorded evidence blocks (15)
Q2
What did Fentanyl's largest trial (27034 people) and its longest (16 years) measure?
27034 people in Fentanyl's largest registered study, 16 years in its longest registered window, measuring plasma levels of pro-inflammatory cytokine IL-6. ClinicalTrials.gov · 2026-09-01
198 phase4, 189 na, 90 phase3, 82 phase2, 42 phase1, 33 na or unstated, 11 early phase1; NCT03105518; 2027-06-30; no ageing endpoint recorded. Last human test completed 2026, NCT07443085.
Interpretation These counts include studies where Fentanyl was a comparison treatment, a background treatment or an exposure in an observational study, and the longest window may be a planned end date. Trial roles have not yet been classified for this record.
Show the evidence
phase4
198
na
189
phase3
90
phase2
82
phase1
42
na or unstated
33
2 more recorded rows
early phase1
11
Last recorded human testNCT07443085
2026-08-24
recorded 2026-09-01 · last checked 2026-09-04
Q3
From mouse to human: where has Fentanyl shown lifespan?
"The study was terminated due to slow accrual."; 69 of 612 registered studies
Show the evidence
Trial
NCT00187135
terminated; "The study was terminated due to slow accrual."
NCT00236327
terminated; "Sponsor discontinued the study following the discovery of a number of incompletely sealed batches that were unusable."
NCT00387010
terminated; "The sponsor felt enough information was available for the exploratory assessment of the effect of treatment with FBT on pain anxiety"
NCT00635063
terminated; "Termination is due to a combination of a device defect potentially impacting the quality of the AD 923 IMP and a major change in corporate strategy."
NCT00762554
withdrawn; "Uncertain safety of one of the study medications."
NCT00779038
terminated; "Stopped prematurely in 2008 due to IONSYS withdrawal off the market globally"
14 further recorded trials
NCT00842829
terminated; "Recruitment stopped at the end of the recruitment timeframe"
NCT00899951
terminated; "poor accrual"
NCT00916890
suspended; "difficulties in patients enrolment"
NCT01007773
withdrawn; "Study will not be intiated"
NCT01059929
terminated; "drug and placebo unavailable"
NCT01126957
terminated; "Investigator left institution."
NCT01195103
terminated; "Funding terminated by funding source."
NCT01205204
withdrawn; "This study was registered with Clinical Trials.gov by mistake."
NCT01210066
terminated; "Unable to recruit prescription opioid abusers; ultimately no potential POA recruit passed the pre-screening process"
NCT01315158
terminated; "\- The research team is not able to obtain the necessary support to continue the study."
NCT01315886
terminated; "Recruitment difficulties"
NCT01333059
terminated; "Unable to adequately enroll over a reasonable enrollment period."
NCT01362998
terminated; "Lack of time and help to continue the study"
NCT01563835
terminated; "Recruitment difficulty"
recorded 2026-09-01 · last checked 2026-09-04
Q5
Human studies of Fentanyl used Fentanyl patch 25 ug/nr Sandoz — over how long?
U-shaped in human: "4F-BF, 4F-iBF, and iBF showed inverted U-shaped dose-response curves; the reinforcing potency of three analogs was comparable and intermediate between that of fentanyl and heroin." Europe PMC · dose-response search · 2026-07-15
5 recorded sentences naming Fentanyl; U-shaped, dose response, Dose-response, dose-response
Show the evidence
U-shaped
PMID 42229741
"4F-BF, 4F-iBF, and iBF showed inverted U-shaped dose-response curves; the reinforcing potency of three analogs was comparable and intermediate between that of fentanyl and heroin."
PMID 41535593
"Among the four analogs with N-acyl alkyl side chains, the formation of the nor-metabolites, the metabolites hydroxylated at the ethyl linker, and the metabolites hydroxylated at the piperidine ring increased with increasing side chain length, peaking with fentanyl or butyrylfentanyl, and then decreasing with valerylfentanyl, thereby exhibiting an overall inverted U-shaped trend."
dose responsePMID 42229741
"After 10 days of acquisition, dose response curves were generated for heroin, fentanyl, 4F-BF, 4F-iBF, and iBF."
Dose-responsePMID 42457122
"Dose-response curves were generated for fentanyl (0.01-10 mg/kg) and xylazine (0.3-10 mg/kg) over an 80-min recording period."
dose-responsePMID 41916094
"Co-administration of xylazine produced small, rightward shifts in the dose-response curves for the stimulus effects of fentanyl."
recorded 2026-07-15 · last checked 2026-09-04
Q7
Fentanyl's half-life is 34 hours — which schedules were studied?
34 hours, the half-life Fentanyl's label states. openfda-label · bfa8018a-4cbc-434b-e09e-782872b0340a · 2026-08-30
Show the evidence
half life
34 hours hours; A study conducted with the fentanyl transdermal system patch in elderly patients demonstrated that fentanyl pharmacokinetics did not differ significantly from young adult subjects, although peak serum concentrations tended to be lower and mean half-life values were prolonged to approximately 34 hours.
recorded 2026-08-30 · last checked 2026-09-04
Q8
Which of adverse events, bioequivalence according to us fda guidelines and decreased minute ventilation did Fentanyl's trials measure?
adverse events, bioequivalence according to us fda guidelines and decreased minute ventilation lead 40 outcome terms across Fentanyl's trials. ClinicalTrials.gov · 2026-09-01
Interpretation intraoperative signs of inadequate anesthesia, postoperative recall of events, mlaep parameters, duration of hospital stay, pain at rest and pain relief follow.
Show the evidence
pain
1
primary
1
safety and tolerability
1
intraoperative signs of inadequate anesthesia
1
postoperative recall of events
1
mlaep parameters
1
14 more recorded rows
duration of hospital stay
1
pain at rest
1
pain relief
1
incidence of pain
1
time to analgesia
1
pain reduction
1
onset time of brachial plexus anesthesia
1
adverse events
1
onset time of brachial plexus sensory block
1
pain visual analogue scale
1
quality of sleep
1
bioequivalence according to us fda guidelines
1
rate and extend of absorption
1
intracranial pressure
1
recorded 2026-09-01 · last checked 2026-09-04
Q9
Which of Fentanyl's 55 ongoing trials reports first?
Number of subjects with Breakthrough pain; Amount of Discomfort; latest 2029-07
Show the evidence
Trial
NCT02278601
"Comparison of Regimens MPIB, CIPCEA, PCEA"; n 839; "Number of subjects with Breakthrough pain"; 2027-12-31
NCT03105518
"Predictors of Postoperative Pain Following Oocyte Retrieval for Assisted Reproduction"; n 100; "Amount of Discomfort"; 2027-06-30
NCT03167905
"CODEPAD (Collaborative Outcomes of DEpression and Pain Associated With Delivery)"; n 881; "The incidence of major postnatal depression in both groups"; 2027-12-31
NCT03214510
"Thoracic Epidural Analgesia or Four-Quadrant Transversus Abdominus Plane Block in Reducing Pain in Patients Undergoing Liver Surgery"; n 101; "Total length of inpatient stay"; 2027-07-31
NCT03593408
"Pharmacokinetics of Sedatives and Analgesics During Extracorporeal Membrane Oxygenation (ECMO) Support"; n 20; "Change in plasma concentrations of dexmedetomidine"; 2026-12-01
NCT03735563
"Premedication for Less Invasive Surfactant Administration"; n 40; "Adverse event"; 2026-10-31
14 further recorded trials
NCT03936790
"Dose-response Study of Spinally Administered Ropivacaine for Caesarean Section in Tall Parturients"; n 40; "ED50 of spinal ropivacaine administered to healthy tall parturients for cesarean delivery."; 2025-11
NCT04011150
"Development of Variable Volume Automated Mandatory Boluses for Patient-controlled Epidural Analgesia During Labour"; n 197; "Incidence of motor block in each group"; 2027-08-31
NCT04188418
"Fentanyl Buccal Tablet or Morphine for Exertional Dyspnea in Cancer Patients"; n 150; "Change in modified Borg scale dyspnea intensity before and after the Shuttle Walk Test (SWT)"; 2027-08-31
NCT05437575
"Prehospital Analgesia INtervention Trial (PAIN)"; n 994; "24-hour mortality"; 2029-07
NCT05500599
"Effects on Recovery of Children of Intravenous Formulation of Fentanyl Citrate and Midazolam Orally for Premedication"; n 60; "effect of both premedicants on recovery"; 2025-08-28
NCT05609877
"The NONA-LISA Trial"; n 324; "LISA failure within 24 hours."; 2029-05-31
NCT05856136
"A Study to Investigate of the Effects of Opioid Exposure on the Ability of the Diaphragm Muscle"; n 69; "Change in Young's modulus (derived from shear wave speed)"; 2027-01-01
NCT06051227
"Fentanyl or Esketamine for Traumatic PAIN (FORE-PAIN) Trial"; n 608; "Change in pain score as measured with Numeric Rating Scale (NRS)"; 2026-03
NCT06104059
"NOL Guided Analgesia During Elective Laparoscopic Surgery Under General Anesthesia"; n 50; "Intraoperative total consumption of opioids"; 2026-09-20
NCT06203405
"The Efficacy of P0.1-guided Sedation Protocol in Critically Ill Patients Receiving Invasive Mechanical Ventilation: A Randomized Controlled Trial"; n 214; "Successful extubation within 14 days after randomization"; 2026-06-30
NCT06364540
"Nebulized Ketamine to Nebulized Fentanyl for Treating Acute Painful Conditions in the ED"; n 150; "Reduction of pain scores on the numeric rating pain scale (NRS)"; 2026-12-31
NCT06479655
"Compare the Efficacy and Outcome Between Fentanyl and Morphine as Analgo-sedation in Mechanically Ventilated Patients"; n 116; "RASS score at 12 and 24 hours"; 2025-12-30
NCT06613893
"Effect of Inhalational Anesthesia Versus Total Intravenous Anesthesia on Blood Glucose in Type 2 Diabetes Patients"; n 84; "Blood glucose levels in milligrams per decilitre (mg/dl) at different time points"; 2025-06-30
NCT06636578
"Dexmedetomidine Ropivacaine Versus Plain Ropivacaine in Bilateral Pectoralis Nerve (PECS) Block"; n 90; "pain assessment will be done using VAS scoring system"; 2025-01-08
recorded 2026-09-01 · last checked 2026-09-04
Q10
Which running trial of Fentanyl could settle lifespan?
NCT05437575 measures 24-hour mortality, reading out 2029-07.
1 open trial; n 994; "Prehospital Analgesia INtervention Trial (PAIN)"
Show the evidence
TrialNCT05437575
"Prehospital Analgesia INtervention Trial (PAIN)"; n 994; "24-hour mortality"; 2029-07
Q11
Which 239 trials of Fentanyl posted no result?
Posted no result
239 of 239 completed trials
Registrations
NCT00271453, NCT00004424, NCT00003000, NCT00708318, NCT00864565 and NCT00237341, and 233 more
Completion dates
oldest 1998-10; newest 2024-09-01
Show the evidence
Trial
NCT00271453
1998-10
NCT00004424
2000-03
NCT00003000
2001-06
NCT00708318
2002-06
NCT00864565
2003-06
NCT00237341
2004-01
14 further recorded trials
NCT00236366
2004-04
NCT00027014
2005-05
NCT00216658
2005-09
NCT00115102
2005-10
NCT00000273
2005-11
NCT00108446
2006-03
NCT00241332
2006-07
NCT00236041
2006-08
NCT01173627
2006-08
NCT00216684
2006-09
NCT00857753
2006-10
NCT00635986
2006-11
NCT01902524
2006-11
NCT01780233
2007-05
Q12
At the median, Fentanyl's trials enrolled 70 people — anything larger?
Median enrolment
70
Largest enrolment
27034
Registered trials counted
609
Q13
What do 52 spontaneous reports say about Fentanyl — and not say?
These are reports people sent to a regulator. They do not show the medicine caused the reaction. Nobody counted how many people took the medicine and reported nothing. The same event can be reported more than once, and many reports are incomplete. News coverage, lawsuits and new warnings change how often people report. A count is not a rate and not a risk.
Fentanyl appears in spontaneous reports to regulators. Across the 6 most-reported reaction terms, 52 reaction mentions were counted: application site erythema 15; application site vesicles 12; application site burn 9; application site irritation 6. open-targets-adr · CHEMBL1201159 · 2026-06-24
Show the evidence
application site erythema
15
application site vesicles
12
application site burn
9
application site irritation
6
application site pruritus
5
application site rash
5
recorded 2026-06-24 · last checked 2026-09-04
Q14
Fentanyl and CYP3A4: shared by which compounds?
CYP3A4 appear in Fentanyl's recorded interaction sentences, 4 in all. openfda-label+europepmc · 2026-08-30
Interpretation pharmacokinetics
Show the evidence
CYP3A4
pharmacokinetics
CYP3A4 Inducers Co-administration with agents that induce CYP3A4 activity may reduce the efficacy of fentanyl transdermal system.
pharmacokinetics
Drug Interaction Studies CYP3A4 Inhibitors Fentanyl is metabolized mainly via the human cytochrome P450 3A4 isoenzyme system (CYP3A4).
pharmacokinetics
The interaction between ritonavir, a CYP3A4 inhibitor, and fentanyl was investigated in eleven healthy volunteers in a randomized crossover study.
pharmacokinetics
Carefully monitor patients receiving fentanyl transdermal system and any CYP3A4 inhibitor for signs of respiratory depression for an extended period of time and adjust the dosage if warranted [see Boxed Warning and Warnings and Precautions ( 5.7 ), and Drug Interactions ( 7 )].
recorded 2026-08-30 · last checked 2026-09-04
Q15
Was Fentanyl studied with exercise?
exercise is named in Fentanyl's label sentences: "In this randomized, single-blind, placebo-controlled study, eight FILD patients (two males, 71 ± 6 years of age) performed incremental cardiopulmonary cycle exercise tests following nebulization of either fentanyl citrate (100 µg) or 0.9% saline." openfda-label+europepmc · 2026-08-30
1 recorded statement; exercise
Show the evidence
exercise
In this randomized, single-blind, placebo-controlled study, eight FILD patients (two males, 71 ± 6 years of age) performed incremental cardiopulmonary cycle exercise tests following nebulization of either fentanyl citrate (100 µg) or 0.9% saline.
recorded 2026-08-30 · last checked 2026-09-04
Q16
What is recorded about Fentanyl and sirtuin?
"Anesthetic preconditioning with morphine, fentanyl, propofol and dexmedetomidine reduced kidney injury markers after I-R and modulated sirtuin gene expression." — where Fentanyl and sirtuin appear together. Europe PMC · pathway abstract search · 2019-11-11
"Anesthetic preconditioning with morphine, fentanyl, propofol and dexmedetomidine reduced kidney injury markers after I-R and modulated sirtuin gene expression."
autophagy
PMID 27779694
"N-acetyl‑L‑cysteine is a ROS scavenger and antioxidant, and the inhibition of JNK with SP600125 prevented fentanyl‑induced autophagy."
PMID 27779694
"We also found that 3-methyladenine (3-MA; an autophagy inhibitor) increased the sensitivity of DDP and weakened the inhibition of fentanyl."
PMID 27779694
"In conclusion, fentanyl reduces the sensitivity of cisplatin in lung cancer cells through the ROS-JNK-autophagy pathway, whereas the autophagy inhibitor 3-MA may weaken this effect."
sirtuin
PMID 25520062
"Our data showed that fentanyl could inhibit tumor growth, with increased expression of Sirt1 and down-regulation of Ac-p65 in tumors."
PMID 25520062
"Moreover, fentanyl could increase expression and activity of Sirt1 and inhibitor expression and activity of NF-κB, which might be mechanisms of fentanyl action."
recorded 2019-11-11 · last checked 2026-09-04
Where it is registeredIdentifiers, relations and other names
ClinicalTrials.gov — US Government work · Europe PMC — metadata only, under the recorded legal gate · Open Targets 26.06 — CC0 · derived from this page's own recorded fields; no external licence · mixed register set; per-register licences in docs/specs/corpus-20k-sources.md · openFDA / DailyMed — US Government work
✗ required summary fields resolved: 5 required field(s) not terminal: Why people use it, Best-supported result, Most important common problem, Biggest unanswered question, Human evidence
✓ public claims reviewed: 0 reviewed claim(s); drafts are never rendered
✓ source coverage passed: 11 source rows
✓ no critical contamination: no quarantine open
✓ canonical metadata passed: slug and display name present
✓ no raw internal fields: enforced by the copy-contract test over the rendered page
This is a record of evidence. It is not medical advice, and it does not say this substance suits you. Nothing here says any substance on RNAWiki is appropriate for a child.