This page shows what was measured, who it was measured in, and what that does not settle.
What Zileuton does in the body
Long-term asthma control, for the small number of people who cannot use the alternatives
Inflammatory cells build leukotrienes from a fatty acid using a single enzyme. Zileuton gets inside those cells and jams that enzyme, so none of the leukotrienes get made at all — not the ones that tighten the airway and not the ones that call in more inflammatory cells. That is a bigger intervention than blocking one receptor, and it comes with the cost of blocking an enzyme rather than intercepting a messenger: the liver, which processes the drug, sometimes objects, and it has to be checked.
What happened in people
Steroid-requiring exacerbations in 6.1% against 15.6% on placebo over 13 weeks in 401 patients (p=0.02)
✎ 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 recorded finding that sits closest to something a person would notice. Written into the record, not signed off, and it carries no population or interval.
Zileuton extended-release tablets United States prescribing information — Indications 1, Dosage and Administration 2, Contraindications 4, Warnings and Preca… · a recorded source, not a stored snapshot
Israel E, Cohn J, Dubé L, Drazen JM; Zileuton Clinical Trial Group. Effect of treatment with zileuton, a 5-lipoxygenase inhibitor, in patients with asthma. A… · a recorded source, not a stored snapshot
Approved 9 December 1996 under NDA 020471; the branded immediate-release product is discontinued and only extended-release generics remain
Where it acts
5-lipoxygenase in neutrophils, eosinophils, monocytes and mast cells — the enzyme is intracellular, so this drug acts inside the inflammatory cell rather than on the airway
Kind of result
The kind of result is not recorded
Supervision
RNAWiki has not recorded a supervision or regulatory status for this substance.
What the registries record it as
The substance registry classes this as chemical.
FDA substance registry · V1L22WVE2S · read 2026-08-29
Its recorded molecular formula is C11H12N2O2S, weighing 236.29.
US prescribing information · bc29c998-1324-46aa-8386-e5b2fc9e0b16 · read 2026-08-30
Where each sentence above came from
No recorded sentence describes the change this makes in a way that stands on its own. The page opens with what it is taken for instead, and the recorded explanation follows below.
Shown as the opening line on this page.
A limit recorded against this substance. Not signed off as a reviewed claim.
The four opening statements run to 120 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.
Randomisation
Randomisation means chance decides who gets which treatment.
A picture of it, and where the picture fails
It is like a coin toss deciding the groups.
Where that stops being true. A coin toss is fair once. Fairness here comes from doing it for everyone.
What people get wrong. It is thought to make groups identical. It makes them similar on average, including on things nobody measured.
Allocation of participants to arms by a chance process, so that unmeasured factors are balanced in expectation.
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 9 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 reviewer1 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.
Which registered measures put each goal on this table
Pain
pain scores
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
1 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.
Frequency of asthma exacerbation requiring corticosteroid treatment over 13 weeks in mild to moderate asthma treated only with inhaled beta-agonists
✓ The study showed what it set out to show
Who was studied
Zileuton Clinical Trial Group (JAMA 1996;275:931-936)
How many people
401
Study design
Phase 3, randomised, double-blind, parallel-group, placebo-controlled, three arms
Compared against
A dummy treatment
Kind of result
A number that stands in for health
What was found
6.1% (8 of 132) on zileuton 600 mg four times daily against 15.6% (21 of 135) on placebo, p=0.02; FEV1 at peak concentration +15.7% against +7.7%, p=0.006; overall quality-of-life score p=0.007
Repeated elsewhere
Partially 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. Transaminase elevations above three times normal occurred in five patients on 600 mg (p=0.03 against placebo), three on 400 mg (p=0.12) and none on placebo. All reversed on withdrawal. The efficacy and the liver signal came out of the same trial.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Oral bilayer extended-release tablets of 600 mg, two twice daily within one hour after morning and evening meals
Interval reported. Not recorded in this summary
Written into the record, not signed off as a reviewed claim.
Zileuton extended-release tablets United States prescribing information — Indications 1, Dosage and Administration 2, Contraindications 4, Warnings and Preca… · a recorded source, not a stored snapshot
Israel E, Cohn J, Dubé L, Drazen JM; Zileuton Clinical Trial Group. Effect of treatment with zileuton, a 5-lipoxygenase inhibitor, in patients with asthma. A… · a recorded source, not a stored snapshot
FDA Drug Safety Communication, 4 March 2020 — FDA requires Boxed Warning about serious mental health side effects for asthma and allergy drug montelukast (Si… · a recorded source, not a stored snapshot
Mean change from baseline in trough FEV1 at 12 weeks in patients 12 and over with asthma
0.39 L against 0.27 L, p=0.021, by last-observation-carried-forward; peak flow and rescue beta-agonist use supportive
Repeated elsewhere
Unreplicated
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. No exacerbation endpoint was measured, so the outcome that made the 1996 trial persuasive is absent from the registration package for the formulation now dispensed. The placebo arm gained 0.27 L, more than two thirds of the improvement seen on drug.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Oral bilayer extended-release tablets of 600 mg, two twice daily within one hour after morning and evening meals
Interval reported. Not recorded in this summary
Written into the record, not signed off as a reviewed claim.
Zileuton extended-release tablets United States prescribing information — Indications 1, Dosage and Administration 2, Contraindications 4, Warnings and Preca… · a recorded source, not a stored snapshot
Israel E, Cohn J, Dubé L, Drazen JM; Zileuton Clinical Trial Group. Effect of treatment with zileuton, a 5-lipoxygenase inhibitor, in patients with asthma. A… · a recorded source, not a stored snapshot
FDA Drug Safety Communication, 4 March 2020 — FDA requires Boxed Warning about serious mental health side effects for asthma and allergy drug montelukast (Si… · a recorded source, not a stored snapshot
Rate of ALT elevation at or above three times the upper limit of normal
✗ The study did not show it
Who was studied
Pooled hepatic safety across controlled and open-label immediate-release studies (label section 5.1)
How many people
5000
Study design
Pooled safety analysis across the immediate-release clinical programme
Compared against
Not recorded for this study
Kind of result
A number that stands in for health
What was found
Overall rate 3.2% in more than 5,000 treated patients; one symptomatic hepatitis with jaundice, resolving on discontinuation; three further patients with mild hyperbilirubinaemia below three times normal
Repeated elsewhere
Replicated
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. The label notes there was no evidence of hypersensitivity or other alternative aetiology for these findings, which is the observation that makes the signal a drug effect rather than a coincidence. Two of the five elevations in the 12-week extended-release trial were detected 14 days after treatment ended.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Oral bilayer extended-release tablets of 600 mg, two twice daily within one hour after morning and evening meals
Interval reported. Not recorded in this summary
Written into the record, not signed off as a reviewed claim.
Zileuton extended-release tablets United States prescribing information — Indications 1, Dosage and Administration 2, Contraindications 4, Warnings and Preca… · a recorded source, not a stored snapshot
Israel E, Cohn J, Dubé L, Drazen JM; Zileuton Clinical Trial Group. Effect of treatment with zileuton, a 5-lipoxygenase inhibitor, in patients with asthma. A… · a recorded source, not a stored snapshot
FDA Drug Safety Communication, 4 March 2020 — FDA requires Boxed Warning about serious mental health side effects for asthma and allergy drug montelukast (Si… · a recorded source, not a stored snapshot
What we know
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 eventEvidence recorded. Death, a heart attack, a stroke, a hospital stay.2 registered measures of this kind. No reviewed result.
□What a body can do day to dayNo evidence recorded. Walking, dressing, breathing, recovering.No registered study measures this.
□Measured performanceNo evidence recorded. How much was lifted, how far was run, how fast.No registered study measures this.
■Symptoms and quality of lifeEvidence recorded. Pain, tiredness, mood, sleep, as the person rated it.1 registered measure of this kind.
■A number that stands in for healthEvidence recorded. Cholesterol, blood sugar, bone density. A stand-in, not the thing itself.3 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. 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
Zileuton
What a person takes: Oral bilayer extended-release tablets of 600 mg, two twice daily within one hour after morning and evening meals.
The measurement behind this step
Each tablet combines an immediate-release layer with an extended-release layer. Food increases both peak plasma concentration and total absorption, which is why the label ties administration to meals; tablets must not be chewed, cut or crushed. The original immediate-release product was taken four times a day and is discontinued. The pharmacodynamic marker is inhibition of ex vivo whole-blood LTB4 formation, directly related to plasma level.
Getting in
Four tablets a day, after meals
Two extended-release tablets twice daily, taken within an hour of eating because food increases how much gets absorbed.
──Measured in people. Written by a person from the study named beside the step. Not signed off as a reviewed claim.
The measurement behind this step
Bilayer film-coated tablets with an immediate-release and an extended-release layer, 600 mg each, two twice daily for 2,400 mg a day, not to be chewed, cut or crushed. Food increased both peak plasma concentration and total absorption in the crossover pharmacokinetic study.
Zileuton extended-release tablets United States prescribing information — Indications 1, Dosage and Administration 2, Contraindications 4, Warnings and Preca… · a recorded source, not a stored snapshot
Israel E, Cohn J, Dubé L, Drazen JM; Zileuton Clinical Trial Group. Effect of treatment with zileuton, a 5-lipoxygenase inhibitor, in patients with asthma. A… · a recorded source, not a stored snapshot
The enzyme it targets is not on the cell surface. It works inside neutrophils, eosinophils and mast cells.
╌╌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
5-lipoxygenase is an intracellular enzyme that translocates to the nuclear membrane on cell activation, where it acts with 5-lipoxygenase-activating protein on arachidonic acid released from membrane phospholipid. Zileuton must therefore reach an intracellular compartment, unlike a receptor antagonist acting from outside.
Zileuton extended-release tablets United States prescribing information — Indications 1, Dosage and Administration 2, Contraindications 4, Warnings and Preca… · a recorded source, not a stored snapshot
Israel E, Cohn J, Dubé L, Drazen JM; Zileuton Clinical Trial Group. Effect of treatment with zileuton, a 5-lipoxygenase inhibitor, in patients with asthma. A… · a recorded source, not a stored snapshot
The business end of the molecule grabs the iron atom the enzyme needs to work, and the enzyme stops.
╌╌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
An N-hydroxyurea that coordinates the non-haem active-site iron of 5-lipoxygenase. Both enantiomers of the 50:50 racemate are active. Whole-blood LTB4 inhibition IC50 about 0.46 mcg/mL, at least 80% inhibition at 2 mcg/mL, and 98% mean inhibition at the 5.9 mcg/mL peak levels seen on 600 mg four times daily.
Zileuton extended-release tablets United States prescribing information — Indications 1, Dosage and Administration 2, Contraindications 4, Warnings and Preca… · a recorded source, not a stored snapshot
Israel E, Cohn J, Dubé L, Drazen JM; Zileuton Clinical Trial Group. Effect of treatment with zileuton, a 5-lipoxygenase inhibitor, in patients with asthma. A… · a recorded source, not a stored snapshot
Blocking the enzyme removes the airway-tightening leukotrienes and the ones that call in inflammatory cells. Blocking a receptor removes only the first.
╌╌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
Inhibition of LTB4, LTC4, LTD4 and LTE4 formation, confirmed in humans by reduced whole-blood LTB4 and reduced urinary LTE4. LTB4 is a chemoattractant for neutrophils and eosinophils; the cysteinyl leukotrienes drive capillary permeability, mucus secretion and smooth muscle contraction. Montelukast blocks one receptor for the second group only.
Zileuton extended-release tablets United States prescribing information — Indications 1, Dosage and Administration 2, Contraindications 4, Warnings and Preca… · a recorded source, not a stored snapshot
Israel E, Cohn J, Dubé L, Drazen JM; Zileuton Clinical Trial Group. Effect of treatment with zileuton, a 5-lipoxygenase inhibitor, in patients with asthma. A… · a recorded source, not a stored snapshot
In the original trial, steroid courses dropped from about one in six to about one in sixteen. In the modern registration trial, lung function gained about a tenth of a litre over placebo.
──Measured in people. Written by a person from the study named beside the step. Not signed off as a reviewed claim.
The measurement behind this step
Israel 1996: exacerbation requiring corticosteroid 6.1% against 15.6% (p=0.02), FEV1 at peak concentration +15.7% against +7.7% (p=0.006), in 401 patients over 13 weeks. Extended-release registration trial: trough FEV1 change 0.39 L against 0.27 L (p=0.021) in 397 patients over 12 weeks.
Zileuton extended-release tablets United States prescribing information — Indications 1, Dosage and Administration 2, Contraindications 4, Warnings and Preca… · a recorded source, not a stored snapshot
Israel E, Cohn J, Dubé L, Drazen JM; Zileuton Clinical Trial Group. Effect of treatment with zileuton, a 5-lipoxygenase inhibitor, in patients with asthma. A… · a recorded source, not a stored snapshot
About one in thirty gets a significant rise in liver enzymes, which is why the tests are scheduled and why almost nobody prescribes this drug.
──Measured in people. Written by a person from the study named beside the step. Not signed off as a reviewed claim.
The measurement behind this step
ALT elevation at or above three times the upper limit of normal in 3.2% of more than 5,000 treated patients, and 2.5% against 0.5% on placebo over 12 weeks. Contraindicated in active liver disease or persistent elevations at or above three times normal. Monitoring before treatment, monthly for three months, every two to three months for the rest of the year, periodically thereafter.
Zileuton extended-release tablets United States prescribing information — Indications 1, Dosage and Administration 2, Contraindications 4, Warnings and Preca… · a recorded source, not a stored snapshot
Israel E, Cohn J, Dubé L, Drazen JM; Zileuton Clinical Trial Group. Effect of treatment with zileuton, a 5-lipoxygenase inhibitor, in patients with asthma. A… · a recorded source, not a stored snapshot
No suggested links are held for this record, so nothing is hidden from this path.
What we know
The record describes 6 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 scores
Measured
Things only a test, a scale or a device shows.
inflammatory lesions
urinary pge m levels
urinary lte4 levels
Meaningful
Things that change how a life goes, not only a number.
disease free survival
survival at 2 years
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 (3)
length of hospital stay
forced expiratory volume in 1 second
ki measure of fdg uptake
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. 3.2 hours hours
Read from the label, which states: “Elimination Elimination of zileuton is predominantly via metabolism with a mean terminal half-life of 3.2 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.
Very few people. It is a third-line agent, used mainly where the leukotriene pathway is dominant — aspirin-exacerbated respiratory disease — and where montelukast has not worked or is not wanted.
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 and effectiveness of zileuton extended-release tablets in pediatric patients under 12 years of age have not been established.”
US prescribing information · bc29c998-1324-46aa-8386-e5b2fc9e0b16 · read 2026-08-30
On older people, the label states: “Subgroup analysis of controlled and open-label clinical studies with zileuton immediate-release tablets suggests that females ≥65 years of age appear to be at increased risk of ALT elevations.”
US prescribing information · bc29c998-1324-46aa-8386-e5b2fc9e0b16 · read 2026-08-30
On people who are pregnant, the label states: “Risk Summary There are no adequate human data on zileuton extended-release tablets use in pregnant women to inform a drug associated risk.”
US prescribing information · bc29c998-1324-46aa-8386-e5b2fc9e0b16 · read 2026-08-30
On people who are breastfeeding, the label states: “Risk Summary Zileuton and/or its metabolites are excreted in rat milk.”
US prescribing information · bc29c998-1324-46aa-8386-e5b2fc9e0b16 · read 2026-08-30
On people with reduced liver function, the label states: “Zileuton extended-release tablets are contraindicated in patients with active liver disease or persistent ALT elevations ≥3xULN [see Warnings and Precautions ( 5 ) and Pharmacokinetics ( 12.3 ) ].”
US prescribing information · bc29c998-1324-46aa-8386-e5b2fc9e0b16 · read 2026-08-30
On people with reduced kidney function, the label states: “Dosing adjustment in patients with renal dysfunction or patients undergoing hemodialysis is not necessary [see Pharmacokinetics ( 12.3 ) ].”
US prescribing information · bc29c998-1324-46aa-8386-e5b2fc9e0b16 · read 2026-08-30
Where the result stopped carrying
The liver: a 3.2% rate of significant transaminase elevation, a contraindication in active liver disease, and a monitoring schedule that begins monthly
The regimen: 2,400 mg a day in four tablets taken after meals, against a once-daily competitor
The interactions: theophylline exposure doubled and warfarin anticoagulation clinically increased, both requiring the other drug to be changed
The market: the originator immediate-release brand is discontinued and four generic products remain listed
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
Prescription only
❝ 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
Oral bilayer extended-release tablets of 600 mg, two twice daily within one hour after morning and evening meals
✎ 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
RNAWiki has not recorded a supervision or regulatory status for this substance.
❝ Quoted from a source
Where this came from
Copied from a source RNAWiki stored, with the source named.
No register row and no identity class settled the question.
No source is stored against this line.
What is in the pack
Each tablet combines an immediate-release layer with an extended-release layer. Food increases both peak plasma concentration and total absorption, which is why the label ties administration to meals; tablets must not be chewed, cut or crushed. The original immediate-release product was taken four times a day and is discontinued. The pharmacodynamic marker is inhibition of ex vivo whole-blood LTB4 formation, directly related to plasma level.
✎ 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 and what that means for what is in the pack.
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
Contraindicated in active liver disease or persistent hepatic enzyme elevations at or above three times the upper limit of normal, and in prior allergic reaction to zileuton. Hepatotoxicity requiring ALT measurement before treatment, monthly for three months, every two to three months for the rest of the first year and periodically thereafter, with discontinuation at five times normal or on symptoms of liver dysfunction. Neuropsychiatric events including sleep disorders and behaviour changes reported postmarketing, some with clinical details the label describes as consistent with a drug-induced effect. Commonest adverse reactions at 5% or more were sinusitis, nausea and pharyngolaryngeal pain. Clinically significant interactions with theophylline, warfarin and propranolol, each requiring the other drug to be adjusted. Caution in substantial alcohol consumption or a history of liver disease. Not for an acute asthma attack.
Nobody counted how many people took this and were fine, so this cannot be turned into a rate.
Where this came from
Zileuton extended-release tablets United States prescribing information — Indications 1, Dosage and Administration 2, Contraindications 4, Warnings and Preca… · a recorded source, not a stored snapshot
Israel E, Cohn J, Dubé L, Drazen JM; Zileuton Clinical Trial Group. Effect of treatment with zileuton, a 5-lipoxygenase inhibitor, in patients with asthma. A… · a recorded source, not a stored snapshot
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.
Zileuton appears in spontaneous reports to regulators. Across the 8 most-reported reaction terms, 48 reaction mentions were counted. One report can name several reactions.
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
Oral bilayer extended-release tablets of 600 mg, two twice daily within one hour after morning and evening meals
✎ 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
Food increases both peak plasma concentration and total absorption, which is why the label ties administration to meals; tablets must not be chewed, cut or crushed. The original immediate-release product was taken four times a day and is discontinued. The pharmacodynamic marker is inhibition of ex vivo whole-blood LTB4 formation, directly related to plasma level.
✎ 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
14 products list this as an active ingredient in the United States drug directory. 14 of them contain it and nothing else.
FDA National Drug Code directory · 10122-901 · read 2026-08-29
They are sold as powder, tablet, tablet, extended release, tablet, film coated, extended release and tablet, multilayer, extended release, taken oral.
FDA National Drug Code directory · 10122-901 · read 2026-08-29
The regulator's established pharmacologic class for it is 5-lipoxygenase inhibitor [epc], 5-lipoxygenase inhibitors [moa] and decreased leukotriene production [pe].
FDA National Drug Code directory · 10122-901 · read 2026-08-29
6 published labels name it as an active ingredient. 6 of them describe this substance alone, which is where its own label text on this page comes from.
US prescribing information · a826d16f-df07-447b-b050-b9a02ea1f89e · read 2026-08-29
Those labels are classed as human prescription drug.
US prescribing information · a826d16f-df07-447b-b050-b9a02ea1f89e · read 2026-08-29
Zileuton is oral at 3 DOSAGE FORMS AND STRENGTHS • Extended-release tablets, 600 mg., recorded as fda label in effect 2024-05-02 in the United States.
US prescribing information · bc29c998-1324-46aa-8386-e5b2fc9e0b16 · read 2026-08-30
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.
RNAWiki could not confidently classify this substance, so no self-experiment plan is offered.
Questions worth asking
Which of the trials of Zileuton 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 blocking the enzyme beats blocking the receptor in patients, an argument made from six animal species and never tested head to head
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 the absence of a boxed warning makes it neuropsychiatrically safer than montelukast, when its own label reports sleep disorders and behaviour changes consistent with a drug effect
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 the 1996 exacerbation result transfers to the extended-release formulation, whose registration trial measured only lung function
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 generic status implies affordability, when four listed products sustain a price of US$2.07 per tablet at four tablets a day
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.
How much did people take in the studies?
The sources RNAWiki checked hold nothing for this field.
Why it matters. A result belongs to an amount. Without the amount the result floats free.
What would answer it
A stored source that records 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 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 Zileuton 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.
It more than halved steroid-requiring exacerbations in its original trial
In plain words
Four hundred people with mild to moderate asthma on nothing but a rescue inhaler were randomised. Over three months, 6% of those on the full dose needed a course of steroids, against 16% on placebo.
What was measured
Frequency of asthma exacerbation requiring corticosteroid treatment, and FEV1 at expected peak concentration, over 13 weeks
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
The Zileuton Clinical Trial Group randomised 401 patients with mild to moderate asthma — FEV1 40% to 80% of predicted, treated only with inhaled beta-agonists — to zileuton 600 mg, zileuton 400 mg or placebo, each four times daily, after a 10-day placebo lead-in, for 13 weeks. Asthma exacerbation requiring corticosteroid treatment occurred in 8 of 132 (6.1%) on 600 mg against 21 of 135 (15.6%) on placebo (p=0.02). At expected peak drug concentration, average FEV1 improved 15.7% on 600 mg against 7.7% on placebo (p=0.006). Quality-of-life scores improved significantly on 600 mg and not on placebo (p=0.007 overall). This is the trial that established that 5-lipoxygenase products are mediators with an important role in the biology of asthma, and it is a genuinely good result on an endpoint that matters. It is also the trial in which the liver signal appeared: transaminase elevations above three times normal in five patients on 600 mg (p=0.03 against placebo), three on 400 mg (p=0.12) and none on placebo, all reversing on withdrawal.
Source
Israel E, Cohn J, Dubé L, Drazen JM. Effect of treatment with zileuton, a 5-lipoxygenase inhibitor, in patients with asthma. A randomized controlled trial. JAMA 1996;275:931-936
Role in the trial
Not matched to a registered study
Identity check
no open identity hold
Audit mark
verified
Review state
Written into the record, not signed off as a reviewed claim
The extended-release trial won on a 0.12 litre difference
In plain words
The trial that registered the modern twice-daily tablet measured only lung function. Zileuton gained 0.39 litres and placebo gained 0.27, a difference of about a tenth of a litre, at p=0.021.
What was measured
Mean change from baseline in trough FEV1 at 12 weeks, zileuton extended-release against placebo
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
The extended-release registration trial was a randomised, double-blind, parallel-group, placebo-controlled, multicentre study of 12 weeks in patients 12 and over with asthma, with 199 on two 600 mg extended-release tablets twice daily and 198 on placebo. Mean baseline FEV1 was 58.5% of predicted. Efficacy was assessed on trough FEV1 at 12 weeks: mean change from baseline 0.39 L against 0.27 L, p=0.021, by last-observation-carried-forward. Secondary endpoints of peak flow and rescue beta-agonist use were described as supportive. Two things are worth naming. First, the placebo arm gained 0.27 L, which is more than two thirds of the improvement seen on the drug — a reminder of how much of a twelve-week asthma trial is regression, seasonality and study effect. Second, no exacerbation endpoint was measured, so the outcome that made the original 1996 trial persuasive is absent from the registration package for the formulation people actually take.
Source
Zileuton extended-release tablets United States prescribing information, section 14 Clinical Studies
Role in the trial
Not matched to a registered study
Identity check
no open identity hold
Audit mark
caution
Review state
Written into the record, not signed off as a reviewed claim
The liver is the reason nobody prescribes it
In plain words
Roughly one person in thirty gets liver enzymes above three times normal. That is why the label requires blood tests before starting, monthly for three months, and regularly after that — and why a once-daily competitor with no monitoring took the market.
What was measured
Rate of ALT elevation at or above three times the upper limit of normal, and the monitoring schedule that follows from it
Effect estimate
No reviewed effect estimate exists for this record.
Limits
This entry records a failure.
From the source
In controlled and open-label studies involving more than 5,000 patients treated with immediate-release zileuton, the overall rate of ALT elevation at or above three times the upper limit of normal was 3.2%. One patient developed symptomatic hepatitis with jaundice, which resolved on discontinuation; three others with transaminase elevations developed mild hyperbilirubinaemia below three times normal. In the 12-week extended-release trial the incidence was 2.5% (5 of 199) against 0.5% (1 of 198) on placebo, with 60% of elevations occurring in the first month and two detected 14 days after the study treatment finished. Zileuton is contraindicated in active liver disease or persistent enzyme elevations at or above three times normal. The label directs assessing ALT before starting, monthly for three months, every two to three months for the rest of the first year and periodically thereafter, with discontinuation at five times normal or at symptoms. A drug that requires a venepuncture a month for its first quarter is competing against one that requires none, and that is not a pharmacological contest.
Source
Zileuton extended-release tablets United States prescribing information, Contraindications 4, Warnings and Precautions 5.1, Adverse Reactions 6.1, Dosage and Administration 2
Role in the trial
Not matched to a registered study
Identity check
no open identity hold
Audit mark
caution
Review state
Written into the record, not signed off as a reviewed claim
Same class of harm as montelukast, a different class of warning
In plain words
Montelukast got the FDA’s strongest warning in 2020 for psychiatric effects. Zileuton’s label describes sleep disorders and behaviour changes, says some reports look drug-induced, and carries no boxed warning.
What was measured
That zileuton is neuropsychiatrically safer than montelukast because it lacks a boxed warning — a comparison of regulatory actions taken under very different exposure volumes and benefit-risk contexts
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
Section 5.2 of the zileuton label states that neuropsychiatric events have been reported in adult and adolescent patients taking zileuton, that postmarketing reports include sleep disorders and behaviour changes, and that the clinical details of some of those reports appear consistent with a drug-induced effect. It directs patients and prescribers to be alert for such events and to evaluate the risks and benefits of continuing if they occur. Montelukast, which acts on the receptor at the end of the same pathway, received a boxed warning on 4 March 2020 for serious neuropsychiatric events including suicidal thoughts and behaviour, with the allergic rhinitis indication restricted at the same time. The difference between a boxed warning and a warnings-section paragraph is a regulatory judgement about benefit-risk in a population, not a finding about mechanism. Zileuton is prescribed to a tiny fraction of the number of people who take montelukast, for asthma alone rather than for mild hay fever, which changes both the size of the signal available to detect and the benefit side of the calculation. A reader comparing the two labels should not read the absence of a box as evidence of absence of the effect.
Source
Zileuton extended-release tablets United States prescribing information, section 5.2; FDA Drug Safety Communication, 4 March 2020, on montelukast
Role in the trial
Not matched to a registered study
Identity check
no open identity hold
Audit mark
contested
Review state
Written into the record, not signed off as a reviewed claim
A page of animal pharmacology ending in one sentence
In plain words
The mechanism section describes effects in mice, rats, rabbits, dogs, sheep and monkeys across a full page, then closes with: the clinical relevance of these findings is unknown.
What was measured
That inhibiting the enzyme rather than blocking one receptor produces better asthma control in humans — supported across six animal species and never tested head to head against a receptor antagonist
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
Section 12.1 records that zileuton inhibits ex vivo LTB4 formation in mice, rats, rabbits, dogs, sheep and monkeys; inhibits arachidonic-acid-induced ear oedema in mice, neutrophil migration in mice and eosinophil migration into the lungs of antigen-challenged sheep; in a mouse allergic inflammation model inhibited neutrophil and eosinophil influx, reduced multiple cytokines in bronchoalveolar lavage fluid and reduced serum IgE; inhibits leukotriene-dependent smooth muscle contraction in guinea pig and human airways; inhibits leukotriene-dependent bronchospasm in challenged guinea pigs; and inhibits late-phase bronchoconstriction and airway hyperreactivity in antigen-challenged sheep. The section then ends: "The clinical relevance of these findings is unknown." That closing sentence is doing exactly the right job and it is easy to miss. The upstream position of 5-lipoxygenase in the pathway, and the removal of LTB4 as well as the cysteinyl leukotrienes, is the strongest argument anyone makes for this drug over montelukast. It is an argument from mechanism and from animal models, and no head-to-head clinical trial has been run to convert it into a clinical claim.
Source
Zileuton extended-release tablets United States prescribing information, section 12.1 Mechanism of Action
Role in the trial
Not matched to a registered study
Identity check
no open identity hold
Audit mark
caution
Review state
Written into the record, not signed off as a reviewed claim
Four tablets, after food, with two interactions that change other drugs’ doses
In plain words
The regimen is four 600 mg tablets a day taken after meals. It doubles theophylline levels and pushes up warfarin’s effect on clotting, both enough that the other drug has to be adjusted.
What was measured
Theophylline clearance and area under the curve, R-warfarin exposure and prothrombin time, during co-administration
Effect estimate
No reviewed effect estimate exists for this record.
Limits
This entry records a failure.
From the source
The labelled regimen is two 600 mg extended-release tablets twice daily within one hour after morning and evening meals, a total daily dose of 2,400 mg, with tablets not to be chewed, cut or crushed, and food increasing both peak concentration and total absorption. In a 16-subject interaction study, zileuton reduced steady-state theophylline clearance by approximately 50%, approximately doubled theophylline area under the curve and raised peak concentration by 73%, with theophylline-related adverse reactions occurring more often during co-administration; the label directs halving the theophylline dose. In 30 subjects, zileuton reduced R-warfarin clearance by 15% and raised its exposure by 22%, accompanied by what the label calls a clinically significant increase in prothrombin times, with S-warfarin unaffected; the label directs prothrombin time monitoring and warfarin dose titration. Propranolol levels and beta-blocker activity also rise. Set against montelukast — once daily, no monitoring, no comparable interactions — this is a full account of why a drug with a good 1996 exacerbation result occupies four products in the entire acquisition-cost survey.
Source
Zileuton extended-release tablets United States prescribing information, Dosage and Administration 2, Drug Interactions 7.1 to 7.3, Clinical Pharmacology 12.3
Role in the trial
Not matched to a registered study
Identity check
no open identity hold
Audit mark
caution
Review state
Written into the record, not signed off as a reviewed claim
How many documents were read
6 documents were read for this substance.
RNAWiki source record
6 of them state the same volumeOfDistribution, and they agree.
RNAWiki source record
Where else this substance is registered
FDA substance identifier (UNII)
V1L22WVE2S
RxNorm concept
730834
Checks this page had to pass
✓ Passed
Identity resolved
no open identity hold
✓ Passed
No unresolved merge across substance families
no quarantine open
✓ Passed
Every public sentence names a source
The opening statement carries the origin: Written into the record, not signed off.
✗ Not passed
Trial roles classified for highlighted evidence
No registered study is classified as testing this substance.
✓ Passed
No internal keys in reader text
enforced by the copy-contract test over the rendered page
✗ Not passed
Safety mode resolved
No register row and no identity class settled the question.
✓ Passed
Canonical metadata present
slug and display name present
What is missing or unclear◇Read from sources, not yet reviewed
How this medicine reached us
Kept near the foot of the page. A historical event moves up only when it changes something about this substance today.
What the approval register records
8 approved applications cover products containing this substance. The earliest was NDA020471, approved 19961209 to CHIESI.
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.
A 5-lipoxygenase inhibitor that cut steroid-requiring exacerbations from 15.6% to 6.1% over three months in its original 401-patient trial, and whose extended-release registration trial gained 0.39 L of FEV1 against placebo’s 0.27 L (p=0.021) — bought with ALT elevations above three times normal in 3.2% of more than 5,000 treated patients, monthly liver testing, four tablets a day, and a daily acquisition cost about 120 times montelukast’s.
Recorded evidence blocks (12)
Q1
What did Zileuton's largest trial (400 people) and its longest (7.4 years) measure?
400 people in Zileuton's largest registered study, 7.4 years in its longest registered window, measuring Bronchial dysplasia number and grade at 6 months. ClinicalTrials.gov · 2026-09-01
10 phase2, 6 phase1, 3 phase4, 1 early phase1, 1 phase3; NCT00070486; 2011-05; no ageing endpoint recorded. Last human test completed 2021, NCT02348203.
Interpretation These counts include studies where Zileuton 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
phase2
10
phase1
6
phase4
3
early phase1
1
phase3
1
Last recorded human testNCT02348203
2021-03-09
recorded 2026-09-01 · last checked 2026-09-04
Q2
From mouse to human: where has Zileuton shown mechanism-only?
"insufficient enrollment"; 5 of 18 registered studies
Show the evidence
Trial
NCT00467831
terminated; "insufficient enrollment"
NCT00486343
terminated; "Slower than anticipated enrollment"
NCT00493974
terminated; "Lack of feasibility due to low recruitment"
NCT01130688
terminated; "Lack of enrollment"
NCT02047149
terminated; "Low accrual"
recorded 2026-09-01 · last checked 2026-09-04
Q4
Zileuton's half-life is 3.2 hours — which schedules were studied?
3.2 hours, the half-life Zileuton's label states. openfda-label · aee65202-fddb-497f-9f11-17cc727cb157 · 2026-08-30
Show the evidence
half life
3.2 hours hours; Elimination Elimination of zileuton is predominantly via metabolism with a mean terminal half-life of 3.2 hours.
tmax
PHARMACOKINETICS Zileuton is rapidly absorbed upon oral administration with a mean time to peak plasma concentration (T max ) of 1.7 hours and a mean peak level (C max ) of 4.98 μg/mL. The absolute bioavailability of ZYFLO is unknown.
bioavailability
PHARMACOKINETICS Zileuton is rapidly absorbed upon oral administration with a mean time to peak plasma concentration (T max ) of 1.7 hours and a mean peak level (C max ) of 4.98 μg/mL. The absolute bioavailability of ZYFLO is unknown.
metabolism
Elimination of zileuton is predominantly via metabolism with a mean terminal half-life of 2.5 hours.
recorded 2026-08-30 · last checked 2026-09-04
Q5
Could one person measure Zileuton's effect on disease free survival?
Disease free survival: measured in Zileuton's trials.
Interpretation disease free survival is the recorded endpoint.
2; NCT01130688; PHASE1; the smallest recorded human enrolment at or below 30; the registry states no direction of its result; TERMINATED
Q6
Which of disease free survival, forced expiratory volume in 1 second and inflammatory lesions did Zileuton's trials measure?
disease free survival, forced expiratory volume in 1 second and inflammatory lesions lead 9 outcome terms across Zileuton's trials. ClinicalTrials.gov · 2026-09-01
length of hospital stay, forced expiratory volume in 1 second, urinary pge m levels, urinary lte4 levels, ki measure of fdg uptake and pain scores follow.
Show the evidence
disease free survival
1
inflammatory lesions
1
survival at 2 years
1
length of hospital stay
1
forced expiratory volume in 1 second
1
urinary pge m levels
1
3 more recorded rows
urinary lte4 levels
1
ki measure of fdg uptake
1
pain scores
1
recorded 2026-09-01 · last checked 2026-09-04
Q7
Which 8 trials of Zileuton posted no result?
Posted no result
8 of 8 completed trials
Registrations
NCT00299065, NCT00262405, NCT00575861, NCT00534625, NCT00056004 and NCT00070486, and 2 more
Completion dates
oldest 2006-06; newest 2014-03
Show the evidence
Trial
NCT00299065
2006-06
NCT00262405
2007-05
NCT00575861
2007-11
NCT00534625
2008-03
NCT00056004
2009-03
NCT00070486
2011-05
2 further recorded trials
NCT01136941
2013-04
NCT01174056
2014-03
Q8
At the median, Zileuton's trials enrolled 41.5 people — anything larger?
Median enrolment
41.5
Largest enrolment
400
Registered trials counted
18
Q9
What do 48 spontaneous reports say about Zileuton — 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.
Zileuton appears in spontaneous reports to regulators. Across the 8 most-reported reaction terms, 48 reaction mentions were counted: alanine aminotransferase increased 19; aspartate aminotransferase increased 12; hepatic enzyme increased 8; blood bilirubin increased 4. open-targets-adr · CHEMBL93 · 2026-06-24
Show the evidence
alanine aminotransferase increased
19
aspartate aminotransferase increased
12
hepatic enzyme increased
8
blood bilirubin increased
4
laryngospasm
2
bacteria urine
1
2 more recorded rows
lymphatic fistula
1
nasal polypectomy
1
recorded 2026-06-24 · last checked 2026-09-04
Q10
Zileuton and CYP1A2, CYP2C9 and CYP3A4: shared by which compounds?
CYP1A2, CYP2C9 and CYP3A4 appear in Zileuton's recorded interaction sentences, 3 in all. openfda-label+europepmc · 2026-08-30
Interpretation pharmacokinetics
Show the evidence
CYP1A2pharmacokinetics
Metabolism In vitro studies utilizing human liver microsomes have shown that zileuton and its N-dehydroxylated metabolite can be oxidatively metabolized by CYP1A2, CYP2C9 and CYP3A4.
CYP2C9pharmacokinetics
Metabolism In vitro studies utilizing human liver microsomes have shown that zileuton and its N-dehydroxylated metabolite can be oxidatively metabolized by CYP1A2, CYP2C9 and CYP3A4.
CYP3A4pharmacokinetics
Metabolism In vitro studies utilizing human liver microsomes have shown that zileuton and its N-dehydroxylated metabolite can be oxidatively metabolized by CYP1A2, CYP2C9 and CYP3A4.
recorded 2026-08-30 · last checked 2026-09-04
Q11
Was Zileuton studied with fasting and exercise?
fasting and exercise are named in Zileuton's label sentences: "In a nonblinded crossover study, 18 healthy male volunteers who had fasted overnight were randomised to receive a single oral dose of zileuton 600mg in the presence or absence of food consisting of a standardised breakfast on the following morning." openfda-label+europepmc · 2026-08-30
2 recorded statements; fasting, exercise
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fasting
In a nonblinded crossover study, 18 healthy male volunteers who had fasted overnight were randomised to receive a single oral dose of zileuton 600mg in the presence or absence of food consisting of a standardised breakfast on the following morning.
exercise
Seventeen healthy athletes (9 men, 8 women; age 23 +/- 3 yr) with varying degrees of EIAH completed maximal incremental treadmill exercise tests after administration of fexofenadine, zileuton, and nedocromil sodium or placebo in a randomized double-blind crossover study.
recorded 2026-08-30 · last checked 2026-09-04
Q12
What is recorded about Zileuton and AMPK?
"These results show that 5-LO inhibition by either zileuton or 5-LO siRNA protects C2C12 myotubes from PA-induced lipotoxicity, at least partly via AMPK activation, and suggest that the in vivo insulin-sensitizing effects of zileuton are in part attributable to its direct action on skeletal muscle via LTB4 downregulation followed by AMPK…" — where Zileuton and AMPK appear together. Europe PMC · pathway abstract search · 2017-07-10
AMPK; PMID 28694473
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AMPKPMID 28694473
"These results show that 5-LO inhibition by either zileuton or 5-LO siRNA protects C2C12 myotubes from PA-induced lipotoxicity, at least partly via AMPK activation, and suggest that the in vivo insulin-sensitizing effects of zileuton are in part attributable to its direct action on skeletal muscle via LTB4 downregulation followed by AMPK activation."
recorded 2017-07-10 · last checked 2026-09-04
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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
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