This page shows what was measured, who it was measured in, and what that does not settle.
What Omeprazole does in the body
Heartburn, acid reflux and stomach or duodenal ulcers
Omeprazole is swallowed in a coating that survives the stomach, so the drug is absorbed from the small intestine into the bloodstream instead. It is chemically inert at the pH of blood and tissue, which means it does nothing anywhere in the body until it drifts into the acid-secreting pocket of a stomach cell. There the acid itself converts it into a reactive form that cannot escape, and that form bonds permanently to the pump that makes the acid. Because the bond is permanent, the cell has to build new pumps before it can make acid again, which is why the effect builds over several days and lasts well beyond the time the drug is in the blood.
What happened in people
Upper gastrointestinal events 1.1% against 2.9% on placebo in 3,761 randomised patients on aspirin and clopidogrel (HR 0.34, P<0.001)
✎ 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.
That protecting the stomach protects the gut — CONDOR measured the whole gastrointestinal tract and found 4.3 times the event rate with omeprazole plus diclofenac against a coxib alone
Where it acts
Gastric parietal cell — inside the secretory canaliculus, the only compartment in the body where the pH falls below 2
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
Its recorded molecular formula is C17H19N3O3S, weighing 345.42.
US prescribing information · 5a09ce48-7139-4fc7-9b6e-439459c8e866 · 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 153 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.
Comparator
A comparator is whatever the treatment was measured against.
A picture of it, and where the picture fails
It is like the other runner in a race.
Where that stops being true. A race has one winner. A study can show both arms improved.
What people get wrong. Results are read without asking what the other group got. Beating nothing is not beating a treatment.
The control condition against which the experimental intervention is assessed.
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.
Absolute difference
An absolute difference is how many more people in a hundred were affected.
A picture of it, and where the picture fails
It is like counting heads in two rooms of a hundred.
Where that stops being true. Heads are easy to count. Study results carry a margin of error too.
What people get wrong. It is confused with a percentage change, which can look far larger.
The arithmetic difference in event rates between arms.
Confidence interval
A confidence interval is the range the true answer is likely to sit in.
A picture of it, and where the picture fails
It is like a weather forecast giving a range rather than one number.
Where that stops being true. A forecast range covers tomorrow. This one covers what the study could resolve.
What people get wrong. The middle number is read as the answer. A range crossing zero means no change is still possible.
An interval estimate that would contain the true parameter in a stated proportion of repeated studies.
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.
Composite of overt or occult gastrointestinal bleeding, symptomatic gastroduodenal ulcer or erosion, obstruction or perforation
1.1% against 2.9% at 180 days; hazard ratio 0.34 (95% CI 0.18 to 0.63), P<0.001
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. The trial stopped early when the sponsor lost its financing, at 3,873 of a planned 5,000 randomised. The co-primary cardiovascular comparison was therefore underpowered, and the authors state it does not rule out a clinically meaningful difference.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Oral delayed-release capsule and tablet, oral suspension, and an over-the-counter magnesium salt tablet
Interval reported. 95% CI 0
Written into the record, not signed off as a reviewed claim.
3.8% on diclofenac plus omeprazole against 0.9% on celecoxib; hazard ratio 4.3 (95% CI 2.6 to 7.0), P<0.0001
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. Funded by the manufacturer of the comparator. The result is nonetheless a direct measurement of what a proton pump inhibitor cannot do: the excess was in the small and large bowel, outside its mechanism.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Oral delayed-release capsule and tablet, oral suspension, and an over-the-counter magnesium salt tablet
Interval reported. 95% CI 2
Written into the record, not signed off as a reviewed claim.
Registered as precancerous gastric lesions; reported here is the prespecified 14.7-year gastric cancer incidence and cause-specific mortality follow-up
Gastric cancer 3.0% against 4.6%; odds ratio 0.61 (95% CI 0.38 to 0.96), P=0.032. Gastric cancer death 1.5% against 2.1%, hazard ratio 0.67 (95% CI 0.36 to 1.28), not significant.
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. The effect belongs to Helicobacter pylori eradication, not to acid suppression. Omeprazole was the adjunct that raised gastric pH so the amoxicillin would work.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Oral delayed-release capsule and tablet, oral suspension, and an over-the-counter magnesium salt tablet
Interval reported. 95% CI 0
Written into the record, not signed off as a reviewed claim.
Prespecified safety events collected every six months over a median 3.01 years: pneumonia, Clostridioides difficile, other enteric infections, fracture, gastric atrophy, chronic kidney disease, diabetes, chronic obstructive lung disease, dementia, cardiovascular disease, cancer, hospitalisation, death
RNAWiki holds 4 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 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
Omeprazole
What a person takes: Oral delayed-release capsule and tablet, oral suspension, and an over-the-counter magnesium salt tablet.
The measurement behind this step
Every oral form is enteric-protected, because the free base is destroyed by gastric acid within minutes. Absorption is from the small intestine; the drug then reaches the parietal cell through the bloodstream, not from the stomach lumen.
Getting in
Protected from the acid it is meant to block
The drug is destroyed by stomach acid within minutes, so the capsule is coated to survive the stomach intact and dissolve further down. Chewing it or opening it into something acidic wastes the dose.
──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
Omeprazole free base degrades rapidly below pH 4. Commercial products are enteric-coated granules that release above pH 5.5 in the duodenum. Oral bioavailability is around 30 to 40% on first dose and rises with repeated dosing as acid-mediated presystemic degradation falls. Plasma half-life is roughly one hour — far shorter than the duration of effect, because the effect outlives the molecule.
From the small intestine it enters the bloodstream and circulates through the whole body. At the pH of blood it is chemically inert, which is why it has no effect on any other tissue.
╌╌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
Circulating omeprazole is a neutral weak base, about 95% protein bound, with no meaningful affinity for any receptor. Selectivity is not achieved by molecular recognition of the target but by the chemistry of activation: nothing happens until pH falls far enough to protonate the pyridine nitrogen.
The acid-secreting cells of the stomach have a tiny internal channel where the pH drops below 2 — lower than anywhere else in a person. The drug drifts in, becomes electrically charged, and can no longer get back out.
──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
The pyridine nitrogen has a pKa near 4. In a compartment at pH 1 essentially every molecule is protonated, and the charged species cannot cross the membrane back out. The result is roughly thousandfold accumulation in the secretory canaliculus relative to plasma, achieved with no transporter and no binding partner.
The same acid that traps the drug also rearranges it into a highly reactive form. The drug does not arrive active; the target manufactures its own inhibitor on the spot.
╌╌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
A second protonation on the benzimidazole triggers intramolecular rearrangement to a tetracyclic cyclic sulfenamide. That species is a potent thiophile with a very short lifetime, which is precisely why it cannot escape the canaliculus to react with cysteines anywhere else in the body.
The reactive form welds itself to the pump through a sulfur-to-sulfur bond. That pump never works again. The cell can only recover by building new ones.
──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
The sulfenamide forms a disulfide with cysteine 813 on the luminal loop between transmembrane segments 5 and 6 of the H+/K+-ATPase alpha subunit, and with cysteine 892 for some members of the class. Inhibition is reversed in vitro by dithiothreitol, which is the experimental signature of a disulfide. In vivo, recovery depends on pump resynthesis, with a half-life of roughly 50 hours, so a one-hour plasma half-life produces a multi-day effect.
Acid falls and erosions heal. What it does not do is fix the leaking valve that let acid into the oesophagus, or protect any part of the gut below the stomach — which is exactly where the CONDOR trial found the harm.
╌╌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
Only pumps actively secreting at the time of exposure are inhibited, so full effect takes three to five days of repeated dosing. Suppression drives a compensatory rise in gastrin and an increase in total pump mass, which is the basis of rebound acid hypersecretion after withdrawal. No component of the mechanism touches lower oesophageal sphincter tone or small-bowel and colonic mucosa.
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 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.
Roughly one in twenty adults in high-income countries in any given year, most of them without a prescription. It is among the most-dispensed drugs in the world and one of the few on the WHO Model List of Essential Medicines that is also sold off a supermarket shelf.
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 omeprazole delayed-release capsules have been established in pediatric patients 2 to 16 years for the treatment of symptomatic GERD, treatment of EE due to acid-mediated GERD, and maintenance of healing of EE due to acid-mediated GERD.”
US prescribing information · 5a09ce48-7139-4fc7-9b6e-439459c8e866 · read 2026-08-30
On older people, the label states: “Omeprazole was administered to over 2000 elderly individuals (≥65 years of age) in clinical trials in the U.S. and Europe.”
US prescribing information · 5a09ce48-7139-4fc7-9b6e-439459c8e866 · read 2026-08-30
On people who are pregnant, the label states: “Risk Summary There are no adequate and well-controlled studies with omeprazole in pregnant women.”
US prescribing information · 5a09ce48-7139-4fc7-9b6e-439459c8e866 · read 2026-08-30
On people who are breastfeeding, the label states: “Risk Summary Limited data suggest omeprazole may be present in human milk.”
US prescribing information · 5a09ce48-7139-4fc7-9b6e-439459c8e866 · read 2026-08-30
On people with reduced liver function, the label states: “In patients with hepatic impairment (Child-Pugh Class A, B, or C) exposure to omeprazole substantially increased compared to healthy subjects.”
US prescribing information · 5a09ce48-7139-4fc7-9b6e-439459c8e866 · read 2026-08-30
Where the result stopped carrying
CONDOR: the standard gastroprotective strategy lost outright to a coxib once events below the duodenum were counted
COGENT stopped early when its sponsor ran out of money, leaving the cardiovascular question underpowered rather than answered
CYP2C19 genotype changes exposure several-fold and nobody is tested before the first capsule
Acid rebound above baseline after withdrawal is a predictable consequence of the mechanism and a common reason people never stop
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 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 (11)
It was studied for a different goal
The studies measured something else entirely. Nothing in this record points to this reason.
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 delayed-release capsule and tablet, oral suspension, and an over-the-counter magnesium salt tablet
✎ 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
Every oral form is enteric-protected, because the free base is destroyed by gastric acid within minutes. Absorption is from the small intestine; the drug then reaches the parietal cell through the bloodstream, not from the stomach lumen.
✎ 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
The label carries warnings for acute interstitial nephritis, Clostridioides difficile-associated diarrhoea, bone fracture with long-term high-dose use, cutaneous and systemic lupus erythematosus, cyanocobalamin deficiency, hypomagnesaemia, and fundic gland polyps with use beyond one year. Commonest adverse events in trials are headache, abdominal pain, nausea and diarrhoea. Interactions run through CYP2C19 — clopidogrel, and drugs whose absorption depends on gastric pH — and coadministration with rilpivirine is contraindicated.
Nobody counted how many people took this and were fine, so this cannot be turned into a rate.
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 delayed-release capsule and tablet, oral suspension, and an over-the-counter magnesium salt tablet
✎ 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
Absorption is from the small intestine; the drug then reaches the parietal cell through the bloodstream, not from the stomach lumen.
✎ 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
366 products list this as an active ingredient in the United States drug directory. 324 of them contain it and nothing else.
FDA National Drug Code directory · 72288-606 · read 2026-08-29
They are sold as capsule, capsule, delayed release, capsule, delayed release pellets, capsule, gelatin coated, for suspension and powder, taken oral.
FDA National Drug Code directory · 72288-606 · read 2026-08-29
The regulator's established pharmacologic class for it is cytochrome p450 2c19 inhibitors [moa], proton pump inhibitor [epc] and proton pump inhibitors [moa].
FDA National Drug Code directory · 72288-606 · read 2026-08-29
309 published labels name it as an active ingredient. 280 of them describe this substance alone, which is where its own label text on this page comes from.
US prescribing information · 9cdde58a-ae8a-451f-92cf-cab178e4ba92 · read 2026-08-29
Those labels are classed as human otc drug and human prescription drug.
US prescribing information · 9cdde58a-ae8a-451f-92cf-cab178e4ba92 · read 2026-08-29
1 marketed supplement label lists this ingredient, classed as other combinations.
Those labels carry all other, nutrient and structure/function claims. A claim of that kind is written by the manufacturer and is not assessed by any regulator, so its presence says nothing about whether it is true.
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 Omeprazole 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 protecting the stomach protects the gut — CONDOR measured the whole gastrointestinal tract and found 4.3 times the event rate with omeprazole plus diclofenac against a coxib alone
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 measured drop in clopidogrel platelet inhibition causes heart attacks, which the only randomised test of it did not reproduce (HR 0.99, 95% CI 0.68 to 1.44)
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 observational links to dementia, kidney disease and fracture are causal, when a three-year randomised trial in 17,598 people found none of them
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 endoscopic healing is a measure of how long or how well someone lives; no trial in this class has been powered on mortality
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 Omeprazole 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.
COGENT: upper gastrointestinal bleeding cut from 2.9% to 1.1% against placebo
In plain words
People taking aspirin plus clopidogrel were randomly given omeprazole or a dummy capsule. Bleeding and ulcers in the upper gut fell by about two thirds. This is the cleanest placebo-controlled result the drug has on an outcome a patient would notice.
What was measured
Composite of overt or occult bleeding, symptomatic gastroduodenal ulcer or erosion, obstruction or perforation at 180 days, against matching placebo
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
COGENT randomised patients with an indication for dual antiplatelet therapy to clopidogrel with omeprazole or with placebo, on a background of aspirin. Of a planned 5,000, 3,873 were randomised and 3,761 analysed before the trial stopped early when the sponsor lost its financing. Fifty-one patients had a gastrointestinal event: 1.1% on omeprazole against 2.9% on placebo at 180 days (hazard ratio 0.34, 95% CI 0.18 to 0.63, P<0.001). Overt upper gastrointestinal bleeding fell further (HR 0.13, 95% CI 0.03 to 0.56, P=0.001). Diarrhoea was more common on omeprazole.
Written into the record, not signed off as a reviewed claim
The clopidogrel interaction: a warning built on blood tests, then a randomised trial that did not find it
In plain words
In 2009 regulators warned that omeprazole might blunt clopidogrel and leave heart patients unprotected. The warning came from laboratory measurements of platelet activity and from database studies. When the question was finally put to a randomised trial, cardiovascular events were identical in the two groups.
What was measured
That the measured drop in platelet inhibition translates into more heart attacks and strokes — a mechanistic and observational inference that the only randomised test of it did not reproduce
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
Both drugs use CYP2C19 — clopidogrel needs it to become active, omeprazole inhibits it — and pharmacodynamic studies showed reduced platelet inhibition when the two were combined. Observational analyses reported more cardiovascular events. In COGENT the cardiovascular composite of cardiovascular death, non-fatal myocardial infarction, revascularisation or stroke occurred in 4.9% on omeprazole against 5.7% on placebo (hazard ratio 0.99, 95% CI 0.68 to 1.44, P=0.96), with no significant heterogeneity across high-risk subgroups. The authors were explicit that the trial stopped early and cannot rule out a clinically meaningful difference, so this is a null result with wide confidence limits rather than a proof of no effect. The label interaction statement remains.
Written into the record, not signed off as a reviewed claim
CONDOR: an anti-inflammatory plus omeprazole produced 4.3 times the whole-gut event rate of a coxib alone
In plain words
The standard way to protect the stomach from an anti-inflammatory drug is to add a proton pump inhibitor. When someone counted problems along the entire gut rather than just the stomach, that strategy lost badly — because the drug protects only the part of the gut that makes acid.
What was measured
Adjudicated composite of clinically significant upper and lower gastrointestinal events over six months
Effect estimate
No reviewed effect estimate exists for this record.
Limits
This entry records a failure.
From the source
CONDOR randomised 4,484 patients with osteoarthritis or rheumatoid arthritis at increased gastrointestinal risk, all Helicobacter pylori negative, to celecoxib 200 mg twice daily or to slow-release diclofenac 75 mg twice daily plus omeprazole 20 mg daily, for six months across 196 centres in 32 countries. The adjudicated composite of clinically significant upper or lower gastrointestinal events occurred in 20 of 2,238 on celecoxib (0.9%) against 81 of 2,246 on diclofenac plus omeprazole (3.8%), hazard ratio 4.3 (95% CI 2.6 to 7.0, P<0.0001). Early withdrawal for gastrointestinal adverse events was 6% against 8% (P=0.0006). The excess was overwhelmingly in the small and large bowel, where a proton pump inhibitor has no mechanism of action.
Written into the record, not signed off as a reviewed claim
Shandong: two weeks of amoxicillin with omeprazole, and 1.6 fewer gastric cancers per hundred people fifteen years later
In plain words
A trial in a high-risk Chinese county gave people either antibiotics to clear a stomach bacterium or a placebo, then followed them for fifteen years. Three in a hundred treated people developed stomach cancer, against nearly five in a hundred untreated.
What was measured
Gastric cancer incidence and cause-specific mortality at 14.7 years
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
The Shandong Intervention Trial was a masked factorial placebo-controlled study in Linqu County. Among 3,365 randomly assigned subjects followed 14.7 years, gastric cancer was diagnosed in 3.0% of those who received the two-week Helicobacter pylori regimen of amoxicillin with omeprazole against 4.6% of those who received placebo (odds ratio 0.61, 95% CI 0.38 to 0.96, P=0.032). Gastric cancer deaths were 1.5% against 2.1% (hazard ratio 0.67, 95% CI 0.36 to 1.28), which did not reach significance. Garlic extract and vitamin supplementation, tested in the same factorial design, produced no statistically significant reduction. The omeprazole here is an adjunct that raises pH so the antibiotic works, not the active agent — the effect belongs to eradication, and this page does not claim it for acid suppression.
Written into the record, not signed off as a reviewed claim
The healing figure that made the class: 83.6% against 51.9% and 28.2%
In plain words
Pooling 43 randomised trials in 7,635 people, proton pump inhibitors healed erosive damage to the oesophagus in about five in six patients, H2 blockers in about half, and placebo in about a quarter. They also healed it nearly twice as fast.
What was measured
Proportion healed and heartburn-free at up to 12 weeks, pooled across 43 randomised trials in 7,635 patients
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
Chiba and colleagues applied strict inclusion criteria to single- or double-blind randomised studies in adults with endoscopically proven erosive or ulcerative oesophagitis. Mean healing proportion within 12 weeks was 83.6% (SD 11.4) for proton pump inhibitors, 51.9% (17.1) for H2-receptor antagonists, 39.2% (22.4) for sucralfate and 28.2% (15.6) for placebo. Healing speed was 11.7% per week for PPIs against 5.9% for H2 blockers and 2.9% for placebo. Heartburn-free proportions were 77.4% against 47.6%. This is a class-level surrogate: it counts mucosa seen down an endoscope, not bleeds, cancers or deaths.
Written into the record, not signed off as a reviewed claim
The long-term harms attached to this class came from cohorts, and the randomised test found almost none of them
In plain words
Between 2006 and 2017 database studies linked proton pump inhibitors to dementia, kidney disease, fractures, pneumonia and death. A randomised trial then gave 17,598 people a proton pump inhibitor or placebo for three years and found none of those differences except a small excess of gut infections.
What was measured
That long-term proton pump inhibitor use causes dementia, kidney disease and fracture — an inference from observational cohorts that a three-year randomised trial in 17,598 people did not reproduce
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
Gomm and colleagues reported a hazard ratio of 1.44 (95% CI 1.36 to 1.52) for incident dementia in German claims data, and Lazarus and colleagues reported a hazard ratio of 1.50 (95% CI 1.14 to 1.96) for incident chronic kidney disease in the ARIC cohort. Both are observational and both are vulnerable to confounding by indication: people prescribed acid suppression differ systematically from people who are not. The COMPASS trial randomised 17,598 participants to pantoprazole 40 mg daily or placebo and followed them for a median of 3.01 years across 53,152 patient-years, collecting pneumonia, Clostridioides difficile, other enteric infections, fracture, gastric atrophy, chronic kidney disease, diabetes, chronic obstructive lung disease, dementia, cardiovascular disease, cancer, hospitalisation and all-cause mortality every six months. No safety outcome differed significantly except enteric infections, 1.4% against 1.0% (odds ratio 1.33, 95% CI 1.01 to 1.75). Three years is not twenty, and this is pantoprazole rather than omeprazole; the class inference is stated here rather than assumed.
Written into the record, not signed off as a reviewed claim
Between a quarter and a third of people cannot metabolise it the same way
In plain words
Omeprazole is broken down by an enzyme that comes in fast, normal and slow versions. Which version someone inherited changes how much drug they are exposed to several-fold, and nobody is tested for it before the first capsule.
What was measured
Not recorded
Effect estimate
No reviewed effect estimate exists for this record.
Limits
This entry records a failure.
From the source
Omeprazole is cleared predominantly by CYP2C19, with a minor CYP3A4 route. Poor metabolisers — around 3% of people of European ancestry and 15 to 20% of people of East Asian ancestry — have several-fold higher exposure than extensive metabolisers, and rapid or ultrarapid metabolisers carrying CYP2C19*17 have correspondingly lower exposure and worse acid control. The label records the pharmacokinetic difference and the interaction with clopidogrel that follows from the same enzyme, and no genotyping is required before dispensing. This is a known, measured, unaddressed source of variability in a drug taken by hundreds of millions of people.
Source
PRILOSEC United States prescribing information, Clinical Pharmacology and Drug Interactions (NDA 019810, AstraZeneca)
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
280 documents were read for this substance.
RNAWiki source record
135 of them state the same halfLife, and they agree.
RNAWiki source record
135 of them state the same bioavailability, and they agree.
RNAWiki source record
130 of them state the same tMax, and they agree.
RNAWiki source record
135 of them state the same proteinBinding, and they agree.
RNAWiki source record
Where else this substance is registered
FDA substance identifier (UNII)
KG60484QX9
CAS registry number
73590-58-6
PubChem compound
4594
RxNorm concept
283742
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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
52 approved applications cover products containing this substance. The earliest was NDA019810, approved 19890914 to ASTRAZENECA.
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What is not here
7 questions this page could not answer
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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 prodrug that does nothing until it reaches the one compartment in the body below pH 2, where it rearranges into a reactive sulfenamide and welds itself permanently to the stomach’s proton pump — healing erosive oesophagitis in 83.6% of patients pooled across 43 trials against 51.9% for an H2 blocker and 28.2% for placebo, and cutting upper gastrointestinal bleeding from 2.9% to 1.1% in 3,761 patients on aspirin and clopidogrel, while a trial of the whole gut found the same drug paired with an anti-inflammatory produced 4.3 times the rate of clinically significant events as a coxib alone.
Recorded evidence blocks (11)
Q1
On the Omeprazole label: indicated for what?
"Omeprazole delayed-release capsules are a proton pump inhibitor (PPI) indicated for the: Treatment of active duodenal ulcer in adults ( 1.1 ) Eradication of Helicobacter pylori to reduce the risk of duodenal ulcer recurrence in adults ( 1.2 ) Treatment of active benign gastric ulcer in adults ( 1.3 ) Treatment of…": indications and usage on Omeprazole's label. DailyMed label · ded0df8b-1813-4595-ac2b-5499704bfd48 · 2026-08-05
Q2
315 registered trials of Omeprazole — at which phases?
Registered studies posting no result
238 of 315
315 registered studies of Omeprazole: 156 phase1, 60 phase4, 39 phase3, 29 phase2, 22 na, 9 early phase1, 5 na or unstated. CLINICALTRIALS_SNAPSHOT · 2026-09-01
futility/efficacy (2), accrual/recruitment (8), funding/business (4), sponsor decision unspecified (1) and other (16): Omeprazole's stop wording, clustered. CLINICALTRIALS_SNAPSHOT · 2026-09-01
"Superiority of iv omeprazole to ranitidine has already been proven by others."; 31 of 315 registered studies
Show the evidence
Trial
NCT00247130
withdrawn; "Superiority of iv omeprazole to ranitidine has already been proven by others."
NCT00364481
withdrawn; "Not enough subjects enrolled"
NCT00537732
terminated; "recruitment problems"
NCT00668317
terminated; "Primary care physicians began prescribing antacid therapy for chronic cough"
NCT00857597
terminated; "Study was terminated after unplanned interim analysis of single centre data and results were reported"
NCT01016717
withdrawn; "Since the published data resolved the study goals we decided not to start it"
14 further recorded trials
NCT01408849
terminated; "Lack of adherence and huge loss of follow up."
NCT01678053
withdrawn; "Was not able to recruit patients for randomization."
NCT01762644
withdrawn; "This study was withdrawn prior to enrollment."
NCT01777854
terminated; "Lack of patient interest in the study."
NCT01782560
withdrawn; "Unable to recruit a sufficient amount of subjects"
NCT01824199
withdrawn; "funding"
NCT02013453
withdrawn; "Lack of funding"
NCT02016820
terminated; "Lack of funding"
NCT02039869
withdrawn; "Could not recruit patients - modifying protocol and plan resubmission to our IRB"
NCT02123498
withdrawn; "IRB not approved"
NCT02153177
withdrawn; "The study was withdrawn prior to any participants being enrolled."
NCT02262169
terminated; "This study was terminated due to internal technical issues at study site"
NCT02760615
withdrawn; "No enrollment"
NCT03059303
terminated; "Decision to discontinue development of investigational Hep C treatment regimen JNJ-4178: 3 direct acting antivirals - AL-335, ODV \& SMV."
recorded 2026-09-01 · last checked 2026-09-04
Q4
Human studies of Omeprazole used Omeprazole (20 mg) — over how long?
Human studies of Omeprazole used "Omeprazole (20 mg)". ClinicalTrials.gov · 2026-09-01
20 recorded entries; human; also "omeprazole magnesium (20 mg equivalent)", "Omeprazole Tablet, 20 mg", "20 mg omeprazole"
Show the evidence
human
NCT00741468
Omeprazole (20 mg)
NCT00765206
omeprazole magnesium (20 mg equivalent)
NCT00930306
Omeprazole Tablet, 20 mg
NCT00952978
20 mg omeprazole
NCT01045434
Prilosec 20 mg tablets
NCT01045642
Prilosec OTC 20 mg Tablets
14 more recorded rows
humanNCT01170169
Prelosec 40 mg
humanNCT01170182
Prilosec® 40 mg
humanNCT01489943
Omeprazole 40 mg
humanNCT01587885
Omeprazole 20 mg + Sodium Bicarbonate 1100 mg
humanNCT01587885
Omeprazole 20 mg
humanNCT01731067
omeprazole 5 mg
humanNCT02056743
Omeprazole 20mg
humanNCT02438072
Omeprazole (10 mg, A02BC01)
humanNCT02476097
Esomeprazole: Nexium® 20mg, Astra Zeneca
humanNCT02476097
omeprazole 40mg
humanNCT02922699
OMEPRAZOLE 40MG
humanNCT02922699
OMEPRAZOLE 80 MG
humanNCT03163680
Omeprazole 40 MG
humanNCT03551691
Omeprazole 20mg Capsule
recorded 2026-09-01 · last checked 2026-09-04
Q5
Omeprazole's half-life is 0.5 to 1 hour — which schedules were studied?
tmax 0.5 to 3.5 hours; bioavailability 30 to 40 %.
Show the evidence
half lifepharmacokinetics
0.5 to 1 hour; In healthy subjects the plasma half-life is 0.5 to 1 hour, and the total body clearance is 500 to 600 mL/min.
tmaxpharmacokinetics
0.5 to 3.5 hours; Absorption is rapid, with peak plasma concentrations of omeprazole occurring within 0.5 to 3.5 hours.
bioavailabilitypharmacokinetics
30 to 40 %; Absolute bioavailability (compared with intravenous administration) is about 30 to 40% at doses of 20 to 40 mg, due in large part to presystemic metabolism.
metabolismpharmacokinetics
Absolute bioavailability (compared with intravenous administration) is about 30 to 40% at doses of 20 to 40 mg, due in large part to presystemic metabolism.
recorded 2026-08-05 · last checked 2026-09-04
Q6
Which running trial of Omeprazole could settle inflammatory markers?
NCT06150898 measures To detect a reduced increase in systemic inflammation (from baseline to up to 24 hours after surgery) using peri-operative ketorolac, reading out 2027-10.
2 open trials; n 112; "Ketorolac and Pregabalin Effects on breaSt Cancer (KePreSt)"
Show the evidence
Trial
NCT06150898
"Ketorolac and Pregabalin Effects on breaSt Cancer (KePreSt)"; n 112; "To detect a reduced increase in systemic inflammation (from baseline to up to 24 hours after surgery) using peri-operative ketorolac"; 2027-10
NCT05646862
"A Study Evaluating the Efficacy and Safety of Inavolisib Plus Fulvestrant Compared With Alpelisib Plus Fulvestrant in Participants With HR-Positive, HER2-Negative, PIK3CA Mutated, Locally Advanced or Metastatic Breast Cancer Post CDK4/6i and Endocrine Combination Therapy"; n 420; "Blinded Independent Central Review (BICR)-Assessed Progression Free Survival (PFS)"; 2029-03-30
Q7
Which 144 trials of Omeprazole posted no result?
Posted no result
144 of 144 completed trials
Registrations
NCT01599858, NCT02518373, NCT00002682, NCT00641264, NCT00259077 and NCT00259051, and 138 more
Completion dates
oldest 1996-10; newest 2024-02-20
Show the evidence
Trial
NCT01599858
1996-10
NCT02518373
2001-02
NCT00002682
2001-10-08
NCT00641264
2003-06
NCT00259077
2004-07
NCT00259051
2004-08
14 further recorded trials
NCT00953381
2005-05
NCT00164866
2005-09
NCT00256737
2005-10
NCT03979989
2005-11-16
NCT01170169
2006-03
NCT01170182
2006-04
NCT00952978
2006-05
NCT00442052
2007-01
NCT00374101
2007-03
NCT01045434
2007-03
NCT01045642
2007-03
NCT00441519
2007-04
NCT00519519
2007-11
NCT00001191
2007-12-10
Q8
At the median, Omeprazole's trials enrolled 40 people — anything larger?
Median enrolment
40
Largest enrolment
4238504
Registered trials counted
312
Q9
What do 16156 spontaneous reports say about Omeprazole — 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.
Omeprazole appears in spontaneous reports to regulators. Across the 10 most-reported reaction terms, 16156 reaction mentions were counted: chronic kidney disease 2973; acute kidney injury 2774; hyponatraemia 1936; hypomagnesaemia 1868. FAERS via Open Targets · CHEMBL1503 · 2026-06-24
Show the evidence
chronic kidney disease
2973
acute kidney injury
2774
hyponatraemia
1936
hypomagnesaemia
1868
drug interaction
1622
hypocalcaemia
1124
4 more recorded rows
tubulointerstitial nephritis
1124
renal failure
1041
hypokalaemia
925
gastrooesophageal reflux disease
769
recorded 2026-06-24 · last checked 2026-09-04
Q10
Which 10 reactions does Omeprazole's label not list?
Other Clinical Impact: There have been clinical reports of interactions with other drugs metabolized via the cytochrome P450 system (e.g., cyclosporine, disulfiram).
drug_interactions
Table 4 Clinically Relevant Interactions Affecting Omeprazole When Co-Administered with Other Drugs CYP2C19 or CYP3A4 Inducers Clinical Impact: Decreased exposure of omeprazole when used concomitantly with strong inducers [see Clinical Pharmacology ( 12.3 )].
drug_interactions
CYP2C19 or CYP3A4 Inhibitors Clinical Impact: Increased exposure of omeprazole [see Clinical Pharmacology ( 12.3 )].
pharmacokinetics
Elimination Metabolism Omeprazole is extensively metabolized by the cytochrome P450 (CYP) enzyme system.
pharmacokinetics
The remaining part is dependent on another specific isoform, CYP3A4, responsible for the formation of omeprazole sulphone.
pharmacokinetics
Effect of Other Drugs on Omeprazole Voriconazole Concomitant administration of omeprazole and voriconazole (a combined inhibitor of CYP2C19 and CYP3A4) resulted in more than doubling of the omeprazole exposure.
2 more recorded rows
Interaction statementclinical_pharmacology
Elimination Metabolism Omeprazole is extensively metabolized by the cytochrome P450 (CYP) enzyme system.
Interaction statementclinical_pharmacology
The remaining part is dependent on another specific isoform, CYP3A4, responsible for the formation of omeprazole sulphone.
ChEMBL 37 — CC BY-SA 3.0 Unported · ChEMBL ATC CC BY-SA · ClinicalTrials.gov — US Government work · Open Targets 26.06 — CC0 · mixed register set; per-register licences in docs/specs/corpus-20k-sources.md · openFDA / DailyMed — US Government work
✗ required summary fields resolved: 4 required field(s) not terminal: Why people use it, Best-supported result, Biggest unanswered question, Human evidence
✓ public claims reviewed: 0 reviewed claim(s); drafts are never rendered
✓ source coverage passed: 6 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
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