This page shows what was measured, who it was measured in, and what that does not settle.
What Metronidazole does in the body
Infections caused by parasites and by bacteria that grow without oxygen, including bacterial vaginosis and trichomoniasis
The tablet you swallow is not yet a drug. It only becomes one inside microbes that live without oxygen, because only they have the machinery to hand it a spare electron. That electron turns the molecule into something violently reactive that tears the microbe DNA apart within its own cell. Your own cells, and bacteria that use oxygen, cannot perform that first step, so the drug drifts through them unchanged.
What happened in people
No rise in blood acetaldehyde and no objective or subjective reaction when 12 volunteers took metronidazole for 5 days and then ethanol
✎ 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 metronidazole inhibits aldehyde dehydrogenase and produces a disulfiram-like reaction with alcohol — six case reports, none demonstrating the mechanism, and one controlled study that looked for it and did not find it
Where it acts
Cytoplasm of anaerobic bacteria and protozoa; vaginal, intestinal and abscess environments
Kind of result
A number that stands in for health
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 · 140QMO216E · read 2026-08-29
Its recorded molecular formula is C6H9N3O3, weighing 171.16.
US prescribing information · 585d2553-e19f-4227-82db-e4c2034863bf · 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 110 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.
Trichomonas vaginalis infection at test of cure four weeks after treatment completion
✓ The study showed what it set out to show
Who was studied
Kissinger trichomoniasis trial
How many people
623
Study design
Multicentre randomised open-label
Compared against
Not recorded for this study
Kind of result
A number that stands in for health
What was found
P < 0.0001 (relative risk 0.55, 95% CI 0.34 to 0.70)
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. The trial stopped early at 623 of a planned 1,664 participants because of funding limitations, not because of a data-driven stopping rule.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Oral tablet and capsule, intravenous infusion, vaginal gel and topical gel, cream and lotion
Interval reported. 95% CI 0
Written into the record, not signed off as a reviewed claim.
Clinical success, defined as resolution of diarrhoea and absence of severe abdominal discomfort for more than 2 consecutive days including day 10
✗ The study did not show it
Who was studied
Tolevamer comparator trials (NCT00106509 and NCT00196794), pooled
How many people
1118
Study design
Two multinational randomised controlled trials
Compared against
Not recorded for this study
Kind of result
A number that stands in for health
What was found
P = 0.02 for metronidazole inferior to vancomycin (72.7% versus 81.1%)
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. In severe disease the difference was 66.3% versus 78.5% and did not reach significance (P=0.059), so the severe-disease conclusion rests partly on the later observational cohort.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Oral tablet and capsule, intravenous infusion, vaginal gel and topical gel, cream and lotion
Interval reported. Not recorded in this summary
Written into the record, not signed off as a reviewed claim.
Blood acetaldehyde concentration and objective signs of a disulfiram-like reaction after ethanol 0.4 g/kg
✗ The study did not show it
Who was studied
Visapaa metronidazole and ethanol volunteer study
How many people
12
Study design
Double-blind human volunteer study
Compared against
Not recorded for this study
Kind of result
A number that stands in for health
What was found
No rise in blood acetaldehyde and no objective or subjective reaction were observed
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. Twelve healthy young men is a small and narrow sample; the authors explicitly did not exclude a reaction in some subgroup or by another mechanism.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Oral tablet and capsule, intravenous infusion, vaginal gel and topical gel, cream and lotion
Interval reported. Not recorded in this summary
Written into the record, not signed off as a reviewed claim.
RNAWiki holds 3 written-up human studies for this substance, each with the question it asked.
How we know it
Each card names the study, the number of people and what the study set out to measure.
What this does not prove
These summaries were written by a person and have not been signed off as reviewed claims.
Why it matters
A study that failed is as informative as one that worked, and both are here.
What we still do not know
No reviewed claim exists, so no exact population, effect size or interval is published yet.
What 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
Metronidazole
What a person takes: Oral tablet and capsule, intravenous infusion, vaginal gel and topical gel, cream and lotion.
The measurement behind this step
Given by mouth two or three times daily, or intravenously in serious infection. Because oral bioavailability approaches 100%, the intravenous route offers no pharmacokinetic advantage in a patient who can swallow. Topical and vaginal formulations deliver the same molecule to a local site with much lower systemic exposure.
Getting in
Swallowed and absorbed almost completely, then distributed everywhere
Metronidazole gets into essentially every body compartment, including abscesses, bone and the fluid around the brain.
╌╌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
Oral bioavailability approaches 100%. The molecule is small and only weakly protein-bound, so it distributes into cerebrospinal fluid, bile, saliva, breast milk and abscess cavities. Elimination is mainly hepatic, with hydroxy and acetic acid metabolites excreted in urine.
Diffuses into every cell it meets, and does nothing in most of them
It passes into human cells and aerobic bacteria alike, and simply leaves again unchanged.
──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
Entry is by passive diffusion, so uptake is not selective. Selectivity appears only at the next step, because human cells and aerobes lack electron carriers with a redox potential low enough to reduce the 5-nitro group.
Anaerobic electron carriers hand it a single electron
Inside an organism that lives without oxygen, the drug is handed an electron and becomes a highly reactive radical.
╌╌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
Pyruvate:ferredoxin oxidoreductase reduces ferredoxin, which transfers a single electron to the nitro group to give a nitroradical anion. Maintaining the concentration gradient that keeps drug flowing inward is itself a consequence of this reduction, since the activated species no longer diffuses back out.
The reactive species attacks whatever is close by, and what is close by is the microbe own genetic material.
╌╌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
Short-lived nitroso and hydroxylamine intermediates and radical fragments cause strand breakage and helix destabilisation in microbial DNA. Killing is concentration-dependent and rapid, and it happens only where the reduction occurred.
The anaerobe or protozoan dies, aerobic flora is largely spared
The oxygen-avoiding organisms are killed while the ones that use oxygen carry on.
╌╌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
The narrow activation requirement means aerobic gut and skin flora are relatively unaffected, which is why metronidazole is usually combined with a separate agent when aerobic cover is needed. The same chemistry that gives that selectivity is what underlies the rodent carcinogenicity labelling.
No suggested links are held for this record, so nothing is hidden from this path.
What we know
The record describes 5 steps from taking it to an effect in a person.
How we know it
Each step names the study behind it in the technical detail beside it.
What this does not prove
A change inside the body is a reason to look. It is not a result in a person.
Why it matters
A reader can see exactly where the chain stops being measured in people.
What we still do not know
No reviewed claim binds any of these steps to a named population.
What 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.
People with trichomoniasis, bacterial vaginosis, amoebic or giardial infection, and patients with serious anaerobic bacterial infection, usually in combination with an agent covering aerobes.
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 metronidazole vaginal gel in pediatric subjects below the age of 12 years have not been established.”
US prescribing information · 585d2553-e19f-4227-82db-e4c2034863bf · read 2026-08-30
On older people, the label states: “Clinical studies with metronidazole vaginal gel did not include sufficient numbers of subjects 65 years of age or older to determine whether they respond differently than younger subjects.”
US prescribing information · 585d2553-e19f-4227-82db-e4c2034863bf · read 2026-08-30
On people who are pregnant, the label states: “Risk Summary There are no data available on the use of metronidazole vaginal gel in pregnant women.”
US prescribing information · 585d2553-e19f-4227-82db-e4c2034863bf · read 2026-08-30
On people who are breastfeeding, the label states: “Risk Summary There are no data on the presence of metronidazole in human milk following intravaginal administration.”
US prescribing information · 585d2553-e19f-4227-82db-e4c2034863bf · read 2026-08-30
Where the result stopped carrying
Metronidazole was inferior to vancomycin in the pooled randomised comparison for Clostridioides difficile infection, and lost its first-line position accordingly
The single 2 g dose for trichomoniasis, standard for decades, left almost twice as many women infected at test of cure as the seven-day course
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
Given by a clinician
❝ Quoted from a source
Where this came from
Copied from a source RNAWiki stored, with the source named.
Read from the recorded approval status.
No source is stored against this line.
Form and route
Oral tablet and capsule, intravenous infusion, vaginal gel and topical gel, cream and lotion
✎ 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
Given by mouth two or three times daily, or intravenously in serious infection. Because oral bioavailability approaches 100%, the intravenous route offers no pharmacokinetic advantage in a patient who can swallow. Topical and vaginal formulations deliver the same molecule to a local site with much lower systemic exposure.
✎ 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 warns of carcinogenicity in mice and rats and directs that unnecessary use be avoided. Peripheral neuropathy and central nervous system effects, including rare encephalopathy and cerebellar syndromes, are documented with prolonged or high-dose use. A metallic taste and nausea are common. The alcohol interaction is on the label and is discussed on this page as a contested claim rather than a demonstrated one, which is a statement about the evidence and not advice to disregard the label.
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 tablet and capsule, intravenous infusion, vaginal gel and topical gel, cream and lotion
✎ 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
Because oral bioavailability approaches 100%, the intravenous route offers no pharmacokinetic advantage in a patient who can swallow. Topical and vaginal formulations deliver the same molecule to a local site with much lower systemic exposure.
✎ 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
191 products list this as an active ingredient in the United States drug directory. 185 of them contain it and nothing else.
FDA National Drug Code directory · 72789-195 · read 2026-08-29
They are sold as capsule, cream, gel, injection, solution, liquid and lotion, taken cutaneous, intravenous, oral and topical.
FDA National Drug Code directory · 72789-195 · read 2026-08-29
The regulator's established pharmacologic class for it is nitroimidazole antimicrobial [epc] and nitroimidazoles [cs].
FDA National Drug Code directory · 72789-195 · read 2026-08-29
160 published labels name it as an active ingredient. 154 of them describe this substance alone, which is where its own label text on this page comes from.
US prescribing information · e3a32908-9db1-6ca7-e053-2a95a90a82fb · read 2026-08-29
Those labels are classed as human otc drug and human prescription drug.
US prescribing information · e3a32908-9db1-6ca7-e053-2a95a90a82fb · read 2026-08-29
Recorded price in US: 0.10116–7.30796 USD per one unit as the pricing file counts it — a tablet, capsule, patch or single item, across 54 priced products whose strengths and pack forms differ, as of 2026-08-26, paid by retail pharmacies buying the product, as surveyed by the Centers for Medicare & Medicaid Services. It is not a list price, an insurance price, or what anyone pays at a counter..
Recorded source · 2026-08-26 · read 2026-08-28
Recorded price in US: 0.26843 USD per one gram, across 6 priced products whose strengths and pack forms differ, as of 2026-08-26, paid by retail pharmacies buying the product, as surveyed by the Centers for Medicare & Medicaid Services. It is not a list price, an insurance price, or what anyone pays at a counter..
Recorded source · 2026-08-26 · read 2026-08-28
Recorded price in US: 1.79226 USD per one millilitre, across 2 priced products whose strengths and pack forms differ, as of 2026-08-26, paid by retail pharmacies buying the product, as surveyed by the Centers for Medicare & Medicaid Services. It is not a list price, an insurance price, or what anyone pays at a counter..
Recorded source · 2026-08-26 · read 2026-08-28
Evidence carries across two names for one substance. It does not carry across a salt, a mirror form or a mixture.
What it would be like to take◇Read from sources, not yet reviewed
What you could measure
This one is decided with a clinician, so this section holds questions to ask rather than a plan to run.
RNAWiki could not confidently classify this substance, so no self-experiment plan is offered.
Questions worth asking
Which of the trials of Metronidazole 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 metronidazole inhibits aldehyde dehydrogenase and produces a disulfiram-like reaction with alcohol — six case reports, none demonstrating the mechanism, and one controlled study that looked for it and did not find it
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 metronidazole acts on a molecular target, when its selectivity comes from being reduced inside anaerobes rather than from binding anything
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 Metronidazole 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.
Trichomoniasis: seven days beat the single dose, 89% versus 81% cured
In plain words
A randomised trial found that a week of twice-daily tablets left fewer women still infected than the traditional single large dose.
What was measured
Trichomonas vaginalis positivity by nucleic acid amplification or culture at four-week test of cure
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
Multicentre open-label randomised trial at three US sexual health clinics, 623 HIV-uninfected non-pregnant women with Trichomonas vaginalis. At test of cure four weeks after treatment, 34 of 312 (11%) in the seven-day arm and 58 of 311 (19%) in the single-dose arm remained positive, relative risk 0.55 (95% CI 0.34 to 0.70; P<0.0001). Bacterial vaginosis status did not significantly modify the effect (P=0.17). Self-reported adherence was 96% and 99%. The trial stopped early for funding reasons at 623 of a planned 1,664.
Written into the record, not signed off as a reviewed claim
Metronidazole lost first-line status in Clostridioides difficile infection to a randomised comparison
In plain words
For decades metronidazole was the standard first treatment for C. difficile. A head-to-head trial found vancomycin cured more patients, and guidelines changed.
What was measured
Clinical success at day 10, and 30-day all-cause mortality in the matched cohort
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
Two multinational randomised controlled trials, pooled, allocated patients 2:1:1 to tolevamer, vancomycin 125 mg every 6 hours for 10 days, or metronidazole 375 mg every 6 hours for 10 days. Clinical success was 44.2% for tolevamer (n=534), 72.7% for metronidazole (n=278) and 81.1% for vancomycin (n=259); metronidazole was inferior to vancomycin (P=0.02). In severe disease the gap was 66.3% versus 78.5% (P=0.059). A separate propensity-matched cohort of 10,137 US veterans found no difference in recurrence but lower 30-day all-cause mortality with vancomycin overall (adjusted relative risk 0.86, 95% CI 0.74 to 0.98) and in severe disease (0.79, 95% CI 0.65 to 0.97).
Written into the record, not signed off as a reviewed claim
The alcohol warning is one of the best-known claims in medicine and has never been demonstrated
In plain words
Everyone is told not to drink on metronidazole. When a controlled human study looked for the reaction, it did not happen.
What was measured
That metronidazole inhibits aldehyde dehydrogenase and produces a disulfiram-like reaction with alcohol
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
A systematic review of reports published between 1969 and 1982 found six case reports involving eight patients and concluded that none provided evidence that could justify the presumed disulfiram-like interaction; four of the eight cases were serious and one involved a death, but in every report the interaction was assumed rather than demonstrated. A subsequent double-blind study gave 12 healthy male volunteers metronidazole or placebo for 5 days followed by ethanol 0.4 g/kg, and sampled blood acetaldehyde and ethanol every 20 minutes for 4 hours alongside blood pressure, heart rate and skin temperature. Metronidazole did not raise blood acetaldehyde and produced no objective or subjective disulfiram-like effect. The authors were explicit that a reaction in some subgroup by another mechanism is not excluded.
Written into the record, not signed off as a reviewed claim
Carcinogenic in rodents, and labelled as such since the 1970s
In plain words
Metronidazole causes tumours in mice and rats at doses used lifelong, and the label says so. Human data have not shown the same, but the warning has never been withdrawn.
What was measured
Not recorded
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
The US prescribing information carries a warning that metronidazole has been shown to be carcinogenic in mice and rats and that unnecessary use should be avoided, and directs that it be reserved for the conditions described in the indications. The mechanism is consistent with the drug reduction chemistry: the same nitroradical that damages microbial DNA is mutagenic in bacterial assays. Epidemiological studies in humans have not established a corresponding risk, which is why the drug remains in wide use with the warning intact rather than being withdrawn.
Source
FLAGYL (metronidazole) capsules, US prescribing information, warnings section
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
Selectivity is by activation, not by binding, which limits what resistance can mean
In plain words
The drug has no receptor and no binding site. It works by being switched on inside anaerobes, so resistance means failing to switch it on.
What was measured
That metronidazole acts on a defined protein target, and that resistance therefore reflects target-site mutation
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
Metronidazole is reduced by low-redox-potential electron carriers, principally ferredoxin reduced by pyruvate:ferredoxin oxidoreductase, that exist only in anaerobic and microaerophilic organisms. Resistance in Trichomonas vaginalis, Helicobacter pylori and Bacteroides arises from downregulated or mutated nitroreductases and from efflux, not from an altered drug target, because there is no drug target in the usual sense. Any claim that metronidazole has a specific molecular receptor should be treated as a category error.
Source
FLAGYL (metronidazole) capsules, US prescribing information, clinical pharmacology section
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
How many documents were read
150 documents were read for this substance.
RNAWiki source record
99 of them state the same halfLife, and they agree.
RNAWiki source record
Where else this substance is registered
FDA substance identifier (UNII)
140QMO216E
CAS registry number
443-48-1
PubChem compound
4173
RxNorm concept
103866
Checks this page had to pass
✓ Passed
Identity resolved
no open identity hold
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no quarantine open
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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.
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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.
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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.
Withdrawn in United States, 2016, for "Presence of Particulate Matter: identified as a cloth fiber." (openFDA drug enforcement Class I recall)
What the approval register records
97 approved applications cover products containing this substance. The earliest was NDA012623, approved 19630718 to PFIZER.
This order is fixed in code and does not count clicks or time on the page.
What is not here
7 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 was measured, goal by goal — found nothing in the sources checked.
How close this is to real life — found nothing in the sources checked.
Felt, measured, or meaningful — found nothing in the sources checked.
How long anything takes — found nothing in the sources checked.
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
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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 nitroimidazole prodrug activated only inside anaerobes and protozoa, where a seven-day course cured trichomoniasis in 89% of 312 women against 81% for the single dose, and which lost its first-line place in Clostridioides difficile infection to a head-to-head randomised comparison.
Recorded evidence blocks (8)
Q1
On the Metronidazole label: indicated for what?
"Metronidazole Gel USP, 1% is indicated for the topical treatment of inflammatory lesions of rosacea. Metronidazole gel is a nitroimidazole indicated for the topical treatment of inflammatory lesions of rosacea.": indications and usage on Metronidazole's label. DailyMed label · 5842a554-58d1-4ee4-99aa-1e6029a69be2 · 2026-07-15
Q2
294 registered trials of Metronidazole — at which phases?
Registered studies posting no result
234 of 294
294 registered studies of Metronidazole: 95 phase4, 61 na, 61 phase2, 53 phase3, 26 phase1, 9 na or unstated, 8 early phase1. CLINICALTRIALS_SNAPSHOT · 2026-09-01
2591 with a PubMed record
Show the evidence
phase4
95
na
61
phase2
61
phase3
53
phase1
26
na or unstated
9
9 more recorded rows
early phase1
8
completed
166
unknown
65
recruiting
20
terminated
19
not yet recruiting
10
withdrawn
6
active not recruiting
4
enrolling by invitation
4
recorded 2026-09-01 · last checked 2026-09-04
Q3
23 of Metronidazole's trials stopped: safety, futility/efficacy, accrual/recruitment, funding/business, other?
safety (3), futility/efficacy (1), accrual/recruitment (8), funding/business (4) and other (7): Metronidazole's stop wording, clustered. CLINICALTRIALS_SNAPSHOT · 2026-09-01
"Inadequate recruitment to meet completion date"; 23 of 294 registered studies
Show the evidence
Trial
NCT00257699
terminated; "Inadequate recruitment to meet completion date"
NCT00353743
terminated; "Rate of cure was higher than expected, IRB suspended for no additional benefit"
NCT01322971
terminated; "Disease prevalence lower than expected in population."
NCT01472978
withdrawn; "Too difficult to enroll patients."
NCT01658852
withdrawn; "Because of difficulties on recruiting participants"
NCT01762670
terminated; "Company decided to stop study for reasons other than safety"
14 further recorded trials
NCT02099240
terminated; "Not enough patient enrollment and lack of staffing"
NCT02168816
terminated; "The study was stopped for feasibility (i.e., low recruitment)"
NCT02197182
terminated; "Not for safety reasons"
NCT02200328
terminated; "Patients noncompliant with instructions and follow ups could not be completed."
NCT02301000
terminated; "Slow recruitment in pilot phase. A follow-up trial is launched (NCT03796650)."
NCT02376972
terminated; "According to the Recommendation of the Indipendent Data Monitoring Committee"
NCT02561117
withdrawn; "Lack of funding"
NCT02713139
withdrawn; "Due to budget limitations, the company decided to withdraw this study."
NCT02942485
terminated; "Extremely slow enrollment"
NCT03769688
withdrawn; "Replaced with different study at another site."
NCT03954990
terminated; "Lack of significance/futile study"
NCT04186247
terminated; "The DSMB concluded that feasibility endpoints were reached in time for Week 4 but no participants receiving standard of care dietary treatment could be randomized based on the at-risk of the microbiome signature."
NCT04554693
terminated; "Principal investigator did not have the necessary staffing resources to continue the study."
NCT04578015
terminated; "After screening many patients for BV, it was determined that the rate of BV is less in our population that the 30% rate mentioned in the literature. It was determined that completing the study will not be feasible due to cost and time…"
recorded 2026-09-01 · last checked 2026-09-04
Q4
Human studies of Metronidazole used MetroGel® 1% — over how long?
Human studies of Metronidazole used "MetroGel® 1%". ClinicalTrials.gov · 2026-09-01
20 recorded entries; human; oral, vaginal; also "Oracea® Capsules 40 mg", "Metrogel 1%", "Metronidazole 0.75% cream"
Azelaic Acid Gel including: Finacea (Azelaic Acid Gel 15%, BAY39-6251)
humanNCT03091777
Metronidazole Vaginal Gel 0.75%
humanNCT03130452
Metronidazole 500 mg
recorded 2026-09-01 · last checked 2026-09-04
Q5
Which 102 trials of Metronidazole posted no result?
Posted no result
102 of 102 completed trials
Registrations
NCT00002682, NCT01380522, NCT01380509, NCT01020396, NCT00021671 and NCT00417872, and 96 more
Completion dates
oldest 2001-10-08; newest 2024-07-16
Show the evidence
Trial
NCT00002682
2001-10-08
NCT01380522
2002-09
NCT01380509
2002-10
NCT01020396
2003-03
NCT00021671
2004-11
NCT00417872
2005-09
14 further recorded trials
NCT00456729
2006-07
NCT00304369
2007-06
NCT00503542
2008-02
NCT00668655
2008-03
NCT00774722
2008-03
NCT00774969
2008-04
NCT00331994
2008-07
NCT00355602
2008-12
NCT00066001
2009-12
NCT01055106
2010-04
NCT00491426
2010-11
NCT00841854
2010-11
NCT00720291
2010-11-23
NCT01792700
2010-12
Q6
At the median, Metronidazole's trials enrolled 100 people — anything larger?
Median enrolment
100
Largest enrolment
30024
Registered trials counted
294
Q7
What do 3 spontaneous reports say about Metronidazole — 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.
Metronidazole appears in spontaneous reports to regulators. Across the 2 most-reported reaction terms, 3 reaction mentions were counted: pseudomembranous colitis 2; disbacteriosis 1. FAERS via Open Targets · CHEMBL1200869 · 2026-06-24
Show the evidence
pseudomembranous colitis
2
disbacteriosis
1
recorded 2026-06-24 · last checked 2026-09-04
Q8
Which 2 reactions does Metronidazole's label not list?
ChEMBL 37 — CC BY-SA 3.0 Unported · 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 · openFDA enforcement — 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: 7 source rows
✓ no critical contamination: no quarantine open
✓ canonical metadata passed: slug and display name present
✓ no raw internal fields: enforced by the copy-contract test over the rendered page
This is a record of evidence. It is not medical advice, and it does not say this substance suits you. Nothing here says any substance on RNAWiki is appropriate for a child.