This page shows what was measured, who it was measured in, and what that does not settle.
What Guaifenesin does in the body
A chesty cough with mucus that is hard to clear.
The idea is that the drug irritates the stomach lining slightly, and a nerve reflex from stomach to airway makes the glands in your chest produce more, thinner fluid — so the mucus becomes easier to cough up. That is the theory the whole product category rests on. When researchers actually collected and measured people’s sputum on the drug, it was not thinner, there was no more of it, and it did not flow any differently.
What happened in people
A larger study found no change in mucus amount, thickness or other measured properties after one week.
✓ Reviewed first-read answer
Where this came from
A person wrote this and a reviewer approved it against this exact record. It carries no effect size.
A reviewer approved this against this record. The reviewed-claim record carrying the exact population and effect size does not exist yet.
No source is stored against this line.
The limit that matters most
Adult cough studies were few, inconsistent and too poorly reported for a firm answer.
Where it acts
Proposed rather than demonstrated: gastric mucosa, via a vagal reflex to airway submucosal glands. Direct measurement of airway secretions has not confirmed an effect
Kind of result
The kind of result is not recorded
Supervision
RNAWiki has not recorded a supervision or regulatory status for this substance.
What the registries record it as
The substance registry classes this as chemical.
FDA substance registry · 495W7451VQ · read 2026-08-29
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.
The limit a reviewer approved as the one that matters most here.
The four opening statements run to 104 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.
Placebo
A placebo is a dummy treatment given so the real one can be compared with it.
A picture of it, and where the picture fails
A placebo is like a blank control in an experiment.
Where that stops being true. A blank does nothing. People given a placebo often do get better.
What people get wrong. A placebo effect is read as imaginary. The improvement is measured and real.
An inactive intervention matched in appearance to the test intervention, used to control for non-specific effects.
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.
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.
Sputum volume and physical properties, and cold symptoms, on extended-release guaifenesin against placebo
✗ The study did not show it
Who was studied
NCT01046136 (Hoffer-Schaefer 2014, Respir Care 59:631-636)
How many people
378
Study design
Multi-centre, randomised, double-blind, placebo-controlled, 8 days
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. 151 of 188 on guaifenesin and 144 of 190 on placebo completed the protocol, so roughly a fifth of each arm did not. Sputum collection depends on subjects being able to produce a sample.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Oral extended-release bilayer tablet (600 mg), immediate-release tablet, and liquid
Interval reported. Not recorded in this summary
Written into the record, not signed off as a reviewed claim.
Guaifenesin extended release in acute respiratory tract infection — sputum volume and properties (NCT01046136) · a recorded source, not a stored snapshot
No antitussive effect demonstrated on recorded cough counts; on questionnaire, 96% against 54% reported decreased sputum thickness (p=0.01) and 88% against 62.5% reported reduced quantity (p=0.07)
Repeated elsewhere
Failed to Replicate
What this does not prove. A study that did not show an effect does not show that no effect exists anywhere.
The limits of this study, and where it came from
Main limit. The objective and subjective results point in opposite directions in the same patients, and the paper notes that patients’ own estimates of cough frequency failed to detect the diurnal variation the recorder measured.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Oral extended-release bilayer tablet (600 mg), immediate-release tablet, and liquid
Interval reported. Not recorded in this summary
Written into the record, not signed off as a reviewed claim.
Guaifenesin extended release in acute respiratory tract infection — sputum volume and properties (NCT01046136) · a recorded source, not a stored snapshot
In subjects with upper respiratory infection, log C5 0.92 ± 0.17 against 0.66 ± 0.14 on placebo (p=0.028); no effect in healthy volunteers
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. Fourteen subjects per group, single dose, a challenge model rather than a clinical cough outcome. The effect measured is cough suppression, which is not the expectorant claim on the label.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Oral extended-release bilayer tablet (600 mg), immediate-release tablet, and liquid
Interval reported. Not recorded in this summary
Written into the record, not signed off as a reviewed claim.
Guaifenesin extended release in acute respiratory tract infection — sputum volume and properties (NCT01046136) · a recorded source, not a stored snapshot
Cough outcomes against placebo in community settings
✗ The study did not show it
Who was studied
Cochrane CD001831.pub5 — over-the-counter medications for acute cough
How many people
4835
Study design
Systematic review of 29 placebo-controlled randomised trials
Compared against
A dummy treatment
Kind of result
A number that stands in for health
What was found
Pooling judged inappropriate. Of three adult guaifenesin trials, one indicated significant benefit and two did not; no paediatric expectorant trial met inclusion criteria
Repeated elsewhere
Failed to Replicate
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. Risk-of-bias assessment was limited by poor reporting, particularly in the earlier studies. Twenty-one trials reported adverse effects, with higher numbers in preparations containing antihistamines and dextromethorphan.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Oral extended-release bilayer tablet (600 mg), immediate-release tablet, and liquid
Interval reported. Not recorded in this summary
Written into the record, not signed off as a reviewed claim.
Guaifenesin extended release in acute respiratory tract infection — sputum volume and properties (NCT01046136) · a recorded source, not a stored snapshot
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
Guaifenesin
What a person takes: Oral extended-release bilayer tablet (600 mg), immediate-release tablet, and liquid.
The measurement behind this step
The extended-release tablet must be swallowed whole with a full glass of water and not crushed, chewed or broken, because breaking the bilayer destroys the release profile that the application was approved on. It can be taken without regard to meals.
Getting in
Swallowed and absorbed quickly
A small, water-soluble molecule that enters the blood fast and leaves fast. The extended-release tablet exists because the plain form clears too quickly to be dosed conveniently.
╌╌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
Glyceryl guaiacolate is rapidly absorbed with a short elimination half-life, metabolised largely to beta-(2-methoxyphenoxy)-lactic acid and excreted renally. The bilayer extended-release tablet approved as NDA 021282 in 2002 was the pharmaceutical innovation; the molecule itself dates to the 1940s.
Guaifenesin extended release in acute respiratory tract infection — sputum volume and properties (NCT01046136) · a recorded source, not a stored snapshot
The classical explanation is that the drug slightly irritates the stomach lining. This is where the mechanism becomes a proposal rather than an observation.
──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 gastric-irritant model is inherited from ipecac and ammonium chloride, agents that provoke secretion at doses close to emetic ones. No study has demonstrated that guaifenesin produces gastric afferent activation at the plasma concentrations reached from an ordinary tablet.
Guaifenesin extended release in acute respiratory tract infection — sputum volume and properties (NCT01046136) · a recorded source, not a stored snapshot
The proposed step: a vagal reflex to the airway glands
The irritation is supposed to travel by nerve to the glands lining the airways and make them release more, thinner fluid. Nobody has recorded that reflex happening with this drug.
╌╌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 postulated pathway runs from gastric vagal afferents through brainstem nuclei to efferent parasympathetic innervation of bronchial submucosal glands. There is no established receptor for guaifenesin anywhere along it, and no direct measurement of increased submucosal gland output in humans on the drug.
Guaifenesin extended release in acute respiratory tract infection — sputum volume and properties (NCT01046136) · a recorded source, not a stored snapshot
This is where the theory meets an instrument. Sputum collected from people taking the drug for a week was no thinner, no more copious and no different in how it flowed than sputum from people taking a dummy.
──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
In 378 randomised subjects, guaifenesin against placebo gave p=0.41 for sputum volume, p=0.69 for percent solids, p=0.88 for interfacial tension, p=0.71 for elasticity, p=0.45 for viscosity and p=0.75 for mechanical impedance. Interfacial tension and mechanical impedance are the properties most closely tied to whether mucus can be cleared by cough, and neither moved.
Guaifenesin extended release in acute respiratory tract infection — sputum volume and properties (NCT01046136) · a recorded source, not a stored snapshot
One measured effect that is not the advertised one
A small study did find something: in people with a cold, the cough reflex became less easily triggered. It had no effect in healthy volunteers, and it is not what the packet claims.
──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
Log C5 on capsaicin challenge rose from 0.66 ± 0.14 on placebo to 0.92 ± 0.17 on guaifenesin in 14 subjects with upper respiratory infection (p=0.028), with no change in 14 healthy volunteers. The authors offered a central antitussive action or a peripheral shielding effect as candidate explanations, without distinguishing between them.
Guaifenesin extended release in acute respiratory tract infection — sputum volume and properties (NCT01046136) · a recorded source, not a stored snapshot
What the person experiences is the infection ending
Coughs from a virus get better over one to two weeks whatever you take. In the trial, drug and dummy groups improved by the same amount over the same eight days.
──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
Symptom trajectories in the guaifenesin and placebo arms of the 378-subject trial were similar throughout. The Cochrane review of 29 placebo-controlled trials in 4,835 people concluded there is no good evidence for or against the effectiveness of over-the-counter cough medicines in acute cough.
Guaifenesin extended release in acute respiratory tract infection — sputum volume and properties (NCT01046136) · a recorded source, not a stored snapshot
No suggested links are held for this record, so nothing is hidden from this path.
What we know
The record describes 6 steps from taking it to an effect in a person.
How we know it
Each step names the study behind it in the technical detail beside it.
What this does not prove
A change inside the body is a reason to look. It is not a result in a person.
Why it matters
A reader can see exactly where the chain stops being measured in people.
What we still do not know
No reviewed claim binds any of these steps to a named population.
What 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.
Adults and children aged 12 and over for the extended-release products, sold without a prescription. It appears in a large fraction of combination cough and cold products.
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.
Where the result stopped carrying
Every physical property of sputum measured in the 378-subject trial was unchanged, with p-values from 0.41 to 0.88
The 1982 objective cough-counting trial found no antitussive effect while the questionnaire in the same patients did
Two of the three adult guaifenesin trials in the Cochrane review found no benefit
No paediatric expectorant trial met the Cochrane inclusion criteria at all, in a category sold widely for children
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 extended-release bilayer tablet (600 mg), immediate-release tablet, and liquid
✎ 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
The extended-release tablet must be swallowed whole with a full glass of water and not crushed, chewed or broken, because breaking the bilayer destroys the release profile that the application was approved on.
✎ Source-linked record
Where this came from
A person wrote this into the record with the study named beside it. No reviewer has signed it off.
Recorded notes on how this is sold. The rest of the recorded wording: It can be taken without regard to meals.
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
Adverse effects are few and mild, and this is one of the few genuinely reassuring facts about the drug. In the Cochrane review, the higher adverse event counts across the cough shelf were in preparations containing antihistamines and dextromethorphan rather than expectorants. The practical hazards attach to the combination products — pseudoephedrine in one, dextromethorphan in another — rather than to guaifenesin itself. Reported effects include nausea and vomiting, and very high intake has been associated with kidney stones containing guaifenesin metabolites.
Nobody counted how many people took this and were fine, so this cannot be turned into a rate.
Guaifenesin extended release in acute respiratory tract infection — sputum volume and properties (NCT01046136) · a recorded source, not a stored snapshot
Over a long time. No completed tested study window is recorded, so long-term effects are not established by the registry record.
Groups the studies covered thinly. Which groups were under-represented in the studies has not been recorded for this substance. Pregnancy, breastfeeding, children, older adults, and people with liver or kidney conditions are commonly excluded from trials; nothing here says whether they were.
What is missing or unclear◇Read from sources, not yet reviewed
Does the exact form matter?
Evidence belongs to the exact thing that was tested. A different salt, a different mixture or a different preparation is a different question.
The form that was studied
Oral extended-release bilayer tablet (600 mg), immediate-release tablet, and liquid
✎ 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
It can be taken without regard to meals.
✎ Source-linked record
Where this came from
A person wrote this into the record with the study named beside it. No reviewer has signed it off.
Recorded notes on which forms are sold and how they compare.
No source is stored against this line.
What is recorded as being sold
1552 products list this as an active ingredient in the United States drug directory. 360 of them contain it and nothing else.
FDA National Drug Code directory · 71610-499 · read 2026-08-29
They are sold as capsule, capsule, coated, capsule, gelatin coated, capsule, liquid filled, granule and liquid, taken oral and topical.
FDA National Drug Code directory · 71610-499 · read 2026-08-29
The regulator's established pharmacologic class for it is decreased respiratory secretion viscosity [pe], expectorant [epc] and increased respiratory secretions [pe].
FDA National Drug Code directory · 71610-499 · read 2026-08-29
1414 published labels name it as an active ingredient. 309 of them describe this substance alone, which is where its own label text on this page comes from.
US prescribing information · 88b68447-b016-4d5b-a5e3-c4ebccb14f8c · read 2026-08-29
Those labels are classed as human otc drug and human prescription drug.
US prescribing information · 88b68447-b016-4d5b-a5e3-c4ebccb14f8c · read 2026-08-29
Guaifenesin is oral at HOW SUPPLIED Guaifenesin Liquid USP 100 mg/5 mL NDC 72162-2278-2: Bottle of 16 fl. oz., recorded as fda label in effect 2026-03-18 in the United States.
US prescribing information · 1e9887f6-209f-4f1f-9afa-a5ca649721cb · read 2026-08-30
Recorded price in US: 0.01117 USD per one millilitre, across 3 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: 0.03266–0.06525 USD per one unit as the pricing file counts it — a tablet, capsule, patch or single item, 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 Guaifenesin studied people like me?
What was measured, and for how long?
Was the result a laboratory value or a health outcome?
What would we watch for, and when would we stop?
Tracking can show whether something changed for you. It cannot show what caused it.
RNAWiki records evidence. It does not say whether this substance is right for you.
What is missing or unclear◇Read from sources, not yet reviewed
Claims that go past the evidence
Things said about this substance that sound reasonable, and the exact step that is missing between the evidence and the claim.
✗Goes past the evidence
That the drug thins mucus — the property was measured directly on an instrument and did not change
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 being the monograph’s sole recognised expectorant reflects a demonstrated expectorant action
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 gastric-vagal reflex mechanism operates at concentrations reached from a tablet — it is inherited from ipecac and has not been shown for this molecule
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 patient-reported improvement in mucus thickness measures mucus thickness rather than the experience of an illness resolving
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 Guaifenesin 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.
Sputum was measured directly in 378 people, and nothing changed
In plain words
A trial gave the recommended extended-release amount for a week to people with a chesty cough, collected their sputum, and put it on instruments. It was not thinner, there was not more of it, and it did not flow differently. Symptoms improved on the drug and on the dummy at the same rate.
What was measured
Sputum volume, percent solids, interfacial tension, elasticity, viscosity and mechanical impedance against placebo
Effect estimate
No reviewed effect estimate exists for this record.
Limits
This entry records a failure.
From the source
An eight-day multi-centre randomised trial gave two 600 mg extended-release guaifenesin tablets twice daily or placebo for one week to 378 otherwise healthy adolescents and adults with productive cough from an acute respiratory infection of up to five days’ duration, requiring at least two of cough, thickened mucus and chest congestion. Single sputum samples were taken on days 1, 3, 4 and 8, with 24-hour collections on days 1 and 4. There were no significant differences between guaifenesin and placebo for sputum volume (p=0.41), percent solids (p=0.69), interfacial tension (p=0.88), elasticity (p=0.71), viscosity (p=0.45) or mechanical impedance (p=0.75). Symptoms improved to a similar degree in both groups over time. The authors concluded the recommended amount is unlikely to be an expectorant or a mucolytic in acute respiratory infection.
Written into the record, not signed off as a reviewed claim
A tape recorder heard no change in coughing while the questionnaire reported thinner mucus
In plain words
In a 1982 trial, coughs were recorded on tape and counted, and the drug made no difference to how much people coughed. The same patients filled in a questionnaire, and almost all of them said their mucus felt thinner. The subjective answer is the one the product claim was built on.
What was measured
That patients reporting thinner mucus establishes that the mucus is thinner — the objective cough count in the same trial was null, and the instrumented sputum measurement thirty-two years later found no change in any physical property
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
Forty-two patients with acute respiratory disease had their coughs recorded on tape over a 24-hour baseline and a 36-hour treatment period, comparing a guaifenesin preparation with its syrup vehicle in double-blind fashion, with efficacy assessed between equivalent six-hour periods on successive days to control for the pronounced diurnal variation in cough frequency. No antitussive effect was demonstrated. A questionnaire given to 65 patients including those 42 found that 25 of 26 patients with productive cough on guaifenesin (96%) reported a decrease in sputum thickness against 13 of 24 (54%) on vehicle (p=0.01, Fisher exact test), and 23 of 26 (88%) reported reduced sputum quantity against 15 of 24 (62.5%) on vehicle (p=0.07). The paper also records that the diurnal variation the tape recorder detected was not apparent in the patients’ own estimates of how often they coughed.
Written into the record, not signed off as a reviewed claim
It did reduce cough reflex sensitivity in people with a cold — in 14 subjects, by a route nobody expected
In plain words
A small study measured how much capsaicin it took to make someone cough five times. People with a cold needed more of it after taking the drug, so their cough reflex was less twitchy. Healthy volunteers showed no change at all.
What was measured
Log capsaicin concentration inducing five or more coughs, guaifenesin against placebo
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
A randomised, double-blind, placebo-controlled crossover gave a single 400 mg guaifenesin capsule or matched placebo to 14 subjects with acute viral upper respiratory infection and 14 healthy volunteers, with capsaicin cough challenge 1 to 2 hours later. Among subjects with infection, mean log C5 — the concentration inducing five or more coughs — was 0.92 ± 0.17 after guaifenesin against 0.66 ± 0.14 after placebo (p=0.028). No effect was seen in healthy volunteers. The authors proposed either a central antitussive effect or a peripheral effect in which increased sputum volume shields cough receptors, and noted explicitly that studies of the drug’s action had yielded contrasting results.
Written into the record, not signed off as a reviewed claim
Cochrane looked at the whole shelf and found no good evidence either way
In plain words
The systematic review of every over-the-counter cough medicine tested against a dummy found the trials too few, too different and too poorly reported to combine. Of the three adult trials of this drug, one showed benefit and two did not.
What was measured
That an ingredient sold in 189 separate products across a shelf worth billions rests on a settled evidence base — the systematic review found no good evidence for or against, and no paediatric expectorant trial that met inclusion criteria at all
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
The Cochrane review of over-the-counter medications for acute cough in community settings included 29 placebo-controlled randomised trials in 4,835 people, 19 in adults and 10 in children. The authors judged pooling inappropriate because of the small number of trials in each category, the limited quantitative data and marked differences in participants, interventions and outcome measurement, and noted that risk-of-bias assessment was limited by poor reporting particularly in earlier studies. Three adult trials compared guaifenesin with placebo: one indicated significant benefit and two did not. No studies using expectorants in children met the inclusion criteria at all. The overall conclusion was that there is no good evidence for or against the effectiveness of over-the-counter medicines in acute cough.
Written into the record, not signed off as a reviewed claim
It is the only recognised expectorant, and there is no molecular target to describe
In plain words
Federal regulation names exactly one ingredient as an expectorant, and this is it. Nobody has identified what the molecule binds to in the body. The mechanism given in textbooks is a nerve reflex from the stomach, inherited from an older class of medicines.
What was measured
That recognition as the monograph expectorant implies a demonstrated expectorant action — the regulation defines the category, and the direct measurement of the effect it names has been negative
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
21 CFR 341.18 states that the expectorant active ingredient of the monograph is guaifenesin when used within the specified dosage limits — no other ingredient holds that status. No receptor, enzyme or transporter has been established as a target. The mechanism usually offered, reflex stimulation of bronchial secretion via gastric vagal afferents, descends from the ipecac and ammonium chloride tradition and has not been demonstrated for this molecule at achievable plasma concentrations; the direct test of its consequence, sputum rheology, was negative in 378 subjects. This is a regulatory category with one occupant and no mechanism, which is a different situation from a drug whose mechanism is disputed.
Source
21 CFR 341.18, Expectorant active ingredient; Hoffer-Schaefer A et al., Respir Care 2014;59:631-636
Role in the trial
Not matched to a registered study
Identity check
no open identity hold
Audit mark
contested
Review state
Written into the record, not signed off as a reviewed claim
Both groups got better, and that is the result most often mistaken for the drug working
In plain words
In the trial that measured sputum, people on the drug improved over the week. So did people on the dummy tablet, by the same amount. Acute cough from a virus resolves on its own, which is why an untreated comparison group is the only way to see whether a medicine did anything.
What was measured
Cold symptom improvement over 8 days, guaifenesin against placebo
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
In the 378-subject trial, symptoms in both the guaifenesin and placebo groups improved to a similar degree over the eight days. Of 188 subjects randomised to guaifenesin and 190 to placebo, 151 and 144 respectively completed the full protocol. The natural history of acute viral cough — improvement over one to two weeks regardless of treatment — is the dominant effect in any uncontrolled observation of this drug, and it is what a person taking it experiences.
Written into the record, not signed off as a reviewed claim
Where else this substance is registered
FDA substance identifier (UNII)
495W7451VQ
RxNorm concept
636522
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Trial roles classified for highlighted evidence
No registered study is classified as testing this substance.
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Canonical metadata present
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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, 2023, for "Product mix-up: incorrect product was found inside the G-Supress DX product carton." (openFDA drug enforcement Class I recall)
Withdrawn in United States, 2019, for "Labeling: Incorrect Instructions; The product has been found to provide incorrect dosage information on its label due to a typographical error. The drug facts label incorrectly states children 6 to…" (openFDA drug enforcement Class I recall)
Withdrawn in United States, 2015, for "Labeling: Label Mix-Up; Bottles of Mucinex Fast-Max liquid are correctly labeled on the front of the label, however the back of the bottle where the Drug Facts labeling is, is missing certain Active…" (openFDA drug enforcement Class I recall)
What the approval register records
29 approved applications cover products containing this substance. The earliest was NDA021282, approved 20020712 to RECKITT BENCKISER.
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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
The full record, for auditing
Everything above is built from what is below. This layer keeps the technical vocabulary, record identifiers and every stored row, so a reader who wants to check the page can.
The older medicine-wide conclusion held in this record
Written for a clinical reader, and about the medicine as a whole rather than about one indication, population and set of trials. RNAWiki does not treat it as a programme conclusion and no reviewer has signed it off in that form. It is here word for word because it is what the record holds.
The only active ingredient the FDA’s over-the-counter monograph recognises as an expectorant, sold on the claim that it thins mucus — and when 378 people with acute respiratory infection were given the recommended extended-release amount for a week and their sputum was measured, there was no difference from placebo in volume (p=0.41), percent solids (p=0.69), viscosity (p=0.45), elasticity (p=0.71), interfacial tension (p=0.88) or mechanical impedance (p=0.75).
Recorded evidence blocks (6)
Q1
On the Guaifenesin label: indicated for what?
"USE(S) helps loosen phlegm (mucus) and thin bronchial secretions to rid the bronchial passageways of bothersome mucus and make coughs more productive": indications and usage on Guaifenesin's label. DailyMed label · c648e711-e944-4574-83b3-ccce8732384e · 2025-06-02
Q2
21 registered trials of Guaifenesin — at which phases?
Human studies of Guaifenesin used Mucinex 1200mg — over how long?
Human studies of Guaifenesin used "Mucinex 1200mg". ClinicalTrials.gov · 2026-09-01
2 recorded entries; human; also "Mucinex® ER 600 mg"
Show the evidence
human
NCT00902707
Mucinex 1200mg
NCT03644108
Mucinex® ER 600 mg
recorded 2026-09-01 · last checked 2026-09-04
Q4
Which 4 trials of Guaifenesin posted no result?
Posted no result
4 of 4 completed trials
Registrations
NCT00902707, NCT02902640, NCT02879981 and NCT07398924
Completion dates
oldest 2012-05; newest 2023-06-23
Show the evidence
Trial
NCT00902707
2012-05
NCT02902640
2017-07-31
NCT02879981
2017-08-28
NCT07398924
2023-06-23
Q5
At the median, Guaifenesin's trials enrolled 38 people — anything larger?
Median enrolment
38
Largest enrolment
2810
Registered trials counted
21
Q6
What do 3005 spontaneous reports say about Guaifenesin — 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.
Guaifenesin appears in spontaneous reports to regulators. Across the 10 most-reported reaction terms, 3005 reaction mentions were counted: drug hypersensitivity 660; pain 353; fatigue 305; nausea 295. FAERS via Open Targets · CHEMBL980 · 2026-06-24
Show the evidence
drug hypersensitivity
660
pain
353
fatigue
305
nausea
295
headache
279
vomiting
270
4 more recorded rows
dyspnoea
249
rheumatoid arthritis
211
somnolence
198
rash
185
recorded 2026-06-24 · last checked 2026-09-04
Where it is registered
Where it’s registered
Withdrawn in United States, 2023, for "Product mix-up: incorrect product was found inside the G-Supress DX product carton." (openFDA drug enforcement Class I recall)
Withdrawn in United States, 2019, for "Labeling: Incorrect Instructions; The product has been found to provide incorrect dosage information on its label due to a typographical error. The drug facts label incorrectly states children 6 to…" (openFDA drug enforcement Class I recall)
Withdrawn in United States, 2015, for "Labeling: Label Mix-Up; Bottles of Mucinex Fast-Max liquid are correctly labeled on the front of the label, however the back of the bottle where the Drug Facts labeling is, is missing certain Active…" (openFDA drug enforcement Class I recall)
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 · 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
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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.