This page shows what was measured, who it was measured in, and what that does not settle.
What Benzonatate does in the body
Suppressing a cough.
The idea is that the drug is a numbing agent, chemically close to the ones a dentist uses, and that swallowing it lets it reach the sensors in your airways and deaden them, so they stop sending the signal that triggers a cough. That is what the label says and it is what has been said since 1958. What has never been done is a measurement in a person showing those sensors being deadened, or a properly sized trial showing that people cough less on it than on a dummy capsule.
What happened in people
Modern evidence for cough relief is weak, while accidental ingestion has killed young children within an hour.
✓ 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
Its claimed numbing action in human airways has never been directly measured.
Where it acts
Stated on the label as the stretch receptors of the respiratory passages, lungs and pleura — a site asserted in 1958 and not confirmed by direct human measurement since
Kind of result
The kind of result is not recorded
Supervision
Professional supervision is normally required. A regulator classifies this substance in a way that restricts how it is supplied.
What the registries record it as
The substance registry classes this as chemical.
FDA substance registry · 5P4DHS6ENR · 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 113 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.
Biomarker
A biomarker is a number from a test that stands in for something about health.
A picture of it, and where the picture fails
A biomarker is like a fuel gauge.
Where that stops being true. A gauge is wired to the tank. Many biomarkers are only loosely tied to health.
What people get wrong. A better number is read as a better life. Several medicines improved a number and helped nobody.
A measurable indicator used as a substitute for a clinical outcome of interest.
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.
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.
Effectiveness, tolerability and safety of benzonatate across all identified original research
Systematic review of four databases, January 1956 to August 2022
Compared against
Not recorded for this study
Kind of result
A number that stands in for health
What was found
No pooled estimate. 21 cohort studies, 5 experimental studies and 11 case studies or series; quality assessment flagged high risk of bias throughout
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. The sample size given here is the number of studies, not participants. No adequately powered randomised placebo-controlled trial was identified in sixty-six years of literature.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Oral soft gelatin capsule (100 mg and 200 mg) containing the drug as a liquid
Interval reported. Not recorded in this summary
Written into the record, not signed off as a reviewed claim.
Drugs@FDA: TESSALON (benzonatate) capsules, NDA 011210, Pfizer — original approval 10 February 1958 (https://www.accessdata.fda.gov/scripts/cder/daf/index.cf… · a recorded source, not a stored snapshot
Rate of serious adverse effects — seizure, ECG change, coma or CNS depression, or death
✓ The study showed what it set out to show
Who was studied
Cicci 2025 poison centre review (Clin Toxicol 63:488-494)
How many people
265
Study design
Retrospective single-centre case review, 2000 to 2019
Compared against
Not recorded for this study
Kind of result
Living longer, or avoiding a major event
What was found
22% of 106 intentional exposures had at least one serious adverse effect and 38% were hospitalised, against 0.7% and 2% of 143 unintentional exposures; 0 of 77 unintentional paediatric exposures had a serious effect; 2 deaths, both intentional
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. Single regional poison centre, so ascertainment is partial and the denominator of total exposures is unknown. No standard treatment guideline for benzonatate toxicity exists.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Oral soft gelatin capsule (100 mg and 200 mg) containing the drug as a liquid
Interval reported. Not recorded in this summary
Written into the record, not signed off as a reviewed claim.
Drugs@FDA: TESSALON (benzonatate) capsules, NDA 011210, Pfizer — original approval 10 February 1958 (https://www.accessdata.fda.gov/scripts/cder/daf/index.cf… · a recorded source, not a stored snapshot
What we know
RNAWiki holds 2 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
Benzonatate
What a person takes: Oral soft gelatin capsule (100 mg and 200 mg) containing the drug as a liquid.
The measurement behind this step
Must be swallowed whole. The contents are an oily local anaesthetic; releasing them in the mouth produces rapid oropharyngeal numbness and can cause choking. The label instructs patients not to break, chew, dissolve, cut or crush the capsule, and not to take two doses at once if one is missed.
Getting in
An oil inside a soft capsule
Unlike most tablets, this drug is a liquid. It is held inside a gelatin shell that has to reach the stomach intact, because if it leaks in the mouth it numbs the throat.
╌╌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
Benzonatate is a nine-unit polyethylene glycol ester of p-(butylamino)benzoic acid, an oily liquid formulated in soft gelatin capsules of 100 or 200 mg. The label instructs that capsules be swallowed whole and never broken, chewed, dissolved, cut or crushed.
Absorbed and distributed within about a quarter of an hour
The label puts onset at fifteen to twenty minutes and duration at three to eight hours. That is also, exactly, how quickly a poisoned child becomes symptomatic.
╌╌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 label states onset within 15 to 20 minutes and effect lasting 3 to 8 hours, and notes that drugs of the para-aminobenzoate anaesthetic type are generally well absorbed after ingestion. The same 15-to-20-minute figure appears in the Overdosage section as the time to first signs of poisoning.
The asserted step: numbing the airway stretch sensors
The label says the drug reaches the sensors in the airways, lungs and lining of the chest and dampens their activity, so the cough reflex is stopped at its source. No published measurement shows this happening.
╌╌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 Clinical Pharmacology section asserts peripheral anaesthesia of stretch receptors in the respiratory passages, lungs and pleura. No recording of slowly or rapidly adapting airway afferent firing on benzonatate has been published, and the label carries no Clinical Studies section.
The active end of the molecule is the same chemical family as dental anaesthetics. Those work by blocking the sodium channels nerves use to fire, and that is what happens in overdose — first excitation, then seizures, then collapse.
╌╌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 label places the drug in the para-aminobenzoic acid anaesthetic class alongside procaine and tetracaine. Toxicology attributes its systemic effects to voltage-gated sodium channel blockade by a tetracaine-like metabolite, which accounts for the reported sequence in overdose: central nervous system stimulation, clonic convulsions, then profound depression, with prolonged QT interval, ventricular dysrhythmias and cardiac arrest.
The clinical result nobody has measured against a placebo
People are prescribed it for cough and many say it helps. In sixty-six years of literature, a systematic search of four databases found no adequately sized randomised comparison against a dummy capsule.
╌╌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 2023 systematic review identified 37 articles from 1956 to 2022 — 21 cohort studies, 5 experimental studies and 11 case studies or series — with quality assessment flagging high risk of bias from limited sample size, data collection, generalisability and study design throughout.
The safety profile that exists is the poisoning profile
Because there are no trials, what is known about its harms comes almost entirely from overdose reports and poison centre records rather than from controlled comparison.
╌╌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 systematic review notes that safety is primarily assessed in terms of toxicity due to overdose or inappropriate use. Twenty years of one poison centre’s records give 22% serious adverse effects among 106 intentional exposures against 0.7% among 143 unintentional ones, with two deaths, both intentional.
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 over ten, on prescription. It must never be within reach of a young child: accidental ingestion has killed children under ten within an hour.
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
The only systematic review concluded the approval rests on evidence that would not survive current regulatory review
Accidental ingestion has killed children under ten, with death reported within one hour, and the FDA added this to the label
Chewing or sucking the capsule has caused bronchospasm, laryngospasm and cardiovascular collapse requiring vasopressors
No paediatric or adult placebo-controlled cough-count trial has ever been published for a drug approved sixty-eight years ago
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 soft gelatin capsule (100 mg and 200 mg) containing the drug as a 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
Professional supervision is normally required. A regulator classifies this substance in a way that restricts how it is supplied.
❝ Quoted from a source
Where this came from
Copied from a source RNAWiki stored, with the source named.
Suppression classes recorded: S6.
No source is stored against this line.
What is in the pack
Must be swallowed whole. The contents are an oily local anaesthetic; releasing them in the mouth produces rapid oropharyngeal numbness and can cause choking. The label instructs patients not to break, chew, dissolve, cut or crush the capsule, and not to take two doses at once if one is missed.
✎ 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
Severe hypersensitivity reactions including bronchospasm, laryngospasm and cardiovascular collapse have been reported, possibly related to local anaesthesia from sucking or chewing the capsule, some requiring vasopressors. Isolated reports of bizarre behaviour, mental confusion and visual hallucinations in patients taking it with other drugs. Accidental ingestion has caused death in children below age 10, with symptoms at 15 to 20 minutes and death within one hour; overdose produces convulsions, coma, cerebral oedema and cardiac arrest, and central nervous system stimulants must not be used in treatment. The label caps a single dose at 200 mg and a total daily amount at 600 mg, and states that fatal overdose can occur in adults. Pregnancy Category C with no animal reproduction studies conducted.
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 soft gelatin capsule (100 mg and 200 mg) containing the drug as a 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
The contents are an oily local anaesthetic; releasing them in the mouth produces rapid oropharyngeal numbness and can cause choking. The label instructs patients not to break, chew, dissolve, cut or crush the capsule, and not to take two doses at once if one is missed.
✎ 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
145 products list this as an active ingredient in the United States drug directory. 145 of them contain it and nothing else.
FDA National Drug Code directory · 72162-1316 · read 2026-08-29
They are sold as capsule, capsule, liquid filled, liquid and powder, taken oral.
FDA National Drug Code directory · 72162-1316 · read 2026-08-29
The regulator's established pharmacologic class for it is decreased tracheobronchial stretch receptor activity [pe] and non-narcotic antitussive [epc].
FDA National Drug Code directory · 72162-1316 · read 2026-08-29
112 published labels name it as an active ingredient. 112 of them describe this substance alone, which is where its own label text on this page comes from.
US prescribing information · a2f6acff-70ff-79f1-e053-2a95a90a6005 · read 2026-08-29
Those labels are classed as human prescription drug.
US prescribing information · a2f6acff-70ff-79f1-e053-2a95a90a6005 · read 2026-08-29
Benzonatate is oral at HOW SUPPLIED Benzonatate Capsules, USP are available as: 100 mg (oval, yellow) soft gelatin capsules with imprint “A1”., recorded as fda label in effect 2024-10-23 in the United States.
US prescribing information · 199a42ae-4d19-4e68-934d-dabd27084988 · read 2026-08-30
Recorded price in US: 0.06878–0.10208 USD per one unit as the pricing file counts it — a tablet, capsule, patch or single item, across 39 priced products whose strengths and pack forms differ, as of 2026-08-26, paid by retail pharmacies buying the product, as surveyed by the Centers for Medicare & Medicaid Services. It is not a list price, an insurance price, or what anyone pays at a counter..
Recorded source · 2026-08-26 · read 2026-08-28
Evidence carries across two names for one substance. It does not carry across a salt, a mirror form or a mixture.
What it would be like to take◇Read from sources, not yet reviewed
What you could measure
This one is decided with a clinician, so this section holds questions to ask rather than a plan to run.
Self-experiment planning is not offered for a prescription or clinician-supervised medicine. The questions below are for a clinician or pharmacist.
Questions worth asking
Which of the trials of Benzonatate 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 anaesthetises airway stretch receptors — asserted in labelling since 1958 with no published measurement of those receptors
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 it relieves cough better than a matched placebo capsule — no adequately sized randomised comparison exists
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 continued prescription-only marketing reflects a maintained regulatory judgement of efficacy
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 tetracaine chemical relationship establishes the airway mechanism rather than merely the toxicology
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 Benzonatate 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.
The only systematic review of the drug says its approval would not survive current review
In plain words
Researchers searched four databases for every study of this drug published since 1956. They found thirty-seven, none of them a properly sized randomised trial, and most of them small, old or case reports. Their conclusion was that the evidence behind its approval would not stand up today.
What was measured
Systematic search of four databases, 1956 to 2022 — count and design of all identified studies
Effect estimate
No reviewed effect estimate exists for this record.
Limits
This entry records a failure.
From the source
A systematic review searched PubMed, Embase, the Cochrane Library and Scopus for original research on the effectiveness, tolerability and safety of benzonatate from January 1956 through August 2022. Screening yielded 37 articles: 21 cohort studies, 5 experimental studies and 11 case studies or series. The authors record that initial clinical studies exploring therapeutic benefit collected data from very small populations in limited clinical settings, that safety is primarily assessed in terms of overdose or inappropriate use rather than in trials, and that quality assessment raised concerns for high degrees of bias related to limited sample size, data collection, generalisability and study design. Their stated conclusion is that rising safety concerns should bring closer scrutiny upon the prescription of benzonatate, "whose approval is founded upon evidence that would not stand up to current regulatory review."
Written into the record, not signed off as a reviewed claim
Accidental ingestion has killed children under ten within an hour
In plain words
The capsules are soft, shiny and yellow, and a small child who swallows them can be dead within an hour. Symptoms start in fifteen to twenty minutes. This is written on the label.
What was measured
Time from ingestion to symptom onset and to death, as recorded in labelling
Effect estimate
No reviewed effect estimate exists for this record.
Limits
This entry records a failure.
From the source
The Warnings section of the label states that accidental ingestion of benzonatate resulting in death has been reported in children below age 10, that signs and symptoms of overdose have been reported within 15 to 20 minutes, and that death has been reported within one hour of ingestion. The Overdosage section describes the sequence: rapid oropharyngeal anaesthesia with choking and airway compromise if capsules are chewed or dissolved, then central nervous system stimulation with restlessness and tremors proceeding to clonic convulsions, then profound central nervous system depression, with convulsions, coma, cerebral oedema and cardiac arrest leading to death reported within one hour. Treatment is supportive and the label directs explicitly that central nervous system stimulants must not be used. A published case describes a 13-year-old presenting with coma, seizures, hypotension, prolonged QT interval and metabolic acidosis after overdose, and records that the FDA issued a Drug Safety Communication warning of increased risk of death from accidental ingestion in children under 10 and added that information to the Warnings and Precautions section.
Written into the record, not signed off as a reviewed claim
Twenty years of poison centre calls: severe in deliberate overdose, rarely otherwise
In plain words
A regional poison centre reviewed every call about this drug over twenty years. Among people who took it deliberately, more than one in five had a seizure, a heart rhythm change, coma or died. Among accidental exposures, including seventy-seven in children, almost none did.
What was measured
Rate of seizure, ECG change, coma or death by intent of exposure, across 265 poison centre cases
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
A retrospective review of all benzonatate exposures reported to the Wisconsin Poison Center from 1 January 2000 to 31 December 2019 identified 313 calls, of which 265 had complete records. Median age was 19 years and 61% were female. Of 106 intentional exposures (40%), 23 (22%) experienced at least one serious adverse effect — defined as seizure, electrocardiogram change, coma or central nervous system depression, or death — and 40 (38%) were hospitalised. Of 143 unintentional exposures (54%), one (0.7%) had a serious adverse effect and three (2%) were hospitalised. Among 77 unintentional paediatric exposures, none had a serious adverse effect and two (3%) were hospitalised. Two deaths occurred over the twenty years, both after intentional exposure. No therapeutic intervention beyond supportive care was consistently used, and the authors note that no standard treatment guideline for benzonatate toxicity exists.
Written into the record, not signed off as a reviewed claim
The mechanism on the label has been asserted since 1958 and never demonstrated
In plain words
The label says the drug numbs the stretch sensors in your airways. That sentence has been in the labelling for nearly seventy years. Nobody has published a measurement of those sensors quietening in a person who has taken it.
What was measured
That the drug anaesthetises airway stretch receptors and reduces the cough reflex at its source — a mechanism asserted in labelling since 1958, chemically plausible from the tetracaine relationship, and never confirmed by a published measurement of the receptors or the reflex
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
The Clinical Pharmacology section states in full: "Benzonatate acts peripherally by anesthetizing the stretch receptors located in the respiratory passages, lungs, and pleura by dampening their activity and thereby reducing the cough reflex at its source. It begins to act within 15 to 20 minutes and its effect lasts for 3 to 8 hours." There is no Clinical Studies section in the label. The chemical rationale is stated in Precautions — the drug is related to anaesthetics of the para-aminobenzoic acid class such as procaine and tetracaine — and the toxicology literature independently describes sodium channel blocking properties and local anaesthetic effects attributed to a tetracaine-like metabolite. What is absent is any published recording of airway afferent activity, or any human pharmacodynamic measure such as a cough challenge threshold, confirming the effect the label names.
Source
Benzonatate prescribing information, Clinical Pharmacology and Precautions sections; Thimann DA et al., J Pediatr Pharmacol Ther 2012;17:270-273
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
Chewing the capsule can cause laryngospasm and cardiovascular collapse
In plain words
The liquid inside the capsule is a numbing agent. If it gets into the mouth it deadens the throat within minutes, and severe reactions have followed — the airway closing, the circulation collapsing, needing drugs to restore blood pressure.
What was measured
Labelled adverse reactions attributed to release of capsule contents in the mouth
Effect estimate
No reviewed effect estimate exists for this record.
Limits
This entry records a failure.
From the source
The Warnings section records severe hypersensitivity reactions including bronchospasm, laryngospasm and cardiovascular collapse, described as possibly related to local anaesthesia from sucking or chewing the capsule instead of swallowing it, with severe reactions requiring intervention with vasopressor agents and supportive measures. The same section records isolated instances of bizarre behaviour including mental confusion and visual hallucinations in patients taking benzonatate with other prescribed drugs. Precautions add that release of the contents in the mouth can produce temporary local anaesthesia of the oral mucosa and that choking could occur, and instruct patients to avoid food and liquid until any numbness of tongue, mouth, throat or face has resolved.
Source
Benzonatate prescribing information, Warnings and Precautions sections (NDA 011210 and generics)
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
It was approved four years before proof of efficacy became law, and never revisited
In plain words
The drug was approved in February 1958. In 1962 Congress required, for the first time, that a manufacturer prove a medicine works before selling it. Benzonatate was already on the market, and the standard that would have applied to a new drug was never applied to it.
What was measured
That continued marketing and prescription status reflect a maintained judgement that the drug is effective — the approval predates the efficacy requirement, and no subsequent regulatory step has re-tested it
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
NDA 011210 was approved on 10 February 1958. The Kefauver-Harris amendment of 1962 introduced the requirement for substantial evidence of effectiveness. The 200 mg Tessalon capsule now carries a Federal Register determination that it was not discontinued or withdrawn for safety or effectiveness reasons, which is a statement about why it left the market rather than about whether it works. Generic entry began in 1993 under abbreviated applications, which establish bioequivalence to the reference product and do not re-examine efficacy. The 2023 systematic review found no randomised controlled trial of adequate size in sixty-six years of literature and concluded that the evidence base underlying approval would not survive current regulatory review.
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What is not here
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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.
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The record as stored
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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 liquid polyethylene-glycol ester of a para-aminobenzoic acid — chemically a relative of tetracaine — approved on 10 February 1958 on the stated mechanism of anaesthetising airway stretch receptors, whose only systematic review found 37 studies comprising 21 cohorts, 5 experimental studies and 11 case reports with high risk of bias throughout, and concluded that its approval "is founded upon evidence that would not stand up to current regulatory review"; the label meanwhile records death in children under ten within one hour of accidental ingestion.
ClinicalTrials.gov — US Government work · mixed register set; per-register licences in docs/specs/corpus-20k-sources.md · openFDA / DailyMed — US Government work
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