This page shows what was measured, who it was measured in, and what that does not settle.
What Clobazam does in the body
Drop attacks and other seizures in Lennox-Gastaut syndrome, added to other seizure medicines
GABA is the brain main calming signal, and it works by opening a channel that lets chloride into a nerve cell and makes it harder to fire. Clobazam does not open that channel itself. It sits at a separate spot on the same receptor and makes GABA better at its job, so every pulse of natural GABA produces a bigger calming effect. Most of the work is done not by clobazam but by a long-lived breakdown product, N-desmethylclobazam, which circulates at three to five times the concentration of the drug swallowed.
What happened in people
Weekly drop seizure rate down 68.3% at 1.0 mg/kg/day against 12.1% on placebo in 238 patients (P<0.0001)
✎ 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.
Clobazam United States prescribing information: boxed warning, Warnings and Precautions 5.1 to 5.9, Clinical Studies 14, Clinical Pharmacology 12.3 and 12.5,… · a recorded source, not a stored snapshot
Drugs@FDA: ONFI (clobazam) tablets and oral suspension, NDA 202067, original approval 21 October 2011 (https://www.accessdata.fda.gov/scripts/cder/daf/index.… · a recorded source, not a stored snapshot
The limit that matters most
That every effective dose helps patients: at the lowest dose the responder rate did not separate from placebo
Where it acts
GABA-A receptors on cortical and thalamic neurons, at the interface between the alpha and gamma subunits
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 · 2MRO291B4U · read 2026-08-29
Its recorded molecular formula is C16H13ClN2O2, weighing 300.74.
US prescribing information · 574a3f91-d73e-46bc-b4a1-2388439521fb · 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 130 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.
Percentage decrease in mean weekly drop seizure rate from a 4-week baseline to a 12-week maintenance phase
✓ The study showed what it set out to show
Who was studied
Clobazam Lennox-Gastaut Study 1 (Ng 2011, label Clinical Studies 14)
Decrease of 41.2% (P=0.0120), 49.4% (P=0.0015) and 68.3% (P<0.0001) at 0.25, 0.5 and 1.0 mg/kg/day against 12.1% on placebo
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 responder rate at the lowest dose did not separate from placebo (43.4% against 31.6%, P=0.3383), and the placebo responder rate was itself 31.6%. Of patients enrolled after a mid-trial protocol amendment, 125 of 157 (79.6%) completed.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Oral tablet, oral suspension and orally dissolving film
Interval reported. Not recorded in this summary
Written into the record, not signed off as a reviewed claim.
Clobazam United States prescribing information: boxed warning, Warnings and Precautions 5.1 to 5.9, Clinical Studies 14, Clinical Pharmacology 12.3 and 12.5,… · a recorded source, not a stored snapshot
Drugs@FDA: ONFI (clobazam) tablets and oral suspension, NDA 202067, original approval 21 October 2011 (https://www.accessdata.fda.gov/scripts/cder/daf/index.… · a recorded source, not a stored snapshot
Percentage reduction in weekly drop seizure frequency from a 4-week baseline to a 4-week maintenance phase
✓ The study showed what it set out to show
Who was studied
Clobazam Lennox-Gastaut Study 2 (label Clinical Studies 14)
How many people
68
Study design
Randomised double-blind high-dose versus low-dose comparison, 4-week maintenance
Compared against
Not recorded for this study
Kind of result
A number that stands in for health
What was found
Median reduction 93% on high dose against 29% on low dose, P<0.05
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. There is no placebo arm. The trial establishes dose-response, not efficacy against no additional treatment, and its maintenance phase is a third the length of Study 1.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Oral tablet, oral suspension and orally dissolving film
Interval reported. Not recorded in this summary
Written into the record, not signed off as a reviewed claim.
Clobazam United States prescribing information: boxed warning, Warnings and Precautions 5.1 to 5.9, Clinical Studies 14, Clinical Pharmacology 12.3 and 12.5,… · a recorded source, not a stored snapshot
Drugs@FDA: ONFI (clobazam) tablets and oral suspension, NDA 202067, original approval 21 October 2011 (https://www.accessdata.fda.gov/scripts/cder/daf/index.… · a recorded source, not a stored snapshot
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
Clobazam
What a person takes: Oral tablet, oral suspension and orally dissolving film.
The measurement behind this step
The orally dissolving film Sympazan exists for a specific reason in this population: many people with Lennox-Gastaut syndrome have swallowing difficulty or refuse tablets, and a film that dissolves on the tongue is harder to spit out than a suspension. It is a separate FDA application rather than a reformulation. There is no intravenous clobazam.
Getting in
Swallowed, absorbed, and converted into something longer-lived
The tablet is absorbed and the liver strips a methyl group off it, producing a breakdown product that lasts much longer and builds up to several times the concentration of the original 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
Clobazam is extensively metabolised, with about 2% recovered unchanged in urine and 1% in faeces. N-demethylation proceeds primarily via CYP3A4 and to a lesser extent CYP2C19 and CYP2B6 to give N-desmethylclobazam, which at therapeutic doses circulates at 3 to 5 times the parent concentration and is itself cleared mainly by CYP2C19.
Clobazam United States prescribing information: boxed warning, Warnings and Precautions 5.1 to 5.9, Clinical Studies 14, Clinical Pharmacology 12.3 and 12.5,… · a recorded source, not a stored snapshot
Drugs@FDA: ONFI (clobazam) tablets and oral suspension, NDA 202067, original approval 21 October 2011 (https://www.accessdata.fda.gov/scripts/cder/daf/index.… · a recorded source, not a stored snapshot
Reaching the cell
Both molecules distribute widely and reach the brain
The drug and its breakdown product are both fat-soluble enough to spread through the body and cross into the brain, where GABA receptors sit.
──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
Apparent volume of distribution at steady state is approximately 100 L. Plasma protein binding is roughly 80 to 90% for clobazam and 70% for N-desmethylclobazam, so a higher free fraction of the metabolite compounds its concentration advantage.
Clobazam United States prescribing information: boxed warning, Warnings and Precautions 5.1 to 5.9, Clinical Studies 14, Clinical Pharmacology 12.3 and 12.5,… · a recorded source, not a stored snapshot
Drugs@FDA: ONFI (clobazam) tablets and oral suspension, NDA 202067, original approval 21 October 2011 (https://www.accessdata.fda.gov/scripts/cder/daf/index.… · a recorded source, not a stored snapshot
What it acts on
It binds a site next to the GABA site, not the GABA site itself
It does not open the calming channel. It attaches at a separate spot on the same receptor and makes the brain own GABA work better, so nothing happens where there is no GABA to amplify.
╌╌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 that the exact mechanism of clobazam, a 1,5-benzodiazepine, is not fully understood but is thought to involve potentiation of GABAergic neurotransmission resulting from binding at the benzodiazepine site of the GABA-A receptor, which lies at the interface between alpha and gamma subunits. The 1,5 nitrogen arrangement distinguishes it from every classical 1,4-benzodiazepine.
Clobazam United States prescribing information: boxed warning, Warnings and Precautions 5.1 to 5.9, Clinical Studies 14, Clinical Pharmacology 12.3 and 12.5,… · a recorded source, not a stored snapshot
Drugs@FDA: ONFI (clobazam) tablets and oral suspension, NDA 202067, original approval 21 October 2011 (https://www.accessdata.fda.gov/scripts/cder/daf/index.… · a recorded source, not a stored snapshot
The change it makes
Each pulse of GABA lets more chloride in
When GABA arrives, the channel opens more readily and more chloride enters the cell, which pushes it further from firing. The effect scales with the brain own calming activity rather than replacing it.
╌╌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
Benzodiazepine-site occupancy increases the frequency of GABA-A channel opening in response to sub-maximal GABA, raising chloride conductance and hyperpolarising the membrane. The same mechanism produces the sedation, the abuse potential and the withdrawal syndrome; nothing in the pharmacology separates the wanted effect from the class risks.
Clobazam United States prescribing information: boxed warning, Warnings and Precautions 5.1 to 5.9, Clinical Studies 14, Clinical Pharmacology 12.3 and 12.5,… · a recorded source, not a stored snapshot
Drugs@FDA: ONFI (clobazam) tablets and oral suspension, NDA 202067, original approval 21 October 2011 (https://www.accessdata.fda.gov/scripts/cder/daf/index.… · a recorded source, not a stored snapshot
What that does for a person
Two thirds fewer drop attacks, at the highest dose
Weekly drop seizures fell 68.3% at the highest dose against 12.1% on placebo, and 77.6% of that group halved their seizures against 31.6% on placebo.
──Measured in people. Written by a person from the study named beside the step. Not signed off as a reviewed claim.
The measurement behind this step
Efficacy is established in one placebo-controlled trial of 238 patients with a 12-week maintenance phase and one high-versus-low-dose trial of 68 patients with a 4-week maintenance phase, both in Lennox-Gastaut syndrome. No tolerance to the therapeutic effect was observed over the 3-month maintenance period, which is the length of the observation rather than the length of treatment.
Clobazam United States prescribing information: boxed warning, Warnings and Precautions 5.1 to 5.9, Clinical Studies 14, Clinical Pharmacology 12.3 and 12.5,… · a recorded source, not a stored snapshot
Drugs@FDA: ONFI (clobazam) tablets and oral suspension, NDA 202067, original approval 21 October 2011 (https://www.accessdata.fda.gov/scripts/cder/daf/index.… · 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 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.
Children and adults with Lennox-Gastaut syndrome, almost always alongside two or three other anti-seizure drugs. Outside the United States clobazam has been used far more broadly in epilepsy for decades.
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: “Safety and effectiveness in patients less than 2 years of age have not been established.”
US prescribing information · 574a3f91-d73e-46bc-b4a1-2388439521fb · read 2026-08-30
On older people, the label states: “Clinical studies of clobazam did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects.”
US prescribing information · 574a3f91-d73e-46bc-b4a1-2388439521fb · read 2026-08-30
On people who are pregnant, the label states: “Registry There is a pregnancy exposure registry that monitors pregnancy outcomes in women exposed to AEDs, such as clobazam, during pregnancy.”
US prescribing information · 574a3f91-d73e-46bc-b4a1-2388439521fb · read 2026-08-30
On people who are breastfeeding, the label states: “Risk Summary Clobazam is excreted in human milk (see Data).”
US prescribing information · 574a3f91-d73e-46bc-b4a1-2388439521fb · read 2026-08-30
On people with reduced liver function, the label states: “Clobazam is hepatically metabolized; however, there are limited data to characterize the effect of hepatic impairment on the pharmacokinetics of clobazam.”
US prescribing information · 574a3f91-d73e-46bc-b4a1-2388439521fb · read 2026-08-30
On people with reduced kidney function, the label states: “The pharmacokinetics of clobazam were evaluated in patients with mild and moderate renal impairment.”
US prescribing information · 574a3f91-d73e-46bc-b4a1-2388439521fb · read 2026-08-30
Where the result stopped carrying
Benzodiazepines were largely abandoned for long-term epilepsy on tolerance grounds, which is the objection the clobazam programme was designed to answer and answered only for three months
The drug was available in Europe from the 1970s and took until 2011 to reach the United States market, arriving with an orphan indication far narrower than its European use
Only one of the two registration trials has a placebo arm; the other compares two doses of the same drug
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 tablet, oral suspension and orally dissolving film
✎ 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
The orally dissolving film Sympazan exists for a specific reason in this population: many people with Lennox-Gastaut syndrome have swallowing difficulty or refuse tablets, and a film that dissolves on the tongue is harder to spit out than a suspension.
✎ 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 is a separate FDA application rather than a reformulation. There is no intravenous clobazam.
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
A three-part boxed warning: profound sedation, respiratory depression, coma and death with concomitant opioids; abuse, misuse and addiction leading to overdose or death; and physical dependence with potentially life-threatening acute withdrawal on abrupt discontinuation or rapid dose reduction. It is a Schedule IV controlled substance. Somnolence and sedation are the commonest adverse effects, with pyrexia, upper respiratory infection and lethargy also frequent in the trials. Stevens-Johnson syndrome, toxic epidermal necrolysis, DRESS and multi-organ hypersensitivity are labelled. Use in pregnancy can cause neonatal sedation and neonatal withdrawal syndrome. The class-wide suicidality warning applies. Exposure to the active metabolite is five-fold higher in CYP2C19 poor metabolisers.
Nobody counted how many people took this and were fine, so this cannot be turned into a rate.
Clobazam United States prescribing information: boxed warning, Warnings and Precautions 5.1 to 5.9, Clinical Studies 14, Clinical Pharmacology 12.3 and 12.5,… · a recorded source, not a stored snapshot
Drugs@FDA: ONFI (clobazam) tablets and oral suspension, NDA 202067, original approval 21 October 2011 (https://www.accessdata.fda.gov/scripts/cder/daf/index.… · 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 tablet, oral suspension and orally dissolving film
✎ 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 is a separate FDA application rather than a reformulation. There is no intravenous clobazam.
✎ 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
48 products list this as an active ingredient in the United States drug directory. 48 of them contain it and nothing else.
FDA National Drug Code directory · 69037-0009 · read 2026-08-29
They are sold as film, powder, suspension and tablet, taken oral.
FDA National Drug Code directory · 69037-0009 · read 2026-08-29
The regulator's established pharmacologic class for it is benzodiazepine [epc], benzodiazepines [cs] and cytochrome p450 2d6 inhibitors [moa].
FDA National Drug Code directory · 69037-0009 · read 2026-08-29
22 published labels name it as an active ingredient. 22 of them describe this substance alone, which is where its own label text on this page comes from.
US prescribing information · 574a3f91-d73e-46bc-b4a1-2388439521fb · read 2026-08-29
Those labels are classed as human prescription drug.
US prescribing information · 574a3f91-d73e-46bc-b4a1-2388439521fb · read 2026-08-29
Clobazam is oral at 3 DOSAGE FORMS AND STRENGTHS Oral Suspension: 2.5 mg/mL for oral administration., recorded as fda label in effect 2023-03-07 in the United States.
US prescribing information · 574a3f91-d73e-46bc-b4a1-2388439521fb · read 2026-08-30
Recorded price in US: 0.16869 USD per one millilitre, across 7 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: 0.24734–0.39018 USD per one unit as the pricing file counts it — a tablet, capsule, patch or single item, across 16 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 Clobazam 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 every effective dose helps patients: at the lowest dose the responder rate did not separate from placebo
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 tolerance does not develop over years of treatment, when the observation covers twelve weeks
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 1,5-benzodiazepine structure exempts clobazam from benzodiazepine class risks, a position the boxed warning does not accept
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 clinical effect belongs to clobazam rather than to N-desmethylclobazam, when the metabolite is present at 3 to 5 times the concentration and its relative potency is uncertain five-fold
Why it sounds right. It follows from something real on this page: a body step, an animal result or a related finding.
The missing step. Nobody measured this in people for this use, or the study that did measure it did not show it.
What would change this
A study in people, for this exact use, measuring this exact thing, that a reviewer signs off.
RNAWiki has not yet published a reviewed conclusion for this use.
What is missing or unclear◇Read from sources, not yet reviewed
What nobody knows yet
Open questions, each with why it is open and what would close it.
How much did people take in the studies?
The sources RNAWiki checked hold nothing for this field.
Why it matters. A result belongs to an amount. Without the amount the result floats free.
What would answer it
A stored source that records it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
Missing populations
Which groups were under-represented in the studies has not been recorded.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
Missing long-term data
No completed tested study window is recorded.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
No reviewed conclusion
RNAWiki has not yet published a reviewed conclusion for this use.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
Missing interaction studies
No interaction was found in the registers checked. Not finding one is not the same as showing there is none.
Why it matters. Recorded by the evidence model as a gap on this record.
What would answer it
A study that measures it, and a reviewer to sign it off.
Last checked 2026-09-04. Searched: The sources listed in the receipts at the foot of this page.
Formulation uncertainty
Several salts, forms or products of Clobazam 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.
Drop seizures fell 68.3% at the highest dose against 12.1% on placebo
In plain words
Two hundred and thirty-eight patients with Lennox-Gastaut syndrome added clobazam or a dummy to their existing drugs. Weekly drop attacks fell by 68.3% at the highest dose and by 12.1% on placebo, and the effect grew at each dose step.
What was measured
Percentage decrease in mean weekly drop seizure rate, maintenance against baseline, by dose
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
Ng and colleagues randomised patients aged 2 to 60 to placebo or clobazam 0.25, 0.5 or 1.0 mg/kg/day, with a 4-week baseline, 3-week titration and 12-week maintenance phase. Of 305 screened, 238 were randomised and 217 formed the modified intention-to-treat population. Average weekly drop seizure rates decreased 12.1% on placebo against 41.2% (p=0.0120), 49.4% (p=0.0015) and 68.3% (p<0.0001) at the three doses. Responder rates at 50% or more were 31.6% on placebo against 43.4% (p=0.3383), 58.6% (p=0.0159) and 77.6% (p<0.0001). Physicians and caregivers global assessments both improved significantly. The commonest adverse events were somnolence, pyrexia, upper respiratory infection and lethargy. The authors classified the result as Class II evidence, not Class I. The label records that there was no evidence of tolerance to the therapeutic effect over the 3-month maintenance period, which for a benzodiazepine in epilepsy is the specific question that needed answering.
Written into the record, not signed off as a reviewed claim
The lowest dose beat placebo on percentages and not on people
In plain words
At the lowest dose the average percentage reduction was significantly better than placebo. The proportion of patients who actually halved their seizures was not: 43.4% against 31.6%, p=0.34.
What was measured
Responder rate at 50% or greater reduction, by dose, against a 31.6% placebo responder rate
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
The label states that all dose groups were statistically superior to placebo, which is true of the primary endpoint, the percentage decrease in mean weekly drop seizure rate. The responder analysis tells a different story at the bottom of the dose range: 43.4% at 0.25 mg/kg/day against 31.6% on placebo, p=0.3383. The two higher doses cleared it comfortably (58.6%, p=0.0159; 77.6%, p<0.0001). A mean percentage reduction can be moved by a small number of large responders in a population whose baseline seizure counts ran from 61 to 105 per week; a responder rate cannot. The placebo responder rate of 31.6% is itself worth noting, because it is what a third of this population achieved with no change in treatment at all.
Written into the record, not signed off as a reviewed claim
The second trial had no placebo: high dose against low dose
In plain words
The other registration study randomised 68 patients between a high and a low dose of clobazam, with no placebo group. Drop seizures fell by a median of 93% on the high dose and 29% on the low.
What was measured
Median percentage reduction in weekly drop seizure frequency, high dose against low dose
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
Study 2 was a randomised, double-blind comparison of high- and low-dose clobazam in 68 patients aged 2 to 25 with current or prior Lennox-Gastaut syndrome, with a 4-week baseline, 3-week titration and 4-week maintenance phase, stratified by weight. The primary measure was percentage reduction in weekly drop seizure frequency, and the high-dose group achieved a median reduction of 93% against 29% in the low-dose group (p<0.05). The design demonstrates dose-response rather than efficacy against no treatment, and the four-week maintenance period is a third the length of Study 1. Both studies are described as establishing effectiveness; only one of them has a placebo arm.
Source
Clobazam United States prescribing information, Clinical Studies 14, Study 2 (openFDA drug label endpoint)
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
Most of the drug effect belongs to a metabolite whose potency is uncertain five-fold
In plain words
At therapeutic doses, the breakdown product N-desmethylclobazam circulates at three to five times the concentration of clobazam itself. How strong it is, relative to the parent, is stated on the label as somewhere between one fifth and equal.
What was measured
Metabolite-to-parent plasma concentration ratio of 3 to 5, and a stated relative potency range of one fifth to equal
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
Clobazam is extensively metabolised in the liver, with only about 2% of a dose recovered unchanged in urine and 1% in faeces. N-demethylation proceeds primarily via CYP3A4 with lesser contributions from CYP2C19 and CYP2B6, producing N-desmethylclobazam, the major circulating metabolite, at plasma concentrations 3 to 5 times those of the parent at therapeutic doses. The label states that estimates of the relative potency of the metabolite compared with the parent, based on animal and in vitro receptor binding data, range from one fifth to equal potency. N-desmethylclobazam is itself cleared mainly by the polymorphic CYP2C19, and it plus its metabolites make up about 94% of drug-related material in urine. Combining a three to five-fold concentration advantage with a five-fold potency uncertainty leaves the share of clinical effect attributable to the parent compound genuinely unresolved.
Source
Clobazam United States prescribing information, Clinical Pharmacology 12.3 (openFDA drug label endpoint)
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
A common inherited variant raises the active metabolite five-fold
In plain words
The enzyme that clears the active metabolite is CYP2C19, and some people inherit a version that barely works. In them, the metabolite sits at five times the usual plasma level on the same dose.
What was measured
Five-fold higher plasma N-desmethylclobazam in CYP2C19 poor metabolisers than in extensive metabolisers
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
The label states that the polymorphic CYP2C19 is the major contributor to the metabolism of the pharmacologically active N-desmethylclobazam, and that in CYP2C19 poor metabolisers, levels of N-desmethylclobazam were 5-fold higher in plasma and 2 to 3-fold higher in urine than in extensive metabolisers. Poor metaboliser status is common enough to matter at population scale, and the same effect is produced pharmacologically by any co-prescribed CYP2C19 inhibitor. Cannabidiol is one such inhibitor, which is directly relevant here because the cannabidiol trials in Lennox-Gastaut syndrome enrolled populations largely already taking clobazam, and how much of the observed benefit in those trials belongs to raised N-desmethylclobazam rather than to cannabidiol itself has not been settled.
Source
Clobazam United States prescribing information, Clinical Pharmacology 12.3 and 12.5 (openFDA drug label endpoint)
Role in the trial
Not matched to a registered study
Identity check
no open identity hold
Audit mark
verified
Review state
Written into the record, not signed off as a reviewed claim
The boxed warning arrived in 2020 and describes the class, not this trial
In plain words
Clobazam was approved in 2011 with no boxed warning. It has one now, covering opioid co-prescription, abuse and addiction, and dependence and withdrawal. That warning came from a class-wide benzodiazepine review, not from anything measured in the Lennox-Gastaut trials.
What was measured
That the 1,5-benzodiazepine structure places clobazam outside the benzodiazepine class risks. Regulators concluded otherwise and applied the class boxed warning to it in full.
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
The current boxed warning has three parts: concomitant use with opioids may result in profound sedation, respiratory depression, coma and death, with observational studies showing raised drug-related mortality compared with opioids alone; benzodiazepine use exposes patients to risks of abuse, misuse and addiction that can lead to overdose or death, requiring risk assessment before and throughout treatment; and continued use may lead to clinically significant physical dependence, with abrupt discontinuation or rapid dose reduction precipitating acute withdrawal reactions that can be life-threatening. None of these derives from the two registration trials, which measured drop seizure frequency over 12 and 4 weeks in a population of children and young adults with severe epilepsy. They derive from the class-wide benzodiazepine labelling changes the FDA required across the category. Clobazam entire European history is as a drug positioned as gentler than a classical benzodiazepine because it is a 1,5 rather than a 1,4 isomer; the boxed warning declines to make that distinction.
Source
Clobazam United States prescribing information, boxed warning and Warnings and Precautions 5.1 to 5.3 (openFDA drug label endpoint)
Role in the trial
Not matched to a registered study
Identity check
no open identity hold
Audit mark
verified
Review state
Written into the record, not signed off as a reviewed claim
The absence of tolerance was measured over three months, not over the years people take it
In plain words
Benzodiazepines historically lost their anti-seizure effect over months, which is why they were abandoned for long-term epilepsy. The clobazam trial found no such loss, but it only ran for twelve weeks of maintenance.
What was measured
That clobazam does not lose its anti-seizure effect over the years it is actually taken. The measurement covers twelve weeks.
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
The label states there was no evidence that tolerance to the therapeutic effect of clobazam developed during the 3-month maintenance period of Study 1. That is a genuine finding and it addresses the specific historical objection to benzodiazepines in epilepsy. It is also bounded exactly by the length of the observation: twelve weeks of maintenance in Study 1 and four weeks in Study 2. Lennox-Gastaut syndrome is a lifelong condition and clobazam is taken for years or decades. The claim that tolerance does not develop is supported for three months and inferred for everything beyond it. The open-label extension that followed the trial is not a controlled comparison and cannot separate maintained efficacy from selective continuation by the patients in whom the drug was still working.
Written into the record, not signed off as a reviewed claim
Serious skin reactions, in a population already taking two or three rash-prone drugs
In plain words
Clobazam can cause Stevens-Johnson syndrome and toxic epidermal necrolysis. The people who take it are usually also on lamotrigine and valproate, which is one of the highest-risk rash combinations there is.
What was measured
Labelled occurrence of SJS, TEN and DRESS, against the recorded baseline concomitant medication profile of the trial population
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
The label directs discontinuation at the first sign of rash unless it is clearly not drug-related, and names Stevens-Johnson syndrome and toxic epidermal necrolysis, with DRESS and multi-organ hypersensitivity in a separate warning. The clinical difficulty is attribution rather than incidence: the label records that the commonest concomitant anti-seizure drugs at baseline in the clobazam trials were valproate, lamotrigine, levetiracetam and topiramate, and lamotrigine carries its own boxed warning for serious rash whose risk is highest in children and when valproate is co-prescribed. In a child on three or four such drugs, a rash has several plausible causes and no test distinguishes them, so the instruction to stop the drug is easy to write and hard to act on.
Source
Clobazam United States prescribing information, Warnings and Precautions 5.6 and 5.7, and Clinical Studies 14 (openFDA drug label endpoint)
Role in the trial
Not matched to a registered study
Identity check
no open identity hold
Audit mark
caution
Review state
Written into the record, not signed off as a reviewed claim
How many documents were read
22 documents were read for this substance.
RNAWiki source record
21 of them state the same bioavailability, and they agree.
RNAWiki source record
22 of them state the same volumeOfDistribution, and they agree.
RNAWiki source record
Where else this substance is registered
FDA substance identifier (UNII)
2MRO291B4U
RxNorm concept
1366192
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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.
What the approval register records
34 approved applications cover products containing this substance. The earliest was NDA202067, approved 20111021 to LUNDBECK PHARMS LLC.
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What is not here
7 questions this page could not answer
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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 1,5-benzodiazepine used in Europe since the 1970s and approved in the United States only in 2011, which cut weekly drop seizures by 68.3% at the highest dose against 12.1% on placebo in 238 patients with Lennox-Gastaut syndrome, and which carries a boxed warning for opioid co-prescription, abuse and dependence that reflects its chemical class rather than any signal from that trial.
Recorded evidence blocks (9)
Q2
On the Clobazam label: indicated for what?
"Clobazam oral suspension is indicated for the adjunctive treatment of seizures associated with Lennox-Gastaut syndrome (LGS) in patients 2 years of age or older. Clobazam is a benzodiazepine indicated for adjunctive treatment of seizures associated with Lennox-Gastaut syndrome (LGS) in patients 2 years of age or older…": indications and usage on Clobazam's label. DailyMed label · fd1e63bf-496c-427c-83b7-6acabc00a5e5 · 2026-07-14
Q3
20 registered trials of Clobazam — at which phases?
36 to 42 hours; The estimated mean elimination half-lives (t ½ ) of clobazam and N-desmethylclobazam were 36 to 42 hours and 71 to 82 hours, respectively.
tmaxpharmacokinetics
0.5 to 4 hours; The time to peak concentrations (T max ) of clobazam tablets under fasted conditions ranged from 0.5 to 4 hours after single- or multiple-dose administrations.
bioavailabilitypharmacokinetics
100 %; The relative bioavailability of clobazam tablets compared to an oral solution is approximately 100%.
metabolismpharmacokinetics
Metabolism and Excretion Clobazam is extensively metabolized in the liver, with approximately 2% of the dose recovered in urine and 1% in feces as unchanged drug.
recorded 2026-07-14 · last checked 2026-09-04
Q6
Which 4 trials of Clobazam posted no result?
Posted no result
4 of 4 completed trials
Registrations
NCT01011036, NCT01291316, NCT01179828 and NCT03196466
Completion dates
oldest 2010-06; newest 2023-06-15
Show the evidence
Trial
NCT01011036
2010-06
NCT01291316
2011-11
NCT01179828
2015-12
NCT03196466
2023-06-15
Q7
At the median, Clobazam's trials enrolled 46.5 people — anything larger?
Median enrolment
46.5
Largest enrolment
5000
Registered trials counted
20
Q8
What do 2550 spontaneous reports say about Clobazam — 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.
Clobazam appears in spontaneous reports to regulators. Across the 10 most-reported reaction terms, 2550 reaction mentions were counted: seizure 690; somnolence 521; drug interaction 231; epilepsy 195. FAERS via Open Targets · CHEMBL70418 · 2026-06-24
Show the evidence
seizure
690
somnolence
521
drug interaction
231
epilepsy
195
sedation
175
status epilepticus
161
4 more recorded rows
convulsion
157
drug resistance
154
abnormal behaviour
142
abortion spontaneous
124
recorded 2026-06-24 · last checked 2026-09-04
Q9
Which 10 reactions does Clobazam's label not list?
Alcohol: Increases blood levels of clobazam by about 50% ( 7.2 ) Drugs metabolized by CYP2D6: Lower doses of these drugs may be required when used concomitantly with clobazam ( 7.3 ) Strong or Moderate CYP2C19 Inhibitors: Dosage adjustment of clobazam may be necessary ( 7.4 ) 7.1 Opioids The concomitant use of benzodiazepines and opioids increases the risk of respiratory depression because of…
drug_interactions
7.3 Effect of Clobazam on Other Drugs Hormonal Contraceptives Clobazam is a weak CYP3A4 inducer.
drug_interactions
As some hormonal contraceptives are metabolized by CYP3A4, their effectiveness may be diminished when given with clobazam.
drug_interactions
Drugs Metabolized by CYP2D6 Clobazam inhibits CYP2D6.
drug_interactions
Dose adjustment of drugs metabolized by CYP2D6 may be necessary [see Clinical Pharmacology (12.3) ] .
pharmacokinetics
The major metabolic pathway of clobazam involves N-demethylation, primarily by CYP3A4 and to a lesser extent by CYP2C19 and CYP2B6.
2 more recorded rows
Interaction statementpharmacokinetics
Drug Interaction Studies In vitro studies: Clobazam did not inhibit CYP1A2, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP3A4, UGT1A1, UGT1A4, UGT1A6, or UGT2B4 in vitro .
Interaction statementpharmacokinetics
N-desmethylclobazam showed weak inhibition of CYP2C9, UGT1A4, UGT1A6 and UGT2B4.
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
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