This page shows what was measured, who it was measured in, and what that does not settle.
What Loratadine does in the body
Hay fever and itchy hives
Histamine is what makes an allergic reaction itch and run, and it works by switching on a receptor in your nose, eyes and skin. Loratadine sits in that receptor and holds it closed. What makes it different from the older antihistamines is the amount you take: the strength on the box is set just below the point where the drug starts crossing into the brain enough to make you sleepy. That is why it does not make you drowsy, and it is also why there is no stronger version to move up to.
What happened in people
Rhinoconjunctivitis quality of life improved by 0.32 points against placebo (95% CI -0.55 to -0.097) across 13 trials in 6,867 patients
✎ 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.
Centers for Disease Control and Prevention. Evaluation of an association between loratadine and hypospadias — United States, 1997-2001. MMWR Morb Mortal Wkly… · a recorded source, not a stored snapshot
That loratadine is intrinsically non-sedating rather than sold at a non-sedating amount — its label warns that exceeding the amount may cause drowsiness
Where it acts
Nasal mucosa, conjunctiva and dermal postcapillary venules — peripheral H1 receptors, with limited central nervous system penetration at the marketed strength
Kind of result
Symptoms and quality of life
Supervision
RNAWiki has not recorded a supervision or regulatory status for this substance.
What the registries record it as
The substance registry classes this as chemical.
FDA substance registry · 7AJO3BO7QN · 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.
A limit recorded against this substance. Not signed off as a reviewed claim.
The four opening statements run to 125 words.
Words this page uses
Four words worth knowing first
Chosen from what this page shows, with each one explained before the word it depends on.
Comparator
A comparator is whatever the treatment was measured against.
A picture of it, and where the picture fails
It is like the other runner in a race.
Where that stops being true. A race has one winner. A study can show both arms improved.
What people get wrong. Results are read without asking what the other group got. Beating nothing is not beating a treatment.
The control condition against which the experimental intervention is assessed.
Randomisation
Randomisation means chance decides who gets which treatment.
A picture of it, and where the picture fails
It is like a coin toss deciding the groups.
Where that stops being true. A coin toss is fair once. Fairness here comes from doing it for everyone.
What people get wrong. It is thought to make groups identical. It makes them similar on average, including on things nobody measured.
Allocation of participants to arms by a chance process, so that unmeasured factors are balanced in expectation.
Absolute difference
An absolute difference is how many more people in a hundred were affected.
A picture of it, and where the picture fails
It is like counting heads in two rooms of a hundred.
Where that stops being true. Heads are easy to count. Study results carry a margin of error too.
What people get wrong. It is confused with a percentage change, which can look far larger.
The arithmetic difference in event rates between arms.
Confidence interval
A confidence interval is the range the true answer is likely to sit in.
A picture of it, and where the picture fails
It is like a weather forecast giving a range rather than one number.
Where that stops being true. A forecast range covers tomorrow. This one covers what the study could resolve.
What people get wrong. The middle number is read as the answer. A range crossing zero means no change is still possible.
An interval estimate that would contain the true parameter in a stated proportion of repeated studies.
What happened in people◇Read from sources, not yet reviewed
What happened in people
Each card is one study: the exact question it asked, who was in it, and whether it showed what it set out to show.
Mean change in rhinoconjunctivitis quality of life questionnaire score against placebo
Network meta-analysis of 13 randomised controlled trials
Compared against
Not recorded for this study
Kind of result
A number that stands in for health
What was found
Loratadine -0.32 (95% CI -0.55 to -0.097), p=0.005; cetirizine -0.62 (95% CI -0.90 to -0.34), p<0.001; desloratadine -0.39, p<0.001; montelukast -0.28, p=0.033
Repeated elsewhere
Partially Replicated
What this does not prove. Meeting one endpoint in one population does not carry to other goals or other people.
The limits of this study, and where it came from
Main limit. The ranking rests on point estimates whose confidence intervals overlap. Quality of life is the only outcome pooled; nasal congestion specifically is not separated out.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Oral tablet, rapidly disintegrating tablet, chewable tablet and oral solution, plus extended-release combinations with pseudoephedrine
Interval reported. 95% CI -0
Written into the record, not signed off as a reviewed claim.
Centers for Disease Control and Prevention. Evaluation of an association between loratadine and hypospadias — United States, 1997-2001. MMWR Morb Mortal Wkly… · a recorded source, not a stored snapshot
Combination loratadine/montelukast against pseudoephedrine and placebo in seasonal allergic rhinitis, 1,095 patients, Organon — no results posted (NCT00319995) · a recorded source, not a stored snapshot
Efficacy and safety of combination loratadine/montelukast once daily against pseudoephedrine and placebo
Centers for Disease Control and Prevention. Evaluation of an association between loratadine and hypospadias — United States, 1997-2001. MMWR Morb Mortal Wkly… · a recorded source, not a stored snapshot
Combination loratadine/montelukast against pseudoephedrine and placebo in seasonal allergic rhinitis, 1,095 patients, Organon — no results posted (NCT00319995) · a recorded source, not a stored snapshot
Risk of second- or third-degree hypospadias with loratadine use in early pregnancy
✓ The study showed what it set out to show
Who was studied
National Birth Defects Prevention Study analysis, 1997-2001 (MMWR 2004;53:219-221)
How many people
0
Study design
Population-based case-control analysis, not a trial
Compared against
Not recorded for this study
Kind of result
A number that stands in for health
What was found
No increased risk determined for second- or third-degree hypospadias among women who used loratadine in early pregnancy
Repeated elsewhere
Partially Replicated
What this does not prove. Meeting one endpoint in one population does not carry to other goals or other people.
The limits of this study, and where it came from
Main limit. The report carries a published erratum. A 2006 mouse study subsequently reported disrupted urethral development and oestrogen-like steroid receptor changes after in utero exposure, and drew a published comment and author reply.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Oral tablet, rapidly disintegrating tablet, chewable tablet and oral solution, plus extended-release combinations with pseudoephedrine
Interval reported. Not recorded in this summary
Written into the record, not signed off as a reviewed claim.
Centers for Disease Control and Prevention. Evaluation of an association between loratadine and hypospadias — United States, 1997-2001. MMWR Morb Mortal Wkly… · a recorded source, not a stored snapshot
Combination loratadine/montelukast against pseudoephedrine and placebo in seasonal allergic rhinitis, 1,095 patients, Organon — no results posted (NCT00319995) · a recorded source, not a stored snapshot
What we know
RNAWiki holds 3 written-up human studies for this substance, each with the question it asked.
How we know it
Each card names the study, the number of people and what the study set out to measure.
What this does not prove
These summaries were written by a person and have not been signed off as reviewed claims.
Why it matters
A study that failed is as informative as one that worked, and both are here.
What we still do not know
No reviewed claim exists, so no exact population, effect size or interval is published yet.
What it changes in the body◇Read from sources, not yet reviewed
The path through the body
From what a person takes to what changes. A solid line is a step measured in people. A dashed line is a step nobody has measured that way.
Start
Loratadine
What a person takes: Oral tablet, rapidly disintegrating tablet, chewable tablet and oral solution, plus extended-release combinations with pseudoephedrine.
The measurement behind this step
One dose daily at a single marketed strength. The rapidly disintegrating form exists for people who cannot swallow a tablet rather than for faster onset. The label instructs that the directed amount not be exceeded, because more of it may cause drowsiness.
Getting in
Swallowed once a day
One tablet, one strength, once daily. There is no stronger version, and that constraint is the defining fact about the 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
Marketed at a single strength across tablet, rapidly disintegrating tablet, chewable and liquid forms, and in combination with pseudoephedrine. The over-the-counter label states that taking more than directed may cause drowsiness, which locates the marketed exposure at the boundary of central nervous system effect.
Centers for Disease Control and Prevention. Evaluation of an association between loratadine and hypospadias — United States, 1997-2001. MMWR Morb Mortal Wkly… · a recorded source, not a stored snapshot
Enzymes in the liver strip a piece off the molecule. What is left is the form that does most of the work — and it is itself a separately approved medicine.
╌╌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
Hepatic cytochrome P450 enzymes remove the ethyl carbamate from the piperidine nitrogen to yield desloratadine, approved in its own right as Clarinex under NDA 021165 in December 2001. Activity therefore depends on hepatic conversion, which is why the label singles out liver and kidney disease.
Centers for Disease Control and Prevention. Evaluation of an association between loratadine and hypospadias — United States, 1997-2001. MMWR Morb Mortal Wkly… · a recorded source, not a stored snapshot
It occupies the histamine receptor in the periphery
In the nose, eyes and skin it takes the seat histamine needs, so the histamine released by mast cells has nowhere to signal.
╌╌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
Selective peripheral H1 antagonism. The carbamate and the resulting polarity limit central nervous system penetration at the marketed exposure — a property of the amount taken rather than an absolute property of the molecule, which is what the label’s overdose warning encodes.
Centers for Disease Control and Prevention. Evaluation of an association between loratadine and hypospadias — United States, 1997-2001. MMWR Morb Mortal Wkly… · a recorded source, not a stored snapshot
At the amount on the box, not enough reaches the brain to make you sleepy. Take more and that stops being true, which is exactly what the label warns.
╌╌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
Non-sedation here is established from trial adverse event rates rather than from direct receptor imaging — unlike fexofenadine, whose brain H1 occupancy of -0.1% has been measured by [11C]doxepin PET. The distinction is between a measured absence and an unobserved effect.
Centers for Disease Control and Prevention. Evaluation of an association between loratadine and hypospadias — United States, 1997-2001. MMWR Morb Mortal Wkly… · a recorded source, not a stored snapshot
Symptoms improve, by about a third of a quality-of-life point
Pooled across thirteen trials in nearly seven thousand people, it improved rhinoconjunctivitis quality of life by 0.32 points against a dummy tablet. Cetirizine achieved about twice that.
──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
Mean difference against placebo -0.32 (95% CI -0.55 to -0.097, p=0.005), against cetirizine -0.62 (95% CI -0.90 to -0.34), desloratadine -0.39 and montelukast -0.28, in a network meta-analysis of 13 randomised trials in 6,867 patients. The loratadine and cetirizine intervals overlap.
Centers for Disease Control and Prevention. Evaluation of an association between loratadine and hypospadias — United States, 1997-2001. MMWR Morb Mortal Wkly… · a recorded source, not a stored snapshot
If the tablet is not enough, there is no stronger tablet. The next step has to be a different kind of drug, because more of this one buys drowsiness rather than a guarantee of more relief.
╌╌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
No higher-strength loratadine product is marketed and the label forbids exceeding the directed amount. The classes with evidence beyond this ceiling are intranasal corticosteroids for congestion and intranasal antihistamines, both of which act on symptoms an oral H1 blocker addresses poorly.
Centers for Disease Control and Prevention. Evaluation of an association between loratadine and hypospadias — United States, 1997-2001. MMWR Morb Mortal Wkly… · a recorded source, not a stored snapshot
No suggested links are held for this record, so nothing is hidden from this path.
What we know
The record describes 6 steps from taking it to an effect in a person.
How we know it
Each step names the study behind it in the technical detail beside it.
What this does not prove
A change inside the body is a reason to look. It is not a result in a person.
Why it matters
A reader can see exactly where the chain stops being measured in people.
What we still do not know
No reviewed claim binds any of these steps to a named population.
What is missing or unclear◇Read from sources, not yet reviewed
Were people like you studied?
RNAWiki cannot tell whether a study fits you. It can show who was in it, and where the result stops carrying.
Who was studied
People similar to this profile were included.
Adults and children from two years, sold without a prescription in the United States since November 2002 and now among the cheapest medicines in any pharmacy.
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
Loratadine ranked third of four on quality of life, behind cetirizine and behind its own metabolite
The 2002 Swedish hypospadias signal did not control for family history or maternal age and was not reproduced
A 1,095-patient phase 3 four-arm combination trial has never posted results
There is no stronger version of the drug to escalate to, because the marketed strength is the sedation ceiling
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, rapidly disintegrating tablet, chewable tablet and oral solution, plus extended-release combinations with pseudoephedrine
✎ Source-linked record
Where this came from
A person wrote this into the record with the study named beside it. No reviewer has signed it off.
The form and route recorded on this substance.
No source is stored against this line.
Who oversees it
RNAWiki has not recorded a supervision or regulatory status for this substance.
❝ Quoted from a source
Where this came from
Copied from a source RNAWiki stored, with the source named.
No register row and no identity class settled the question.
No source is stored against this line.
What is in the pack
One dose daily at a single marketed strength. The rapidly disintegrating form exists for people who cannot swallow a tablet rather than for faster onset. The label instructs that the directed amount not be exceeded, because more of it may cause drowsiness.
✎ 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
Among the most benign labels of any drug in this batch. The over-the-counter label carries no driving warning, no alcohol warning and no contraindication other than prior allergic reaction to the product. Its two substantive cautions are a direction not to exceed the stated amount, because doing so may cause drowsiness, and an instruction to consult a clinician in liver or kidney disease, which follows from the drug’s dependence on hepatic conversion to desloratadine and renal clearance. Pregnancy safety was the subject of a hypospadias signal in 2002 that a national birth defects study did not reproduce.
Nobody counted how many people took this and were fine, so this cannot be turned into a rate.
Centers for Disease Control and Prevention. Evaluation of an association between loratadine and hypospadias — United States, 1997-2001. MMWR Morb Mortal Wkly… · 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, rapidly disintegrating tablet, chewable tablet and oral solution, plus extended-release combinations with pseudoephedrine
✎ 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 rapidly disintegrating form exists for people who cannot swallow a tablet rather than for faster onset. The label instructs that the directed amount not be exceeded, because more of it may cause drowsiness.
✎ 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
457 products list this as an active ingredient in the United States drug directory. 403 of them contain it and nothing else.
FDA National Drug Code directory · 72288-511 · read 2026-08-29
They are sold as capsule, capsule, liquid filled, powder, solution, tablet and tablet, chewable, taken oral.
FDA National Drug Code directory · 72288-511 · read 2026-08-29
409 published labels name it as an active ingredient. 359 of them describe this substance alone, which is where its own label text on this page comes from.
US prescribing information · f59f3400-da77-4eb7-be02-842071d87fae · read 2026-08-29
Those labels are classed as human otc drug and human prescription drug.
US prescribing information · f59f3400-da77-4eb7-be02-842071d87fae · read 2026-08-29
Loratadine is oral at How Supplied/ Storage and Handling Loratidine is supplied as: Bottles of 30 Tablets NDC: 80425-0352-01 store at 20-25°C (68-77°F) (see USP Controlled Room Temperature), recorded as fda label in effect 2024-12-31 in the United States.
US prescribing information · 01cb43cf-57a9-f189-e063-6294a90afd88 · read 2026-09-12
Recorded price in US: 0.04132 USD per one millilitre, across 2 priced products whose strengths and pack forms differ, as of 2026-08-26, paid by retail pharmacies buying the product, as surveyed by the Centers for Medicare & Medicaid Services. It is not a list price, an insurance price, or what anyone pays at a counter..
Recorded source · 2026-08-26 · read 2026-08-28
Recorded price in US: 0.05315–0.5326 USD per one unit as the pricing file counts it — a tablet, capsule, patch or single item, across 32 priced products whose strengths and pack forms differ, as of 2026-08-26, paid by retail pharmacies buying the product, as surveyed by the Centers for Medicare & Medicaid Services. It is not a list price, an insurance price, or what anyone pays at a counter..
Recorded source · 2026-08-26 · read 2026-08-28
Evidence carries across two names for one substance. It does not carry across a salt, a mirror form or a mixture.
What it would be like to take◇Read from sources, not yet reviewed
What you could measure
This one is decided with a clinician, so this section holds questions to ask rather than a plan to run.
RNAWiki could not confidently classify this substance, so no self-experiment plan is offered.
Questions worth asking
Which of the trials of Loratadine 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 loratadine is intrinsically non-sedating rather than sold at a non-sedating amount — its label warns that exceeding the amount may cause drowsiness
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 metabolite is therapeutically superior to the parent — the pooled estimates sit inside each other’s confidence intervals while the price differs fivefold
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 loratadine causes hypospadias — the registry signal was not reproduced in a national case-control analysis
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 ranking of these four drugs is established — the confidence intervals overlap and only one outcome was pooled
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 Loratadine 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.
It beats placebo, at roughly half the effect size of cetirizine
In plain words
A network meta-analysis pooled thirteen trials in nearly seven thousand people and compared four allergy drugs on how much they improved quality of life. All four beat placebo. Cetirizine came first and this drug came third, at about half the improvement.
What was measured
Mean change in rhinoconjunctivitis quality of life questionnaire score against placebo, network meta-analysis of 13 trials
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
A network meta-analysis of randomised controlled trials in allergic rhinitis identified 386 studies and included 13 high-quality randomised trials with a combined 6,867 patients across loratadine, cetirizine, montelukast and desloratadine, using rhinoconjunctivitis quality of life questionnaire scores as the outcome. Against placebo, mean differences were: cetirizine -0.62 (95% CI -0.90 to -0.34, p<0.001); desloratadine -0.39 (95% CI -0.60 to -0.18, p<0.001); loratadine -0.32 (95% CI -0.55 to -0.097, p=0.005); montelukast -0.28 (95% CI -0.54 to -0.023, p=0.033). Surface-under-the-cumulative-ranking analysis placed cetirizine first. The loratadine and cetirizine confidence intervals overlap between -0.34 and -0.55, so the ranking is a point-estimate ordering rather than a demonstrated separation.
Written into the record, not signed off as a reviewed claim
The strength is set at the sedation threshold, and the label says what happens above it
In plain words
This drug is famous for not making people sleepy. The reason is the number on the box: it is the amount that stays below the point where the molecule starts affecting the brain. The label states plainly that taking more than directed may cause drowsiness.
What was measured
That loratadine is intrinsically a non-sedating molecule rather than a molecule sold at a non-sedating amount — its own label states that exceeding the marketed amount may cause drowsiness, and no higher strength exists to test what it would do for symptoms
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
The over-the-counter label carries, under "When using this product", the statement: "do not take more than directed. Taking more than directed may cause drowsiness." No higher strength of loratadine is marketed. The structural basis is the ethyl carbamate cap on the piperidine nitrogen, which lowers basicity and raises polarity enough to limit central nervous system penetration at the marketed exposure — a property that is a function of amount rather than an absolute. The clinical consequence is visible in the comparative data: in the network meta-analysis the point estimate for loratadine was roughly half that of cetirizine, and cetirizine is the drug that carries the sedation warning loratadine does not. What no public dataset establishes is what a higher loratadine strength would have achieved on symptoms, because no such strength was developed for sale.
Source
Loratadine over-the-counter prescribing information, "When using this product" section, via openFDA drug labelling; Xiao J et al., Am J Ther 2016;23:e1568-e1578
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
The hypospadias alarm of 2002 did not survive a national birth defects study, and a mouse study kept it alive
In plain words
A Swedish study reported that boys born to women who took this drug in pregnancy had twice the usual rate of a urethral birth defect. A large United States birth defects study then found no increased risk. A mouse experiment afterwards did produce the defect, which is why the question has never fully closed.
What was measured
That loratadine causes hypospadias — an uncontrolled registry signal that a national case-control study did not reproduce, complicated rather than settled by a mouse model showing oestrogen-like disruption of urethral development
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
In 2002 a Swedish study reported hypospadias prevalence twice that of the general population among male infants born to women who took loratadine during pregnancy; it had insufficient data to determine severity and did not control for confounders such as family history or maternal age. In 2003 a prospective study across four countries found five of 142 loratadine-exposed pregnancies resulted in major malformations, a prevalence consistent with the general population, and none of them hypospadias. The CDC then analysed the National Birth Defects Prevention Study for 1997 to 2001 and determined that no increased risk for second- or third-degree hypospadias existed among women who used loratadine in early pregnancy; that report carries a published erratum. Separately, in 2006 a mouse study gavaging pregnant dams with over-the-counter loratadine syrup from gestational day 12 to 17 reported disrupted urethral development on gross and histological assessment and a steroid receptor messenger RNA expression profile resembling that produced by ethinyl estradiol, and it drew a published comment and author reply.
Written into the record, not signed off as a reviewed claim
The active metabolite became a new prescription brand eleven months before the parent went over the counter
In plain words
What your liver turns this drug into was launched as a separate prescription medicine in December 2001. The original drug moved to the open shelf in November 2002. The sequence put a new branded product in place before the old one lost its prescription status.
What was measured
That the metabolite is a therapeutic advance over its parent — the pooled comparison places the two within each other’s confidence intervals, while the price and prescription status differ by a factor of five
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
Clarinex, desloratadine, was approved under NDA 021165 on 21 December 2001. The over-the-counter efficacy supplement to Claritin’s NDA 019658 was approved on 27 November 2002, and Alavert followed under NDA 021375 on 19 December 2002. Desloratadine is the active metabolite formed from loratadine by hepatic cytochrome P450 conversion, so the two are pharmacologically continuous rather than distinct. In the network meta-analysis of allergic rhinitis quality of life, desloratadine improved scores by -0.39 (95% CI -0.60 to -0.18) against loratadine’s -0.32 (95% CI -0.55 to -0.097) — a difference lying well inside the overlap of the two intervals. Twenty-four years later loratadine costs $0.0532 per unit as a generic and desloratadine $0.2553, roughly five times as much, and remains prescription-only.
Written into the record, not signed off as a reviewed claim
Its activity depends on the liver converting it, and the label reflects that
In plain words
Loratadine is largely a starting material: the liver strips off part of the molecule to make the form that does most of the work. That is why the label singles out liver and kidney disease as reasons to check with a doctor.
What was measured
Labelled hepatic and renal cautions, and the existence of the metabolite as a separately approved product
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
Loratadine bears an ethyl carbamate on the piperidine nitrogen which hepatic cytochrome P450 enzymes remove to yield desloratadine, itself an approved active drug. The over-the-counter label instructs: "Ask a doctor before use if you have liver or kidney disease. Your doctor should determine if you need a different dose." That caution is unusual on a monograph-style antihistamine label and follows directly from the metabolic dependence: anything that inhibits the converting enzymes, or impairs renal clearance of the metabolite, shifts exposure. This is a difference of kind from fexofenadine, which is excreted largely unchanged and has no meaningful hepatic enzyme interactions.
Source
Loratadine over-the-counter prescribing information, "Ask a doctor before use" section, via openFDA drug labelling; Drugs@FDA CLARINEX (desloratadine) NDA 021165
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 1,095-patient phase 3 combination trial has no public result
In plain words
The manufacturer ran a phase 3 trial of this drug combined with montelukast against a decongestant and a placebo, in over a thousand people with hay fever. The registry entry has no results.
What was measured
That the published trial set characterises this drug’s performance in combination and against an active decongestant, when a 1,095-patient phase 3 designed to answer that has never reported
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
NCT00319995, "Efficacy and Safety of Combination Loratadine/Montelukast QD vs Pseudoephedrine and Placebo in the Treatment of Subjects With Seasonal Allergic Rhinitis", is a phase 3 study with an actual enrolment of 1,095 sponsored by Organon. The registry record carries no posted results section. A four-arm comparison of that size against both an active decongestant and placebo would be among the more informative datasets on how an oral antihistamine performs on nasal congestion specifically, which is the symptom the class relieves least well.
Source
NCT00319995 registry record, Organon — actual enrolment 1,095, no results posted
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
Where else this substance is registered
FDA substance identifier (UNII)
7AJO3BO7QN
CAS registry number
79794-75-5
PubChem compound
3957
RxNorm concept
28889
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Trial roles classified for highlighted evidence
No registered study is classified as testing this substance.
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No register row and no identity class settled the question.
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Canonical metadata present
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What is missing or unclear◇Read from sources, not yet reviewed
How this medicine reached us
Kept near the foot of the page. A historical event moves up only when it changes something about this substance today.
What the approval register records
56 approved applications cover products containing this substance. The earliest was NDA019658, approved 19930412 to BAYER HEALTHCARE LLC.
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What is not here
7 questions this page could not answer
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How close this is to real life — found nothing in the sources checked.
Felt, measured, or meaningful — found nothing in the sources checked.
How long anything takes — found nothing in the sources checked.
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Other ways to the same goal — found nothing in the sources checked.
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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 tricyclic H1 antagonist that reliably beats placebo without sedating at the one strength it is sold in — a network meta-analysis of 13 randomised trials in 6,867 patients put its improvement in rhinoconjunctivitis quality of life at -0.32 (95% CI -0.55 to -0.097, p=0.005) against cetirizine’s -0.62 (95% CI -0.90 to -0.34), and its own over-the-counter label states that taking more than directed may cause drowsiness.
Recorded evidence blocks (7)
Q1
On the Loratadine label: indicated for what?
"USE(S) temporarily relieves these symptoms due to hay fever or other upper respiratory allergies: runny nose sneezing itchy, water eyes itching of the nose or throat": indications and usage on Loratadine's label. DailyMed label · 0d74af21-3ef7-418b-a2ef-78737b0af288 · 2025-06-13
Q2
55 registered trials of Loratadine — at which phases?
Registered studies posting no result
35 of 55
55 registered studies of Loratadine: 16 phase2, 15 phase4, 9 phase3, 8 phase1, 4 na, 2 early phase1, 2 na or unstated. CLINICALTRIALS_SNAPSHOT · 2026-09-01
356 with a PubMed record
Show the evidence
phase2
16
phase4
15
phase3
9
phase1
8
na
4
early phase1
2
7 more recorded rows
na or unstated
2
completed
35
unknown
8
recruiting
5
terminated
4
not yet recruiting
2
withdrawn
1
recorded 2026-09-01 · last checked 2026-09-04
Q3
5 of Loratadine's trials stopped: accrual/recruitment, funding/business, other?
"Original PI left institution."; 5 of 55 registered studies
Show the evidence
Trial
NCT00927329
withdrawn; "Original PI left institution."
NCT01390441
terminated; "The study was terminated early by the Sponsor for business reasons."
NCT02392039
terminated; "Slow Accrual"
NCT03883386
terminated; "Poor enrollment"
NCT04248712
terminated; "low enrollment"
recorded 2026-09-01 · last checked 2026-09-04
Q4
Human studies of Loratadine used Loratadine Syrup 1 mg/mL Rescue Treatment — over how long?
Human studies of Loratadine used "Loratadine Syrup 1 mg/mL Rescue Treatment". ClinicalTrials.gov · 2026-09-01
7 recorded entries; human; also "Loratadine 10 mg Rescue Treatment", "Loratadine 10 Mg", "loratadine 10 mg"
Show the evidence
human
NCT00550550
Loratadine Syrup 1 mg/mL Rescue Treatment
NCT00550550
Loratadine 10 mg Rescue Treatment
NCT03640273
Loratadine 10 Mg
NCT05265910
loratadine 10 mg
NCT06217367
10 mg Loratadine
NCT06217367
5 mg Desloratadine
1 more recorded row
humanNCT07575464
Loratadine 10mg
recorded 2026-09-01 · last checked 2026-09-04
Q5
Which 16 trials of Loratadine posted no result?
Posted no result
16 of 16 completed trials
Registrations
NCT02932774, NCT00963573, NCT00762983, NCT02513290, NCT02593747 and NCT03151720, and 10 more
Completion dates
oldest 2001-07; newest 2022-10-31
Show the evidence
Trial
NCT02932774
2001-07
NCT00963573
2006-11
NCT00762983
2009-02
NCT02513290
2014-08
NCT02593747
2016-03
NCT03151720
2017-07-08
10 further recorded trials
NCT02305979
2017-09
NCT02576808
2017-10
NCT03196531
2018-03-31
NCT03376594
2018-03-31
NCT02339714
2018-06
NCT03640273
2018-06-24
NCT02583594
2021-03-01
NCT05265910
2022-04-23
NCT05043350
2022-07-30
NCT05750875
2022-10-31
Q6
At the median, Loratadine's trials enrolled 88 people — anything larger?
Median enrolment
88
Largest enrolment
1025
Registered trials counted
55
Q7
What do 1792 spontaneous reports say about Loratadine — 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.
Loratadine appears in spontaneous reports to regulators. Across the 10 most-reported reaction terms, 1792 reaction mentions were counted: somnolence 328; extra dose administered 252; coma 210; gastrooesophageal reflux disease 196. FAERS via Open Targets · CHEMBL998 · 2026-06-24
Show the evidence
somnolence
328
extra dose administered
252
coma
210
gastrooesophageal reflux disease
196
pneumonia aspiration
189
drug hypersensitivity
179
4 more recorded rows
accidental exposure to product by child
170
urticaria
126
angioedema
75
suicide attempt
67
recorded 2026-06-24 · last checked 2026-09-04
Where it is registeredIdentifiers, relations and other names
ChEMBL 37 — CC BY-SA 3.0 Unported · ChEMBL ATC CC BY-SA · ClinicalTrials.gov — US Government work · Open Targets 26.06 — CC0 · mixed register set; per-register licences in docs/specs/corpus-20k-sources.md · openFDA / DailyMed — US Government work
✗ required summary fields resolved: 4 required field(s) not terminal: Why people use it, Best-supported result, Biggest unanswered question, Human evidence
✓ public claims reviewed: 0 reviewed claim(s); drafts are never rendered
✓ source coverage passed: 6 source rows
✓ no critical contamination: no quarantine open
✓ canonical metadata passed: slug and display name present
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