This page shows what was measured, who it was measured in, and what that does not settle.
What Tamsulosin does in the body
A weak, slow or hesitant urine stream, and getting up at night, caused by an enlarged prostate
The prostate is not just bulk pressing on the urethra. It is also muscle, held permanently tense by nerve signals, and that tension squeezes the tube urine flows through. Tamsulosin blocks the receptor those nerve signals act on, so the muscle in the prostate and at the neck of the bladder relaxes and the channel widens. The gland itself is exactly the same size afterwards, which is why the effect starts within hours and disappears within days of stopping.
What happened in people
AUA symptom score fell 8.3 and 5.1 points on 0.4 mg in the two US registration studies, against 5.5 and 3.6 on placebo
✎ Source-linked record
Where this came from
A person wrote this into the record with the study named beside it. No reviewer has signed it off.
The recorded finding that sits closest to something a person would notice. Written into the record, not signed off, and it carries no population or interval.
That relaxing prostatic smooth muscle also expels ureteric stones — SUSPEND randomised 1,136 analysed patients and found an adjusted risk difference of 1.3% (p=0.73)
Where it acts
Smooth muscle of the prostatic stroma, prostatic urethra and bladder neck
Kind of result
Symptoms and quality of life
Supervision
RNAWiki has not recorded a supervision or regulatory status for this substance.
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 126 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.
Change in AUA symptom score and peak urine flow rate versus placebo
Statistically significant improvement in all efficacy parameters versus placebo; the long-term extension reports P < 0.001 for AUA symptom score change from baseline in all groups
Repeated elsewhere
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. Intraoperative floppy iris syndrome was not an endpoint, was not looked for, and was not described until 2005. Abnormal ejaculation was captured, at 8.4% on 0.4 mg against 0.2% on placebo.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Oral modified-release capsule, taken once daily
Interval reported. Not recorded in this summary
Written into the record, not signed off as a reviewed claim.
CombAT — Combination of Avodart and Tamsulosin, 4-year randomised trial (NCT00090103) · a recorded source, not a stored snapshot
Relative risk of acute urinary retention or BPH-related surgery with combination therapy versus each monotherapy
✗ The study did not show it
Who was studied
CombAT (NCT00090103)
How many people
4844
Study design
Phase 3 randomised double-blind, 4 years
Compared against
Not recorded for this study
Kind of result
A number that stands in for health
What was found
Combination was significantly superior to tamsulosin monotherapy but not to dutasteride monotherapy for acute urinary retention or BPH-related surgery
Repeated elsewhere
Replicated
What this does not prove. A study that did not show an effect does not show that no effect exists anywhere.
The limits of this study, and where it came from
Main limit. The published report notes an imbalance in the composite term of cardiac failure across the three arms. `endpoint met: false` here records that tamsulosin monotherapy was the arm that lost, not that the trial failed.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Oral modified-release capsule, taken once daily
Interval reported. Not recorded in this summary
Written into the record, not signed off as a reviewed claim.
CombAT — Combination of Avodart and Tamsulosin, 4-year randomised trial (NCT00090103) · a recorded source, not a stored snapshot
Proportion of participants needing no further intervention for stone clearance within four weeks
✗ The study did not show it
Who was studied
SUSPEND (medical expulsive therapy for ureteric colic)
How many people
1136
Study design
Randomised double-blind placebo-controlled, 24 UK hospitals, 4 weeks
Compared against
A dummy treatment
Kind of result
A number that stands in for health
What was found
P = 0.73 for tamsulosin versus placebo (adjusted risk difference 1.3%, 95% CI -5.7 to 8.3)
Repeated elsewhere
Failed to Replicate
What this does not prove. A study that did not show an effect does not show that no effect exists anywhere.
The limits of this study, and where it came from
Main limit. The 1,167 randomised included participants without primary-outcome data; the analysed comparison is 379 placebo, 378 tamsulosin and 379 nifedipine. The health technology assessment of the same trial found no QALY or cost difference either.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Oral modified-release capsule, taken once daily
Interval reported. 95% CI -5
Written into the record, not signed off as a reviewed claim.
CombAT — Combination of Avodart and Tamsulosin, 4-year randomised trial (NCT00090103) · a recorded source, not a stored snapshot
Change in AUA symptom score index versus terazosin
✗ The study did not show it
Who was studied
FLOMAX versus HYTRIN head-to-head (NCT02244255)
How many people
1993
Study design
Phase 4 randomised comparison
Compared against
Not recorded for this study
Kind of result
A number that stands in for health
What was found
No result posted. The registry entry records completion with no results section and no linked publication.
Repeated elsewhere
Unreplicated
What this does not prove. A study that did not show an effect does not show that no effect exists anywhere.
The limits of this study, and where it came from
Main limit. A 1,993-man head-to-head against the older, cheaper drug in the same class, completed and never reported. `endpoint met: false` here means no result exists, not that the endpoint was missed.
How far it carries. This study is recorded from the curated record, not from the registry match.
Form and route. Oral modified-release capsule, taken once daily
Interval reported. Not recorded in this summary
Written into the record, not signed off as a reviewed claim.
CombAT — Combination of Avodart and Tamsulosin, 4-year randomised trial (NCT00090103) · a recorded source, not a stored snapshot
What we know
RNAWiki holds 4 written-up human studies for this substance, each with the question it asked.
How we know it
Each card names the study, the number of people and what the study set out to measure.
What this does not prove
These summaries were written by a person and have not been signed off as reviewed claims.
Why it matters
A study that failed is as informative as one that worked, and both are here.
What we still do not know
No reviewed claim exists, so no exact population, effect size or interval is published yet.
What it changes in the body◇Read from sources, not yet reviewed
The path through the body
From what a person takes to what changes. A solid line is a step measured in people. A dashed line is a step nobody has measured that way.
Where a source records it acting
Pelvic and reproductive organs: An alpha 1 adrenoceptor blocking agent that exhibits selectivity for alpha 1 receptors in the human prostate, most of which are of the alpha 1A subtype
US prescribing information · 00097e78-9c04-4e62-8260-ddb50e9a6a93 · read 2026-08-28
Bladder and urinary tract: Blockade of alpha 1 adrenoceptors abundant in the prostatic urethra and bladder neck can cause smooth muscles in the bladder neck and prostate to relax, improving urine flow rate
US prescribing information · 00097e78-9c04-4e62-8260-ddb50e9a6a93 · read 2026-08-28
Start
Tamsulosin
What a person takes: Oral modified-release capsule, taken once daily.
The measurement behind this step
The modified-release formulation exists to blunt the peak concentration after each dose, which is what drives the dizziness and orthostatic effects. The label instructs administration approximately 30 minutes after the same meal each day, because food alters the absorption profile and consistency matters more than timing.
Getting in
Swallowed, absorbed slowly, and carried almost entirely on protein
The capsule is designed to release slowly so the drug level rises gently rather than spiking. Almost all of what enters the blood is stuck to a carrier protein, and only the small free fraction can do anything.
──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
Modified-release capsule; 94% to 99% bound to plasma proteins, chiefly alpha-1 acid glycoprotein. Apparent half-life 9 to 13 hours in healthy volunteers and 14 to 15 hours in the target population. Metabolised by CYP3A4 and CYP2D6, which is why strong inhibitors of either raise exposure.
It reaches the prostate without ever entering a cell
The target sits on the outside surface of the muscle cell, facing the bloodstream. The drug never has to get inside anything — it simply arrives at the surface and sits on the receptor.
──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
Alpha-1 adrenoceptors are G-protein-coupled receptors in the plasma membrane with an extracellular-facing orthosteric pocket. There is no transporter step and no intracellular accumulation requirement, which is the structural reason the effect appears within hours of the first dose and fades within days of stopping.
Nerve endings in the prostate constantly release a signal that tells the muscle to stay tense. Tamsulosin sits in the receptor that signal binds to, so the message stops arriving.
──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
Competitive antagonism at the alpha-1A adrenoceptor, with preference over the alpha-1B subtype that predominates in vasculature. The label gives the anatomical basis: roughly 70% of alpha-1 receptors in the human prostate are alpha-1A. Alpha-1D antagonism in the bladder body probably contributes to the storage symptoms that improve.
The calcium signal that holds the muscle tense stops
Tension in smooth muscle is maintained by a continuous internal calcium signal. With the receptor blocked, that signal falls and the muscle lets go.
╌╌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
Loss of Gq/11 coupling ends phospholipase C activation, so inositol trisphosphate falls, sarcoplasmic reticulum calcium release drops and myosin light-chain kinase activity declines. Prostatic stromal and bladder-neck smooth muscle relaxes. The prostate is not reduced in volume by any amount.
The outlet widens, flow rises, the score falls — and the gland is unchanged
Urine meets less resistance leaving the bladder. Flow rate rises by under two millilitres a second on average, and the symptom questionnaire improves by a few points more than placebo.
╌╌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
Peak flow rose 1.75 and 1.52 mL/sec over baseline in the two registration studies against 0.52 and 0.93 on placebo, with AUA symptom score falling 8.3 and 5.1 against 5.5 and 3.6. Because only the dynamic component of obstruction is addressed, four years of monotherapy in CombAT did not deliver the retention and surgery reduction that shrinking the gland did.
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.
Men with moderate to severe lower urinary tract symptoms attributed to benign prostatic hyperplasia. It is the most prescribed drug in its class in the United States and is also widely given off-label to help ureteric stones pass, a use the largest randomised trial did not support.
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: “Tamsulosin hydrochloride capsules are not indicated for use in pediatric populations.”
US prescribing information · f543f5d1-3348-4066-99a4-7a00aee1530d · read 2026-08-30
On older people, the label states: “Of the total number of subjects (1783) in clinical studies of tamsulosin, 36% were 65 years of age and over.”
US prescribing information · f543f5d1-3348-4066-99a4-7a00aee1530d · read 2026-08-30
On people who are pregnant, the label states: “Risk Summary Tamsulosin hydrochloride is not indicated for use in women.”
US prescribing information · f543f5d1-3348-4066-99a4-7a00aee1530d · read 2026-08-30
On people who are breastfeeding, the label states: “8.3 Females and Males of Reproductive Potential Infertility Males Abnormal ejaculation including ejaculation failure, ejaculation disorder, retrograde ejaculation, and ejaculation decrease has been associated with tamsulosin hydrochloride [ see Clinical Trials Experience (6.1) ] .”
US prescribing information · f543f5d1-3348-4066-99a4-7a00aee1530d · read 2026-08-30
On people with reduced liver function, the label states: “Patients with moderate hepatic impairment do not require an adjustment in tamsulosin hydrochloride capsules dosage.”
US prescribing information · f543f5d1-3348-4066-99a4-7a00aee1530d · read 2026-08-30
On people with reduced kidney function, the label states: “Patients with renal impairment do not require an adjustment in tamsulosin hydrochloride capsules dosing.”
US prescribing information · f543f5d1-3348-4066-99a4-7a00aee1530d · read 2026-08-30
Where the result stopped carrying
Medical expulsive therapy for ureteric colic: a decade of routine off-label use, supported by meta-analyses of small trials, overturned by one adequately powered trial
Tamsulosin monotherapy over four years in CombAT, which was the arm combination therapy beat on retention and surgery
The 1,993-man head-to-head against terazosin, completed and never published, leaving the comparison with the cheaper older drug unresolved in the public record
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 modified-release capsule, taken once daily
✎ Source-linked record
Where this came from
A person wrote this into the record with the study named beside it. No reviewer has signed it off.
The form and route recorded on this substance.
No source is stored against this line.
Who oversees it
RNAWiki has not recorded a supervision or regulatory status for this substance.
❝ Quoted from a source
Where this came from
Copied from a source RNAWiki stored, with the source named.
No register row and no identity class settled the question.
No source is stored against this line.
What is in the pack
The modified-release formulation exists to blunt the peak concentration after each dose, which is what drives the dizziness and orthostatic effects. The label instructs administration approximately 30 minutes after the same meal each day, because food alters the absorption profile and consistency matters more than timing.
✎ 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.
The recorded stepping schedule
What follows is the schedule printed on the label, recorded as it is written there. It is a record of what was done, not a recommendation.
US prescribing information · 00097e78-9c04-4e62-8260-ddb50e9a6a93 · read 2026-08-28
Recorded starting amount: 0.4 mg once daily taken approximately one-half hour following the same meal each day
US prescribing information · 00097e78-9c04-4e62-8260-ddb50e9a6a93 · read 2026-08-28
After 2 to 4 weeks of dosing, for those who fail to respond to 0.4 mg: Can be increased to 0.8 mg once daily
US prescribing information · 00097e78-9c04-4e62-8260-ddb50e9a6a93 · read 2026-08-28
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
Commonest effects are dizziness, abnormal ejaculation and rhinitis. Orthostatic hypotension and syncope can occur, particularly at initiation and on restarting after an interruption, and claims data show the risk concentrated in the first eight weeks. The label carries warnings for intraoperative floppy iris syndrome in cataract and glaucoma surgery, for priapism, and for concomitant use with strong CYP3A4 inhibitors. It states explicitly that the drug is not indicated for hypertension.
Nobody counted how many people took this and were fine, so this cannot be turned into a rate.
Over a long time. No completed tested study window is recorded, so long-term effects are not established by the registry record.
Groups the studies covered thinly. Which groups were under-represented in the studies has not been recorded for this substance. Pregnancy, breastfeeding, children, older adults, and people with liver or kidney conditions are commonly excluded from trials; nothing here says whether they were.
What is missing or unclear◇Read from sources, not yet reviewed
Does the exact form matter?
Evidence belongs to the exact thing that was tested. A different salt, a different mixture or a different preparation is a different question.
The form that was studied
Oral modified-release capsule, taken once daily
✎ 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 label instructs administration approximately 30 minutes after the same meal each day, because food alters the absorption profile and consistency matters more than timing.
✎ 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
81 products list this as an active ingredient in the United States drug directory. 76 of them contain it and nothing else.
FDA National Drug Code directory · 0904-7383 · read 2026-08-29
They are sold as capsule, capsule, gelatin coated and powder, taken oral.
FDA National Drug Code directory · 0904-7383 · read 2026-08-29
The regulator's established pharmacologic class for it is adrenergic alpha-antagonists [moa] and alpha-adrenergic blocker [epc].
FDA National Drug Code directory · 0904-7383 · read 2026-08-29
67 published labels name it as an active ingredient. 63 of them describe this substance alone, which is where its own label text on this page comes from.
US prescribing information · f543f5d1-3348-4066-99a4-7a00aee1530d · read 2026-08-29
Those labels are classed as human prescription drug.
US prescribing information · f543f5d1-3348-4066-99a4-7a00aee1530d · read 2026-08-29
Tamsulosin Hydrochloride is hard gelatin capsules at Capsule: 0.4 mg, recorded as prescription product; fda label in effect 2026-01-01 in the United States.
US prescribing information · 00097e78-9c04-4e62-8260-ddb50e9a6a93 · read 2026-08-28
Recorded price in US: 0.05093 USD per one unit as the pricing file counts it — a tablet, capsule, patch or single item, across 26 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 Tamsulosin 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 relaxing prostatic smooth muscle also expels ureteric stones — SUSPEND randomised 1,136 analysed patients and found an adjusted risk difference of 1.3% (p=0.73)
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 tamsulosin causes dementia — a Medicare hazard ratio of 1.17 that appears against every comparator including finasteride, and vanishes in the Korean national database (HR 1.038 versus doxazosin)
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 symptom-score improvement predicts avoided retention or avoided surgery — four years of CombAT show it does not for this arm
Why it sounds right. It follows from something real on this page: a body step, an animal result or a related finding.
The missing step. Nobody measured this in people for this use, or the study that did measure it did not show it.
What would change this
A study in people, for this exact use, measuring this exact thing, that a reviewer signs off.
RNAWiki has not yet published a reviewed conclusion for this use.
✗Goes past the evidence
That being the alpha-blocker which "does not lower blood pressure" means no hypotension risk; the first-dose and restart windows are measurable in claims data
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 Tamsulosin 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.
A real symptom effect over placebo, roughly two to three points on a 35-point scale
In plain words
In the two American registration trials, men on tamsulosin improved more than men on placebo. The placebo groups also improved substantially, and the difference between them was around two to three points on a scale that runs to 35.
What was measured
Change from baseline in AUA symptom score and in peak urine flow rate at 13 weeks, against placebo
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
The US label reports both pivotal studies. In Study 1 the AUA symptom score fell 8.3 ± 6.5 points on 0.4 mg and 9.6 ± 6.7 on 0.8 mg, against 5.5 ± 6.6 on placebo; in Study 2 it fell 5.1 ± 6.4 and 5.8 ± 6.4 against 3.6 ± 5.7. Peak urine flow rose 1.75 ± 3.57 and 1.78 ± 3.35 mL/sec in Study 1 against 0.52 ± 3.39 on placebo, and 1.52 ± 3.64 and 1.79 ± 3.36 in Study 2 against 0.93 ± 3.28. The Lepor phase 3 report of 756 randomised patients describes onset of action on peak flow within 4 to 8 hours of the first 0.4 mg dose. The placebo change is the number readers are least often shown and does two-thirds of the work in Study 1.
Written into the record, not signed off as a reviewed claim
Four years of tamsulosin alone did not prevent retention or surgery in CombAT
In plain words
The largest long-term trial of this drug compared it with a prostate-shrinking drug and with both together. On the outcomes that matter — needing a catheter for retention, or needing an operation — tamsulosin alone was the arm that lost.
What was measured
Relative risk of acute urinary retention or BPH-related surgery over four years, by treatment arm
Effect estimate
No reviewed effect estimate exists for this record.
Limits
This entry records a failure.
From the source
CombAT (NCT00090103) randomised 4,844 men aged 50 and over with an International Prostate Symptom Score of 12 or more, prostate volume of 30 cm3 or more and PSA between 1.5 and 10 ng/mL, to dutasteride 0.5 mg, tamsulosin 0.4 mg, or both, for four years. Combination therapy was significantly superior to tamsulosin monotherapy at reducing the relative risk of acute urinary retention or BPH-related surgery, but was not superior to dutasteride monotherapy for that endpoint. Combination was superior to both monotherapies for BPH clinical progression and for symptom score at four years. The published report also notes an imbalance in the composite term of cardiac failure across the three arms.
Written into the record, not signed off as a reviewed claim
SUSPEND: tamsulosin does not help a kidney stone pass
In plain words
For years men with ureteric stones were given tamsulosin to help the stone come out, on the strength of small trials and meta-analyses. A 1,167-patient placebo-controlled trial across 24 UK hospitals found it made no difference at all.
What was measured
Proportion of patients needing no further intervention for stone clearance within four weeks
Effect estimate
No reviewed effect estimate exists for this record.
Limits
This entry records a failure.
From the source
SUSPEND randomised adults aged 18 to 65 with a single CT-confirmed ureteric stone of 10 mm or less to tamsulosin 400 µg, nifedipine 30 mg or placebo for up to four weeks. The primary outcome was the proportion needing no further intervention by four weeks. It was reached by 303 of 379 (80%) on placebo, 307 of 378 (81%) on tamsulosin (adjusted risk difference 1.3%, 95% CI -5.7 to 8.3, p=0.73) and 304 of 379 (80%) on nifedipine (0.5%, -5.6 to 6.5, p=0.88). The health technology assessment report of the same trial found no difference in quality-adjusted life-years or costs, and concluded medical expulsive therapy was unlikely to be cost-effective. The prior meta-analytic literature that established the practice had reported the opposite.
Written into the record, not signed off as a reviewed claim
Intraoperative floppy iris syndrome was invisible for eight years after approval
In plain words
In 2005, eight years after approval, two eye surgeons noticed that a specific and dangerous behaviour of the iris during cataract surgery was happening almost exclusively in men on tamsulosin. It is now on the label. It was on nobody's list before.
What was measured
Prevalence of intraoperative floppy iris syndrome in consecutive cataract series, by alpha-blocker exposure
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
Chang and Campbell reviewed 706 eyes from 511 consecutive cataract patients retrospectively and 900 consecutive cases from 741 patients prospectively. In the retrospective series, IFIS occurred in 10 of the 16 tamsulosin patients (63.0%) and in none of the 11 patients taking other systemic alpha-1 blockers. In the prospective series the prevalence of IFIS was 2.2% of 741 patients, and 15 of those 16 cases were current or former tamsulosin users. Overall IFIS prevalence in the retrospective series was 2.0%. The current US label carries the warning and instructs patients to tell their ophthalmologist about current or prior use before eye surgery. Nothing in the registration programme could have found this: cataract surgery is not an endpoint in a BPH trial.
Written into the record, not signed off as a reviewed claim
Severe hypotension roughly doubles in the first four weeks, and again on restarting
In plain words
Tamsulosin is marketed as the alpha-blocker that does not drop blood pressure. In a study of 297,596 new users, hospital admission for severe low blood pressure was about twice as likely during the first month, and the risk returned each time a man restarted the drug.
What was measured
Rate ratio for hospital admission with severe hypotension, by week since initiation
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
Bird and colleagues studied 383,567 new users in US healthcare claims — 297,596 starting tamsulosin and 85,971 starting a 5-alpha-reductase inhibitor as comparator — and identified 2,562 hospital admissions for severe hypotension. Incidence was 42.4 events per 10,000 person-years on tamsulosin against 31.3 on 5ARIs. Within the tamsulosin cohort, the rate ratio was 2.12 (95% CI 1.29 to 3.04) during weeks 1 to 4 and 1.51 (1.04 to 2.18) during weeks 5 to 8, with no significant increase at weeks 9 to 12. Comparable increases followed restarting the drug. The authors framed the finding as a first-dose phenomenon requiring counselling rather than as an argument against the drug.
Written into the record, not signed off as a reviewed claim
The dementia signal came from one claims database and did not replicate in another
In plain words
A large US Medicare analysis found 17% more dementia in tamsulosin users. A Korean national study designed to check it found no difference between tamsulosin and the other drugs in its class. Both are observational, and neither settles it.
What was measured
That tamsulosin causes dementia — a claims-database association that appears against every comparator, including drugs with unrelated mechanisms, and disappears in the national database assembled to test it
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
Duan and colleagues compared 253,136 tamsulosin users with propensity-matched Medicare cohorts over a median 19.8 months and reported dementia incidence of 31.3 per 1,000 person-years against 25.9 in men on no BPH medication, hazard ratio 1.17 (95% CI 1.14 to 1.21), with similar excesses against doxazosin, terazosin, alfuzosin, dutasteride and finasteride. Tae and colleagues then analysed 59,263 men in the Korean National Health Insurance Service database from 2011 to 2017 and found no difference between tamsulosin and doxazosin (HR 1.038, 95% CI 0.960 to 1.121) or alfuzosin (HR 1.008, 0.925 to 1.098). A signal that appears against every comparator including two drugs with entirely different mechanisms is the pattern confounding by indication produces, and no randomised trial has ever been powered for a dementia endpoint in this class.
Written into the record, not signed off as a reviewed claim
Abnormal ejaculation is dose-dependent and forty times the placebo rate
In plain words
At the usual dose, about one man in twelve reports abnormal ejaculation, against one in five hundred on placebo. At double the dose it is closer to one in five.
What was measured
Incidence of abnormal ejaculation by dose in the pooled registration trials
Effect estimate
No reviewed effect estimate exists for this record.
Limits
See the technical detail.
From the source
The pooled adverse-event table in the US prescribing information reports abnormal ejaculation in 42 of 502 patients (8.4%) on 0.4 mg once daily and 89 of 492 (18.1%) on 0.8 mg once daily, against 1 of 493 (0.2%) on placebo. The dose-response is close to linear and is mechanistic rather than idiosyncratic: seminal vesicle and vas deferens smooth muscle carries the same alpha-1A receptor the drug was designed to prefer. This is the clearest example on the page of an on-target effect that is therapeutic in one organ and an adverse event in another.
Source
US prescribing information for tamsulosin hydrochloride capsules, Adverse Reactions section, pooled 13-week placebo-controlled studies
Role in the trial
Not matched to a registered study
Identity check
no open identity hold
Audit mark
verified
Review state
Written into the record, not signed off as a reviewed claim
How many documents were read
62 documents were read for this substance.
RNAWiki source record
62 of them state the same halfLife, and they agree.
RNAWiki source record
62 of them state the same bioavailability, and they agree.
RNAWiki source record
62 of them state the same proteinBinding, and they agree.
RNAWiki source record
Where else this substance is registered
FDA substance identifier (UNII)
11SV1951MR
CAS registry number
106133-20-4
PubChem compound
129211
RxNorm concept
236495
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Trial roles classified for highlighted evidence
No registered study is classified as testing this substance.
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Canonical metadata present
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What is missing or unclear◇Read from sources, not yet reviewed
How this medicine reached us
Kept near the foot of the page. A historical event moves up only when it changes something about this substance today.
What the approval register records
21 approved applications cover products containing this substance. The earliest was NDA020579, approved 19970415 to SANOFI.
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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.
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The record as stored
The full record, for auditing
Everything above is built from what is below. This layer keeps the technical vocabulary, record identifiers and every stored row, so a reader who wants to check the page can.
The older medicine-wide conclusion held in this record
Written for a clinical reader, and about the medicine as a whole rather than about one indication, population and set of trials. RNAWiki does not treat it as a programme conclusion and no reviewer has signed it off in that form. It is here word for word because it is what the record holds.
An alpha-1A-selective blocker that relaxes prostate and bladder-neck muscle within hours without shrinking the gland at all: across the two US registration trials it lowered the AUA symptom score by 8.3 and 5.1 points against 5.5 and 3.6 on placebo, a genuine but modest margin that in four years of CombAT never translated into fewer episodes of urinary retention or fewer operations than dutasteride achieved.
Recorded evidence blocks (10)
Q1
On the Tamsulosin label: indicated for what?
"• Tamsulosin hydrochloride capsules are an alpha 1 adrenoceptor antagonist indicated for treatment of the signs and symptoms of benign prostatic hyperplasia ( 1 ) • Tamsulosin hydrochloride capsules are not indicated for the treatment of hypertension ( 1 ) Tamsulosin hydrochloride capsules, USP are indicated for the…": indications and usage on Tamsulosin's label. DailyMed label · e4202c52-be9d-41d9-b5ff-122740298544 · 2026-08-12
Q2
190 registered trials of Tamsulosin — at which phases?
Registered studies posting no result
148 of 190
190 registered studies of Tamsulosin: 56 phase4, 42 phase3, 33 phase1, 27 na, 26 phase2, 8 na or unstated, 5 early phase1. CLINICALTRIALS_SNAPSHOT · 2026-09-01
530 with a PubMed record
Show the evidence
phase4
56
phase3
42
phase1
33
na
27
phase2
26
na or unstated
8
9 more recorded rows
early phase1
5
completed
113
unknown
32
recruiting
20
terminated
12
withdrawn
5
not yet recruiting
4
active not recruiting
3
suspended
1
recorded 2026-09-01 · last checked 2026-09-04
Q3
17 of Tamsulosin's trials stopped: futility/efficacy, accrual/recruitment, funding/business, other?
futility/efficacy (2), accrual/recruitment (6), funding/business (1) and other (8): Tamsulosin's stop wording, clustered. CLINICALTRIALS_SNAPSHOT · 2026-09-01
"Due to frequent turnover of research coordinators and thus poor study accrual."; 17 of 190 registered studies
Show the evidence
Trial
NCT00209131
terminated; "Due to frequent turnover of research coordinators and thus poor study accrual."
NCT00687388
withdrawn; "in order to prepare a new clinical trial to evaluate with pathological change"
NCT01534351
terminated; "Business Reasons"
NCT01560091
withdrawn; "accrual of subjects did not occur as anticipated"
NCT01568918
terminated; "Slow recruitment and enrollment"
NCT01747993
terminated; "low inclusion"
11 further recorded trials
NCT02003742
terminated; "The study was stopped because in two other clinical studies the drug was not superior in comparison with placebo"
NCT02369744
terminated; "due to lack of suitable patient population"
NCT02483793
withdrawn; "The study was withdrawn prior to IRB approval and prior to enrollment. The study was never opened, and no participants were enrolled."
NCT02518971
terminated; "interim analysis revealed no significant difference between study groups \& increased sample size required to gain significance."
Tamsulosin's half-life is 5 to 7 hours — which schedules were studied?
5 to 7 hours, the half-life Tamsulosin's label states: "Following intravenous or oral administration of an immediate-release formulation, the elimination half-life of tamsulosin hydrochloride in plasma ranged from 5 to 7 hours." DailyMed label · e4202c52-be9d-41d9-b5ff-122740298544 · 2026-08-12
tmax 4 to 5 hours; bioavailability 30 %.
Show the evidence
half lifepharmacokinetics
5 to 7 hours; Following intravenous or oral administration of an immediate-release formulation, the elimination half-life of tamsulosin hydrochloride in plasma ranged from 5 to 7 hours.
tmaxpharmacokinetics
4 to 5 hours; Effect of Food The time to maximum concentration (T max ) is reached by 4 to 5 hours under fasting conditions and by 6 to 7 hours when tamsulosin hydrochloride capsules are administered with food.
bioavailabilitypharmacokinetics
30 %; Taking tamsulosin hydrochloride capsules under fasted conditions results in a 30% increase in bioavailability (AUC) and 40% to 70% increase in peak concentrations (C max ) compared to fed conditions (Figure 1).
metabolismpharmacokinetics
Metabolism There is no enantiomeric bioconversion from tamsulosin hydrochloride [R(-) isomer] to the S(+) isomer in humans.
recorded 2026-08-12 · last checked 2026-09-04
Q6
Which 56 trials of Tamsulosin posted no result?
Posted no result
56 of 56 completed trials
Registrations
NCT04552431, NCT01149746, NCT00151567, NCT00333112, NCT00510406 and NCT00600405, and 50 more
Completion dates
oldest 2003-08-31; newest 2024-08-30
Show the evidence
Trial
NCT04552431
2003-08-31
NCT01149746
2004-12
NCT00151567
2006-12
NCT00333112
2007-01
NCT00510406
2007-09
NCT00600405
2007-11
14 further recorded trials
NCT00359905
2008-01
NCT00457457
2008-04
NCT02634489
2009-07
NCT00771394
2010-01
NCT01953887
2010-07
NCT00606983
2010-09
NCT01489696
2011-02
NCT02715024
2011-04
NCT01657851
2012-12-05
NCT02072213
2014-01
NCT00824200
2014-03
NCT02038868
2014-04-04
NCT01880619
2014-07
NCT02169713
2014-08
Q7
At the median, Tamsulosin's trials enrolled 128 people — anything larger?
Median enrolment
128
Largest enrolment
14000
Registered trials counted
188
Q8
What do 1516 spontaneous reports say about Tamsulosin — 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.
Tamsulosin appears in spontaneous reports to regulators. Across the 10 most-reported reaction terms, 1516 reaction mentions were counted: dizziness 320; iris disorder 204; hypotension 190; syncope 166. FAERS via Open Targets · CHEMBL1200914 · 2026-06-24
Show the evidence
dizziness
320
iris disorder
204
hypotension
190
syncope
166
procedural complication
137
orthostatic hypotension
123
4 more recorded rows
loss of consciousness
109
urinary retention
101
miosis
95
cataract operation complication
71
recorded 2026-06-24 · last checked 2026-09-04
Q9
Which 10 reactions does Tamsulosin's label not list?
• Tamsulosin hydrochloride capsules, 0.4 mg should not be used with strong inhibitors of CYP3A4 (e.g., ketoconazole).
drug_interactions
Tamsulosin hydrochloride capsules should be used with caution in combination with moderate inhibitors of CYP3A4 (e.g., erythromycin), in combination with strong (e.g., paroxetine) or moderate (e.g., terbinafine) inhibitors of CYP2D6, or in patients known to be CYP2D6 poor metabolizers, particularly at a dose higher than 0.4 mg (e.g., 0.8 mg) ( 5.2 , 7.1 , 12.3 ) • Concomitant use of PDE5…
drug_interactions
Concomitant treatment with ketoconazole (a strong inhibitor of CYP3A4) resulted in an increase in the C max and AUC of tamsulosin by a factor of 2.2 and 2.8, respectively [see Warnings and Precautions ( 5.2 ) and Clinical Pharmacology ( 12.3 )] .
drug_interactions
The effects of concomitant administration of a moderate CYP3A4 inhibitor (e.g., erythromycin) on the pharmacokinetics of tamsulosin have not been evaluated [see Warnings and Precautions ( 5.2 ) and Clinical Pharmacology ( 12.3 )] .
drug_interactions
Concomitant treatment with paroxetine (a strong inhibitor of CYP2D6) resulted in an increase in the C max and AUC of tamsulosin by a factor of 1.3 and 1.6, respectively [see Warnings and Precautions ( 5.2 ) and Clinical Pharmacology (12.3)] .
drug_interactions
A similar increase in exposure is expected in CYP2D6 poor metabolizers (PM) as compared to extensive metabolizers (EM).
2 more recorded rows
Interaction statementdrug_interactions
Since CYP2D6 PMs cannot be readily identified and the potential for significant increase in tamsulosin exposure exists when tamsulosin hydrochloride capsules, 0.4 mg is coadministered with strong CYP3A4 inhibitors in CYP2D6 PMs, tamsulosin hydrochloride capsules, 0.4 mg should not be used in combination with strong inhibitors of CYP3A4 (e.g., ketoconazole) [see Warnings and Precautions ( 5.2 )…
Interaction statementdrug_interactions
The effects of concomitant administration of a moderate CYP2D6 inhibitor (e.g., terbinafine) on the pharmacokinetics of tamsulosin have not been evaluated [see Warnings and Precautions ( 5.2 ) and Clinical Pharmacology ( 12.3 )] .
ChEMBL 37 — CC BY-SA 3.0 Unported · ClinicalTrials.gov — US Government work · Open Targets 26.06 — CC0 · mixed register set; per-register licences in docs/specs/corpus-20k-sources.md · openFDA / DailyMed — US Government work
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