Tamsulosin
Pronunciation: tam-SOO-loh-sin.
- Generic name
- tamsulosin hydrochloride
- Brand names
- Flomax, Flomaxtra XL, Contiflo XL, Tabphyn MR
- Drug class
- Alpha1-adrenoceptor antagonist (alpha-blocker)
- Form
- Modified/prolonged-release capsule or tablet, 0.4 mg (US) or 400 microgram (UK/Australia)
- Route
- Oral
- Legal status
- Prescription-only medicine
Supply Rules Vary
Trade names by country: United States · United Kingdom · Canada · Australia
Australia: Flomaxtra (5) · Full directory
What tamsulosin hydrochloride is and how it works
Tamsulosin is an alpha1-adrenoceptor antagonist (alpha-blocker) taken by mouth to relieve the urinary symptoms of benign prostatic hyperplasia (BPH), an enlarged but non-cancerous prostate gland. It relaxes smooth muscle in the prostate and bladder neck, which can improve urine flow and reduce urinary frequency, urgency, and incomplete emptying. (1) (2)
Tamsulosin treats symptoms; it does not shrink the prostate or cure BPH, and it is not approved to treat high blood pressure. It carries a specific, clinically important interaction with cataract and other eye surgery that patients must disclose to their eye surgeon even if tamsulosin was stopped some time ago.
Mechanism of action: how tamsulosin hydrochloride works
Tamsulosin selectively antagonises alpha1A/alpha1D-adrenoceptors concentrated in prostatic and bladder-neck smooth muscle, relaxing this tissue and improving urine flow with comparatively less effect on vascular alpha1B-receptors than non-selective alpha-blockers, though clinically relevant blood-pressure effects still occur. (1) (4)
What tamsulosin hydrochloride is used for
Benign prostatic hyperplasia (BPH)
Tamsulosin is indicated for treatment of the signs and symptoms of benign prostatic hyperplasia in adult men, such as difficulty urinating, weak stream, and increased urinary frequency or urgency. It is not indicated for the treatment of hypertension. (1) (4) (2)
Before taking tamsulosin hydrochloride
Do not take / not appropriate for
- Do not take tamsulosin if you have a known hypersensitivity to tamsulosin hydrochloride or any product ingredient; documented reactions include rash, hives, itching, swelling, and breathing symptoms. (all products) (1)
- The UK Flomaxtra XL label additionally lists a history of orthostatic hypotension and severe hepatic impairment as contraindications. (Flomaxtra XL (UK)) (4)
Tell your clinician about
- Any planned cataract or glaucoma surgery, now or in the future — tamsulosin use, even in the past, can cause intraoperative floppy iris syndrome (IFIS) during eye surgery.
- A history of fainting, dizziness on standing, or low blood pressure, because tamsulosin can cause orthostatic hypotension, especially with the first few doses.
- Liver or kidney disease.
- All current medicines, especially other alpha-blockers, strong CYP3A4 or CYP2D6 inhibitors (such as ketoconazole), PDE5 inhibitors (e.g. sildenafil), and warfarin.
- A history of prostate cancer, since prostate symptoms should be properly evaluated before starting treatment.
How to take tamsulosin hydrochloride
- Take tamsulosin exactly as prescribed, usually once daily about 30 minutes after the same meal each day.
- Swallow the capsule or tablet whole; do not split, chew, crush, or open it.
- Continue taking tamsulosin even if you feel well, because it treats ongoing symptoms rather than curing the underlying condition; do not stop without talking to your prescriber.
- Rise slowly from sitting or lying down, particularly when starting treatment or restarting after a break, to reduce the chance of dizziness or fainting.
Procedures and treatment changes
Tell the treating team before surgery, procedures, or any medicine change. Do not alter treatment without the responsible clinician. (1) (2) (3) (4) (5)
Missed dose
Take the missed dose as soon as you remember it, unless it is almost time for the next dose, in which case skip the missed dose and continue the regular schedule. Do not take a double dose to make up for a missed one. If you are unsure, ask your pharmacist or prescriber.
Overdose
If an overdose is suspected, contact a poison control service or emergency department immediately. In the United States call 1-800-222-1222 or use poisonhelp.org. Overdose can cause severe dizziness, fainting, or low blood pressure; lying down can help until emergency help arrives. (2)
Side effects
Most side effects relate to blood-pressure changes or the drug's effect on smooth muscle. Some, such as fainting or a prolonged painful erection, need urgent attention.
Dizziness, drowsiness, or headache
What to notice: Often more noticeable when starting treatment or increasing the dose.
What to do: Avoid driving or hazardous tasks until you know how tamsulosin affects you; tell the prescriber if severe or persistent. (2)
Runny or stuffy nose, or facial pressure
What to notice: Commonly reported nasal/sinus symptoms.
What to do: Tell the prescriber if troublesome. (2)
Abnormal or absent ejaculation
What to notice: A recognised effect of alpha-blockers on the reproductive tract.
What to do: Discuss with the prescriber if bothersome. (2)
Fainting or severe dizziness (orthostatic hypotension)
What to notice: Lightheadedness, a spinning sensation, or fainting, especially on standing up quickly.
What to do: Sit or lie down immediately if this occurs and tell the prescriber; report any fainting episode promptly. (2) (4)
Priapism
What to notice: A painful erection lasting for hours, unrelated to sexual activity.
What to do: This is a medical emergency; seek immediate medical care to prevent permanent damage. (2)
Serious warnings
Intraoperative floppy iris syndrome (IFIS) during cataract or other eye surgery — urgent
Symptoms: Not a symptom the patient will notice in advance; it is a surgical complication in which the iris billows and the pupil narrows during cataract or glaucoma surgery, increasing the risk of surgical complications.
Action: Tell your eye surgeon (ophthalmologist) that you are taking or have ever taken tamsulosin before any eye surgery is scheduled, even if you stopped tamsulosin weeks or months ago, so the surgical team can prepare and adjust their technique. (1) (4) (2)
Orthostatic hypotension and syncope — urgent
Symptoms: Dizziness, lightheadedness, or fainting, particularly with the first few doses or after a missed-dose restart.
Action: Sit or lie down at the first sign of dizziness to avoid injury from a fall, and tell the prescriber; avoid situations where a fall or fainting episode would be dangerous (such as driving) until the effect on you is known. (1) (4)
Priapism — emergency
Symptoms: A prolonged, painful erection lasting for hours, not related to sexual activity.
Action: Seek emergency medical care immediately; delay can cause permanent damage. (2)
Severe allergic reaction — emergency
Symptoms: Rash, hives, swelling of the face, throat, or extremities, or difficulty breathing.
Action: Seek emergency medical care immediately. (1)
Interactions
| Medicine or test | Effect | Action |
|---|---|---|
| Strong CYP3A4 inhibitors (e.g. ketoconazole) and CYP2D6 inhibitors | Can substantially increase tamsulosin blood levels; in one study ketoconazole increased tamsulosin exposure by about 2- to 3-fold. | The prescriber should review all current medicines before combining, and generally avoid combining tamsulosin with strong CYP3A4 inhibitors, especially in people who metabolise CYP2D6 poorly. (4) (1) |
| Other alpha-adrenergic blocking agents | Combining with other alpha-blockers can increase the risk of low blood pressure and fainting. | Should not be combined with other alpha-blockers except under specialist direction. (1) |
| PDE5 inhibitors (e.g. sildenafil, tadalafil) | Concomitant use can cause symptomatic low blood pressure. | Use caution and tell the prescriber about any PDE5-inhibitor use. (1) |
| Warfarin | Caution is advised with concomitant use. | Tell the prescriber and pharmacist if taking warfarin so they can monitor accordingly. (1) |
| Cimetidine | May interact with tamsulosin and increase its levels. | Tell the prescriber about all current medicines including over-the-counter acid-reducing medicines. (2) |
Pregnancy, breastfeeding, kidney/liver function, age
People scheduled for cataract or other eye surgery
Tell the eye surgeon about any tamsulosin use, past or present, before surgery is scheduled, because of the risk of intraoperative floppy iris syndrome. Do not stop tamsulosin before surgery on your own; this decision belongs to the treating clinicians. (1) (4)
Severe hepatic impairment
The UK product information lists severe hepatic impairment as a contraindication. Discuss any liver disease with the prescriber before starting. (4)
Women and children
Tamsulosin is not indicated for use in women or children; it is approved only for BPH symptoms in adult men. (4) (1)
Pregnancy
Tamsulosin is not indicated for use in women, so it is not a medicine used in pregnancy, and there are no human pregnancy data for it. The US label records animal data only: tamsulosin given to pregnant rats at dose levels up to approximately 50 times the human therapeutic AUC exposure (300 mg/kg/day) revealed no evidence of harm to the fetus, and doses up to 50 mg/kg/day in pregnant rabbits produced no evidence of fetal harm; under the older US system it was classed Pregnancy Category B. Animal findings do not establish human safety. If tamsulosin has somehow been prescribed to a woman who is or may become pregnant, ask the prescriber to review it rather than acting on this page. (1)
Breastfeeding
The nursing mothers section of the US tamsulosin label says only that the capsules are not indicated for use in women. There are no human data on whether tamsulosin passes into breast milk, on effects on a breastfed infant, or on milk production. Any use in a breastfeeding woman would be outside the approved indication and is a decision for the prescriber. (1)
Monitoring
Before starting
- Confirm the diagnosis of BPH and rule out other causes of urinary symptoms, including prostate cancer, as clinically appropriate.
- Ask about any planned eye surgery, history of fainting or low blood pressure, liver disease, and all current medicines.
- Review for other alpha-blockers, strong CYP3A4/CYP2D6 inhibitors, PDE5 inhibitors, and warfarin.
During treatment
- Ask about dizziness, fainting, or falls, particularly after starting or restarting treatment.
- Confirm the patient has been told to disclose tamsulosin use before any future eye surgery.
- Reassess urinary symptom control and continued need for treatment periodically.
Storage
Store at room temperature, away from excess heat, light, and moisture (not in a bathroom). Keep out of reach of children, and dispose of unused medicine through a pharmacy take-back programme rather than flushing it.
Study the drug class: Alpha blockers
Professional information
Clinician-facing context only. Use the current local indication, dosing, hepatic/renal guidance, and pre-operative IFIS counselling protocol.
All regions
Indication: Benign prostatic hyperplasia
Dose summary: No universal dose is displayed. Typical starting doses in the sources reviewed are 0.4 mg (US) or 400 microgram (UK) once daily, taken about 30 minutes after the same meal, with possible titration under specialist direction; use the exact current local product information.
Renal context: Hepatic and renal impairment require individual assessment; the UK product information contraindicates severe hepatic impairment. Do not infer a web-based adjustment. (1) (4)
Hepatic guidance
Use local product information and specialist judgement; severe hepatic impairment is a contraindication in the UK product information reviewed.
Overdose note
Overdose management is supportive, addressing hypotension (for example, keeping the patient supine) with poison-centre or specialist advice; hemodialysis is unlikely to be of significant benefit given high protein binding. (1) (4)
Frequently asked questions
Do I need to tell my eye surgeon that I take tamsulosin?
Yes. Tell your ophthalmologist that you take or have ever taken tamsulosin before any cataract or other eye surgery is scheduled, even if you stopped it some time ago, because of the risk of intraoperative floppy iris syndrome. (1) (2)
Why might I feel dizzy when I start tamsulosin?
Tamsulosin can lower blood pressure, especially when standing up, which can cause dizziness or fainting. This risk is highest with the first few doses. Rise slowly and sit or lie down if you feel dizzy. (2) (4)
Can women take tamsulosin?
No. Tamsulosin is approved only to treat BPH symptoms in adult men and is not indicated for women. (4)
What is the mechanism of action of tamsulosin hydrochloride?
Tamsulosin selectively antagonises alpha1A/alpha1D-adrenoceptors concentrated in prostatic and bladder-neck smooth muscle, relaxing this tissue and improving urine flow with comparatively less effect on vascular alpha1B-receptors than non-selective alpha-blockers, though clinically relevant blood-pressure effects still occur. (1) (4)
References
- FLOMAX (tamsulosin hydrochloride) Capsules — full prescribing informationU.S. Food and Drug Administration · United States · dated 2014 · accessed 2026-07-23 · source 1
- Tamsulosin: MedlinePlus Drug InformationMedlinePlus, U.S. National Library of Medicine · United States · accessed 2026-07-23 · source 2
- Tamsulosin: a medicine for symptoms of an enlarged prostateNHS · United Kingdom · accessed 2026-07-23 · source 3
- Flomaxtra XL 400 microgram film-coated prolonged release tablet — Summary of Product Characteristicselectronic Medicines Compendium (UK) · United Kingdom · accessed 2026-07-23 · source 4
- FLOMAXTRA tamsulosin hydrochloride 400 microgram prolonged release tablet blister pack — ARTG entry 115534Therapeutic Goods Administration (TGA) · Australia · accessed 2026-07-23 · source 5
Brand names by country
Single-ingredient tamsulosin hydrochloride names are shown separately by country. Product availability, strengths, and supply rules can change; combination products are not included here.
Priority countries
United States
United Kingdom
Canada
- TAMSULOSIN CR
- FLOMAX CR
- SANDOZ TAMSULOSIN CR
- APO-TAMSULOSIN CR
- TEVA-TAMSULOSIN CR
Australia
- Flomaxtra (5)current register product example · 400 microgram · Astellas Pharma Australia Pty Ltd