Silodosin

Pronunciation: sil-OH-doh-sin.

Generic name
silodosin
Drug class
Alpha-1A adrenergic receptor antagonist (highly uroselective alpha-1 blocker)
Form
Capsule (4 mg, 8 mg)
Route
Oral
Legal status
Prescription-only, male-only indication

Supply Rules Vary

Trade names by country: United States · United Kingdom · Canada · Australia · New Zealand

Australia: UROREC (5) · Full directory

What silodosin is and how it works

Silodosin is a prescription medicine that relaxes muscle in the prostate and bladder neck by selectively blocking alpha-1A adrenergic receptors, making it easier to urinate for men with signs and symptoms of an enlarged prostate (benign prostatic hyperplasia, BPH). It is not a treatment for high blood pressure, and it is not used in women. (1) (2)

Silodosin carries two genuine, well-documented safety considerations: it can cause a drop in blood pressure on standing (orthostatic hypotension), especially when starting treatment or in older adults, and it is linked to a specific eye-surgery risk (intraoperative floppy iris syndrome) that your eye surgeon needs to know about before any cataract or other eye surgery -- even if you stopped silodosin some time ago.

Mechanism of action: how silodosin works

Silodosin is a highly uroselective antagonist at alpha-1A adrenergic receptors, which predominate in prostate and bladder-neck smooth muscle over alpha-1B (vascular) receptors, aiming to relax lower urinary tract smooth muscle and improve BPH voiding symptoms with a comparatively lower burden of vascular (blood-pressure-related) effects than less selective alpha-blockers -- though orthostatic hypotension is still a real, documented effect. (1) (2)

What silodosin is used for

Signs and symptoms of benign prostatic hyperplasia (BPH)

Used to treat urinary symptoms (such as difficulty starting urination, weak stream, and needing to urinate often, including at night) caused by an enlarged prostate gland. Silodosin is not indicated for treating high blood pressure, and is a male-only medicine. (1) (2)

Before taking silodosin

Do not take / not appropriate for

  • Do not take silodosin if you have severe kidney impairment (creatinine clearance below 30 mL/min). (all countries) (1) (2)
  • Do not take silodosin if you have severe liver impairment (Child-Pugh score above 10). (United States) (1)
  • Do not take silodosin together with strong CYP3A4-inhibitor medicines (such as ketoconazole, clarithromycin, itraconazole, or ritonavir). (all countries) (1) (2)
  • Do not take silodosin if you have a known hypersensitivity to silodosin or its other ingredients. (European Union) (2)
  • This medicine is not for use in women. (all countries) (2)

Tell your clinician about

  • Any kidney or liver problems, including how severe they are.
  • If you are scheduled for, or might need, cataract or other eye surgery -- tell both your eye surgeon and your prescriber that you take (or have taken) silodosin.
  • All other medicines you take, especially other alpha-blockers, PDE5 inhibitors (e.g. for erectile dysfunction), ciclosporin, or any strong CYP3A4-inhibitor medicine.
  • Any history of low blood pressure, fainting, or dizziness on standing.
(1) (2)

How to take silodosin

  • Take one capsule once daily, with a meal, at about the same time each day.
  • Swallow the capsule whole -- do not crush, chew, or open it unless your prescriber or pharmacist tells you it is appropriate for your situation.
  • Your prescriber will adjust your dose based on your kidney function.
(1) (2)

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

If you miss a dose, contact your prescriber or pharmacist for guidance rather than doubling your next dose -- resuming your normal once-daily schedule at the next planned time is generally appropriate, but check with them if you are unsure.

Overdose

Seek urgent medical attention if you think you have taken too much silodosin, or if you develop severe dizziness, fainting, or a very fast or irregular heartbeat, since a significant blood-pressure drop is possible. (1)

Side effects

Side effects and their urgency vary; report severe, persistent, or concerning symptoms.

Retrograde ejaculation (semen entering the bladder instead of exiting normally during orgasm) -- the most common effect, reported in around 28% of patients in US trials.

What to notice: Retrograde ejaculation (semen entering the bladder instead of exiting normally during orgasm) -- the most common effect, reported in around 28% of patients in US trials.

What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (1)

Dizziness.

What to notice: Dizziness.

What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (1) (2)

Diarrhoea.

What to notice: Diarrhoea.

What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (1) (2)

Headache.

What to notice: Headache.

What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (1)

Nasopharyngitis (common cold-type symptoms) and nasal congestion.

What to notice: Nasopharyngitis (common cold-type symptoms) and nasal congestion.

What to do: Discuss persistent or troublesome symptoms with the treating clinician or pharmacist. (1)

Serious warnings

Intraoperative floppy iris syndrome (IFIS) during cataract or other eye surgery — high caution

Symptoms: Not a symptom you would notice yourself beforehand -- this is a condition your eye surgeon watches for and manages during surgery.

Action: Tell your eye surgeon (ophthalmologist) that you take, or have ever taken, silodosin before any cataract or other eye surgery -- even if you stopped taking it some time ago. This allows the surgical team to plan and adjust their technique in advance. (1) (2)

Signs of orthostatic hypotension (a drop in blood pressure on standing) — high caution

Symptoms: Dizziness, light-headedness, or feeling faint, especially when standing up quickly -- particularly when treatment is first started or the dose is changed by your prescriber, and more common in adults over 75.

Action: Sit or lie down if you feel dizzy or faint, and avoid driving or hazardous tasks until you know how silodosin affects you, especially when starting treatment. Contact your clinician if these symptoms are severe, persistent, or you actually faint. (1) (2)

Signs of a serious allergic reaction — emergency

Symptoms: Swelling of the face, lips, tongue, or throat; difficulty breathing; widespread rash or hives.

Action: Seek emergency medical help immediately. (2)

Interactions

  • Strong CYP3A4 inhibitors (such as ketoconazole, clarithromycin, itraconazole, ritonavir) significantly raise silodosin levels and must not be combined with it. (1) (2)
  • Should not be combined with other alpha-blocker medicines. (1) (2)
  • PDE5 inhibitors (e.g. medicines for erectile dysfunction) can increase the chance of a drop in blood pressure on standing when combined with silodosin -- use with caution and under your prescriber's guidance. (1)
  • Strong P-glycoprotein inhibitors, such as ciclosporin, are not recommended in combination with silodosin. (1)

Pregnancy, breastfeeding, kidney/liver function, age

Pregnancy

Not applicable -- silodosin is a male-only medicine and is not used in women. (1) (2) (3) (4) (5)

Breastfeeding

Not applicable -- silodosin is a male-only medicine. (1) (2) (3) (4) (5)

Children

Not established for use in children in the sources reviewed; this is an adult male BPH medicine. (1) (2) (3) (4) (5)

Elderly

More commonly used in older men (as BPH is more common with age); the risk of orthostatic hypotension is higher in patients over 75 (5.0% versus 0% with placebo in the US trials reviewed) -- extra caution with standing up quickly is advised. (1) (2) (3) (4) (5)

Hepatic_impairment

Contraindicated in severe hepatic impairment (Child-Pugh score above 10) per the US label reviewed; use with caution and clinical judgement in lesser degrees of impairment. (1) (2) (3) (4) (5)

Renal_impairment

Contraindicated in severe renal impairment (creatinine clearance below 30 mL/min). Dose reduced to 4 mg once daily in moderate renal impairment (creatinine clearance 30-50 mL/min), where plasma concentrations can triple. No adjustment needed for mild renal impairment. (1) (2) (3) (4) (5)

Source_ids

US-DAILYMED-RAPAFLO-2026,EU-EMA-UROREC-EPAR-2026 (1) (2) (3) (4) (5)

Monitoring

Before starting

  • Assessment of kidney and liver function
  • Review of other medicines for CYP3A4-inhibitor, alpha-blocker, PDE5-inhibitor, or ciclosporin interactions
  • Discussion of any upcoming cataract or eye surgery

During treatment

  • Watching for dizziness or fainting, especially after starting or increasing the dose, and particularly in patients over 75.
  • Informing any eye surgeon of silodosin use before cataract or other eye surgery, at any point, even after stopping treatment.
(1) (2)

Storage

Store at room temperature, protected from moisture, in the original packaging, out of reach of children.

Study the drug class: Alpha blockers

Professional information

Clinician-facing context only, sourced from the current US FDA prescribing information and EU EPAR product information; verify against the current full label and local availability before prescribing.

United States / European Union / United Kingdom / Canada / Australia

Indication: Signs and symptoms of BPH

Dose summary: 8 mg once daily with food; 4 mg once daily with food for moderate renal impairment (CrCl 30-50 mL/min); contraindicated in severe renal impairment (CrCl <30 mL/min) and, per the US label, severe hepatic impairment (Child-Pugh >10).

Renal context: Plasma concentrations approximately triple in moderate renal impairment per the US label reviewed, driving the mandatory dose reduction; contraindicated in severe renal impairment. (1) (2)

Mechanism of action

Hepatic guidance

Contraindicated in severe hepatic impairment (Child-Pugh score above 10) per the US label reviewed; not studied in this population beyond that boundary.

Overdose note

Manage overdose with supportive care, including measures to support blood pressure (e.g. keeping the patient supine) given the risk of a significant hypotensive effect; no specific antidote is described in the sources reviewed. (1) (2)

Frequently asked questions

Is silodosin available in the US, UK, EU, Canada, Australia, and New Zealand?

It is confirmed currently available in the United States and Canada (as Rapaflo), the European Union and Australia (as Urorec), and the United Kingdom (as Urorec or generic Silodosin Recordati, per UK product listings). No live New Zealand Medsafe registration record for silodosin as its own product was found in this research round -- this is disclosed as unconfirmed, not as definitely unavailable. Always confirm current local availability with a pharmacist or prescriber. (1) (2) (3) (4) (5)

Why do I need to tell my eye surgeon I take silodosin?

Silodosin and other alpha-1 blockers are linked to a condition called intraoperative floppy iris syndrome (IFIS), which can make cataract or other eye surgery more challenging if the surgical team isn't expecting it. Telling your ophthalmologist you take (or have ever taken) silodosin lets them plan and adjust their surgical approach in advance, even if you stopped the medicine some time before your surgery. (1) (2)

Why might I feel dizzy when I start silodosin?

Silodosin can lower blood pressure, particularly when standing up, an effect called orthostatic hypotension. This is more likely when you first start treatment or when your prescriber changes your dose, and is more common in people over 75. Sit or lie down if you feel dizzy or light-headed, and be cautious with driving or other tasks needing alertness until you know how the medicine affects you. (1) (2)

What is the mechanism of action of silodosin?

Silodosin is a highly uroselective antagonist at alpha-1A adrenergic receptors, which predominate in prostate and bladder-neck smooth muscle over alpha-1B (vascular) receptors, aiming to relax lower urinary tract smooth muscle and improve BPH voiding symptoms with a comparatively lower burden of vascular (blood-pressure-related) effects than less selective alpha-blockers -- though orthostatic hypotension is still a real, documented effect. (1) (2)

What is the generic name of Silodosin?

The generic name is silodosin. (1) (2) (5)

What class of drug is silodosin?

Silodosin is classed as: Alpha-1A adrenergic receptor antagonist (highly uroselective alpha-1 blocker). (1) (2) (5)

References

  1. RAPAFLO (silodosin) capsules -- full prescribing informationU.S. Food and Drug Administration / DailyMed · United States · dated 2020 · accessed 2026-07-30 · source 1
  2. Urorec (silodosin) -- EPAR Annex I Summary of Product CharacteristicsEuropean Medicines Agency · European Union · accessed 2026-07-30 · source 2
  3. Urorec and Silodosin Recordati -- UK product listings (emc)electronic Medicines Compendium (UK) · United Kingdom · accessed 2026-07-30 · source 3
  4. RAPAFLO (silodosin) capsules, 8 mg and 4 mg -- Product MonographHealth Canada · Canada · dated 2011-01 · accessed 2026-07-30 · source 4
  5. UROREC silodosin 4 mg and 8 mg hard capsule blister pack -- ARTG 275256 / 275265Therapeutic Goods Administration · Australia · dated 2017-05-23 · accessed 2026-07-30 · source 5

Brand names by country

Single-ingredient silodosin names are shown separately by country. Product availability, strengths, and supply rules can change; combination products are not included here.

Priority countries

United States

  • RAPAFLO (1)current regulator label · 4 mg, 8 mg · See current FDA prescribing information (initial approval 2008)

United Kingdom

  • Urorec / Silodosin Recordati (generic) (3)current listed product uk page not directly opened · 4 mg, 8 mg · Recordati (Urorec); generic manufacturer for Silodosin Recordati

Canada

  • RAPAFLO

Australia

  • UROREC (5)current register product · 4 mg, 8 mg · Mayne Pharma International Pty Ltd (TGA-confirmed; registered 2017-05-23)

New Zealand

  • No registered New Zealand silodosin product independently confirmed in this research roundstatus being checked · Not confirmed
View brands in additional countries.

European Union

Urorec (2)

This page provides general reference information about silodosin and is not a substitute for advice from the prescriber managing your treatment. All dosing and treatment decisions should be made with your prescriber, and always tell any eye surgeon that you take or have taken silodosin before cataract or other eye surgery.

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