Alpha-1A Selective Blocker Pregnancy: Silodosin is not indicated for use in females (US label section 8.1).

Silodosin

Brand names: Urorec, Silodyx

Silodosin is a selective alpha-1A adrenoceptor antagonist used to treat the lower urinary tract symptoms of benign prostatic hyperplasia in men.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: 8 mg once daily with a meal

Route: Oral — capsule taken with a meal; patients who have difficulty swallowing capsules may carefully open the capsule and sprinkle the powder on a tablespoonful of applesauce, swallowed immediately (within 5 minutes) without chewing and followed with an 8 oz glass of cool water

Frequency: Once daily

Max: 8 mg once daily is the recommended dose; 4 mg once daily in moderate renal impairment (creatinine clearance 30 to 50 mL/min)

Subdividing the contents of a silodosin capsule is not recommended, and any powder/applesauce mixture should be used immediately (within 5 minutes) and not stored. Hepatic impairment: no dosage adjustment is needed in mild or moderate hepatic impairment; silodosin has not been studied in severe hepatic impairment (Child-Pugh score 10 or more) and is contraindicated in those patients. Postural hypotension, with or without symptoms such as dizziness, may develop when beginning treatment, and there is potential for syncope — caution patients about driving, operating machinery or performing hazardous tasks when initiating therapy. Silodosin should not be used in combination with other alpha-blockers. Examine patients thought to have BPH prior to starting therapy to rule out carcinoma of the prostate. Patients planning cataract surgery should tell their ophthalmologist they are taking silodosin because of the possibility of Intraoperative Floppy Iris Syndrome. Paediatric: silodosin is not indicated for use in paediatric patients and safety and effectiveness in paediatric patients have not been established — no per-kg dose exists, hence paedDose is null. NO UK SPC (eMC) RECORD WAS FETCHED — all figures are from the US prescribing information (Lupin Pharmaceuticals, label date 2025-10-07) and must be verified against the UK SPC.

Dose adjustments

Renal

Moderate renal impairment (creatinine clearance 30 to 50 mL/min): reduce the dose to 4 mg once daily taken with a meal. Severe renal impairment (creatinine clearance less than 30 mL/min): contraindicated. Mild renal impairment (creatinine clearance 50 to 80 mL/min): no dosage adjustment needed.

Dose auto-extracted from US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

Severe renal impairment (creatinine clearance less than 30 mL/min)
Severe hepatic impairment (Child-Pugh score 10 or more)
Concomitant administration with strong CYP3A4 inhibitors (e.g. ketoconazole, clarithromycin, itraconazole, ritonavir)
History of hypersensitivity to silodosin or any of the ingredients of silodosin capsules

Side effects

Retrograde ejaculation
Dizziness
Diarrhoea
Orthostatic hypotension
Headache
Nasopharyngitis and nasal congestion

Interactions

Strong CYP3A4 inhibitors (ketoconazole, itraconazole, ritonavir) — concomitant administration is contraindicated; ketoconazole 400 mg produced a 3.8-fold increase in silodosin maximum plasma concentration and a 3.2-fold increase in exposure
Moderate CYP3A4 inhibitors (e.g. diltiazem, erythromycin, verapamil) — may increase silodosin concentrations; exercise caution and monitor for adverse events
Strong P-glycoprotein inhibitors (e.g. ciclosporin) — co-administration may increase plasma silodosin concentration; concomitant use is not recommended
Other alpha-blockers — interactions are expected and concomitant use is not recommended
PDE5 inhibitors — concomitant use with alpha-blockers including silodosin can potentially cause symptomatic hypotension

Clinical monograph

How it works

It selectively blocks alpha-1A adrenoceptors in the prostate, bladder neck and urethra, relaxing smooth muscle and reducing bladder outflow obstruction and associated voiding symptoms.

Prescribing in practice

It commonly causes abnormal or retrograde ejaculation, and patients should be advised of this before starting treatment.
It is associated with intraoperative floppy iris syndrome, so any planned cataract or glaucoma surgery should be flagged to the ophthalmologist before commencing.
Caution is needed in renal or hepatic impairment and with concomitant potent CYP3A4 inhibitors or other antihypertensives because of the risk of hypotension.

Monitoring

Monitor symptom response and blood pressure, particularly for postural hypotension on initiation and dose changes.

Counselling the patient

Reduced or absent semen on ejaculation is expected and not harmful.
Tell your eye surgeon you take this medicine before any cataract operation.
Stand up slowly, especially when first starting, to avoid dizziness.

Evidence & guidelines

Alpha-blockers are recommended by NICE for moderate to severe lower urinary tract symptoms in benign prostatic hyperplasia; see the SPC for product-specific cautions.

Reference: NICE NG97; EAU Guidelines on BPH; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Pathways