α1A-selective adrenergic antagonist

Tamsulosin hydrochloride

Brand names: Flomax, Flomaxtra

Tamsulosin is a uroselective alpha-1A adrenoceptor blocker used to relieve the lower urinary tract symptoms of benign prostatic hyperplasia.

Dosing — being independently re-sourced

ClinCalc Pro is rebuilding its dose data from primary open sources — the manufacturer SmPC (eMC), the WHO Model Formulary and other official references — under clinician review. This drug's structured dose is not yet published here. Confirm all doses against the product SmPC and your local formulary before prescribing.

US labelling (FDA)

Reference — US labelling, may differ from UK

Tamsulosin hydrochloride capsules 0.4 mg once daily is recommended as the dose for the treatment of the signs and symptoms of BPH. It should be administered approximately one-half hour following the same meal each day. Tamsulosin hydrochloride capsules should not be crushed, chewed or opened. For those patients who fail to respond to the 0.4 mg dose after 2 to 4 weeks of dosing, the dose of tamsulosin hydrochloride capsules can be increased to 0.8 mg once daily. 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)]. If tamsulosin hydrochloride capsules administration is …

Source: US FDA prescribing information (openFDA / DailyMed), label dated 2026-01-01. Accessed 2026-06-12. US dosing and indications can differ from UK practice — use UK sources for prescribing decisions.

Clinical monograph

How it works

It selectively blocks alpha-1A adrenoceptors in the prostate, prostatic capsule and bladder neck, relaxing smooth muscle there to improve urine flow.

Prescribing in practice

Warn patients and surgeons of intraoperative floppy iris syndrome — patients must tell the ophthalmologist they take, or have taken, tamsulosin before cataract or other eye surgery.
Postural hypotension and dizziness can occur, though less than with non-selective alpha-blockers.
Retrograde or abnormal ejaculation is a recognised effect.

Monitoring

Check lying and standing blood pressure, particularly early in treatment, and review symptom response; exclude prostate cancer before attributing symptoms to benign disease.

Counselling the patient

Before any eye surgery, including cataract surgery, tell the eye surgeon you take this medicine — even if you stopped it a while ago.
Stand up slowly at first, as you may feel dizzy or light-headed.
You may notice less or no fluid when you ejaculate; this is harmless.

Evidence & guidelines

An established option for moderate-to-severe BPH symptoms in NICE guidance; MHRA advice on intraoperative floppy iris syndrome.

Reference: NICE CG97; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Pathways