Alpha-1 adrenoceptor blocker (selective for alpha-1a)

Tamsulosin

Brand names: Flomax MR, Stronazon MR

Tamsulosin is an alpha-1-adrenoceptor blocker used to relieve the lower urinary tract symptoms of benign prostatic enlargement.

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 α1-adrenoceptors in prostatic and bladder-neck smooth muscle, reducing outflow resistance.

Prescribing in practice

Postural hypotension and dizziness can occur, particularly with the first dose.
It causes intra-operative floppy iris syndrome — patients must tell the ophthalmologist before cataract surgery.
Use caution with other blood-pressure-lowering drugs and PDE5 inhibitors.

Monitoring

Review symptom response and postural blood pressure.

Counselling the patient

The first dose may cause dizziness — take care when standing up.
Tell your eye surgeon you take it before any cataract operation.
It can cause changes to ejaculation.

Evidence & guidelines

Alpha-blockers are first-line for moderate-to-severe lower urinary tract symptoms due to benign prostatic enlargement, per NICE NG97.

Reference: NICE NG118 Lower Urinary Tract Symptoms; EAU Urology Guidelines; 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.

Calculators

Pathways