Indications: relax smooth muscle in benign prostatic hyperplasia producing an increase in urinary flow-rate and an improvement in obstructive symptoms.

Cautions: Since alpha1-selective alpha blockers reduce blood pressure, patients receiving antihypertensive treatment may require reduced dosage and specialist supervision. Caution is required in the elderly and in patients undergoing cataract surgery (risk of intra- operative floppy iris syndrome).

Contra-indications: Alpha-blockers should be avoided in patients with a history of postural hypotension and micturition syncope.

Hepatic impairment: initial dose 2.5mg once daily, adjusted according to response to 2.5mg twice daily in mild to moderate impairment—avoid if severe; avoid modified-release preparations.

Renal impairment: initial dose 2.5mg twice daily and adjust according to response; manufacturers advise avoid use of modified-release preparations if eGFR less than 30 ml/minute/1.73m2 as limited experience.

Side Effects: of alpha1-selective alpha blockers include drowsiness, hypotension (notably postural hypotension), syncope, asthenia, dizziness, depression, headache, dry mouth, gastro-intestinal disturbances, oedema, blurred vision, intra-operative floppy iris syndrome (most strongly associated with tamsulosin), rhinitis, erectile disorders (including priapism), tachycardia, and palpitations. Hypersensitivity reactions including rash, pruritus and angioedema have also been reported.

Dose: benign prostatic hyperplasia 10 mg once daily Acute urinary retention associated with benign prostatic hyperplasia in men over 65 years, 10 mg once daily for 2–3 days during catheterisation and for one day after removal; max. 4 days First dose effect First dose may cause collapse due to hypotensive effect (therefore should be taken on retiring to bed). Patient should be warned to lie down if symptoms such as dizziness, fatigue or sweating develop, and to remain lying down until they abate completely.