Alpha-1 Blocker Pregnancy: §4.6 states that for the benign prostatic hyperplasia indication this section is not applicable. (For the hypertension indication: safety in pregnancy has not been established and doxazosin should be used only when the potential benefit outweighs the potential risk; excretion in breast milk is very low but a risk to the infant cannot be excluded.)

Doxazosin (BPH)

Brand names: Cardura

This is doxazosin used for benign prostatic hyperplasia, relaxing prostatic and bladder-neck smooth muscle to relieve lower urinary tract symptoms. It is an alpha-1 adrenoceptor antagonist that also lowers blood pressure.

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: 1 mg once daily initially, then titrated to 2 mg and thereafter to 4 mg (usual recommended dose 2–4 mg daily)

Route: Oral

Frequency: Once daily (morning or evening)

Max: 8 mg once daily (maximum recommended dose for the benign prostatic hyperplasia indication)

§4.2 benign prostatic hyperplasia: the recommended initial dosage is 1 mg once daily to minimise the potential for postural hypotension and/or syncope; depending on the individual patient's urodynamics and BPH symptomatology the dose may then be increased to 2 mg and thereafter to 4 mg and up to the maximum recommended dose of 8 mg. The recommended titration interval is 1–2 weeks and the usual recommended dose is 2–4 mg daily. (For the separate HYPERTENSION indication the same 1 mg start is used but titration runs 2 mg, 4 mg, 8 mg up to a maximum of 16 mg once daily — do not apply the 16 mg ceiling to BPH.) Elderly: normal adult dosage. Hepatic impairment: limited data — administer with caution to patients with impaired liver function; not recommended in severe hepatic impairment (§4.4). Paediatric: safety and efficacy in children and adolescents have not been established (no per-kg regimen — paedDose null). The fetched SPC is the immediate-release Cardura tablet; §4.4 notes no studies have been conducted with doxazosin prolonged-release formulations, so a modified-release product would need its own SPC.

Dose adjustments

Renal

Since there is no change in pharmacokinetics in patients with impaired renal function, the usual adult dose is recommended. Doxazosin is not dialysable.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; 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

Hypersensitivity to the active substance or other quinazolines (e.g. prazosin, terazosin, doxazosin) or to any of the excipients
History of orthostatic hypotension
Benign prostatic hyperplasia with concomitant congestion of the upper urinary tract, chronic urinary tract infection or bladder stones
Hypotension (for the benign prostatic hyperplasia indication only)
Contraindicated as monotherapy in patients with either overflow bladder or anuria, with or without progressive renal insufficiency

Side effects

Dizziness and headache (common)
Somnolence (common)
Hypotension and postural hypotension (common)
Palpitation and tachycardia (common)
Abdominal pain, dyspepsia, dry mouth and nausea (common)
Asthenia, chest pain, influenza-like symptoms and peripheral oedema (common)
Respiratory tract infection and urinary tract infection (common)

Interactions

UK SPC §4.4: PDE-5 inhibitors (sildenafil, tadalafil, vardenafil) — concomitant use requires caution as both have vasodilating effects and may cause symptomatic hypotension; start a PDE-5 inhibitor only once the patient is haemodynamically stabilised on alpha-blocker therapy, at the lowest possible dose, respecting a 6-hour interval from doxazosin intake
UK SPC §4.2/§4.4: drugs known to influence hepatic metabolism (e.g. cimetidine) — limited data; doxazosin is wholly metabolised by the liver, so administer with caution
US label §7.1 (no §4.5 content in the fetched UK SPC extract): strong CYP3A inhibitors may increase doxazosin exposure and the risk of hypotension — monitor blood pressure and for symptoms of hypotension
UK SPC §4.4: other vasodilatory antihypertensive agents and acute cardiac conditions — caution, as postural hypotension and syncope may occur, particularly on commencement of therapy

Clinical monograph

How it works

It selectively blocks alpha-1 adrenoceptors in prostatic and bladder-neck smooth muscle, reducing outflow resistance and improving urinary flow.

Prescribing in practice

First-dose and postural hypotension can occur, so start at a low dose, preferably at bedtime, and warn patients about dizziness on standing.
Intraoperative floppy iris syndrome is a risk during cataract surgery, so the ophthalmic surgeon should be informed before the procedure.
Caution is needed with other antihypertensives and PDE5 inhibitors owing to additive hypotension as outlined in the SPC.

Monitoring

Monitor blood pressure, particularly after initiation and dose changes, and review urinary symptom response.

Counselling the patient

Rise slowly from sitting or lying to avoid dizziness, especially with the first doses.
Tell your eye surgeon you take this medicine if you are having cataract surgery.
Report fainting or palpitations.

Evidence & guidelines

Established for benign prostatic hyperplasia through trials demonstrating symptom improvement and increased urinary flow rates.

Reference: NICE NG97; 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.

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