Alpha-1 blocker Pregnancy: Safety in pregnancy not established; use only when the potential benefit outweighs the potential risk. Breast-feeding: excretion in milk very low but human data limited; use only if benefit outweighs risk.

Doxazosin

Brand names: Cardura

Doxazosin is an alpha-1 blocker used as add-on therapy in hypertension and for the symptoms of benign prostatic enlargement.

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

Route: Oral

Frequency: Once daily (morning or evening)

Max: 16 mg daily (hypertension); 8 mg daily (benign prostatic hyperplasia)

Hypertension: initial 1 mg once daily to minimise postural hypotension/syncope; may increase to 2 mg after 1-2 weeks, then to 4 mg if needed, and further to 8 mg or the maximum 16 mg. Most responders do so at 4 mg or less. Benign prostatic hyperplasia: initial 1 mg once daily, titrate to 2 mg then 4 mg up to maximum 8 mg; recommended titration interval 1-2 weeks; usual dose 2-4 mg daily. Elderly: normal adult dosage. Caution in hepatic impairment; not recommended in severe hepatic impairment.

Dose adjustments

Renal

No dose change required in renal impairment (no change in pharmacokinetics); doxazosin is not dialysable.

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

US labelling (FDA)

Reference — US labelling, may differ from UK

• For the treatment of BPH: Initiate therapy at 1 mg once daily. Dose may be titrated at 1 to 2 week intervals, up to 8 mg once daily.( 2.2 ) • For the treatment hypertension: Initiate therapy at 1 mg once daily. Dose may be titrated as needed, up to 16 mg once daily. ( 2.3 ) 2.1 Dosing Information Following the initial dose and with each dose increase of doxazosin tablets, monitor blood pressure for at least 6 hours following administration. If doxazosin tablets administration is discontinued for several days, therapy should be restarted using the initial dosing regimen. 2.2 Benign Prostatic Hyperplasia The recommended initial dosage of doxazosin tablets is 1 mg given once daily either in …

Source: US FDA prescribing information (openFDA / DailyMed), label dated 2026-04-24. Accessed 2026-06-12. US dosing and indications can differ from UK practice — use UK sources for prescribing decisions.

Contraindications

Hypersensitivity to doxazosin or other quinazolines (e.g. prazosin, terazosin) or to excipients
History of orthostatic hypotension
BPH with concomitant congestion of the upper urinary tract, chronic urinary tract infection or bladder stones
Hypotension (BPH indication only)
Monotherapy in patients with overflow bladder or anuria with or without progressive renal insufficiency

Side effects

Dizziness
Headache
Hypotension / postural hypotension
Palpitation, tachycardia
Somnolence

Interactions

PDE-5 inhibitors (sildenafil, tadalafil, vardenafil) - additive vasodilation may cause symptomatic hypotension; initiate PDE-5 inhibitor at lowest dose and allow a 6-hour interval
Other vasodilatory antihypertensive agents
Drugs influencing hepatic metabolism (e.g. cimetidine)

Clinical monograph

How it works

It blocks α1-adrenoceptors, causing vasodilatation and relaxing prostatic and bladder-neck smooth muscle.

Prescribing in practice

First-dose and postural hypotension can occur — start low, ideally at night.
It causes intra-operative floppy iris syndrome — patients must tell the ophthalmologist before cataract surgery.
A modified-release form improves tolerability; it is a fourth-line option in resistant hypertension.

Monitoring

Monitor blood pressure (including postural) and symptom response.

Counselling the patient

The first dose may cause dizziness — take care standing up, and take it at bedtime if advised.
Tell your eye surgeon you take it before cataract surgery.

Evidence & guidelines

An add-on (fourth-line) antihypertensive in resistant hypertension (NICE NG136) and an option for benign prostatic enlargement.

Reference: NICE NG136; NICE NG97; BAUS; 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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