Alpha-1 blocker

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.

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

• 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.

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. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

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