[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Pharmacology](https://durgical.com/en/pharmacology/) › [Alpha blockers](https://durgical.com/en/pharmacology/classes/alpha-blockers/) › Doxazosin

[Pharmacology](https://durgical.com/en/pharmacology/) · [Alpha blockers](https://durgical.com/en/pharmacology/classes/alpha-blockers/)

# Doxazosin

A long-acting alpha-1 blocker for benign prostatic hyperplasia and high blood pressure, taken once a day. The first dose can cause fainting.

Updated 2026-11-01

- Class: [Alpha blockers](https://durgical.com/en/pharmacology/classes/alpha-blockers/)
- Receptor: Alpha-1 adrenergic receptors
- ATC code: C02CA04

◎**Alpha-1 adrenergic receptors**Doxazosin

ⓘ The figure shows doxazosin bound to the human alpha-1A adrenergic receptor (cryo-EM structure).

**Target in 3D:** Alpha-1 adrenergic receptors. PDB structure 9M4Q (RCSB PDB, public domain). [View the structure at RCSB PDB](https://www.rcsb.org/structure/9M4Q) · Drag to rotate · pinch to zoom

## Mechanism of action

Doxazosin, a quinazoline, selectively blocks alpha-1 receptors in arterioles, veins, the prostate and the bladder neck. Vascular resistance and blood pressure fall, and the smooth muscle around the urethra relaxes, easing urine flow.

- Doxazosin blocks alpha-1 receptors in vessels and prostate
- Vascular and prostatic smooth muscle relaxes
- Blood pressure falls and urine flows more easily

## Pharmacokinetics

**Absorption**
Oral, once daily

**Metabolism**
Extensive metabolism in the liver; exposure rises in liver disease

**Half-life**
Elimination half-life about 22 hours (label)

## Indications

- Benign prostatic hyperplasia [Benign prostatic hyperplasia →](https://durgical.com/en/conditions/benign-prostatic-hyperplasia/)
- High blood pressure [Arterial hypertension →](https://durgical.com/en/conditions/arterial-hypertension/)

## Adverse effects

### Common

- Dizziness and vertigo
- Fatigue and malaise
- Hypotension, mainly on standing
- Oedema

### Serious (rare, important)

- Syncope, especially after the first dose or a dose increase
- Priapism
- Intraoperative floppy iris syndrome during cataract surgery

## Contraindications

- Hypersensitivity to doxazosin or other quinazolines (prazosin, terazosin)

## Key interactions

**PDE-5 inhibitors**
Additive fall in blood pressure and symptomatic hypotension

**Other antihypertensives**
Additive hypotension

## What is monitored

- Blood pressure lying and standing
- Urinary symptoms
- Prostate cancer is excluded before treating symptoms of an enlarged prostate

## Nursing care

- Warn about dizziness and fainting after the first dose and after a dose increase; avoid driving or hazardous tasks at those times.
- Rise slowly from lying or sitting.
- Before cataract surgery, tell the eye surgeon about alpha blocker use.
- An erection lasting several hours is an emergency.

## Pregnancy and breastfeeding

Human data are limited; it is used in pregnancy only if clearly needed.

## Memory aid

DOXAzosin: once a Day, DOuble use (prostate and pressure), but Dizzy at the first dose.

## Test yourself

Think of the answer, then tap the question to see it.

## What two conditions does doxazosin treat?

Benign prostatic hyperplasia and high blood pressure.

## Why is doxazosin taken once a day while prazosin needs several doses?

Doxazosin has a much longer elimination half-life than prazosin.

## Which drug class must be combined with care because of symptomatic hypotension?

PDE-5 inhibitors such as sildenafil.

[Add to my cards (3)](https://durgical.app/estudiar/?add=/en/pharmacology/doxazosin/)

## Related drugs

- [Prazosin](https://durgical.com/en/pharmacology/prazosin/)
- [Terazosin](https://durgical.com/en/pharmacology/terazosin/)
- [Tamsulosin](https://durgical.com/en/pharmacology/tamsulosin/)

## Related conditions

- [Benign prostatic hyperplasia](https://durgical.com/en/conditions/benign-prostatic-hyperplasia/)
- [Arterial hypertension](https://durgical.com/en/conditions/arterial-hypertension/)

[← Back to the class: Alpha blockers](https://durgical.com/en/pharmacology/classes/alpha-blockers/)

Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.

Sources: [DailyMed - DOXAZOSIN tablet](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=1dbf8366-c606-4253-aa08-ed555a8de4c3) (DailyMed (U.S. National Library of Medicine), 2026); [Doxazosin: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a693045.html) (MedlinePlus (U.S. National Library of Medicine), 2025); [ATCDDD - ATC/DDD Index](https://atcddd.fhi.no/atc_ddd_index/?code=C02CA04) (WHO Collaborating Centre for Drug Statistics Methodology, 2026).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/pharmacology/doxazosin/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/doxazosin/