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
The figure shows doxazosin bound to the human alpha-1A adrenergic receptor (cryo-EM structure).
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 →
- High blood pressure Arterial hypertension →
Adverse effects
Common
- Dizziness and vertigo
- Fatigue and malaise
- Hypotension, mainly on standing
- Oedema
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.
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.
Related drugs
Related conditions
← Back to the class: 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 (DailyMed (U.S. National Library of Medicine), 2026); Doxazosin: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2025); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).
Spotted a mistake?We are always improving for the community. Tell us what is wrong and our team will review it.Report a mistake
Representative model, for educational purposes only.