[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/) › Terazosin

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

# Terazosin

An alpha-1 blocker for benign prostatic hyperplasia and high blood pressure. Like prazosin, it can cause fainting after the first doses.

Updated 2026-11-01

- Class: [Alpha blockers](https://durgical.com/en/pharmacology/classes/alpha-blockers/)
- Receptor: Alpha-1 adrenergic receptors
- ATC code: G04CA03

◎**Alpha-1 adrenergic receptors**Terazosin

ⓘ No structure of terazosin bound to its receptor is available; the figure shows doxazosin, a quinazoline of the same family, in the binding site of the human alpha-1A adrenergic receptor.

**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

Terazosin, a quinazoline, selectively blocks alpha-1 receptors in vessels, the prostate and the bladder neck. Smooth muscle relaxes, so urine flows more easily and peripheral resistance and blood pressure fall.

- Terazosin blocks alpha-1 receptors in vessels and prostate
- Vascular and prostatic smooth muscle relaxes
- Urine flows more easily and blood pressure falls

## Pharmacokinetics

**Absorption**
Oral

**Half-life**
About 12 hours (label), allowing once-daily use

## Indications

- Symptomatic benign prostatic hyperplasia [Benign prostatic hyperplasia →](https://durgical.com/en/conditions/benign-prostatic-hyperplasia/)
- High blood pressure, alone or with other antihypertensives [Arterial hypertension →](https://durgical.com/en/conditions/arterial-hypertension/)

## Adverse effects

### Common

- Dizziness and postural hypotension
- Asthenia (weakness)
- Somnolence
- Nasal congestion
- Peripheral oedema and palpitations

### Serious (rare, important)

- Syncope, mostly at the start of treatment
- Priapism
- Intraoperative floppy iris syndrome during cataract surgery
- Rare anaphylaxis

## Contraindications

- Hypersensitivity to terazosin

## Key interactions

**PDE-5 inhibitors**
Hypotension has been reported

**Other antihypertensives (for example diuretics, beta blockers)**
Additive hypotension

## What is monitored

- Blood pressure lying and standing
- Urinary symptoms
- Drowsiness and falls

## Nursing care

- Warn about dizziness and fainting after the first dose, after a dose increase and when restarting after a break; 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 lacking; it is used in pregnancy only if the benefit justifies the risk.

## Memory aid

TERAzosin: TERrible dizziness at the start, TERrific flow later.

## Test yourself

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

## Why are patients warned to avoid driving after the first dose of terazosin?

The first-dose effect can cause marked postural hypotension and syncope.

## What do terazosin, doxazosin and prazosin have in common chemically?

They are quinazolines that selectively block alpha-1 receptors.

## Which eye surgery complication is linked to terazosin?

Intraoperative floppy iris syndrome during cataract surgery.

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

## Related drugs

- [Prazosin](https://durgical.com/en/pharmacology/prazosin/)
- [Doxazosin](https://durgical.com/en/pharmacology/doxazosin/)
- [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 - TERAZOSIN HYDROCHLORIDE capsule](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=5a95be60-b242-9183-e063-6394a90a89e6) (DailyMed (U.S. National Library of Medicine), 2026); [Terazosin: MedlinePlus Drug Information](https://medlineplus.gov/druginfo/meds/a693046.html) (MedlinePlus (U.S. National Library of Medicine), 2025); [ATCDDD - ATC/DDD Index](https://atcddd.fhi.no/atc_ddd_index/?code=G04CA03) (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/terazosin/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/pharmacology/terazosin/