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
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.
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 →
- High blood pressure, alone or with other antihypertensives Arterial hypertension →
Adverse effects
Common
- Dizziness and postural hypotension
- Asthenia (weakness)
- Somnolence
- Nasal congestion
- Peripheral oedema and palpitations
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.
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.
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 - TERAZOSIN HYDROCHLORIDE capsule (DailyMed (U.S. National Library of Medicine), 2026); Terazosin: MedlinePlus Drug Information (MedlinePlus (U.S. National Library of Medicine), 2025); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026).
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Representative model, for educational purposes only.