An alpha-blocker
Terazosin
An alpha-blocker used for an enlarged prostate and for high blood pressure.
What is Terazosin?
Terazosin is an alpha-blocker, a medicine that relaxes the muscle in blood vessel walls and in the prostate. It is used mainly to ease the urinary symptoms of an enlarged prostate, helping the flow of urine, and it also lowers blood pressure. Like other alpha-blockers, it carries a "first-dose effect": the first dose can cause a sudden drop in blood pressure with dizziness or fainting, so it is started at bedtime. An advantage over some alpha-blockers is that it is usually taken once a day.
Education and reference only. This is a plain-language guide to Terazosin — it deliberately contains no doses. Doses depend on the person, the brand and the reason for treatment, and belong with your prescriber. Always check the BNF, the product labelling (SmPC) and follow medical advice.
What it is
Terazosin is an alpha-blocker, a medicine that blocks the signal keeping muscle in blood vessel walls and the prostate tightened. By relaxing the muscle around the prostate and bladder outlet it eases the urinary symptoms of an enlarged prostate (benign prostatic hyperplasia), and by relaxing blood vessels it lowers blood pressure. It is taken by mouth as a tablet, usually once a day. As with other alpha-blockers, the first dose is treated with care.
How it works
Terazosin blocks alpha receptors, which normally signal the muscle in blood vessel walls and around the prostate to stay tight. When this signal is blocked, the prostate and bladder outlet relax, making it easier to pass urine, and the blood vessels widen, lowering blood pressure. Because the first dose can relax the vessels suddenly, blood pressure may drop sharply to begin with, so the first dose is taken at bedtime.
Company & origin
Originated / developed by: Generic (long-established).
A long-established alpha-blocker used in the UK mainly for prostate-related urinary symptoms and also for high blood pressure.
What it treats
Conditions Terazosin is used for
Practical use
How to take Terazosin
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- Take the very first dose at bedtime to reduce the risk of a sudden drop in blood pressure.
- Take it regularly as prescribed thereafter, usually once a day.
- Get up slowly from sitting or lying down, especially when starting or after a dose increase.
- If you feel faint, sit or lie down until it passes, and tell your prescriber if it keeps happening.
- Take extra care if you also take water tablets or other blood pressure medicines, which add to the effect.
- Do not stop it suddenly without advice, particularly if you take it for blood pressure.
Weighing it up
Advantages & disadvantages of Terazosin
Advantages
- Eases the urinary symptoms of an enlarged prostate and also lowers blood pressure.
- Usually taken once a day, which is convenient.
- A long-established medicine with familiar effects.
Disadvantages
- The first dose can cause a sudden drop in blood pressure with dizziness or fainting.
- Can cause ongoing faintness on standing, tiredness and a stuffy nose.
- Does not shrink the prostate; it relieves symptoms rather than treating the underlying enlargement.
Practical use
Good to know
Terazosin is used mainly to relieve the bothersome urinary symptoms of an enlarged prostate, such as a weak stream, hesitancy and needing to pass urine often. It also lowers blood pressure. Its key caution, shared with other alpha-blockers, is the "first-dose effect": the first dose, or the first after an increase, can cause a sudden fall in blood pressure with dizziness or fainting, so it is taken at bedtime to start, and getting up slowly helps. It is usually taken once a day, which is convenient. Feeling faint on standing, tiredness and a stuffy nose are other common effects.
Who should not take it / use with caution
- People who have fainting when passing urine should avoid it, as it can worsen this.
- Used with caution in those prone to feeling faint on standing, including some older people.
- Care is needed in people having cataract surgery, as alpha-blockers can affect the eye during the operation.
Monitoring
- Blood pressure checks, including for faintness on standing, especially when starting or increasing the dose.
- Reviewing whether prostate-related urinary symptoms are improving.
- Watching for dizziness or fainting and whether dose timing helps.
Side effects
- Dizziness, light-headedness and fainting, especially with the first dose or on standing.
- Tiredness, headache, a stuffy nose and swollen ankles.
- In men, occasionally problems with ejaculation.
Key interactions
- Adds to the blood-pressure-lowering effect of other blood pressure medicines and water tablets.
- Medicines for erectile problems can together cause a marked drop in blood pressure.
- Care is needed with other medicines that cause faintness on standing, so tell your prescriber what you take.
Available as: Tablets taken by mouth.
Answers
Terazosin: frequently asked questions
What is terazosin mainly used for?
It is used mainly to ease the urinary symptoms of an enlarged prostate, such as a weak stream and frequent urination, and it also lowers blood pressure.
Why should I take the first dose at bedtime?
The first dose can cause a sudden drop in blood pressure with dizziness or fainting, so taking it at bedtime means you are lying down if this happens.
Does it cure an enlarged prostate?
No, it relaxes the muscle around the prostate to relieve symptoms rather than shrinking the prostate or treating the underlying enlargement.
How often do I take it?
It is usually taken once a day, which many people find convenient compared with alpha-blockers taken more often.
Why do I feel faint when I stand?
It relaxes blood vessels, which can lower blood pressure on standing; getting up slowly helps, and you should tell your prescriber if it persists.
The wider class
About Alpha-blocker
Terazosin belongs to the alpha-blocker class. For how the class as a whole works, its shared safety principles and monitoring, see the full guide.
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Authoritative sources
- BNF
- NICE CKS
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