terazosin
Meaning of terazosin: An alpha blocker that relaxes the muscle collar around the bladder outlet, easing urine flow within days rather than months.
Definition of terazosin
Terazosin is a drug that relaxes smooth muscle in the prostate, the bladder neck and the walls of blood vessels by blocking alpha-1 receptors. It is used mainly to ease the urinary symptoms caused by an enlarged prostate, such as a weak stream, hesitancy and waking at night to pass urine, and it also lowers blood pressure.
How does it help an enlarged prostate?
Obstruction from an enlarged prostate has two components. One is the bulk of the tissue itself. The other is muscle tone: the prostate and bladder neck contain smooth muscle held partly contracted by alpha-1 receptors, and that tension narrows the channel further. An alpha blocker removes the tension but not the bulk, so the stream improves within days while the gland stays the same size. Drugs that shrink the gland work by a different mechanism and take months.
Why is the first dose different?
The same receptors sit in artery walls, so the first dose can drop blood pressure enough to cause dizziness or fainting on standing. The effect is strongest with the initial dose and after each increase, which is why treatment starts low, is taken at night and is built up in steps. Older people and those already taking blood pressure medicines are more susceptible, and drugs for erectile difficulty add to the effect.
How does it compare with other alpha blockers?
| Drug | Selectivity | Practical difference |
|---|---|---|
| Terazosin and doxazosin | Act on vessels as well as prostate | More lowering of blood pressure, dose built up gradually |
| Tamsulosin and silodosin | More selective for the prostate | Less effect on blood pressure, more effect on ejaculation |
| Alfuzosin | Intermediate | Between the two in both respects |
What else is known about it?
All drugs in this class can cause intraoperative floppy iris syndrome, in which the iris behaves unpredictably during cataract surgery, so current or previous use is relevant to the eye surgeon even years later. Nasal congestion, tiredness and reduced or absent ejaculate are common. It lowers blood pressure effectively, but this class is no longer among the first choices for high blood pressure alone, since other drugs reduce cardiovascular events more reliably. The brand name Hytrin refers to the same medicine.
Also known as
Used in a sentence
Terazosin was increased in steps for lower urinary tract symptoms attributed to benign prostatic enlargement.
Good to know
Alpha blockers relax the muscle around the bladder outlet without shrinking the prostate, and a history of taking one remains relevant to cataract surgery because of intraoperative floppy iris syndrome.