Tamsulosin
A prostate-selective alpha-1 blocker used for urinary symptoms of an enlarged prostate (BPH); it is not a treatment for high blood pressure.
Drug card
- Class
- Alpha-1 blocker
- How it works
- Blocking alpha-1 receptors, relaxing blood vessels and prostate muscle
- Used for
- Urinary symptoms of an enlarged prostate (BPH)
- Kidney stones, to help them pass (off-label)
- Known for
- Abnormal ejaculation: less or no semen
- Dizziness, especially on standing
- Floppy iris syndrome during cataract surgery
Study it as a flashcard, and it comes back before you forget it.
Mechanism of action
How does tamsulosin work?
Tamsulosin is selective for the alpha-1A subtype, which makes up roughly 70% of prostatic alpha-1 receptors, so it acts mainly on the prostate, prostatic urethra and bladder neck and is not used to lower blood pressure. It is a sulfonamide, broken down by CYP3A4 and CYP2D6.
Like other alpha-1 blockers: They block alpha-1 adrenergic receptors on smooth muscle, so norepinephrine can no longer contract it. In arterioles and veins this lowers peripheral resistance and blood pressure; in the prostate, its capsule and the bladder neck the muscle relaxes and urine flows more easily. Tamsulosin favors the alpha-1A subtype that dominates the prostate and is not used for blood pressure.
Uses
What is tamsulosin used for?
- Urinary symptoms of an enlarged prostate (BPH)
- Kidney stones, to help them pass (off-label)
Side effects
Side effects of tamsulosin
- Abnormal ejaculation: less or no semenKnown for
- Dizziness, especially on standingKnown for
- Floppy iris syndrome during cataract surgeryKnown for
- Headache
- Runny or stuffy nose (rhinitis)
- Weakness and tiredness
- Back pain
- Palpitations or a fast heartbeat (rare)
- Blurred vision
- PriapismSerious
- Allergic reactions, including angioedemaSerious
- Stevens-Johnson syndrome (rare)Serious
Known for marks what an exam expects you to know it for.
Watch for
Cautions and what sets it apart
- Not for high blood pressure, and not to be combined with another alpha blocker.
- Avoid with strong CYP3A4 inhibitors such as ketoconazole; take care with CYP2D6 inhibitors such as paroxetine.
- Before cataract or glaucoma surgery, tell the eye surgeon: floppy iris syndrome can occur even after stopping.
- Take care in serious sulfa allergy, and with PDE5 inhibitors or warfarin.
Good to know: The prostate-selective member of the class: used for BPH, not for high blood pressure. It does not change PSA, and ejaculation problems and floppy iris syndrome are its best-known effects.
Remember it
A way to remember it
FAINT
- F
- First-dose fall in blood pressure, with fainting
- A
- Abnormal ejaculation, most with tamsulosin
- I
- Intraoperative floppy iris syndrome in cataract surgery
- N
- Nasal stuffiness
- T
- Tiredness and weakness
Written for biofideX
Its class
Alpha-1 blockers
Easily mixed up with central alpha-2 agonists, 5-alpha reductase inhibitors and beta blockers.
Sources
Checked against
Written for biofideX in plain words, after checking these references:
For learning pharmacology, not for treatment decisions: no doses are given, and a prescriber, pharmacist or the product's own label is the word on any one patient. Spotted a mistake? Tell us and we'll correct it.
Blood pressure
Tamsulosin is one of 27 drugs practiced together here: their classes, how they work, what they treat and what they're known for.
Start Practicing