Alpha blockers
Also known as: alpha-adrenoreceptor antagonists
Alpha blockers, also called alpha-adrenoreceptor antagonists, are medicines that relax muscle; tamsulosin is used to relax the muscle around the bladder and prostate in an enlarged prostate. The NHS describes doxazosin as an alpha blocker used to lower high blood pressure, which can reduce the risk of a heart attack or stroke, and to treat symptoms of an enlarged prostate such as problems with peeing. A StatPearls review lists doxazosin, prazosin and terazosin as selective alpha-1 blockers used for high blood pressure, and describes them as second-line choices because of low blood pressure on standing.
- Also called
- alpha-adrenoreceptor antagonists
Mechanism of action
In an enlarged prostate, tamsulosin relaxes the muscle around the bladder and prostate gland, which makes it easier to pee. The NHS says doxazosin lowers blood pressure by widening the blood vessels. A StatPearls review explains that selective alpha-1 blockers widen blood vessels by stopping noradrenaline from activating alpha-1 receptors. A review says that non-selective alpha blockers also block presynaptic alpha-2 receptors, which normally reduce the release of noradrenaline.
Members of the class
Members with a page on this site are linked.
Class effects
- Dizziness or light-headedness, which a hospital leaflet notes may occur when first starting tamsulosin.
- An allergic reaction to one alpha blocker, such as alfuzosin, doxazosin, prazosin or terazosin, is a reason the NHS lists against tamsulosin.
- For doxazosin the NHS lists headaches, swollen feet, ankles or fingers, needing to pee suddenly or more often, and lower stomach pain as the main side effects, which are usually mild and short-lived.
- For tamsulosin the NHS lists dizziness and problems with ejaculation as the main side effects.
Cautions
- The NHS says other alpha blockers, such as doxazosin, alfuzosin, prazosin or terazosin, may lower blood pressure, and some blood pressure medicines may not mix well with tamsulosin.
- Orthostatic hypotension, low blood pressure causing dizziness on standing, is listed by the NHS as a reason tamsulosin is not suitable.
- The NHS also lists severe liver or kidney problems, planned cataract or glaucoma eye surgery and having fainted while urinating or just afterwards among the reasons tamsulosin may not be suitable.
- For doxazosin, the NHS says dizziness is most likely when first starting or after a dose increase, and suggests avoiding alcohol at first; for tamsulosin it says alcohol can add to the blood-pressure-lowering effect and make dizziness worse. (cite also https://www.nhs.uk/medicines/tamsulosin/common-questions-about-tamsulosin/)
- MedlinePlus says dizziness on standing up quickly is more common with doxazosin when treatment starts, when the dose is increased, or when treatment has been stopped for more than a few days.
- The NHS says anyone due to have cataract or glaucoma surgery should tell the doctor in advance, because tamsulosin may cause complications during the operation.
- The NHS says to tell a doctor or pharmacist about medicines for erectile dysfunction, such as sildenafil, tadalafil or vardenafil, when taking tamsulosin.
- The NHS says to call NHS 111 after taking more than the prescribed amount of tamsulosin or doxazosin, because an extra dose can lower blood pressure and raise heart rate. (cite https://www.nhs.uk/medicines/tamsulosin/how-and-when-to-take-tamsulosin/ and https://www.nhs.uk/medicines/doxazosin/how-and-when-to-take-doxazosin/)
Class interactions
Open the Drug Interaction Checker
Connected pages in detail
What each linked page on Anatomy Nexus covers, in a line, for Alpha blockers.
Medications
- Tamsulosin Tamsulosin is an alpha blocker prescribed mainly for the urinary difficulties caused by an enlarged prostate gland.
Guides and news
- Prostate problems: symptoms and seeing a GP Prostate symptoms are mostly urinary, such as a weak flow or going more often.