Alpha-blockers are medicines that are mainly used to treat high blood pressure (hypertension) and (in men who have enlargement of the prostate gland) problems with passing urine. If you have hypertension, alpha-blockers are usually prescribed after most other medicines have already been tried. If you have problems passing urine (because of an enlarged prostate gland), the decision to start alpha-blockers depends on how much you are bothered by the symptoms. Side-effects are uncommon (slight drowsiness, headaches and dizziness). They are more likely to occur in the first two weeks of treatment and usually go away on their own.

What are alpha-blockers?

Alpha-blockers are medicines that are mainly used to treat high blood pressure (hypertension) and problems with passing urine in men who have enlargement of the prostate gland. Prostate gland enlargement is also called benign prostatic hyperplasia (BPH). An enlarged prostate gland can cause problems with passing urine, such as:

  • Having to wait before your urine starts to flow.
  • Taking longer to pass urine.
  • Dribbling urine.
  • Feeling that your bladder is not quite empty.

In the past, some alpha-blockers were also used to treat heart failure and Raynaud’s phenomenon. However, they are very rarely used to treat these conditions now because there are other medicines that are thought to work better.

Alpha-blockers are also sometimes used to treat ureteric stones. These are stones that have formed in the kidney and have then got stuck in the ureter, which is the tube that goes from the kidney to the bladder. They cause pain called renal or ureteric colic. An alpha-blocker may help to speed up the time it takes for the stone to get into the bladder and stop causing pain.

There are six alpha-blockers available to prescribe in the UK. They are: alfuzosin, doxazosin, indoramin, prazosin, tamsulosin and terazosin. Alpha-blockers come as tablets or capsules which may be taken once a day or up to three times a day. They come in various brand names.

The rest of this leaflet only discusses the use of alpha-blockers to treat hypertension or the symptoms of prostate gland enlargement. See the separate leaflets called High Blood Pressure (Hypertension) and Prostate Gland Enlargement for more information on these conditions.

How do alpha-blockers work?

Alpha-blockers work by blocking the transmission of certain nerve impulses. The ends of some nerves release a chemical (neurotransmitter) called noradrenaline (norepinephrine) when the nerve is stimulated. This chemical then stimulates alpha-adrenergic receptors. These receptors are tiny structures which occur on cells in various parts of the body, including the heart, involuntary (smooth) muscles and blood vessels. When these receptors are stimulated, they cause various effects.

The alpha-blocker medicine attaches to alpha-adrenergic receptors and stops (blocks) the receptor from being stimulated. This can have various effects in the body:

  • For high blood pressure (hypertension): alpha-blockers work by relaxing blood vessels. This allows blood and oxygen to circulate more freely around your body, lowering blood pressure and reducing strain on your heart.
  • For prostate gland enlargement: alpha-blockers work by relaxing the muscles of your bladder and around your prostate gland so that you can pass urine more easily.

When are alpha-blockers usually prescribed?

For high blood pressure (hypertension): alpha-blockers are usually prescribed after most other medicines have been tried. Alpha-blockers are normally only started by doctors who specialise in treating hypertension and only if:

  • Other medicines such as beta-blockers, angiotensin-converting enzyme (ACE) inhibitorsor ‘water’ tablets (diuretics) are not working. They may be used as well as these other medicines.
  • There is a reason you cannot take a beta-blocker, an ACE inhibitor or a diuretic.

Having hypertension increases your risk of having a heart attack or a stroke, or developing chronic kidney disease or heart failure. There are many studies which show that medicines such as beta-blockers, ACE inhibitors and diuretics are better than alpha-blockers at lowering the risk of having these conditions.


For prostate gland enlargement: the decision to start alpha-blockers depends on how much you are bothered by the symptoms. For example, you may be glad for some treatment if you are woken six times a night, every night, with an urgent need to go to the toilet. On the other hand, slight hesitancy when you go to the toilet and getting up once a night to pass urine may cause little problem and not need treatment. Your doctor will help you decide if this treatment is right for you.

Which alpha-blocker is usually prescribed?

For high blood pressure (hypertension): once-daily preparations of doxazosin or terazosinare usually recommended. Once-daily preparations are generally thought to be easier for people to take and to remember to take. Prazosin and indoramin need to be taken two or three times each day and prazosin is more likely to cause a large drop in blood pressure after the first dose has been taken.

For prostate gland enlargement: once-daily preparations of alfuzosin, doxazosin, tamsulosin or terazosin are generally recommended. This is because once-daily preparations cause fewer side-effects than the preparations that need to be taken up to three times a day.

How well/quickly do alpha-blockers work?

For high blood pressure (hypertension): there are very few studies that have looked at how well alpha-blockers work in people with hypertension. However, they have been used for many years to treat this condition.

For prostate gland enlargement: in most cases, symptoms improve with taking an alpha-blocker. However, the amount of improvement varies from person to person. Some improvement usually occurs within a few days but the full effect may take up to six weeks. Alpha-blockers do not cure the problem, nor do they usually make symptoms go completely. However, symptoms often ease if you take a medicine. There is no real difference between how effective each of the alpha-blockers is. However, some tend to cause side-effects more often than others.

What is the usual length of treatment?

Most people with high blood pressure (hypertension) need to take medication for life. However, in some people whose blood pressure has been well controlled for three years or more, medication may be able to be stopped. In particular, in people who have made significant changes to lifestyle (such as having lost a lot of weight or having stopped smoking or heavy drinking, etc). Your doctor can advise you.

For people with symptoms caused by prostate gland enlargement, alpha-blockers are also usually taken long-term. Your doctor will usually review your symptoms every 4-6 weeks after you start treatment. Once your symptoms have settled down, your treatment is usually reviewed every year. This is to make sure it is still working.

Taking other medicines

There are a number of medicines that should usually be avoided if you also take an alpha-blocker. These include:

  • Phosphodiesterase-5 inhibitors – for example, sildenafil for erectile dysfunction.
  • Antidepressants such as tricyclic antidepressants, mirtazapine or venlafaxine.

When these medicines are combined with an alpha-blocker, you may have a sudden drop in blood pressure (postural hypotension).

What about side-effects?

Although side-effects are uncommon, they occur in some people. Side-effects are more likely to occur in the first two weeks of treatment and usually go away on their own. The most common side-effects are slight drowsiness, headaches and dizziness. More rarely they can cause sexual problems. Alpha-blockers are also associated with an increased risk of falling and of breaking a bone (fracture) when they are first started. This is probably due to the effects they have on lowering blood pressure. If you are prescribed an alpha-blocker, read the leaflet that comes with the medicine packet for a full list of possible side-effects and cautions.

Can I buy alpha-blockers?

You cannot buy alpha-blockers. They are only available from your chemist, with a doctor’s prescription.

Who cannot take alpha-blockers?

Most people are able to take an alpha-blocker. However, they are usually not prescribed to people who have had a drop in their blood pressure on standing (postural hypotension) and fainting while urinating (micturition syncope).


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