What are beta-blockers and how do they work?
Beta-blockers are medicines that are used to treat a variety of conditions. Their full correct name is beta-adrenoceptor blocking medicines, but they are commonly just called beta-blockers. There are several types of beta-blocker. They include: acebutolol, atenolol, bisoprolol, carvedilol, celiprolol, esmolol, labetalol, metoprolol, nadolol, nebivolol, oxprenolol, pindolol, sotalol, propranolol, timolol. Each type has one or more brand names.
Beta-blockers work by blocking the transmission of certain nerve impulses. The ends of some nerves release a chemical (neurotransmitter) called noradrenaline when the nerve is stimulated. This chemical then stimulates beta-adrenergic receptors. These receptors are tiny structures which occur on cells in various parts of the body including the heart, brain, and blood vessels. When these receptors are stimulated, they cause various effects. For example, nerve impulses to the heart can stimulate beta-adrenergic receptors on heart cells. This causes an increase in the force and rate of the heartbeat.
The beta-adrenergic receptors are also stimulated by adrenaline, a hormone which circulates in the bloodstream. Adrenaline is made in the adrenal gland. The blood level of adrenaline can vary. For example, you may release a lot of adrenaline into the bloodstream when you are frightened or anxious which can cause an increase in your heart rate, and other effects.
The beta-blocker medicine ‘sits’ on beta-adrenergic receptors and stops (blocks) the receptor from being stimulated. So, for example, if beta-adrenergic receptors in the heart are blocked, the force and rate of the heartbeat is reduced.
Which conditions are treated with beta-blockers?
Heart and blood vessel conditions
Because of their effect on the heart cells, beta-blockers may be used to:
- Prevent angina pains.
- Reduce the risk of a further heart attack if you have already had one.
- Control certain abnormal heart rhythms (arrhythmias).
- Help to treat heart failure.
- Lower blood pressure.
Because beta-adrenergic receptors are found in other parts of the body, beta-blockers are also used for various other conditions. These include:
- Glaucoma. Beta-blocker eye drops reduce the fluid that you make in the front chamber of the eye. This reduces the pressure in the eye.
- Anxiety. Beta-blockers do not reduce anxiety itself, but can reduce some of the symptoms. For example, they can reduce shaking (tremor) and a fast heart rate.
- Overactive thyroid gland. Beta-blockers can help to reduce symptoms such as tremor, and slow down a fast heart rate.
- Migraine. Beta-blockers can reduce the number of migraine attacks if the attacks occur frequently.
Which is the best beta-blocker?
Different beta-blockers are used in different circumstances. There are slight differences between the individual beta-blockers. For example, there are differences in side-effects, as well as how many times a day some beta-blockers are taken.
The choice of beta-blocker depends on the condition being treated. Your doctor will advise which is the right beta-blocker for you.
What are the known side-effects?
Most people who take beta-blockers have no side-effects, or only minor ones. However, because of their action in various parts of the body, some people have unwanted side-effects. For example:
- Sometimes the heart rate can go too slowly. This can make you dizzy or feel faint.
- If you have diabetes you need to be aware that beta-blockers may dull the warning signs of a low blood sugar level (hypoglycaemia – often called a hypo). For example, you may not develop palpitations (the sensation of rapid, irregular, or forceful heartbeats) or tremor, which tend to occur as the blood sugar is going too low.
- Some people develop cool hands and feet when taking beta-blockers. This is because they can constrict (narrow) small blood vessels and reduce the circulation to the skin of the hands and feet.
- Tiredness, depression, impotence (you cannot get a proper erection), vivid dreams, nightmares and other sleeping problems occur in some people.
- There is some evidence to suggest that beta-blockers may provoke type 2 diabetes to develop in some people.
Some people with asthma are advised not to take a beta-blocker. If you have asthma or something similar, discuss this with your GP.
The above is not a full list of possible side-effects, but mentions the main ones that may occur. Read the information leaflet that comes with your particular brand for a full list of possible side-effects and cautions.
Do not stop taking a beta-blocker suddenly without first consulting a doctor. When you take a beta-blocker regularly, the body becomes used to it. So, suddenly stopping taking it can sometimes cause problems such as palpitations, a rise in blood pressure, or a recurrence of angina pains. If you do need to stop taking a beta-blocker then your doctor may advise a gradual reduction in dose.
These medicines sometimes react with other medicines that you may take. So, make sure your doctor knows of any other medicines that you are taking, including ones that you have bought rather than been prescribed.
Can I buy beta-blockers?
No. They are only available from your chemist, with a doctor’s prescription.
What is the usual length of treatment?
The length of treatment depends on why you are taking a beta-blocker. Some people only need to take beta-blockers for a few weeks, or months – for example, if you have an overactive thyroid. Some people need to take beta-blockers for the rest of their life (for example, after a heart attack).
Who cannot take betablockers?
You cannot take a beta-blocker if you have:
- Uncontrolled heart failure.
- Prinzmetal’s angina.
- Bradycardia (a very slow heartbeat).
- Hypotension (low blood pressure).
- Certain problems with the rhythm of your heart – for example, sick sinus syndrome.
How to use the Yellow Card Scheme
If you think you have had a side-effect to one of your medicines you can report this on the Yellow Card Scheme. You can do this online at the following web address: http://yellowcard.mhra.gov.uk
The Yellow Card Scheme is used to make pharmacists, doctors and nurses aware of any new side-effects that your medicines may have caused. If you wish to report a side-effect, you will need to provide basic information about:
- The side-effect.
- The name of the medicine which you think caused it.
- Information about the person who had the side-effect.
- Your contact details as the reporter of the side-effect.
It is helpful if you have your medication and/or the leaflet that came with it with you while you fill out the report.
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