Beta blockers: how do they work and do they have side effects?

What are beta blockers?

Many people in the UK take a beta blocker medicine. Each year there are more than 50 million prescriptions for beta blockers in the UK.

They’re most commonly used for heart and circulatory conditions. They’re prescribed to treat irregular heart rhythms, angina and to help lower blood pressure.

People living with heart valve disease, heart failure or who have had a heart attack may be prescribed a beta blocker too.

Doctors also sometimes prescribe beta blockers for non-heart conditions such as anxiety.

Common beta blockers include:

atenolol (brand names include Tenormin)
bisoprolol (brand names include Cardicor, Congescor)
carvedilol
metoprolol (brand names include Betaloc, Lopresor)
nebivolol (brand names include Nebilet)
propranolol (brand names include Inderal).

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How do beta blockers work?

Beta blockers – whose full name is beta adrenergic blocking agents – mainly work by slowing down the heart rate, which reduces the force at which blood is pumped around your body.

They do this by blocking the effects of the stress hormones adrenaline and noradrenaline which can make the heart work harder and faster.

Diagram of human body with text saying 'How do beta blockers work?

As well as relaxing the heart, some beta blockers relax blood vessels too, which helps to lower blood pressure.

Beta blockers can also block your kidneys from producing a hormone called angiotensin II, which can help to lower blood pressure.

A normal heart rate and blood pressure are:

Heart rate – between 60 and 100 beats per minute (bpm) when resting.
Blood pressure – between 90/60 mmHg and 120/80 mmHg for adults. But for the over-80s it’s higher at 150/90 mmHg (or 145/85 mmHg at home) because arteries get stiffer as we get older.

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Why would I be prescribed a beta blocker?

Angina

Clinical guidelines recommend beta blockers as a first-line treatment for everyone with angina, either on their own or, with another heart medicine called a calcium channel blocker.

Beta blockers slow your heart rate. This reduces the amount of oxygen the heart needs to work, which in turn means fewer angina episodes.

Read more about angina.

Heart failure

If you have a certain type of heart failure that’s caused when the main chamber of the heart is not working properly, beta blockers are known to improve your life expectancy.

This is why clinical guidelines recommend that everyone with ‘heart failure with reduced ejection fraction’ (HFrEF) take a beta blocker, regardless of how bad their symptoms are.

As well as a beta blocker, you will also likely be prescribed an angiotensin converting enzyme (ACE) inhibitor, such as ramipril.

If you have heart valve disease your doctor will also likely prescribe you a beta blocker.

Read more about heart failure.

Irregular heart rhythm (arrythmia)

Because beta blockers help slow the heart rate to normal and can control irregular heart rhythms, they can be used to treat some irregular heart rhythm conditions like atrial fibrillation.

They help improve symptoms of atrial fibrillation, such as heart palpitations and fatigue.

Read Sad's story of living with atrial fibrillation.

Heart attacks

If you’ve had a heart attack, clinical guidelines recommend that you are prescribed a beta blocker before being discharged from hospital.

This is to reduce your risk of having another heart attack. Treatment is usually continued for life.

Read more about heart attacks.

High blood pressure

Beta blockers are prescribed for people with high blood pressure that’s hard to treat with other medicines.

They’re usually given as part of a treatment plan that may also include an ACE inhibitor and/or a calcium channel blocker.

Read more about high blood pressure.

Anxiety

The beta blocker propranolol is commonly used as a short-term treatment for anxiety as it helps alleviate physical symptoms such as sweating, shaking and heart palpitations.

It does this by blocking the effects of the stress hormones adrenaline and noradrenaline, which are released as part of our body’s natural response to perceived threats.

They prepare us to either ‘fight’ or ‘flight’ (runaway) from the threat, causing breathing and heart rates to rise and blood pressure to increase.

Taking a beta blocker can help calm this response down that in turn reduces anxiety symptoms.

Are there different types of beta blockers?

Beta blockers are classed as being either selective or non-selective:

Selective beta blockers – such as atenolol and bisoprolol, are more commonly used for heart conditions because they mostly block adrenaline and noradrenaline in the heart, with less effect on other parts of the body, which reduces side effects.
Non-selective beta blockers – such as propranolol block adrenaline and noradrenaline act in other areas of the body as well as the heart. This is why they’re more commonly used to treat non-heart conditions such as anxiety. However, they can cause side effects, including cold hands and asthma attacks.

Are beta blockers safe for everyone?

Beta blockers are not recommended for some heart conditions.

These include uncontrolled heart failure, very low blood pressure (hypotension), certain heart rhythm disorders and bradycardia (when you have a very slow heartbeat).

If you have an airways disease like asthma or chronic obstructive pulmonary disease (COPD), you will not normally be prescribed beta blockers either.

This is because they can occasionally provoke severe asthma attacks.

Your doctor will weigh up the benefits of having a beta blocker against the risk of having an asthma attack when deciding to prescribe it or not.

Can beta blockers weaken the heart?

Some people worry that beta blockers can make the heart weaker because they slow it down.

But beta blockers have the opposite effect; they can make the heart muscle stronger. They help to protect the heart in people who have had a heart attack or heart failure.

Taking more than your prescribed dose of beta blocker can lead to your heart rate becoming dangerously low.

However, your doctor will closely monitor you to make sure you’re taking the right dose.

Do beta blockers have side effects?

Beta blockers are usually tolerated well without significant side effects.

However, they may cause cold hands and feet, particularly in older people, and may be associated with unusually vivid dreams.

Some people also experience fatigue – perhaps related to excessive slowing of the heart rate. And erectile dysfunction is occasionally a problem for some men who take beta blockers.

If you think you’re experiencing side effects, do not stop taking your beta blocker without consulting your doctor first.

This is because when you take a beta blocker regularly your body becomes used to it and stopping it suddenly could cause problems such as heart palpitations, a recurrence of angina pain, or a rise in blood pressure.

Are there alternatives to beta blockers?

Side effects can often be managed by reducing the dose or switching to a selective beta blocker.

However, if you have problems with beta blockers, there are alternative drugs available.

If you have angina or atrial fibrillation, for example, other drugs that slow the heart rate, such as diltiazem or verapamil, may be substituted.

The recently available ivabradine also slows the heart rate and can be used to treat angina (but not atrial fibrillation) if beta blockers aren’t advised.