About bronchodilators

Bronchodilators are a type of medication that make breathing easier. They do this by relaxing the muscles in the lungs and widening the airways (bronchi).

They're often used to treat long-term conditions where the airways may become narrow and inflamed. This includes:

Bronchodilators may be either:

  • short-acting – used as short-term relief from sudden, unexpected attacks of breathlessness
  • long-acting – used regularly to help control breathlessness in asthma and COPD

Bronchodilators and corticosteroids

Inhaled corticosteroids are the main treatment for asthma. They reduce inflammation and prevent flare-ups.

However, some people may also benefit from taking bronchodilators. These help to keep the airways open and enhance the effects of corticosteroids.

In people with asthma, long-acting bronchodilators should never be taken without corticosteroids.

In COPD, treatment is given with short or long-acting bronchodilators first. Corticosteroids are then added in some severe cases.

Treatment with corticosteroids and bronchodilators may require the use of separate inhalers. However, increasingly these medications are provided together in a single inhaler.

Types of bronchodilator

The 3 most widely used bronchodilators are:

  • beta-2 agonists – like salbutamol, salmeterol, formoterol and vilanterol
  • anticholinergics – like ipratropium, tiotropium, aclidinium and glycopyrronium
  • theophylline

Beta-2 agonists and anticholinergics are available in both short-acting and long-acting forms. Theophylline is only available as an oral tablet in a long-acting form.

Beta-2 agonists

Beta-2 agonists are used for both asthma and COPD, although some types are only available for COPD. They're usually inhaled using a small, hand-held inhaler. They may also be available as tablets or syrup.

For sudden, severe symptoms they can also be injected or nebulised. A nebuliser is a compressor used to turn liquid medication into a fine mist. This allows a large dose of the medicine to be inhaled through a mouthpiece or face mask.

Beta-2 agonists stimulate receptors called beta-2 receptors in the muscles that line the airways. This causes them to relax and allows the airways to dilate (widen).

They should be used with caution in people with:

In rare cases, beta-2 agonists can make some of the symptoms and possible complications of these conditions worse.


Anticholinergics (also known as antimuscarinics) are mainly used for COPD. A few are also licensed for asthma.

They're usually taken using an inhaler. However, some may be nebulised to treat sudden and severe symptoms.

Anticholinergics cause the airways to dilate by blocking the cholinergic nerves. These nerves release chemicals that can cause the muscles lining the airways to tighten.

They should be used with caution in people with:

  • benign prostatic hyperplasia – a non-cancerous swelling of the prostate
  • a bladder outflow obstruction – any condition that affects the flow of urine out of the bladder, like bladder stones or prostate cancer
  • glaucoma – a build-up of pressure in the eye

In people with benign prostatic hyperplasia or a bladder outflow obstruction, anticholinergics can cause problems urinating.

Glaucoma can get worse if anticholinergic medication unintentionally gets into the eyes.


Theophylline is taken in tablet form.

It's unclear exactly how theophylline works. However, it seems to reduce any inflammation (swelling) in the airways and relaxes the muscles lining them.

The effect of theophylline is weaker than other bronchodilators and corticosteroids. It's also more likely to cause side effects, so is often only used alongside these medicines if they're not effective enough.

Theophylline should be used with caution in people with:

  • an overactive thyroid
  • cardiovascular disease
  • liver problems – like liver disease
  • high blood pressure
  • stomach ulcers – open sores that develop on the stomach lining
  • epilepsy – a condition that affects the brain and causes repeated seizures (fits)

Theophylline may cause these conditions to get worse. In people with liver problems, it can sometimes lead to a dangerous build-up of medication in the body.

Other medicines can also cause abnormal build-up of theophylline in the body. This should always be checked by your doctor.

Elderly people may also need extra monitoring while taking theophylline.

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Side effects of bronchodilators

Bronchodilators can sometimes cause side effects, although these are usually mild or short-lived.

The side effects of bronchodilators can vary depending on the specific medication you're taking. Make sure you read the leaflet that comes with your medication to see what the specific side effects are.

Beta-2 agonists

The main side effects of beta-2 agonists like salbutamol include:

  • trembling, particularly in the hands
  • nervous tension
  • headaches
  • suddenly noticeable heartbeats (palpitations)
  • muscle cramps

These side effects often improve and disappear completely after you've been using beta-2 agonists for a few days or weeks. Contact your GP if your side effects persist, as your dose may need to be adjusted.

More serious side effects are rare. However, they can include sudden constriction of the airways (paradoxical bronchospasm). Excessive doses may occasionally cause heart attacks and a severely low level of potassium in the blood (hypokalemia).


The main side effects of anticholinergics like ipratropium include:

Less common side effects include:

  • nausea
  • heartburn
  • difficulty swallowing (dysphagia)
  • palpitations
  • throat irritation
  • difficulty urinating

Glaucoma may worsen if the medication gets in the eyes when using an inhaler or a nebuliser.


Theophylline can cause serious side effects if too much of it builds up in your body. You may need occasional blood level tests during treatment. This will ensure that the levels of theophylline in your body are safe.

Older people are more at risk of developing side effects from theophylline. This is because their livers may not be able to remove it from their body.

The main side effects of theophylline include:

  • nausea and vomiting
  • diarrhoea
  • palpitations
  • a rapid heartbeat (tachycardia)
  • an irregular heartbeat (arrhythmia)
  • headaches
  • problems sleeping (insomnia)

Contact your GP if you have any of these side effects, as your dose may need to be reviewed.

Pregnancy and breastfeeding

In most cases, bronchodilators should be taken as normal while pregnant or breastfeeding.

However, speak to your GP if you regularly use bronchodilators and are considering having a baby or think you might be pregnant.

Pregnancy may affect your asthma. This means it's important to continue taking your medication and have it monitored regularly. This will ensure that the condition is controlled.

Interactions with other medicines

Bronchodilators may interact with other medicines. This could affect the way they work or increase your risk of side effects.

Some of the medicines that can interact with bronchodilators (particularly theophylline) include:

  • some diuretics – a type of medication that helps remove fluid from the body
  • some antidepressants – including monoamine oxidase inhibitors (MAOIs) and tricyclic antidepressants (TCAs)
  • digoxin – a medication used to treat arrhythmias
  • benzodiazepines – a type of sedative that may be used as a short-term treatment for anxiety or sleeping problems (insomnia)
  • lithium – a medication used to treat severe depression and bipolar disorder
  • quinolones – a type of antibiotic medication

This isn't a complete list of all the medications that can interact with bronchodilators. Also, not all of these interactions apply to each type of bronchodilator.

You should always read the patient information leaflet (PIL) that comes with your medication. You may be able to find a specific PIL in the MHRA database on GOV.UK.

If in doubt, speak to your pharmacist or GP.

Last updated:
19 December 2022