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

They're available on prescription as inhalers, nebulisers, tablets or syrup.

The 3 most used types of bronchodilators are:

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

Uses of bronchodilators

Bronchodilators are used to treat long-term conditions where the airways may become narrow and inflamed, such as:

  • asthma
  • chronic obstructive pulmonary disease (COPD)
  • emphysema

Bronchodilators may be either:

  • short-acting – used as short-term relief from sudden, unexpected attacks of breathlessness
  • long-acting – used to help control breathlessness in asthma and COPD, and increase the effects of steroids (corticosteroids) to treat asthma

Get emergency help

You might need emergency help if you have a serious allergic reaction (anaphylaxis) or serious side effect.

Serious allergic reaction

A serious allergic reaction (anaphylaxis) from bronchodilators is rare.

Emergency action required: Go to your nearest emergency department (ED) or phone your GP immediately if you:

  • get heart palpitations
  • have a rapid heartbeat (tachycardia)
  • have an irregular heartbeat (arrhythmia)
  • are wheezy or have difficulties breathing
  • have sudden swelling of your mouth and face
  • develop a rash

Serious side effects

Serious side effects are rare.

Emergency action required: Go to your nearest emergency department (ED) or phone your GP immediately if you have:

  • difficulties breathing
  • heart palpitations
  • a rapid heartbeat (tachycardia)
  • an irregular heartbeat (arrhythmia)

Bronchodilators and steroids

If you have asthma, inhaled steroids are the main treatment to reduce inflammation and prevent flare-ups.

Some people also take bronchodilators to keep the airways open and increase the effects of steroids.

You should never take long-acting bronchodilators without steroids.

If you have COPD, your first treatment is usually with short or long-acting bronchodilators. Steroids are added in some severe cases.

Steroids and bronchodilators are often given together in 1 inhaler. But you may need to use separate inhalers.

Check if you can take bronchodilators

Bronchodilators can be taken by adults and children.

Check with your GP before starting to take a bronchodilator if you:

  • already have a medical condition
  • are taking any other medicine
  • have had an allergic reaction to medicine in the past
  • are trying to get pregnant, already pregnant or breastfeeding

Pregnancy and breastfeeding

Talk to your GP if you use bronchodilators and you're pregnant, trying for a baby or think you might be pregnant.

Bronchodilators can be used while pregnant or breastfeeding if needed. But only under the advice of a GP.

Pregnancy may affect your asthma. It's important to continue taking your medicine as your has GP advised. Have your asthma monitored to make sure it is controlled.

Types of bronchodilators

The 3 most used bronchodilators are:

  • beta-2 agonists
  • anticholinergics
  • theophylline

Beta-2 agonists and anticholinergics are available in both short-acting and long-acting forms.

Theophylline is only available in a long-acting form.

Beta-2 agonists

Beta-2 agonists are used for both asthma and COPD.

Common types of beta-2 agonists are salbutamol, salmeterol, formoterol and vilanterol.

Some types are only available for COPD.

Beta-2 agonists are usually inhaled using a small handheld inhaler. They are also available as tablets or syrup. They can also be injected or nebulised.

A nebuliser is a compressor that turns liquid medicine into a fine mist. A large dose of the medicine can then be inhaled through a mouthpiece or face mask.

Beta-2 agonists work by stimulating beta-2 receptors in the muscles that line the airways. This causes them to relax and the airways can widen or dilate.

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

Read about side effects of beta-2 agonists


Anticholinergics are also known as antimuscarinics. They're mainly used to treat COPD. Some can also be used for asthma.

Common types of anticholinergics are ipratropium, tiotropium, aclidinium and glycopyrronium.

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

Anticholinergics cause the airways to widen by blocking the cholinergic nerves.

These nerves release chemicals that can cause the muscles lining the airways to tighten.

If you have benign prostate enlargement or a bladder outflow obstruction, anticholinergics can cause problems. This could be difficulty peeing and not being able to empty your bladder fully.

Glaucoma can get worse if anticholinergic medicine gets into the eyes.

Read about side effects of anticholinergics


Theophylline is usually taken in tablet or capsule form.

A different version called aminophylline can be given directly into a vein if your symptoms are severe.

Theophylline seems to reduce swelling in the airways, as well as relaxing the muscles lining them. But it's unclear exactly how it works.

The effect of theophylline is weaker than other bronchodilators and steroids.

It's also more likely to cause side effects. It is often only used alongside these medicines if they're not effective enough.

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

If you are aged 65 or older, you may need extra monitoring while taking theophylline.

Read about side effects of theophylline

Take caution when using bronchodilators

Bronchodilators should be used with caution if you have:

  • an overactive thyroid (hyperthyroidism)
  • cardiovascular disease
  • an irregular heartbeat (arrhythmia)
  • high blood pressure (hypertension)
  • diabetes
  • epilepsy, seizures or fits
  • liver or kidney problems
  • eye problems
  • been told you have low levels of potassium in your blood
  • stomach ulcers
  • benign prostate enlargement
  • any condition that affects your pee, such as bladder stones or prostate cancer
  • glaucoma
  • had a heart attack in the last 6 months or have heart problems

Some types of bronchodilators may make these conditions worse. In people with liver problems, it can sometimes lead to a dangerous build-up of medicine in the body.

Taking bronchodilators with other medicines

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

Always read the patient information leaflet that comes with your medicine.

If in doubt, speak to a pharmacist or GP.

Side effects of bronchodilators

Bronchodilators can cause side effects. These are usually mild or do not last long.

But some side effects are serious and may need emergency medical help.

Side effects can also depend on which medicine you're taking.

Read the patient information leaflet that comes with your medicine for a full list of side effects.

Non-urgent advice: Find your patient information leaflet

Your patient information leaflet is the leaflet that comes with your medicine. You can find a digital version of the leaflet online.

Report side effects

You can report any suspected side effects to the the Health Products Regulatory Authority (HPRA): report an issue -

Common side effects

Common side effects of bronchodilators include:

  • trembling, particularly in the hands
  • headaches
  • a dry mouth
  • muscle cramps
  • a cough
  • nausea and vomiting
  • diarrhoea
  • thrush

Side effects of beta-2 agonists

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

  • trembling, particularly in the hands
  • nervous tension
  • headaches
  • muscle cramps

More serious side effects are rare, but can include palpitations and sudden tightening of the airways with some inhalers.

These side effects often improve and disappear completely after you have been using beta-2 agonists for a few days or weeks.

Talk to your a GP if your side effects do not go away. Your dose may need to be changed.

Taking very high does of beta-2 agonists can some times cause heart attacks and a severely low level of potassium in the blood (hypokalemia).

Side effects of anticholinergics

The main side effects of anticholinergics such as ipratropium include:

  • a dry mouth
  • constipation
  • a cough
  • headaches

Less common side effects include:

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

If you have glaucoma, it may get worse if the medicine gets in your eyes when you use an inhaler or a nebuliser.

Side effects of theophylline

Theophylline can cause serious side effects if too much of it builds up in your body.

You'll usually need to have regular blood tests during treatment to make sure the levels of theophylline in your body are safe.

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

The main side effects of theophylline include:

Talk to your GP if you have any of these side effects. Your dose may need to be reviewed.

Fact check

This content was fact checked by a pharmacist, a GP, the National Medication Safety Programme (Safermeds) and the Health Products Regulatory Authority (HPRA).

Page last reviewed: 24 September 2021
Next review due: 24 September 2024

This project has received funding from the Government of Ireland’s Sláintecare Integration Fund 2019 under Grant Agreement Number 123.