A bronchodilator is a medication that relaxes and opens the airways, or bronchi, in the lungs. A doctor may prescribe them for asthma and other respiratory conditions.

Respiratory diseases, such as asthma and chronic obstructive pulmonary disease (COPD), cause bronchospasm, which is constriction or narrowing of the airways.

Narrowed airways make it challenging for a person to cough mucus up. It also makes it difficult for them to get air in and out of the lungs. Taking a bronchodilator helps dilate or widen the airways, making it easier to breathe.

Short-acting and long-acting bronchodilators treat various lung conditions and are available by prescription.

This article examines how bronchodilators work, the various types, and how to take them.

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Bronchodilators work by relaxing the muscles in the airways. The relaxation causes the airways to open up and the bronchial tubes to widen. There are different types, each working in slightly different ways. They include:

Beta-2 agonists

This class of bronchodilator causes the smooth muscles surrounding the airways to relax by stimulating beta-adrenoceptors in the airways. This improves airflow and reduces symptoms, such as shortness of breath.

Beta-2 agonists come in short-acting varieties to dilate the airway immediately, and long-acting varieties, which maintain open airways. Short-acting beta-2 agonists include:

  • salbutamol (albuterol)
  • levalbuterol
  • pirbuterol

Anticholinergic drugs

Anticholinergic bronchodilators block the action of acetylcholine. Acetylcholine is a chemical released by the nerves that can lead to tightening of the bronchial tubes. By blocking the chemical, anticholinergic bronchodilators cause the airways to relax and open.

As with beta-2 agonists, Anticholinergic drugs come in both short-acting and long-acting forms. Some long-acting forms include:

  • aclidinium bromide
  • tiotropium bromide
  • glycopyrrolate or glycopyrronium bromide
  • umeclidinium bromide

Ipratropium is an example of a short-acting anticholinergic.

Xanthine derivatives

Xanthine derivatives also relax the airway muscles, although doctors do not know precisely how they work.

The main xanthine derivative is theophylline. Theophylline comes in an oral and intravenous injectable form. Doctors now rarely prescribe theophylline due to many people experiencing significant side effects. At relatively low doses, it can cause:

For this reason, it is safest to try other drugs first. If those do not work, doctors should start with a low dose, monitoring symptoms consistently, and slowly increase the dosage based on how well a person tolerates the drug.

There are two main types of bronchodilators: long-acting and short-acting. Both types have a role in treating common lung diseases, such as asthma and COPD.

Both beta 2-agonists and anticholinergic bronchodilators come in a short-acting and long-acting form.


Doctors often call short-acting bronchodilators “rescue inhalers” or “fast-acting inhalers” as they treat symptoms that come on suddenly, such as wheezing, shortness of breath, and chest tightness.

Short-acting bronchodilators work quickly, usually within a few minutes. Although they work fast, the therapeutic effects generally only last 4–5 hours. Short-acting bronchodilators treat sudden symptoms, and people do not need to use them when they are symptom-free.

Common short-acting bronchodilators include:

According to the American Academy of Allergy, Asthma and Immunology, if a person needs fast-acting bronchodilators more than twice per week, their symptoms are not well-controlled. They may need a long-acting bronchodilator or controller medication.


Long-acting bronchodilators do not work as quickly as short-acting bronchodilators and do not treat acute or sudden symptoms. The effects can last for up to 24 hours, and people take them daily to prevent symptoms from developing.

Common long-acting bronchodilators include:

People usually use inhaled bronchodilators as this format allows the medication to reach the lungs fast. It also allows a person to take smaller doses of the drug and results in fewer body-wide side effects than when people take them orally.

The best type of bronchodilator to take may depend on a person’s age, preference, and level of consciousness. Matching the best device to the person’s ability will provide the most effective treatment.

It is important to understand how to take bronchodilators correctly to ensure that the most medication possible reaches the lungs. The most common ways of administering bronchodilators include:

Metered dose inhalers

A metered dose inhaler (MDI) is a small, pressurized canister that contains medication. The device releases the medicine when a person presses down on the canister. A propellant in the MDI carries the medication dose into the lungs.


A nebulizer uses bronchodilator medication in the form of a liquid and turns it into an aerosol that the person then inhales through a mouthpiece.

Dry powder inhaler

A dry powder inhaler does not have a propellant, and the bronchodilator is in powder form.

Soft mist inhaler

Some bronchodilators are available in soft mist inhalers. Soft mist inhalers deliver an aerosol cloud into the lungs without a propellant.

Older research indicates that aerosol from a soft mist inhaler is slower-moving and longer-lasting than those from MDIs, meaning they deliver more medication to the lungs and less on the back of the throat.

Other forms

Additional forms of bronchodilators include tablets and syrups.

Determining the best way to administer a bronchodilator is vital to ensure that a person gets the correct dose of medication. For example, if a person cannot effectively coordinate taking an MDI, some of the medication may end up in the back of the throat or the mouth instead of the lungs.

As with most types of medications, bronchodilators may cause side effects.

The severity of the side effects is sometimes dose-dependent. The higher the dose, the more likely it is that side effects may develop. However, side effects can also occur with small doses.

Side effects may also differ depending on whether the bronchodilator is a beta 2-agonist or an anticholinergic. Possible side effects of bronchodilators include:

It is also possible that a bronchodilator can have the opposite effect and make constriction worse or lead to bronchospasm. As with all medications, an allergic reaction is also possible.

The Centers for Disease Control and Prevention (CDC) recommend that pregnant people with asthma continue taking their medication during pregnancy.

Data from the National Birth Defects Prevention Study suggests higher rates of some, but not most, birth defects in babies born to people who take bronchodilators during pregnancy. These include:

  • esophageal atresia, which affects the esophagus
  • anorectal atresia, which affects the anus
  • omphalocele, which affects the abdominal wall

However, it is not clear whether asthma causes these conditions or whether the drugs that control it do.

Researchers have established a correlation between having asthma and a higher risk of negative pregnancy outcomes. This means that, for people whose asthma does not get better during pregnancy, continuing to use medication is usually the safer option.

Pregnant people should discuss the risks and benefits of treatment with a healthcare professional.

Bronchodilators may interact harmfully with many different types of medications. Some common drug interactions include:

This is not an exhaustive list, and it is possible for drugs not on this list to trigger negative drug interactions.

A person should inform a doctor about all the medications they use, including supplements and over-the-counter medicines, before trying a bronchodilator.

Bronchodilators are a class of medication that relaxes the muscles surrounding the airways. Bronchodilators are one of the main treatments for respiratory diseases, such as asthma, COPD, and chronic bronchitis.

There are two broad categories of bronchodilator: short-acting and long-acting. There are also different types and formats, all of which work in slightly different ways. The type a person chooses to use can depend on their circumstances, preferences, age, and symptom severity.

Although bronchodilators can reduce symptoms, such as wheezing and trouble breathing, they may also cause side effects. People with lung conditions can work with their healthcare professional to determine if the benefits of bronchodilators outweigh the possible side effects.