Bronchodilators: What are they? Types and Functions of These Respiratory System Dilating Substances

They are medicines used to help improve airflow to the lungs.

They work to relieve symptoms such as shortness of breath during asthma attacks by relaxing the smooth muscle that surrounds the airways.

This allows the airways to open, allowing more air to move in and out of the lungs. In addition to being effective in asthma, they also help improve breathing in patients with lung diseases such as bronchitis, emphysema, pneumonia, and bronchiolitis in young children.

Bronchodilator medications belong to three main groups: beta two agonists (short and long-acting), xanthines, and muscarinic receptor antagonists.

The most widely used group of bronchodilators are beta two agonists, which are used mainly in patients with asthma to dilate the smooth muscle that surrounds our airways by targeting specific receptors.

Short-acting beta-agonists work to provide immediate and acute emergency relief of symptoms. Longer-acting bronchodilators help control symptoms and prevent asthma attacks.

There are two forms of bronchodilators:


  • Short-acting bronchodilators relieve or stop asthma symptoms; you take these to prevent an asthma attack.
  • Long-acting bronchodilators help control asthma symptoms by keeping the airways open for 12 hours; This helps prevent asthma attacks.

There are two main types of bronchodilator medications:

  • Beta 2-agonists (short and long-acting forms).
  • Anticholinergics.

Beta 2-agonists

Short-acting beta two agonists are called “relievers” or “rescue” medications because they stop asthma symptoms very quickly by opening the airways.

These are the best medications to treat sudden and severe or new asthma symptoms. They run for 15 to 20 minutes and last four to six hours.

They are also medications that should be used 15 to 20 minutes before exercise to prevent asthma symptoms. Talk to your doctor if you need to use your short-acting beta two agonists more than twice a week.

This is a sign of unstable asthma, and your doctor may want to change the dose of the long-term controller medications you take.

Long-acting beta two agonist inhalation medications include:

  • Salmeterol (Serevent®).
  • Formoterol (Foradil®).
  • Combination drugs : salmeterol and fluticasone (Advair®); formoterol and budesonide (Symbicort®); formoterol and mometasone (Dulera®). These contain both the long-acting beta-agonist and an inhaled corticosteroid.

Salmeterol and formoterol are the only long-acting inhaled beta two agonists available. They are used twice a day to keep the airways open for long-term control and should be used with an inhaled corticosteroid to treat asthma.

They have also been shown to help treat exercise-induced asthma. They are available in the form of a dry powder inhaler (IPS).

Side effects of beta two agonists include:

  • Nervous or unsteady feeling.
  • Overexcitement or hyperactivity.
  • Incrise of cardiac frecuency.
  • Upset stomach (rare).
  • Difficulty sleeping (occasional).

Albuterol is also available in pills or syrups. These drugs tend to have more side effects because they are in higher doses and are absorbed through the bloodstream to reach the lungs.

Inhaled forms are preferred because they are deposited directly into the lungs and have fewer side effects.

Anticholinergic drugs

Currently, there are two anticholinergic bronchodilators available: ipratropium bromide (Atrovent® HFA), which is known as a metered-dose inhaler, and nebulizer solution, and tiotropium bromide (Spiriva®), which is a dry powder inhaler. Ipratropium is used four times a day.

Tiotropium is used only once a day and lasts for 24 hours. It should be used at the same time every day. These are not quick-relief medications, but they can increase the bronchodilator effect of certain asthmatics with difficult-to-control symptoms.

The side effects are minor; dry throat is the most common.

If the medicine gets into your eyes, it may cause blurred vision for a short period.


Theophylline is another type of bronchodilator used to control asthma. Trademarks include Uniphyl®, Elixophyllin®, Theochron, and Theo-24®. Theophylline is available as a pill or as an intravenous (through a vein) drug.

It is long-acting and prevents asthma attacks. Theophylline can be used to treat difficult-to-control or severe asthma and should be taken daily. When you take theophylline, blood tests are needed to ensure you are getting the correct amount of medicine.

Side effects include:

  • Nausea and vomiting.
  • Diarrhea.
  • Stomach ache.
  • Headache.
  • Fast or irregular heartbeat
  • Muscle cramps.
  • Nervousness.
  • Hyperactivity

These side effects can be a warning of too much medicine. Call your doctor if you have any of these side effects.

Tell all your doctors if you take theophylline for asthma because certain medications, such as antibiotics containing erythromycin or medicines for seizures and ulcers, can interfere with how theophylline works.

Also, viral diseases and smoking can change how your body responds to theophylline.

Always tell your doctor if you take theophylline for asthma because certain medications, such as erythromycin-containing antibiotics or seizures and ulcers, can interfere with how theophylline works.

Also, viral diseases and smoking can change how your body responds to theophylline.