Why are different kinds of drugs needed to manage asthma?

Asthma medications are directed toward treating the specific cause of the airway narrowing. Although there are many different medications, most can be grouped into 2 categories:

  • bronchodilators that treat the bronchospasm caused by a muscle contraction
  • anti-inflammatory drugs that prevent or treat inflammation in the airways


Bronchodilators are inhaled and can come in short-acting or long-acting formulations.

The most widely used bronchodilators are called beta2-agonists. Beta2-agonists cause the bronchial muscle to relax, thus widening the diameter of the airways. A similar group of drugs, the selective beta2-agonists, are further modified to target their action more specifically on the bronchial muscles. Other types of bronchodilators include anticholinergics and xanthenes.

When should bronchodilators be used?

Short-acting bronchodilators should be used as soon as wheezing or shortness of breath appears. Doctors call this use "as needed." Bronchodilators used in these circumstances are usually short-acting beta2-agonists (SABA), such as salbutamol or terbutaline. Sometimes, if the asthma is moderate or severe, and requires the use of bronchodilators many times a day or night, the doctor will prescribe a long-acting form of bronchodilator. The most commonly used are the long-acting beta2-agonists (LABAs), such as formoterol or salmeterol. Unlike their short acting counterparts, the LABAs must be taken daily to help maintain the airways open, regardless of whether or not wheezing or shortness of breath appears. Warning: these drugs must be used only as directed, as overuse can have very serious effects on the heart and cardiovascular system. In addition, overuse of LABAs can lead to a decrease in the body's ability to respond to these medications over time.

In certain situations, bronchodilators are used preventively. For example, they can be used to prevent exercise-induced asthma – the type of asthma caused by running and other vigorous sports and forms of exercise.

Xanthenes are oral bronchodilators, and include theophylline and oxtriphylline. They are only used for severe asthma that has not been adequately controlled by the inhaled alternatives.

Anti-inflammatory drugs

Anti-inflammatory agents act by preventing or reducing the inflammation that causes asthma symptoms. The inflammation is thought to start when the person's lungs more sensitive to the particles in the air that the general population is otherwise able to tolerate. The particle triggers a series of reactions that cause the airways to swell up and secrete mucus, which causes them to narrow, resulting in an asthma attack. Examples of anti-inflammatory drugs include corticosteroids and leukotriene receptor antagonists (LTRAs).

Corticosteroids are the most commonly used anti-inflammatory agents. They are generally very safe, and are the main treatment for moderately severe to severe asthma. They are most effective at controlling asthma symptoms when used on a regular basis. The largest risk with the use of inhaled corticosteroid (ICS) would be oral thrush, a fungal mouth infection. This can easily be prevented by rinsing out your mouth with water after each time that you use the inhaled corticosteroid.

A common misconception with ICS use is that it stunts growth when used in children. While it has been shown that the use of ICS may slow the rate the child grows, the child is still able to reach full height in adulthood, within about 1cm of what they would have, on average. Your child should take the ICS daily regardless, as it is more important to control the asthma. Otherwise, your child's asthma may worsen, requiring the rescue inhaler more often, and more medications will be required in the long run to provide control.

LTRAs are taken as a pill, and they may be used alone or in addition to corticosteroids. They are also used to prevent symptoms in exercise-induced asthma, and by people who are sensitive to acetylsalicylic acid (ASA). They are not as effective as the corticosteroids.

Omalizumab is an injection that works by blocking the body's response to allergens. It is used for people with asthma whose symptoms are caused by allergies and who continue to have asthma symptoms despite using inhaled corticosteroids. It must be injected every 2 to 4 weeks, depending on the person's weight and the severity of the allergy.

Monitoring asthma at home with a peak-flow meter

Since asthma can change in severity over time due to a number of factors, one way to check whether you're taking the right drug for your asthma is to monitor your condition at home with a peak-flow meter. Peak-flow meters are a reliable, relatively inexpensive, and accurate way of assessing the state of the asthma. They work by measuring airflow in the bronchial tubes, which tells you the amount of narrowing that is occurring.

Peak-flow meters are very useful for determining a plan of action when new drugs have been added, for detecting a worsening of the condition, or for helping an individual assess the severity of their airway obstruction.

Your doctor can tell you what your "predicted flow rate" should be. This value depends on a number of factors, including your age, gender, and height. However, your own "best flow rate" may be less than this value, depending on the state of your asthma. This value will indicate to your doctor what type of action needs to occur.

The medications you take depend on the severity of the asthma

Some people have very mild asthma, such as exercise-induced asthma. However, others experience symptoms more frequently, including cough, coughing up of mucus, wheezing, and shortness of breath. If these symptoms are not relieved by an inhaled bronchodilator, these individuals should be taking an inhaled anti-inflammatory agent. Those with severe asthma often take a number of different agents to help control their symptoms.

Anyone with moderate or severe asthma should be evaluated by a pulmonary (respiratory) or allergy specialist.

The symptoms that a person with asthma suffers from can vary with circumstances. For example, a person's mild asthma may become moderate or severe after catching a respiratory viral infection (such as the cold or flu). During that time, their medication may need to be adjusted. Similarly, sometimes a person with moderately severe asthma becomes better if a source of allergy, for example the family cat, is removed from their environment.