Beta-agonists are medications that mainly affect the muscles around the airways (bronchi and bronchioles). When the lungs are irritated, bands of muscle around the airways tighten, making the airways narrower. This often results in breathlessness. Beta-agonists work by telling the muscles of the airways to relax, widening the airways. This results in easier breathing.

There are two different kinds of beta-agonist, grouped according to how long they work, which are short-acting or long-acting. Beta-agonists can be given in several ways but the most common way is by inhalation. Pills, tablets and intravenous forms of the drugs are used but have more side-effects.

What are short- and long-acting beta-agonists?
Short-acting beta-agonists work quickly (within 3 to 5 minutes), but may only last 46 hours. These medications are often given as reliever medications because they bring such quick relief for breathlessness. They can also be used to prevent or reduce symptoms that are known to be caused by specific situations such as exercise, showering or going out in the cold air. Short-acting drugs are usually inhaled by a MDI, DPI or in liquid form from a nebulizer device. Some short-acting beta-agonists are also available in tablet form.

A list of short-acting beta-agonists

Long-acting beta-agonists last about 12 hours and are considered maintenance drugs. Medications from this group are relatively new and therefore only two are currently available: formoterol (Oxis, Foradil) and salmeterol (Serevent). Formoterol is different from salmeterol in that formoterol is both a short- as well as a long-acting bronchodilator. Formoterol works soon after inhalation (3-5 minutes) and lasts for 4-6 hours, while the long-acting ingredient begins to work in 20 minutes and lasts 12 hours. Conversely, salmeterol contains only a long-acting ingredient. Salmeterol begins to work in about 20 minutes and lasts for 12 hours. The 12-hour protection of these drugs is an important feature in providing stable airways on a day-to-day basis. Some people with COPD sleep better at night or find they need to use their "reliever" medication less frequently because of this benefit.

A list of long-acting beta-agonists

What problems (side-effects) should I watch for with beta-agonists?
Beta-agonists mainly affect the muscles in the airways. They may also affect the muscles in the heart and around the bones. When the muscles in the heart are affected, a fast heart beat and palpitations (fluttering feeling in the chest) may occur. These medications may also affect the muscles of the bones (called skeletal muscles), causing shakiness and cramping of the hands, legs and feet. Often this combination of a fast heart rate and shakiness causes anxiety (nervousness) and worsens breathlessness. These side-effects can last for a few minutes and may go away after a few days of regular use. Sometimes, the side-effects do not go away, and you may need to stop the drug and try another type or brand. Often these effects happen because too much of the medication coats the mouth and it gets absorbed instead of inhaled. This can be avoided by using a good technique, a spacer/chamber device and rinsing your mouth after use. Side-effects may also mean you are taking the medication more often than you should. For example, many short-acting beta-agonists should not be taken more than every 4 hours, unless otherwise instructed by your provider. Long-acting beta-agonists are generally not recommended more than every 12 hours. Taking beta-agonists more often causes side-effects with little improvement and sometimes worsening of your breathing.

How often and how much should I take?
How often you take your medication depends on how long the medication lasts and whether the medication is for maintenance or relief/rescue. For example, if you are prescribed a maintenance medication that lasts 6 hours (short-acting), then you will need to take the medication every 6 hours by dividing the hours you are awake into four parts. Now that long-acting beta-agonists are available, short-acting beta-agonists are being used by some providers mainly as a relief/rescue medication in the treatment of COPD. Reliever medications should be used before strenuous activity or at other times when symptoms worsen, such as during an exacerbation or worsening of your COPD. While short-acting beta-agonists act rapidly, they also leave the body rapidly (4-6 hours). Conversely, long-acting beta-agonists leave the body more slowly (12 hours) and therefore are taken every 12 hours (twice a day).

The amount of medication (dose of drug) you take will depend on the drug and how much your breathing is under control. Your provider will talk to you about the number of inhalers or tablets to take. It is important not to assume that just because a dose of one drug is higher than another that the higher-dosed drug is more powerful. Drug dosages will change with different chemical ingredients. If you have questions about the dose of your medication, discuss your concerns with your healthcare provider.

What should I do if I forget to take my beta-agonist medication?
If you forget to take your regular dosage of beta-agonist medication, do not try to "make up" for missing a dose by taking twice as much. Doubling your dose will probably not improve your breathing, but will most probably cause you to have side-effects.