Why is the difference between short-acting beta-2 agonists and long-acting beta-2 agonists important?

Beta-2 agonists are medications that cause the muscles surrounding the respiratory passages of the lungs to relax. When these muscles tighten up, medically called constrict, the passages become smaller. Think of pulling on the drawstring of a purse, like a noose. The amount of air that can pass through this much decreased passage is reduced. Below a certain amount of air, people feel like they are choking or are short of breath. Beta-2 agonists come in two types: short-acting (SABA) and long-acting (LABA). The division is based on the medication's measurable duration of action. By definition, SABA last on average 4-6 hours, whereas LABA last on average 12 to 24 hours.

All SABA have a rapid onset of action, from 1-15 minutes, which makes them ideal for use when you are having an asthma attack. SABA are available in rescue inhalers (trade names in parenthesis) containing albuterol (Proair HFA, Proventil HFA, Ventolin HFA) or pirbuterol (Maxair AH) or levalbuterol (Xopenex HFA).









The onset of action of LABA varies and may NOT be rapid. Confusion about this point led to some tragic deaths from asthma when salmeterol (Serevent) was first sold in the U.S. Some patients used salmeterol during an asthma attack, however the onset of action is at least 30 minutes, which can seem like an eternity when you are the one having the asthma attack. Salmeterol is also available in the combination product Advair. The only other LABA available in the U.S. is formoterol. This is sold individually as Foradil dry powder inhaler, Perforomist for nebulizers, arformoterol or Brovana for nebulizers, and in the combination product Symbicort Turbuhaler.

In summary, asthmatics and their caregivers should know the difference between SABA and LABA. When you are having an asthma attack, it could be a matter of life or death. If you have questions about SABA or LABA, ask your doctor.