Fast-acting bronchodilators are reliever medications (also called rescue medications) used as needed to relieve acute asthma symptoms (asthma attacks) and to prevent asthma symptoms caused by exercise. They act quickly, but most act only for short periods of time. When your asthma gets worse, your doctor may recommend that you temporarily increase the amount of rescue medication you're taking.

Bronchodilators work by opening up the airways, making it easier to breathe. Beta agonists (also called beta-2 agonists) are the main type of fast-acting bronchodilator for asthma treatment. Side effects for these treatments include nervousness, shaking, fast heartbeat, and palpitations. Anticholinergics are another type of less commonly used fast-acting bronchodilator for asthma.

Most fast-acting bronchodilators start working in 1 to 5 minutes, and their effects last for 4 to 6 hours but can vary depending on the specific medication used. Formoterol is a bronchodilator that can be classified as both fast-acting and long-lasting. It starts working within 1 to 3 minutes, and its effects last about 12 hours. However, formoterol should only be used as a reliever medication when used in combination with a controller medication called budesonide.

Most bronchodilators are inhaled using an asthma inhaler, which is a handheld device that delivers the medication when you inhale so it goes directly into the lungs. Some are also available as liquids that can be delivered through a nebulizer (a machine that vaporizes the medications so they can be inhaled through a mask).