Bronchodilator

Bronchodilator: A bronchodilator is a substance that dilates the bronchi and bronchioles, decreasing resistance in the respiratory airway and increasing airflow to the lungs. Bronchodilators may be endogenous (originating naturally within the body), or they may be medications administered for the treatment of breathing difficulties. They are most useful in obstructive lung diseases, of which asthma and chronic obstructive pulmonary disease are the most common conditions. Although this remains somewhat controversial, they might be useful in bronchiolitis and Bronchiectasis. They are often prescribed but of unproven significance in restrictive lung diseases.

Bronchodilators are either short-acting or long-acting. Short-acting medications provide quick or "rescue" relief from acute bronchoconstriction. Long-acting bronchodilators help to control and prevent symptoms. The three types of prescription bronchodilating drugs are β2-agonists (short- and long-acting), anticholinergics (short-acting), and theophylline (long-acting).

These are quick-relief or "rescue" medications that provide quick, temporary relief from asthma symptoms or flare-ups. These medications usually take effect within 20 minutes or less, and can last from four to six hours. These inhaled medications are best for treating sudden and severe or new asthma symptoms. Taken 15 to 20 minutes ahead of time, these medications can also prevent asthma symptoms triggered by exercise or exposure to cold air. Some short-acting β-agonists (for example salbutamol) are specific to the lungs; they are called β2-agonists and can relieve bronchospasms without unwanted cardiac (β1) side effects of nonspecific β-agonists (for example, ephedrine or epinephrine). Patients who regularly or frequently need to take short-acting β-agonists should consult their doctor, as such usage indicates uncontrolled asthma, and their routine medications may need adjustment.

...
Wikipedia