Bronchodilators are inhaled medications used in bronchiectasis that make it easier to breathe by relaxing the muscles of the airways. The bronchodilators commonly used for bronchiectasis treatment include short-acting bronchodilators, such as albuterol and levalbuterol, and long-acting bronchodilators, such as formoterol, tiotropium and salmeterol.
Short-acting bronchodilators are used as a rescue medication when there is a need for quick relief of shortness of breath, and long-acting bronchodilators are used regularly to control bronchiectasis symptoms.
How do bronchodilators work?
Bronchiectasis is characterized by its abnormal dilation of the bronchi as a result of cycles of infection and inflammation. It is not fully understood how airflow obstruction happens in non-cystic fibrosis bronchiectasis, although this may be due to an excess of mucus production, a distortion of the bronchial wall, or to the constriction of the muscles of the airways. People with bronchiectasis receive bronchodilators because they work on bronchiectasis airway obstruction.
Short-acting bronchodilators, such as albuterol and levalbuterol, are selective beta2-adrenergic receptor agonists. These receptors are present on the smooth muscle of the bronchi and, when stimulated, relax the muscle and bronchodilate the airways. Beta2-adrenergic receptor agonists also increase the flow of calcium and potassium ions through the walls of the bronchi muscle cells, which causes an imbalance of charges and leads to relaxation of the smooth muscle.
Bronchodilators such as formoterol and salmeterol are long-acting beta agonists (LABAs) that work by relaxing and opening the airways, making breathing easier.
As a selective LABA, their effects are caused by the stimulation of an enzyme called adenyl cyclase that’s located in the cells of the lung muscles. This enzyme helps convert adenosine triphosphate (ATP) to cyclic adenosine monophosphate (cAMP). When the levels of cAMP increase, the muscle cells relax.
Tiotropium is a long-acting muscarinic antagonist, also known as an anticholinergic. It connects to the muscarinic receptors subtypes M1 to M5. The M3 receptors are located in the muscle of the bronchi and are responsible for bronchoconstriction. As tiotropium has affinity to the M3 receptors, it works by inhibiting them on the muscle of the bronchi, leading to bronchodilation.
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