Bronchodilators

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Almadhoun K, Sharma S

Bronchodilators

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Abstract

Bronchodilators are indicated for individuals that have lower than optimal air flow through the lungs. The mainstay of treatment is beta-2 agonists that target the smooth muscles in the bronchioles of the lung. Various respiratory conditions may require bronchodilators including asthma and chronic obstructive pulmonary disease. They are used to either reverse the symptoms of asthma or improve lung function in patients with chronic obstructive pulmonary disease. Pulmonary function tests assess lung function. Thus, bronchodilators have an essential role in the diagnosis and treatment of lung conditions based on their effect on pulmonary function tests. The FEV1/FVC ratio compares how much air flows during the first second of exhalation (forced expiratory volume) to the theoretical amount of air someone can push out in a maximum exhalation (forced vital capacity). A typical ratio is 0.7. In reversible increased airway resistance like asthma, pre-bronchodilator pulmonary function tests will typically be lower than 0.7. However, after administration of a short-acting bronchodilator, the ratio may normalize. In nonreversible conditions like chronic obstructive pulmonary disease, giving a short-acting bronchodilator may not normalize pulmonary function test levels in patients. Commonly, inhaled corticosteroids are added to beta-2 agonists to reduce inflammation and pro-inflammatory agents that will further constrict airways. Beta-2 agonist class bronchodilators do not affect the underlying pathology of lung disease; they are only symptomatic treatment. Therefore, adding inhaled corticosteroids to the regimen has been the mainstay of mild to moderate reversible lung diseases with or without long-acting beta-2 agonists. Anticholinergics is the final class of medicine considered bronchodilators. This class's mechanism inhibits the effects of the parasympathetic nervous system mediated by the vagus nerve. A hyperactive parasympathetic nervous system causes bronchial secretions and narrowing of the airways. Medicines that inhibit the actions of the parasympathetic nervous system at the level of the airways will then generate a bronchodilatory effect. These medicines include ipratropium bromide, which is a short-acting medicine (4 to 6 hours), and tiotropium bromide, which is longer acting (24 hours). Anticholinergics are primarily used in the setting of chronic obstructive pulmonary disease. Patients with asthma can usually control their symptoms with the combination of a beta-2 agonist and corticosteroid. The step theory in managing reversible lung diseases like asthma incorporates both short- and long-acting bronchodilators. Those with intermittent asthma should receive a short-acting bronchodilator such as albuterol as needed. Adding a low-dose, inhaled corticosteroid is the next step to more symptomatic disease, followed by adding a long-acting bronchodilator with the inhaled steroid. Increasingly aggressive treatment is deferred to those who specialize in asthma and allergy treatment. Once control is achieved, the patient will consult with their doctor to wean them off these medicines to a smaller dose with fewer adverse effects. Failure to control symptoms with short or long-acting bronchodilators and corticosteroids can cause irreversible lung injury. Frequent monitoring by pulmonary function tests and peak airway flow is the mainstay of treatment success.

DrugBank Data that Cites this Article

Drugs

Ipratropium

Drug Targets

Drug	Target	Kind	Organism	Pharmacological Action	Actions
Ipratropium	Muscarinic acetylcholine receptor M1	Protein	Humans	Yes	Antagonist	Details
Ipratropium	Muscarinic acetylcholine receptor M2	Protein	Humans	Yes	Antagonist	Details
Ipratropium	Muscarinic acetylcholine receptor M3	Protein	Humans	Yes	Antagonist	Details