A bronchodilator or broncholytic (although the latter occasionally includes

secretory Secretion is the movement of material from one point to another, such as a secreted chemical substance from a cell or gland. In contrast, excretion is the removal of certain substances or waste products from a cell or organism. The classical mec ...

inhibition as well) is a substance that dilates the bronchi and

bronchiole The bronchioles ( ) are the smaller branches of the bronchial airways in the lower respiratory tract. They include the terminal bronchioles, and finally the respiratory bronchioles that mark the start of the respiratory zone delivering air to ...

s, decreasing resistance in the respiratory airway and increasing airflow to the

lung The lungs are the primary Organ (biology), organs of the respiratory system in many animals, including humans. In mammals and most other tetrapods, two lungs are located near the Vertebral column, backbone on either side of the heart. Their ...

s. Bronchodilators may be originating naturally within the body, or they may be

medication Medication (also called medicament, medicine, pharmaceutical drug, medicinal product, medicinal drug or simply drug) is a drug used to medical diagnosis, diagnose, cure, treat, or preventive medicine, prevent disease. Drug therapy (pharmaco ...

s administered for the treatment of breathing difficulties, usually in the form of inhalers. They are most useful in obstructive lung diseases, of which

asthma Asthma is a common long-term inflammatory disease of the airways of the lungs. It is characterized by variable and recurring symptoms, reversible airflow obstruction, and easily triggered bronchospasms. Symptoms include episodes of wh ...

and

chronic obstructive pulmonary disease Chronic obstructive pulmonary disease (COPD) is a type of progressive lung disease characterized by chronic respiratory symptoms and airflow limitation. GOLD defines COPD as a heterogeneous lung condition characterized by chronic respiratory s ...

are the most common conditions. They may be useful in bronchiolitis and

bronchiectasis Bronchiectasis is a disease in which there is permanent enlargement of parts of the bronchi, airways of the lung. Symptoms typically include a chronic cough with sputum, mucus production. Other symptoms include shortness of breath, hemoptysis, co ...

, although this remains somewhat controversial. 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 beta-2 adrenergic agonists (short- and long-acting), anticholinergics (short- and long-acting), and theophylline (long-acting).

Short-acting β₂-adrenergic agonists

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, such as

salbutamol Salbutamol, also known as albuterol and sold under the brand name Ventolin among others, is a medication that opens up the medium and large airways in the lungs. It is a short-acting β2 adrenergic receptor agonist that causes relaxation of ...

, are specific to the lungs; they are called β₂-adrenergic agonists and can relieve bronchospasms without unwanted cardiac side effects of nonspecific β-agonists (for example,

ephedrine Ephedrine is a central nervous system (CNS) stimulant and sympathomimetic agent that is often used to prevent hypotension, low blood pressure during anesthesia. It has also been used for asthma, narcolepsy, and obesity but is not the preferred ...

epinephrine Adrenaline, also known as epinephrine, is a hormone and medication which is involved in regulating visceral functions (e.g., respiration). It appears as a white microcrystalline granule. Adrenaline is normally produced by the adrenal glands a ...

). Patients who regularly or frequently need to take a short-acting β₂-adrenergic agonist should consult their doctor, as such usage indicates uncontrolled asthma, and their routine medications may need adjustment.

Long-acting β₂-adrenergic agonists

These are long-term medications taken routinely in order to control and prevent bronchoconstriction. They are not intended for fast relief. These medications may take longer to begin working, but relieve airway constriction for up to 12 hours. Commonly taken twice a day with an anti-inflammatory medication, they maintain open airways and prevent asthma symptoms, particularly at night. Salmeterol and formoterol are examples of these.

Anticholinergics

Some examples of anticholinergics are tiotropium (Spiriva) and ipratropium bromide. Tiotropium is a long-acting, 24-hour, anticholinergic bronchodilator used in the management of

(COPD). Only available as an inhalant, ipratropium bromide is used in the treatment of asthma and COPD. As a short-acting anticholinergic, it improves lung function and reduces the risk of exacerbation in people with symptomatic asthma. However, it will not stop an asthma attack already in progress. Because it has no effect on asthma symptoms when used alone, it is most often paired with a short-acting β₂-adrenergic agonist. While it is considered a relief or rescue medication, it can take a full hour to begin working. For this reason, it plays a secondary role in acute asthma treatment. Dry throat is the most common side effect. If the medication gets in contact with the eyes, it may cause blurred vision for a brief time. The use of anticholinergics in combination with short-acting β₂-adrenergic agonists has been shown to reduce hospital admissions in children and adults with acute asthma exacerbations.

Other

Available in oral and injectable form, theophylline is a long-acting bronchodilator that prevents asthma episodes. It belongs to the chemical class methylxanthines (along with caffeine). It is prescribed in severe cases of asthma or those that are difficult to control. It must be taken 1–4 times daily, and doses cannot be missed. Blood tests are required to monitor therapy and to indicate when dosage adjustment is necessary. Side effects can include nausea, vomiting, diarrhea, stomach or headache, rapid or irregular heart beat, muscle cramps, nervous or jittery feelings, and hyperactivity. These symptoms may signal the need for an adjustment in medication. It may promote acid reflux, also known as GERD, by relaxing the lower esophageal sphincter muscle. Some medications, such as seizure and ulcer medications and antibiotics containing

erythromycin Erythromycin is an antibiotic used for the treatment of a number of bacterial infections. This includes respiratory tract infections, skin infections, chlamydia infections, pelvic inflammatory disease, and syphilis. It may also be used ...

, can interfere with the way theophylline works. Coffee, tea, colas, cigarette-smoking, and viral illnesses can all affect the action of theophylline and change its effectiveness. A physician should monitor dosage levels to meet each patient's profile and needs. Additionally, some psychostimulant drugs that have an amphetamine like mode of action, such as

amphetamine Amphetamine (contracted from Alpha and beta carbon, alpha-methylphenethylamine, methylphenethylamine) is a central nervous system (CNS) stimulant that is used in the treatment of attention deficit hyperactivity disorder (ADHD), narcolepsy, an ...

methamphetamine Methamphetamine (contracted from ) is a potent central nervous system (CNS) stimulant that is mainly used as a recreational drug use, recreational or Performance-enhancing substance, performance-enhancing drug and less commonly as a secon ...

, and

cocaine Cocaine is a tropane alkaloid and central nervous system stimulant, derived primarily from the leaves of two South American coca plants, ''Erythroxylum coca'' and ''Erythroxylum novogranatense, E. novogranatense'', which are cultivated a ...

, have bronchodilating effects and were used often for

due to the lack of effective β₂-adrenergic agonists for use as bronchodilator, but are now rarely, if ever, used medically for their bronchodilatory effects. Gaseous

carbon dioxide Carbon dioxide is a chemical compound with the chemical formula . It is made up of molecules that each have one carbon atom covalent bond, covalently double bonded to two oxygen atoms. It is found in a gas state at room temperature and at norma ...

also relaxes airway musculature: hypocapnia caused by deliberate

hyperventilation Hyperventilation is irregular breathing that occurs when the rate or tidal volume of breathing eliminates more carbon dioxide than the body can produce. This leads to hypocapnia, a reduced concentration of carbon dioxide dissolved in the blo ...

increases respiratory resistance while

hypercapnia Hypercapnia (from the Greek ''hyper'', "above" or "too much" and ''kapnos'', "smoke"), also known as hypercarbia and CO2 retention, is a condition of abnormally elevated carbon dioxide (CO2) levels in the blood. Carbon dioxide is a gaseous pro ...

induced by carbon dioxide inhalation reduces it; however, this bronchodilating effect of carbon dioxide inhalation only lasts 4 to 5 minutes. Nonetheless, this observation has inspired the development of S-1226, carbon dioxide-enriched air formulated with nebulized perflubron.

Common bronchodilators

The bronchodilators are divided into short- and long-acting groups. Short-acting bronchodilators are used for relief of bronchoconstriction, while long-acting bronchodilators are predominantly used for prevention. Short-acting bronchodilators include: *

Salbutamol Salbutamol, also known as albuterol and sold under the brand name Ventolin among others, is a medication that opens up the medium and large airways in the lungs. It is a short-acting β2 adrenergic receptor agonist that causes relaxation of ...

/albuterol (Proventil or Ventolin) * Levosalbutamol/levalbuterol (Xopenex) * Pirbuterol (Maxair) *

Epinephrine Adrenaline, also known as epinephrine, is a hormone and medication which is involved in regulating visceral functions (e.g., respiration). It appears as a white microcrystalline granule. Adrenaline is normally produced by the adrenal glands a ...

(Primatene Mist) * Racemic Epinephrine (Asthmanefrin, Primatene Mist Replacement) *

Ephedrine Ephedrine is a central nervous system (CNS) stimulant and sympathomimetic agent that is often used to prevent hypotension, low blood pressure during anesthesia. It has also been used for asthma, narcolepsy, and obesity but is not the preferred ...

(Bronkaid) * Terbutaline Long-acting bronchodilators include: * Salmeterol (Serevent or Seretide) * Clenbuterol (Spiropent) * Formoterol * Bambuterol * Indacaterol

References

External links

Drug information
{{Authority control Respiratory physiology Respiratory therapy Pulmonary function testing

Short-acting β2-adrenergic agonists