Asthma
Asthma affects 300 million people worldwide and is characterized by respiratory symptoms that burden patients and can lead to exacerbations which require medical attention and can be fatal. Common symptoms of asthma include wheezing, chest tightness, cough and shortness of breath. These symptoms are caused by inflammation and hyperreactivity in the airways leading to bronchoconstriction or airway narrowing. There are many triggers for patients with asthma including dust and allergens, pollution, cigarette smoke and even exercise or stress. Identifying and avoiding these triggers is the first step towards managing asthma.
Asthma cannot be cured but it can be controlled with a variety of medications in addition to avoiding common triggers. Asthma medications can be: A.relievers (“rescue” medications helping quickly in an asthma attack) or B. controllers (preventing asthma attacks). Relievers are bronchodilators with rapid onset of action. Every patient with asthma should be given a short acting or “rescue” inhaler to help with sudden-onset symptoms. The most common type of rescue inhaler is albuterol(INN salbutamol) which is a short acting beta-2 agonist (SABA). Albuterol selectively stimulates beta-2 adrenoceptors which leads to relaxation of smooth muscle in the lungs, and opens up the airways to relieve the symptoms of asthma. The peak effects of albuterol occur within 30 minutes which is ideal for managing symptoms when they occur. Other SABAs include levoalbuterol, the R-isomer of albuterol, fenoterol and terbutaline. Short-acting muscarinic antagonists (SAMA, e.g. ipratropium) and xanthines (aminophylline – only i.v.) can be also used to dilate the bronchi and relieve acute asthma attacks.
In addition to a rescue inhaler, most patients with persistent asthma symptoms should use a “controller” medication as well. Persistent asthma is defined as having symptoms requiring the use of a rescue inhaler more than two times per week. Control inhalers are categorized by their mechanism and include inhaled corticosteroids, long-acting beta-2 agonists (LABA), and long-acting muscarinic antagonists (LAMA). Inhaled corticosteroids work to decrease the inflammation in the lungs thus targeting the source of the disease, making these agents the preferred choice. Long-acting beta-2 agonists such as salmeterol can be added to inhaled corticosteroids in patients who are not controlled on their current treatment but should never be used as monotherapy. Long-acting beta-2 agonists work the same way as albuterol, but they have a longer duration of action making them ideal for preventing symptoms. Their slower onset of action, however, precludes their use for treatment of acute symptoms. Long-acting anticholinergic agents like tiotropium, are not considered first-line but can be used in patients who don’t respond to or still have symptoms while on inhaled corticosteroids and long-acting beta agonists. Mast cell stabilizers such as cromolyn and nedocromil that are used mostly in allergic conjunctivitis and rhinitis may also have some benefit in asthma. Common agents in each drug class are listed below.
Inhaled Corticosteroids:
Long-acting beta-2 agonists (LABAs) approved to treat asthma:
Long acting anticholinergics approved to treat asthma:
Mast cell stabilizers:
Some patients may require systemic medications to control their asthma symptoms. Retard formulations of xanthines (oral theophylline) can be used for this purpose. Leukotriene inhibitors (leukotriene receptor antagonists such as montelukast and inhibitors of leukotriene synthesis such as zileuton) work by reducing airway inflammation, edema and smooth muscle contraction. These agents are given orally and are often used to treat allergies in addition to asthma. Monoclonal antibodies against IgE (omalizumab) and against IL-5 (reslizumab, mepolizumab, benralizumab) can be injected s.c. or i.v. every 2-4 weeks in allergic/eosinophilic asthma. These drugs will not help acute symptoms, but can be used to prevent symptoms in the future. For patients that are experiencing an acute asthma exacerbation, systemic steroids should be used to decrease inflammation. Patients with an increased heart or respiratory rate with low oxygen saturations (<90%) should be admitted to the hospital for treatment with a short-acting beta-2 agonist, systemic steroids and oxygen therapy.
Asthma Long-term Treatments – Khan Academy
Included in the 6.5-minute video are different delivery mechanisms for inhaled medications, the classes of medications used for chronic management of asthma, and their mechanisms of action. It also describes the different levels of severity of asthma and how they are treated differently based on the patient’s symptom control. Suitable for beginners.
National Institute of Health
The NIH Quick Reference for Asthma Care includes guidelines for diagnosing and managing asthma. It provides information on the classification of asthma at the initial visit, initial treatment recommendations and information on how to assess asthma control on follow-up visits. It also displays a stepwise approach for the treatment of asthma, dosage recommendations for medications and patient education. Suitable for intermediate level learners.
Global Initiative for Asthma
The 2018 pocket guide for asthma management and prevention is a shortened document from the 2016 GINA Guidelines on the management and prevention of asthma. Within the pocket guide is information on diagnosis and assessment for patients with asthma. It also outlines the treatment algorithm including step-up and step-down therapy. Finally, it includes recommendations for the treatment of exacerbations. Suitable for intermediate level learners.
Amy Fan from Khan Academy reviews the pharmacology of short-term or rescue medications used for the treatment of asthma. Included in this 5-minute video are short acting inhalers, IV medications, and oxygen therapy. This video will provide an overview for the treatment of an asthma attack depending on the severity of symptoms. It is suitable for beginners.