Anti-Asthmatic Drugs: Essentials For The KAPS Exam

Classification and Uses of Anti-Asthmatic Drugs 

Anti-asthmatic drugs are designed to manage and relieve the symptoms of asthma. These medications can be broadly classified as:

1. Bronchodilators

(a) Sympathomimetics

(i) Selective B2-adrenergic agonists:

Salbutamol and terbutaline (short-acting): These drugs provide quick relief from acute asthma attacks with a rapid onset (within 1-5 minutes) and short duration of action.

These selective B2-agonists are administered via inhalation, providing a rapid onset of action for acute asthma attacks. The typical dosage for salbutamol is 100-200mcg every 6 hours through a metered dose inhaler (MDI).

Salmeterol and formoterol (long-acting): These are used for maintenance therapy due to their prolonged effects but are not suitable for acute attacks due to their slower onset.

Salmeterol: Typically dosed at 50mcg twice daily via inhalation, is used for maintenance therapy but is not suitable for acute attacks.

Formoterol: Dosed at 12-24mcg twice daily via inhalation, used for chronic management of asthma symptoms.

(ii) Nonselective:

Adrenaline: This nonselective sympathomimetic induces rapid and potent bronchodilation by stimulating β2-adrenergic receptors. It is administered as 0.2–0.5 mL of a 1:1000 solution subcutaneously. However, its usage has decreased due to severe cardiac side effects.

(b) Methylxanthines

Theophylline, aminophylline, etophylline: These drugs relax the smooth muscles of the airways and have anti-inflammatory effects. They are used less frequently now due to their narrow therapeutic range and potential for serious side effects.

(c) Anticholinergics

Ipratropium bromide and tiotropium bromide: These drugs block the action of acetylcholine on muscarinic receptors in the airways, leading to bronchodilation. They are particularly useful for patients who cannot tolerate B2-agonists.

2. Leukotriene Receptor Antagonists

Zafirlukast and montelukast: These drugs block the effects of leukotrienes, inflammatory mediators that contribute to bronchoconstriction, mucus production, and airway inflammation. They are often used as add-on therapy for chronic asthma management.

3. Mast Cell Stabilisers

Sodium cromoglycate, nedocromil sodium, and ketotifen: These agents prevent the release of inflammatory mediators from mast cells, thus reducing airway inflammation and hyperresponsiveness. They are used for prophylactic treatment rather than acute relief.

4. Glucocorticoids

(a) Inhaled glucocorticoids

Beclomethasone, budesonide, and fluticasone are the cornerstones of chronic asthma management. They effectively reduce inflammation and prevent exacerbations.

(b) Systemic glucocorticoids

Hydrocortisone, prednisolone, methylprednisolone: These are used for severe asthma exacerbations that do not respond to other treatments. Due to their significant side effects, they are reserved for short-term use.

5. Anti-IgE Monoclonal Antibody

Omalizumab: This targets IgE, an antibody involved in allergic responses. It is used for moderate to severe allergic asthma not controlled by standard therapies.

Common Side-effects and Precautions

The common side-effects and precautions of the anti-asthmatic drugs are:

To Sum Up

The management of asthma involves a variety of drugs, each targeting different aspects of the disease process. From rapid-relief bronchodilators to long-term anti-inflammatory agents, the appropriate use of these medications can significantly improve the quality of life for individuals with asthma. 

This is a comprehensive guide to anti-asthmatic drugs for medical and pharmacological students. If you need an elaborate explanation or have questions regarding this topic, join Academically’s KAPS Preparation Course. You will get access to detailed explanations on each topic, practice questions and personalised guidance.

Fill out this form for one-on-one counselling with the expert.