Pharmacology: Receptor Agonists and Antagonists

A type of receptor that is responsible for vasoconstriction and increased heart rate.

A type of receptor that causes smooth muscle relaxation in the bronchi, leading to bronchodilation.

A medication class that stimulates β2 receptors to relax airway smooth muscle and relieve bronchospasm.

A commonly used SABA that provides rapid bronchodilation in asthma.

A medication class that blocks α1 receptors to cause vasodilation and reduce blood pressure.

A drug that blocks α1 receptors and is commonly used to treat hypertension.

A medication class that blocks β1 receptors, slowing down heart rate and decreasing contractility.

A commonly used β1 blocker that is often prescribed for hypertension and other conditions.

Inhaled corticosteroids (ICS) are a first-line treatment for persistent asthma. They help reduce airway inflammation and block late-phase reactions to allergens.

Oral corticosteroids like prednisone are used to reduce asthma exacerbation risk and mortality. They should be initiated early on in the course of therapy.

Monoclonal antibodies like Omalizumab target IgE antibodies, reducing IgE-mediated cytokine and histamine release. It's indicated for refractory asthma or patients maximized on other therapies.

IL-5 inhibitors like Mepolizumab, Reslizumab, and Benralizumab reduce IL-5 mediated eosinophil recruitment. These are useful for patients with eosinophilic asthma.

Ivacaftor is a medication used in cystic fibrosis patients with the specific G551D mutation. It targets the G551D mutation and increases the opening of the protein.

Ivacaftor is a CYP3A4 substrate, meaning it interacts with other medications that are metabolized by the same enzyme. This can lead to potential drug interactions and changes in drug levels.

Long-acting beta-2 agonists (LABAs) are bronchodilators that stimulate adenylyl cyclase, increasing cAMP levels and relaxing airway smooth muscle. They have a longer duration of action compared to short-acting beta-2 agonists (SABAs).

LABAs should not be used as monotherapy in asthma due to a significantly increased risk of asthma-related death. They can only be used for asthma in combination with inhaled corticosteroids.

Short-acting anticholinergics (SAMAs) are used for acute asthma exacerbations in the emergency room. They block the effects of acetylcholine on muscarinic receptors, resulting in airway relaxation. This can be helpful in preventing hospitalization in patients with severe asthma attacks.

Leukotriene modifiers (LTRA-Ms) are drugs that either block the leukotriene receptor or prevent synthesis of leukotrienes, which are inflammatory mediators released during an asthma attack. They help reduce granulocyte migration, inflammation and improve bronchodilation.

Methylxanthines, like theophylline and caffeine, inhibit phosphodiesterase 4, resulting in increased cAMP levels and inhibition of cytokine and leukotriene synthesis, leading to bronchodilation. They also block adenosine receptors, which promotes bronchodilation.

Methylxanthines are generally considered last-line agents for asthma due to their narrow therapeutic index, meaning it requires precise dosing and cautious monitoring. High levels can lead to severe side effects including nausea, vomiting, CNS toxicity and arrythmias. They are not commonly used for asthma.

Inhaled corticosteroids (ICS) are the most effective medications for long-term asthma control. They reduce inflammation in the airways, preventing asthma exacerbations and improving lung function.

Combination therapy often involves using an inhaled corticosteroid (ICS) and a long-acting beta-2 agonist (LABA) together to manage asthma. Combining ICS and LABA provides both anti-inflammatory and bronchodilator effects, offering superior control over asthma symptoms.