Drugs acting on the respiratory system

Drugs used in the treatment of asthma

Drug	Mechanism of action	Adverse effects
Beta 2 agonists: albuterol, terbutaline, salmeterol, formoterol	Relax bronchiolar smooth muscle by stimulating bronchodilating beta 2 receptors → activation of adenylate cyclase → increased cAMP. Salmeterol and formoterol have greater specificity for beta 2 receptors.	Tremors, tachycardia, tolerance, cramps; salmeterol can increase the risk of severe asthma attacks and death.
Corticosteroids (budesonide, beclomethasone, fluticasone, triamcinolone, prednisone, methylprednisone, prednisolone)	Anti-inflammatory: reduce secretions and mucosal inflammation, decreasing the severity and frequency of asthma attacks.	Oral candidiasis, cough, adrenal suppression, osteoporosis, growth suppression, peptic ulcers, myopathy, hypertension, Cushing’s syndrome.
Methylxanthines (theophylline)	Inhibit phosphodiesterase, preventing cAMP breakdown → increased cAMP and cGMP levels → bronchodilation. Also decrease release of inflammatory mediators from mast cells; adenosine receptor antagonist.	Narrow therapeutic index, tachycardia, arrhythmias, sudden death, CNS excitation, nervousness, insomnia, tremors, seizures, gastric upset.
Cromolyn, nedocromil	Inhibit release of inflammatory mediators from mast cells and suppress leukocyte chemotaxis. Used to prevent asthma, including exercise- and allergen-induced bronchoconstriction.	Cough, unpleasant taste, dermatitis, myositis; generally well tolerated.
Zileuton	Inhibits 5-lipoxygenase, an enzyme required for leukotriene synthesis.	Headache, nausea, gastric upset, myalgia, Churg Strauss syndrome.
Leukotriene modifiers (montelukast, zafirlukast)	Block leukotriene receptors in the airways, antagonizing leukotriene effects. Also effective in aspirin induced asthma.	Headache, nausea, gastric upset, myalgia, Churg Strauss syndrome, elevation of liver enzymes.
Muscarinic antagonists (ipratropium, tiotropium)	Block muscarinic receptors in the airways, decreasing bronchoconstriction and mucosal secretion.	Anticholinergic effects (especially in elderly), cough, dry mouth, throat irritation, urinary retention, tachycardia, delirium, blurred vision.
Monoclonal antibodies (omalizumab)	Humanized recombinant monoclonal antibody to IgE that blocks IgE binding to mast cells, preventing degranulation.	Injection site reactions, risk of malignancies, rarely anaphylaxis, high cost.

Beta 2 agonists (albuterol, terbutaline, salmeterol, formoterol)

Stimulate beta 2 receptors → bronchodilation via increased cAMP
Short-acting (albuterol, terbutaline) vs. long-acting (salmeterol, formoterol)
Adverse: tremors, tachycardia, tolerance, salmeterol risk of severe attacks

Corticosteroids (budesonide, beclomethasone, fluticasone, etc.)

Anti-inflammatory: decrease airway inflammation and secretions
Reduce frequency/severity of attacks
Adverse: oral candidiasis, adrenal suppression, osteoporosis, growth suppression

Methylxanthines (theophylline)

Inhibit phosphodiesterase → ↑cAMP/cGMP → bronchodilation
Adenosine receptor antagonist; decreases mast cell mediator release
Adverse: narrow therapeutic index, arrhythmias, seizures, CNS excitation

Cromolyn, nedocromil

Stabilize mast cells, inhibit mediator release
Prevent exercise/allergen-induced asthma
Adverse: cough, unpleasant taste, generally well tolerated

Zileuton

Inhibits 5-lipoxygenase → blocks leukotriene synthesis
Adverse: headache, gastric upset, myalgia, Churg-Strauss syndrome

Leukotriene modifiers (montelukast, zafirlukast)

Block leukotriene receptors in airways
Effective in aspirin-induced asthma
Adverse: headache, liver enzyme elevation, Churg-Strauss syndrome

Muscarinic antagonists (ipratropium, tiotropium)

Block muscarinic receptors → ↓bronchoconstriction, ↓mucosal secretion
Adverse: anticholinergic effects (dry mouth, urinary retention), cough

Monoclonal antibodies (omalizumab)

Anti-IgE antibody; prevents IgE binding to mast cells
Used in severe allergic asthma
Adverse: injection site reactions, rare anaphylaxis, high cost

Drugs acting on the respiratory system

Drugs used in the treatment of asthma

Drug	Mechanism of action	Adverse effects
Beta 2 agonists: albuterol, terbutaline, salmeterol, formoterol	Relax bronchiolar smooth muscle by stimulating bronchodilating beta 2 receptors → activation of adenylate cyclase → increased cAMP. Salmeterol and formoterol have greater specificity for beta 2 receptors.	Tremors, tachycardia, tolerance, cramps; salmeterol can increase the risk of severe asthma attacks and death.
Corticosteroids (budesonide, beclomethasone, fluticasone, triamcinolone, prednisone, methylprednisone, prednisolone)	Anti-inflammatory: reduce secretions and mucosal inflammation, decreasing the severity and frequency of asthma attacks.	Oral candidiasis, cough, adrenal suppression, osteoporosis, growth suppression, peptic ulcers, myopathy, hypertension, Cushing’s syndrome.
Methylxanthines (theophylline)	Inhibit phosphodiesterase, preventing cAMP breakdown → increased cAMP and cGMP levels → bronchodilation. Also decrease release of inflammatory mediators from mast cells; adenosine receptor antagonist.	Narrow therapeutic index, tachycardia, arrhythmias, sudden death, CNS excitation, nervousness, insomnia, tremors, seizures, gastric upset.
Cromolyn, nedocromil	Inhibit release of inflammatory mediators from mast cells and suppress leukocyte chemotaxis. Used to prevent asthma, including exercise- and allergen-induced bronchoconstriction.	Cough, unpleasant taste, dermatitis, myositis; generally well tolerated.
Zileuton	Inhibits 5-lipoxygenase, an enzyme required for leukotriene synthesis.	Headache, nausea, gastric upset, myalgia, Churg Strauss syndrome.
Leukotriene modifiers (montelukast, zafirlukast)	Block leukotriene receptors in the airways, antagonizing leukotriene effects. Also effective in aspirin induced asthma.	Headache, nausea, gastric upset, myalgia, Churg Strauss syndrome, elevation of liver enzymes.
Muscarinic antagonists (ipratropium, tiotropium)	Block muscarinic receptors in the airways, decreasing bronchoconstriction and mucosal secretion.	Anticholinergic effects (especially in elderly), cough, dry mouth, throat irritation, urinary retention, tachycardia, delirium, blurred vision.
Monoclonal antibodies (omalizumab)	Humanized recombinant monoclonal antibody to IgE that blocks IgE binding to mast cells, preventing degranulation.	Injection site reactions, risk of malignancies, rarely anaphylaxis, high cost.

Beta 2 agonists (albuterol, terbutaline, salmeterol, formoterol)

Stimulate beta 2 receptors → bronchodilation via increased cAMP
Short-acting (albuterol, terbutaline) vs. long-acting (salmeterol, formoterol)
Adverse: tremors, tachycardia, tolerance, salmeterol risk of severe attacks

Corticosteroids (budesonide, beclomethasone, fluticasone, etc.)

Anti-inflammatory: decrease airway inflammation and secretions
Reduce frequency/severity of attacks
Adverse: oral candidiasis, adrenal suppression, osteoporosis, growth suppression

Methylxanthines (theophylline)

Inhibit phosphodiesterase → ↑cAMP/cGMP → bronchodilation
Adenosine receptor antagonist; decreases mast cell mediator release
Adverse: narrow therapeutic index, arrhythmias, seizures, CNS excitation

Cromolyn, nedocromil

Stabilize mast cells, inhibit mediator release
Prevent exercise/allergen-induced asthma
Adverse: cough, unpleasant taste, generally well tolerated

Zileuton

Inhibits 5-lipoxygenase → blocks leukotriene synthesis
Adverse: headache, gastric upset, myalgia, Churg-Strauss syndrome

Leukotriene modifiers (montelukast, zafirlukast)

Block leukotriene receptors in airways
Effective in aspirin-induced asthma
Adverse: headache, liver enzyme elevation, Churg-Strauss syndrome

Muscarinic antagonists (ipratropium, tiotropium)

Block muscarinic receptors → ↓bronchoconstriction, ↓mucosal secretion
Adverse: anticholinergic effects (dry mouth, urinary retention), cough

Monoclonal antibodies (omalizumab)

Anti-IgE antibody; prevents IgE binding to mast cells
Used in severe allergic asthma
Adverse: injection site reactions, rare anaphylaxis, high cost

Drugs acting on the respiratory system

Drugs used in the treatment of asthma

Drug	Mechanism of action	Adverse effects
Beta 2 agonists: albuterol, terbutaline, salmeterol, formoterol	Relax bronchiolar smooth muscle by stimulating bronchodilating beta 2 receptors → activation of adenylate cyclase → increased cAMP. Salmeterol and formoterol have greater specificity for beta 2 receptors.	Tremors, tachycardia, tolerance, cramps; salmeterol can increase the risk of severe asthma attacks and death.
Corticosteroids (budesonide, beclomethasone, fluticasone, triamcinolone, prednisone, methylprednisone, prednisolone)	Anti-inflammatory: reduce secretions and mucosal inflammation, decreasing the severity and frequency of asthma attacks.	Oral candidiasis, cough, adrenal suppression, osteoporosis, growth suppression, peptic ulcers, myopathy, hypertension, Cushing’s syndrome.
Methylxanthines (theophylline)	Inhibit phosphodiesterase, preventing cAMP breakdown → increased cAMP and cGMP levels → bronchodilation. Also decrease release of inflammatory mediators from mast cells; adenosine receptor antagonist.	Narrow therapeutic index, tachycardia, arrhythmias, sudden death, CNS excitation, nervousness, insomnia, tremors, seizures, gastric upset.
Cromolyn, nedocromil	Inhibit release of inflammatory mediators from mast cells and suppress leukocyte chemotaxis. Used to prevent asthma, including exercise- and allergen-induced bronchoconstriction.	Cough, unpleasant taste, dermatitis, myositis; generally well tolerated.
Zileuton	Inhibits 5-lipoxygenase, an enzyme required for leukotriene synthesis.	Headache, nausea, gastric upset, myalgia, Churg Strauss syndrome.
Leukotriene modifiers (montelukast, zafirlukast)	Block leukotriene receptors in the airways, antagonizing leukotriene effects. Also effective in aspirin induced asthma.	Headache, nausea, gastric upset, myalgia, Churg Strauss syndrome, elevation of liver enzymes.
Muscarinic antagonists (ipratropium, tiotropium)	Block muscarinic receptors in the airways, decreasing bronchoconstriction and mucosal secretion.	Anticholinergic effects (especially in elderly), cough, dry mouth, throat irritation, urinary retention, tachycardia, delirium, blurred vision.
Monoclonal antibodies (omalizumab)	Humanized recombinant monoclonal antibody to IgE that blocks IgE binding to mast cells, preventing degranulation.	Injection site reactions, risk of malignancies, rarely anaphylaxis, high cost.

Key points

Beta 2 agonists (albuterol, terbutaline, salmeterol, formoterol)

Stimulate beta 2 receptors → bronchodilation via increased cAMP
Short-acting (albuterol, terbutaline) vs. long-acting (salmeterol, formoterol)
Adverse: tremors, tachycardia, tolerance, salmeterol risk of severe attacks

Corticosteroids (budesonide, beclomethasone, fluticasone, etc.)

Anti-inflammatory: decrease airway inflammation and secretions
Reduce frequency/severity of attacks
Adverse: oral candidiasis, adrenal suppression, osteoporosis, growth suppression

Methylxanthines (theophylline)

Inhibit phosphodiesterase → ↑cAMP/cGMP → bronchodilation
Adenosine receptor antagonist; decreases mast cell mediator release
Adverse: narrow therapeutic index, arrhythmias, seizures, CNS excitation

Cromolyn, nedocromil

Stabilize mast cells, inhibit mediator release
Prevent exercise/allergen-induced asthma
Adverse: cough, unpleasant taste, generally well tolerated

Zileuton

Inhibits 5-lipoxygenase → blocks leukotriene synthesis
Adverse: headache, gastric upset, myalgia, Churg-Strauss syndrome

Leukotriene modifiers (montelukast, zafirlukast)

Block leukotriene receptors in airways
Effective in aspirin-induced asthma
Adverse: headache, liver enzyme elevation, Churg-Strauss syndrome

Muscarinic antagonists (ipratropium, tiotropium)

Block muscarinic receptors → ↓bronchoconstriction, ↓mucosal secretion
Adverse: anticholinergic effects (dry mouth, urinary retention), cough

Monoclonal antibodies (omalizumab)

Anti-IgE antibody; prevents IgE binding to mast cells
Used in severe allergic asthma
Adverse: injection site reactions, rare anaphylaxis, high cost