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Questions and Answers
What is a potential adverse effect of β2-agonists related to glucose metabolism?
What is a potential adverse effect of β2-agonists related to glucose metabolism?
- Hypoglycemia
- Increased plasma concentrations of glucose (correct)
- Insulin resistance
- Decreased blood glucose levels
Why should caution be exercised when using β2-agonists in diabetic patients?
Why should caution be exercised when using β2-agonists in diabetic patients?
- They can raise plasma glucose levels. (correct)
- They can cause severe hypoglycemia.
- They lead to increased insulin secretion.
- They enhance glucose uptake by cells.
What mechanism leads to tachycardia when using β2-agonists?
What mechanism leads to tachycardia when using β2-agonists?
- Reflex stimulation due to peripheral vasodilation (correct)
- Direct stimulation of β1 receptors only
- Inhibition of adenosine action
- Increase in potassium concentration
What adverse effect may β2-agonists cause related to potassium levels?
What adverse effect may β2-agonists cause related to potassium levels?
What is the primary reason for the declining use of theophylline in countries where it was once common?
What is the primary reason for the declining use of theophylline in countries where it was once common?
Which of the following describes how theophylline acts as a bronchodilator?
Which of the following describes how theophylline acts as a bronchodilator?
What common side effect is associated with β2-agonist use due to skeletal muscle stimulation?
What common side effect is associated with β2-agonist use due to skeletal muscle stimulation?
Which condition would particularly increase the risk of adverse effects when using β2-agonists?
Which condition would particularly increase the risk of adverse effects when using β2-agonists?
What percentage of the total drug delivered by a metered-dose inhaler typically ends up in the lower airways?
What percentage of the total drug delivered by a metered-dose inhaler typically ends up in the lower airways?
Which of the following statements about inhaled drugs is true?
Which of the following statements about inhaled drugs is true?
What is a potential disadvantage of using a metered-dose inhaler (MDI)?
What is a potential disadvantage of using a metered-dose inhaler (MDI)?
What advantage do spacer chambers provide when using inhalers?
What advantage do spacer chambers provide when using inhalers?
In patients with asthma or COPD, why is inhalation the preferred route for drug delivery?
In patients with asthma or COPD, why is inhalation the preferred route for drug delivery?
What may happen to an inhaled drug with a large molecular weight?
What may happen to an inhaled drug with a large molecular weight?
What is a characteristic of dry powder inhalers (DPIs)?
What is a characteristic of dry powder inhalers (DPIs)?
Why is it important for patients to be taught how to use an inhaler properly?
Why is it important for patients to be taught how to use an inhaler properly?
What is the primary mechanism by which β2-agonists promote bronchodilation?
What is the primary mechanism by which β2-agonists promote bronchodilation?
Which of the following mechanisms do β2-agonists utilize to induce relaxation in airway smooth muscle cells?
Which of the following mechanisms do β2-agonists utilize to induce relaxation in airway smooth muscle cells?
What is one strategy used to minimize β1-mediated adverse effects in β2-agonist development?
What is one strategy used to minimize β1-mediated adverse effects in β2-agonist development?
Which of the following compounds is known to constrict the airways?
Which of the following compounds is known to constrict the airways?
What role does phosphodiesterase (PDE) play in bronchodilation?
What role does phosphodiesterase (PDE) play in bronchodilation?
Which treatment method is the preferred choice for managing asthma?
Which treatment method is the preferred choice for managing asthma?
How does activation of β2 receptors affect intracellular calcium levels?
How does activation of β2 receptors affect intracellular calcium levels?
What is the effect of increased intracellular cAMP on airway smooth muscle cells?
What is the effect of increased intracellular cAMP on airway smooth muscle cells?
What is one effect of corticosteroids on β2-agonists?
What is one effect of corticosteroids on β2-agonists?
Which of the following is a systemic side effect of corticosteroid use?
Which of the following is a systemic side effect of corticosteroid use?
How do corticosteroids enhance the effects of β2-agonists in asthma therapy?
How do corticosteroids enhance the effects of β2-agonists in asthma therapy?
What potential adverse effect can corticosteroids cause related to bones?
What potential adverse effect can corticosteroids cause related to bones?
What interaction occurs between corticosteroids and glucocorticoid receptors?
What interaction occurs between corticosteroids and glucocorticoid receptors?
Corticosteroid use can lead to which psychiatric disturbance?
Corticosteroid use can lead to which psychiatric disturbance?
What is the advantage of using budesonide, fluticasone, and mometasone over beclomethasone dipropionate?
What is the advantage of using budesonide, fluticasone, and mometasone over beclomethasone dipropionate?
Which of the following possible adverse effects of corticosteroids relates to vision?
Which of the following possible adverse effects of corticosteroids relates to vision?
Which corticosteroid is characterized as a prodrug?
Which corticosteroid is characterized as a prodrug?
Which of the following corticosteroids is considered to have the lowest potency?
Which of the following corticosteroids is considered to have the lowest potency?
What is the primary mechanism by which corticosteroids prevent tolerance to β2-agonists?
What is the primary mechanism by which corticosteroids prevent tolerance to β2-agonists?
What common characteristic do budesonide, fluticasone, and mometasone share regarding hepatic metabolism?
What common characteristic do budesonide, fluticasone, and mometasone share regarding hepatic metabolism?
Which corticosteroid is indicated as lung-selective with lower systemic adverse effects?
Which corticosteroid is indicated as lung-selective with lower systemic adverse effects?
What is the reason for preferring inhaled corticosteroids in pediatric patients?
What is the reason for preferring inhaled corticosteroids in pediatric patients?
Among the following corticosteroids, which one has a higher risk of systemic adverse effects due to its first-pass metabolism?
Among the following corticosteroids, which one has a higher risk of systemic adverse effects due to its first-pass metabolism?
What factor primarily influences the development of systemic adverse effects from corticosteroids?
What factor primarily influences the development of systemic adverse effects from corticosteroids?
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Study Notes
Inhalation for Asthma and COPD
- Inhalation is the preferred method for drug delivery in asthma and COPD due to lower risks of adverse effects.
- Only 10-20% of the drug delivered via a metered-dose inhaler reaches the lower airways.
- The rest is absorbed through the gut and undergoes first-pass metabolism before entering systemic circulation.
- Proper inhaler technique is essential to optimize drug delivery.
Inhalation Drug Delivery Devices
- Spacer Chambers: Reduce drug deposition in the oropharynx.
- Dry Powder Inhalers (DPI): Can be irritating to the mouth.
- Metered-Dose Inhalers (MDI): May be difficult to use.
- Nebulisers: Easier to use than MDIs.
Bronchodilation Mechanisms
- cAMP: promotes bronchodilation.
- β-agonists: Increase cAMP synthesis by activating adenylyl cyclase (AC).
- Phosphodiesterase (PDE) inhibitors: Slow cAMP breakdown (e.g., theophylline).
- Acetylcholine and adenosine: Constrictor agents, inhibited by muscarinic and adenosine antagonists.
β2-Selective Agonists
- Strategies for minimizing β1-mediated adverse effects:
- Develop drugs with β2 selectivity.
- Modify structure for reduced metabolism by COMT and increased bioavailability.
- Administer via inhalation (aerosol or dry powder).
- Treatment of choice in asthma.
- Primary mechanism: bronchodilation through cAMP elevation.
Molecular Actions of β2-agonists
- Activation of β2 receptors leads to:
- Increased intracellular cAMP through Gs protein activation.
- Activation of PKA.
- PKA phosphorylation of target substrates promotes:
- Opening of KCa channels for smooth muscle relaxation.
- Inhibition of PLC-IP3 pathway, reducing cellular Ca2+.
- Increased Na+/Ca2+ exchange.
- Increased Na+,Ca2+-ATPase activity.
Adverse Effects of β2-agonists
- Tachyphylaxis: Rapid tolerance to bronchodilator effects.
- Tremor: Stimulation of β2 receptors in skeletal muscle.
- Tachycardia: Reflex cardiac stimulation due to β2-mediated vasodilation and direct activation of cardiac β1 and β2 receptors.
- Hyperglycemia: Increased plasma concentrations of glucose, lactate, and free fatty acids.
- Hypokalaemia: Promotes entry of K+ ions into skeletal muscle, potentially dangerous in cardiac disease.
Theophylline
- Structurally similar to caffeine.
- Inexpensive, widely used in developing countries.
- Declining use due to side effects and less effectiveness compared to inhaled β2-agonists or corticosteroids.
- Mechanisms:
- Bronchodilation: inhibits PDE, increases cAMP.
- Antagonises adenosine action.
Synergism Between Corticosteroids and β2-agonists
- Corticosteroids:
- Enhance β2 responsiveness.
- Prevent tolerance to β2-agonists.
- β2-agonists:
- Increase translocation of liganded GR receptors.
- Enhance binding of GR to DNA.
- The combination enhances each other's effects in asthma therapy.
Corticosteroids: Adverse Effects
- Local: Dysphonia, oropharyngeal candidiasis, cough.
- Systemic: Adrenal suppression, growth supression, bruising, osteoporosis, cataracts, glaucoma, metabolic abnormalities, psychiatric disturbances, pneumonia.
Corticosteroids: Pharmacokinetics and Choice
- First-Pass Metabolism: Influences systemic adverse effects.
- Low Oral Bioavailability: Budesonide, fluticasone, and mometasone are preferred due to reduced systemic effects.
- Ciclesonide: Lung-selective prodrug with lower risk of systemic adverse effects.
Corticosteroids: Potency Comparison
- Least potent: Triamcinolone, flunisolide.
- Intermediate: Beclomethasone dipropionate, budesonide.
- Most potent: Fluticasone propionate.
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