A 35-year-old woman with severe persistent asthma is switched from oral prednisolone to inhaled budesonide for maintenance therapy. The primary pharmacological advantage that allows inhaled budesonide to achieve comparable anti-inflammatory efficacy in the airways with markedly fewer systemic adverse effects is:

• A Budesonide has higher intrinsic glucocorticoid receptor binding affinity than prednisolone
• B Budesonide has a shorter plasma half-life than prednisolone, preventing accumulation
• C Budesonide is administered via metered-dose inhaler, which bypasses gastrointestinal absorption entirely
• D Budesonide undergoes extensive first-pass hepatic metabolism, reducing systemic bioavailability ✓

Explanation

Inhaled budesonide achieves high local concentrations in the airway with minimal systemic effects because the fraction swallowed undergoes extensive first-pass hepatic metabolism, yielding low systemic bioavailability (~10%). This is the key pharmacological principle enabling inhaled corticosteroids to replace oral steroids for chronic asthma management. Option A is incorrect because receptor affinity alone does not explain the reduced systemic toxicity.

Reference: Katzung Basic and Clinical Pharmacology, 15th ed.

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