A patient receiving norepinephrine infusion develops severe hypertension but no significant bronchodilation. This differs from epinephrine because norepinephrine has negligible activity at which receptor?

• A Beta-2 receptor ✓
• B Beta-1 receptor
• C Alpha-1 receptor
• D Alpha-2 receptor

Explanation

Norepinephrine is a potent agonist at alpha-1, alpha-2, and beta-1 receptors but has very weak beta-2 activity. Bronchial smooth muscle relaxation is mediated by beta-2 receptors, so norepinephrine does not produce significant bronchodilation. Epinephrine stimulates beta-2 receptors, causing bronchodilation, which explains the clinical difference.

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

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.