Which statement correctly describes the receptor pharmacology of dobutamine?
- A Pure beta-1 agonist with no activity at other adrenergic receptors
- B Mixed alpha-1 and beta-1 agonist with equal potency at both receptors
- C Racemic mixture producing predominant beta-1 agonism with weak alpha-1 antagonism from one enantiomer ✓
- D Beta-2 selective agonist with significant chronotropic activity
Correct answer: C. Racemic mixture producing predominant beta-1 agonism with weak alpha-1 antagonism from one enantiomer
Explanation
Dobutamine is a racemic mixture. The levo enantiomer is a potent alpha-1 agonist while the dextro enantiomer is an alpha-1 antagonist, so their peripheral alpha effects largely cancel, leaving net beta-1 mediated increase in contractility with modest reflex reduction in heart rate. This profile makes it useful in acute heart failure. Calling it a pure beta-1 agonist ignores its stereochemical complexity, a favourite exam trap.
Reference: Goodman and Gilman's The Pharmacological Basis of Therapeutics, 14th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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