SBA — Single Best Answer · Review
Question 437
Pharmacology → General
Classification
Question
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A patient taking clonidine for hypertension abruptly stops treatment. Shortly afterwards she develops marked rebound hypertension. Which pharmacological property most directly explains why clonidine should normally be withdrawn gradually?
Question Stem
Select the single best answer.
Options
A
Peripheral beta-2 receptor blockade
B
Central presynaptic alpha-2 receptor agonism
C
Irreversible alpha-1 receptor antagonism
D
Direct inhibition of renin synthesis
E
Blockade of catecholamine synthesis in the adrenal medulla
Explanation
Clonidine is an alpha-adrenergic agonist that acts centrally at presynaptic alpha-2 receptors, suppressing catecholamine release through negative feedback. Sudden withdrawal may therefore produce severe rebound hypertension, so withdrawal should be gradual.
Option Validity
A) Clonidine is not a peripheral beta-2 receptor blocker.
C) Clonidine is an alpha-2 agonist rather than an irreversible alpha-1 antagonist.
D) Direct inhibition of renin synthesis is not the mechanism described for clonidine.
E) Clonidine suppresses catecholamine release centrally rather than blocking catecholamine synthesis in the adrenal medulla.
Further Reading
Saxena R. Textbook for MRCOG-1. Chapter 12: Pharmacology. Adrenergic Agents, p.345.