SBA — Single Best Answer · Review
Question 478
Pharmacology → General
Classification
Question
SSBAQuestion Header
A patient receiving clonidine is assessed before surgery. Which combination of effects is characteristic of this drug?
Question Stem
Select the single best answer.
Options
A
Increased catecholamine release with increased anaesthetic requirement
B
Suppressed catecholamine release with reduced minimum alveolar concentration of volatile anaesthetic agents
C
Dopamine receptor blockade with increased minimum alveolar concentration
D
Beta-2 blockade with bronchodilatation and reduced sedation
E
Increased catecholamine release with marked diuresis
Explanation
Clonidine is an alpha-adrenergic agonist that acts centrally at presynaptic alpha-2 receptors, suppressing catecholamine release by negative feedback. It has analgesic and sedative properties, and preoperative administration reduces the minimum alveolar concentration of volatile anaesthetic agents.
Option Validity
A) Clonidine suppresses rather than increases catecholamine release and reduces anaesthetic requirement.
C) Dopamine receptor blockade characterises antipsychotic drugs rather than clonidine.
D) Clonidine acts through central alpha-2 receptors, not beta-2 blockade.
E) Increased catecholamine release and marked diuresis are not characteristic effects of clonidine.
Further Reading
Saxena R. Textbook for MRCOG-1. Chapter 12: Pharmacology. Adrenergic Agents, p.345.