A patient is started on clonidine for hypertension. The drug is abruptly stopped after 4 weeks. Which life-threatening adverse effect is MOST likely to occur?

• A Rebound hypertension with sympathetic overactivity ✓
• B Severe bradycardia and complete heart block
• C Hypokalemia-induced ventricular arrhythmia
• D Acute pulmonary edema from fluid retention

Explanation

Clonidine activates central alpha-2 receptors (imidazoline I1 receptors) in the nucleus tractus solitarius to reduce sympathetic outflow. Abrupt discontinuation leads to a rebound surge of sympathetic activity causing severe hypertension, tachycardia, sweating, and anxiety—the clonidine withdrawal syndrome. This is managed by reintroducing clonidine or switching to an alternative antihypertensive. Gradual tapering over 2–4 days is recommended to avoid this complication.

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

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