A patient with severe refractory hypertension is started on minoxidil. Which pharmacological property necessitates the co-administration of a beta-blocker and a loop diuretic with minoxidil?
- A Lupus-like syndrome
- B Severe hyperkalemia
- C Reflex tachycardia and fluid retention ✓
- D Methemoglobinemia
Correct answer: C. Reflex tachycardia and fluid retention
Explanation
Minoxidil is a direct arteriolar vasodilator that activates ATP-sensitive potassium channels. Its potent vasodilation triggers baroreceptor-mediated reflex sympathetic activation, causing reflex tachycardia and renin-mediated fluid retention. Therefore, it must be combined with a beta-blocker to blunt tachycardia and a diuretic to counteract edema.
Reference: Katzung Basic and Clinical Pharmacology, 15th ed.
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